Ashly DPX-100 User manual

Brand: Ashly

Model: DPX-100

Category: Audio equalizers

Type: User manual

DPX-100

Graphic Equalizer

Compressor/Limiter

Operating Manual

ASHLY AUDIO INC.

847 Holt Road Webster, NY 14580-9103 Phone: (585) 872-0010

Toll-Free: (800) 828-6308 Fax: (585) 872-0739 Internet: www.ashly.com

HPF EQ

20Hz

Out

10K

Gain

∞

+20

+15

+10

-3

-6

-10

-20

Sec

.2 20

1.5

∞

2.5

+22-40

+20

+10

-3

-6

-10

-20

2Th. 4 6 8 10 12 14 16 18 20 -1 5-18 -12 -9 -6 -3 0 +3 +6 +9 +20

Gain Reduction (dB) Input/Output Level (dB)

Clip

Gain

Threshold Ratio Attack Release Output Level I n

Power

Output

Input

6.3K16K4K2.5K1.8K1K63040025018 0100634025

-3

-9

∞

+15

+10

-5

-10

-15

Sig Clip

Range

±6dB

±15dB

Model DPX-100

Graphic Equalizer

Com pressor/Lim it er

+15-15

-3

-6

-10

+10

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

Table Of Contents

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 UNPACKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 AC POWER REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4 MECHANICAL INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5 EQ CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.1 EQ Boost/Cut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

5.2 Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.3 Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.4 HPF (Hi-Pass Filter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.5 EQ In/Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5.6 Signal Present and Clip LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6 COMPRESSOR/LIMITER CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.1 Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.2 Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.3 Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.4 Attack Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.5 Release Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6.6 Output Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6.7 In/Out Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6.8 Threshold/Gain Reduction Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6.9 Input/Output Meter Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7 CONNECTIONS AND CABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7.1 Balanced vs Unbalanced Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7.2 Inputs and Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

7.3 Chain Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

7.4 Compressor/Limiter Detector Loop/Ducking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8 TYPICAL APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8.1 Graphic Equalizer Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

8.2 Compressor/Limiter Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

8.3 Special Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

9 DESIGN THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

10 BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

11 TROUBLESHOOTING TIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

12 WARRANTY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

13 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

14 DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

15 SCHEMATICS

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

1. INTRODUCTION

The Ashly DPX-100 combines a 15 band graphic

equalizer and full function peak compressor/limiter in a

single rack space product. Both equalizer and compres-

sor/limiter can be used as stand-alone processors, or can

be automatically chained together with a back panel

switch.

The graphic equalizer section uses professional

quality 25mm faders for maximum resolution and long

life. Ashly graphic equalizers use "Q" enhanced Wein

bridge filters with interleaved summing for constant "Q",

low ripple, and minimum filter interaction.

The Ashly compressor limiter circuit was de-

signed in response to the need for universal peak-sensi-

tive automatic gain control (AGC) devices with

exceptional audio performance and rugged durability.

The result is a wide-bandwidth, ultra-low-distortion, low

noise VCA (voltage controlled amplifier) which is versa-

tile and highly listenable.

Premium components are used throughout the

DPX-100, and computerized automatic assembly equip-

ment verifies that each component's electrical specifica-

tions are within tight tolerances before becoming part of

the circuit assembly. Each finished unit is then tested

twice before leaving the factory, guaranteeing you a

worry-free, professional product for many years.

Please read this instruction manual thoroughly

before operation so that you may realize all the features

and benefits the Ashly DPX-100 has to offer.

2. UNPACKING

As a part of our system of quality control, every

Ashly product is carefully inspected before leaving the

factory to ensure flawless appearance. After unpacking,

please inspect for any physical damage. Save the ship-

ping carton and all packing materials , as they were care-

fully designed to reduce to minimum the possibility of

transportation damage should the unit again require pack-

ing and shipping. In the event that damage has occurred,

immediately notify your dealer so that a written claim to

cover the damages can be initiated.

The right to any claim against a public carrier

can be forfeited if the carrier is not notified promptly and

if the shipping carton and packing materials are not avail-

able for inspection by the carrier. Save all packing mate-

rials until the claim has been settled.

3. AC POWER REQUIREMENTS

A standard IEC-320 AC inlet is provided on the

rear panel to accept the detachable power cord shipped

with the unit. Units distributed within the United States

are preselected for 120VAC, 60Hz and should be plugged

into a standard NEMA 5-15 3-wire grounded AC recep-

tacle. Most units distributed outside the US are

preselected and labeled for 240VAC, 50-60Hz and are

shipped with the appropriate power cord.

The DPX-100 will perform normally from 95 to

125 volts AC. An internal line fuse is used. In the event

of fuse failure, refer to a qualified service technician for

servicing. Power consumption is less than 20 watts.

WARNING:

THIS APPARATUS MUST BE EARTHED

The exclamation point within an eqilateral

triangle is intended to alert the user to the

presence of important operating and

maintenance instructions in the literature

accompanying the device.

The lightning flash with arrowhead

symbol, within an equilateral triangle, is

intended to alert the user to the presence

of uninsulated "dangerous voltage"

within the product's enclosure that may be

of sufficient magnitude to constitute a risk

of electric shock to persons.

TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT RE-

MOVE COVER. NO USER SERVICEABLE PARTS INSIDE.

REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.

TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK,

DO NOT EXPOSE THIS APPlIANCE TO RAIN OR MOISTURE.

TO REDUCE THE RISK OF FIRE, REPLACE ONLY WITH

SAME TYPE FUSE. REFER REPLACEMENT TO QUALIFIED

SERVICE PERSONNEL.

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

5. EQ CONTROLS

5.1 EQ Boost/Cut

The individual equalization faders adjust the

boost or cut at each filter frequency. By adjusting a com-

bination of faders, an overall frequency response can be

developed and the physical position of the faders will give

an approximate visual indication of this response.

5.2 Gain

The gain control adjusts the overall gain of the

equalizer when the EQ switch is “in”. It is generally used

to compensate for level changes due to the equalization

process, but can also allow the equalizer to adjust overall

system level and gain structure. Overall gain with this

control is from +6dB to -∞.

5.3 Range

This switch selects the operating range of the

individual equalization faders to either ±15dB or ±6dB.

The ±15dB settings should be used when much equaliza-

tion is needed. The ±6dB setting allows finer resolution

on the fader settings.

5.4 HPF (Hi-Pass Filter)

The high-pass filter can be used to supplement

the frequency response achieved by the bandpass filters.

It’s function is to “roll off” low end response to eliminate

subsonic interference like wind noise, floor rumble, and

boomy microphone pops. The high-pass frequency is fixed

at 20Hz with an 18dB/octave slope.

5.5 EQ In/Out

This switches out the boost/cut controls and EQ

gain adjustments. This way, the effect of any equaliza-

tion can be compared to a “flat” response. This switch

does not defeat the high-pass filter.

5.6 Sig and Clip LEDs

The signal present LED comes on when a signal

greater than -20dBu arrives at the EQ input. The clip

LED indicates any EQ signal level exceeding +19dBu.

4. MECHANICAL INSTALLATION

The DPX-100 mounts in a standard 19 inch

equipment rack. The mounting screw threads vary with

different rack manufactures and you should refer to your

rack instructions for proper hardware. An oval head or

flat head screw with a plastic countersink washer is pre-

ferred to protect the finish of the DPX-100 under the screw.

This unit is housed in a rugged steel case and

will tolerate moderate abuse. However, for road systems

which may be dropped or otherwise subjected to extreme

forces, we recommend some rear support for the chassis

to prevent bending the front panel the front panel when

these forces occur.

For installations where it is desirable to protect

the front panel controls from tampering or accidental

misadjustment, use the Ashly security cover. Installation

is simple and does not require removal of the equipment

from your rack. See your Ashly dealer for details.

HPF

20Hz

Out

10K

Gain

6.3K16K4K2.5K1.8K1K630400250180100634025

-3

-9

∞

+15

+10

-5

-10

-15

Sig Clip

Range

±6dB

±15dB

Model DPX-100

Graphic Equalizer

Compressor/Limiter

Ashly Security Cover Installation

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

6. COMPRESSOR/LIMITER CONTROLS

6.1 GAIN

The Gain control is used to adjust incoming sig-

nal level to the VCA circuit. It is always active, so

switching out the limiter function has no effect on this

control. Used in conjunction with the input/output level

meter display, this control is useful for setting up optimal

system levels. This control should normally be left at

"0" to achieve accurate threshold calibration.

6.2 THRESHOLD

The threshold control has a range of -40dB to

+22 dB, allowing applications from low level compres-

sion to high level limiting. The threshold control de-

termines the audio level above which gain reduction

occurs. When the threshold LED comes on, that means

that gain reduction is beginning to occur, due to input

signal peaks exceeding the selected threshold in dB.

6.3 RATIO

This control determines the resultant change in

output level to changes in input level for all signals above

threshold. The numbers printed around the ratio con-

trol are calibrated in db and indicate the increase in

input (above threshold) required to produce a 1db in-

crease in output. This can be expressed conveniently as

a ratio. If the output remains constant no matter how high

the input level, we have an infinite (∞) input/output ra-

tio. It should be remembered that the ratio control has no

effect on signals which are below threshold.

There is a common but incorrect notion that lim-

iting always implies the use of an infinite ratio. Although

there are times when an infinite ratio is desirable, there

will be situations where infinite, or “hard”, limiting ac-

tion is neither appropriate nor necessary. In fact, it should

be noted that an infinite ratio setting is likely to cause

noticeable side effects in the sound, and may not be us-

able on programs where subtle control is desired.

6.4 ATTACK TIME

The response of the compressor/limiter to signal

levels above threshold is further defined by the attack time

control. Attack time is the amount of time it takes to

attenuate the output level after threshold has been

reached. For very fast transients, such as hand claps, snare

drums, or other percussive sounds, a fast attack time is

usually desirable so that the limiter can respond in time

to control the peak level. On other types of program ma-

terial, a slower attack time may be preferred. An abrupt

attack may, on some material, “square off” the top of a

waveform, producing a distorted sound. The DPX-100 pro-

vides continuously variable attack times from 200 micro-

seconds to 20 milliseconds.

6.5 RELEASE TIME

Another parameter which affects compressor/lim-

iter performance is release time, or the time required to

restore system gain to normal after the input signal

has fallen below threshold level. Again, proper release

time will depend on the type of program material being

processed and the way in which the limiter is being used.

When subtle limiting is desired, slow release

times are often chosen to avoid condition referred to as

“pumping” or “breathing”. This occurs when overall gain

is modulated up and down by repeated peaks which are

followed by quieter intervals. If the release time is set

too fast, then the overall level will jump up and down,

producing an objectionable and unsettling effect. Note

that, in some cases, an individual track or channel which

seems to be pumping may sound acceptable when heard

in context of a complete mix.

A unique feature of Ashly Compressor/Limiters

is the incorporation of a double release-time constant.

When a conventional compressor/limiter is adjusted for

slow release times, transients such as mic “pops” may

cause a severe reduction in gain followed by a slow fade-

up, making the action of the limiter very obvious. With

∞

+20

+15

+10

-3

-6

-10

-20

Sec

.2 20

1.5

∞

2.5

+22-40

+20

+10

-3

-6

-10

-20

2Th. 4 6 8 10 12 14 16 18 20 -15-18 -12 -9 -6 -3 0 +3 +6 +9 +20

Gain Reduction (dB) Input/Output Level (dB)

Clip

Gain

Threshold Ratio Attack Release Output Level In

Power

Output

Input

+15-15

-3

-6

-10

+10

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

the double time constant, release from gain reduction af-

ter a brief transient is always fast, with a slower release

after a sustained overdrive.

6.6 OUTPUT LEVEL

Output level control is provided to fully cut or

restore up to 18 dB of system gain. For unity gain, set

the control to 0. NOTE: When the compressor/limiter is

switched out, the output control still functions.

6.7 IN/OUT SWITCH

This switch enables you to quickly hear the com-

pressor/limiter in or out of the audio chain. When the

switch is in the out position, all limiting and compres-

sion controls and functions are bypassed, with the excep-

tion of the gain and output controls, which continue to

function as straightforward level controls.

6.8 THRESHOLD/GAIN REDUCTION DISPLAY

As soon as the threshold level is reached, the yel-

low LED illuminates. Depending on how far the input

level rises above threshold, successive red LED’s will il-

luminate, indicating gain reduction. Gain reduction can

best be described as the difference between input level

and the resulting change to output level. For signals

below threshold, there will of course be no gain reduc-

tion, that is, a 10dB increase in input will yield a 10dB

increase in output. For signals above threshold however,

output level will increase only to the extent that the ratio

control allows. With a high ratio, say 20 or so, it will take

20dB of increased input level to increase output level by

1dB. With a gentler ratio of 3:1, input signals above

threshold will be “gain-reduced” at the output by 1/3. In

other words, with threshold set at 0dB, a signal peak at

+12 dBV that is 3:1 compressed (ratio at 3) will produce

only +4 dB (12÷3) at the output, and 8 dB of gain reduc-

tion has occurred (12 dBV input minus 4 dBV output=8

dB reduction.)

6.9 INPUT/OUTPUT METER SELECT

While the Gain Reduction display accurately rep-

resents the action of the limiter, comparing input to out-

put levels in real time is somewhat more intuitive, and is

made simple using the input/output meter select switch.

The input meter takes its signal just after the gain con-

trol, and will indicate input signal level regardless of out-

put levels or limiter settings. The output meter display

takes its signal from the actual output of the unit, so ev-

ery control that affects the output will also have an effect

on output meters. Used in conjunction with the gain re-

duction meters, input/output meters prove to be an ex-

tremely useful diagnostic tool when working with system

dynamics and level control.

7. CONNECTIONS AND CABLES

7.1 Balanced vs. Unbalanced Audio Connections

Balanced signal connections are preferred in pro

audio applications because of their improved immunity

to induced hum and noise. A properly shielded and wired

balanced input stage on any audio product will reject most

unwanted noise (RFI, EMI) picked up by the cable, as

well as minimize ground loop problems. Therefore it is

always advantageous to use balanced connections when

running signal more than ten or fifteen feet, although par-

ticularly noisy environments may require that even short

patch cables be balanced.

Unbalanced connections are used mostly for short

distance, high level signals (0dBu nominal). Most exter-

nal EMI noise pick-up will be masked under the noise

floor of the signal, assuming there is little or no gain fol-

lowing the unbalanced signal. If a gain stage does follow

a signal, or if externally sourced noise persists, use bal-

anced connectors.

Model DPX-100

Made In USA

100-120VAC

50-60Hz 12W

(-)(+)

INPUTS are Active Balanced.

OUTPUTS May Be Wired

B ala nced O r Un ba la nc ed .

TIP = Detec

(Use

RIN

Output

Com

Risk of Electric

Shock. Do

Not Open

CAUTION

XLR

Fem ale

Shown

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

7.2 Inputs and Outputs

The DPX-100 uses two different audio connec-

tor types. 1/4" TRS (tip-ring-sleeve) phone jacks, and

three pin XLR connectors will allow interfacing to most

professional audio products. Ashly TRS balanced con-

nections use the tip as (+) and the ring as (-) signal, with

sleeve used for ground. Ashly XLR connectors use pin 2

(+) and pin 3 (-) with pin 1 ground. Inputs are 20KΩ

active balanced using precision 1% metal film resistors,

outputs are 200Ω "pseudo-balanced", which means they

have balanced impedance with a single-ended signal

source, and can be wired balanced or unbalanced. When

possible, we recommend balanced connections between

all components in your system.

If inputs are used unbalanced, the signal should

be on the (+) connection and the (-) connection must be

tied to ground, or signal loss will result. While a mono

phone plug used as an unbalanced connection will auto-

matically ground the (-) ring of the jack, XLR's will not

automatically do this, so attention must be given to proper

wiring.

7.3 Chain

The chain button on the back panel allows the

output of the equalizer to be fed directly to the input of

the compressor/limiter, with no external cable required.

When the chain switch is in, the input connectors to the

compressor/limiter are removed from the circuit, while

the graphic equalizer outputs remain functional.

7.4 Detector Loop - Ducking

The DPX-100 compressor/limiter has a TRS In-

sert DETECTOR PATCH point which can be used as a

"ducking" input, or in conjunction with an equalizer to

produce frequency-sensitive limiting. Various uses of the

detector patch are discussed under TYPICAL APPLICA-

TIONS.

8. TYPICAL APPLICATIONS

By itself, the 15 band graphic EQ is useful for

general tone control, feedback control, and room reso-

nance correction. The compressor/limiter provides many

solutions where dynamic signal level processing is re-

quired. The combination of graphic EQ and compressor/

limiter allows for additional applications, such as a full

range speaker processor, 70 volt distributed system pro-

cessor, mixing console channel insert, and frequency sen-

sitive limiting, to name a few. In most cases, the DPX-100

should be the last device before the power amp or cross-

over, or right before a recording device or transmitter.

8.1 GRAPHIC EQUALIZER APPLICATIONS

General Tone Control

The graphic equalizer is a very useful device for

general tone shaping because it is intuitive and easy to

adjust. The visual reference provided by the slider posi-

tion gives an approximate idea of the frequency response

generated, with the lower frequencies on the left and

higher frequencies on the right. To use the power of an

ector Return/Ducking Input

Mono Plug For Ducking)

ING = Detector Send

Input

Detector

pressor/Limiter Graphic Equalizer

Output

Input

Out

Chain

PUSH

Audio Connector Types

Tip (+)

Ring (-)

Sleeve (Gnd)

Stereo Phone Plug

used for balanced

2 = (+)

3 = (-)

1 = (gnd)

XLR pins are

numbered

on the

connector

insert.

XLR Male

XLR Female

Tip (+)

Sleeve (Gnd)

Mono Phone Plug

used for unbalanced

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

equalizer effectively, you need to translate your idea of

the tone you want to produce into a range of numerical

frequencies. This is simple after a little practise. Here are

a few references which are useful for starting points:

- Very low bass (the “wind” in a kick drum,

almost felt as much as heard -40Hz-80Hz.

- The low register of a male voice - 200Hz

- The low register of a female voice - 350Hz

- Lower midrange (“warmth” frequencies) -

400Hz-1KHz

- Upper midrange (“harshness”, snare drum

“bite”, “hot” sound) -2.5KHz-4KHz.

- Sibilance (“sss” sounds, cymbal “sizzle”) -

8KHz-15KHz.

Try using these starting points as a guide when

you want more or less of these types of sounds. Adjust

by ear from there. It is always a good idea to remember

that a little equalization usually works out much better

than a lot, and that there are many audio problems which

can not be solved with equalization alone.

Feedback Control

A graphic equalizer can be used to provide some

control over moderate feedback problems, but does not

have enough flexibility or resolution to handle severe situ-

ations. You will achieve the best results when you can

eliminate one or two feedback points by setting one or

two sliders for no more than a 6dB cut. Often you can

find a feedback point by boosting sliders in succession to

determine which frequency ranges contain the feedback

modes, and then cutting those ranges. Be very careful in

this process to avoid explosive feedback and possible sys-

tem and hearing damage! If you find feedback points

with many equalizer bands, remember that cutting every

band may not help (all you will do is reduce system gain).

The combination of a graphic equalizer for tone control

and a parametric equalizer (such as the Ashly PQX-571

or PQX-572) for feedback control is highly recommended.

Console Channel Equalization

Many mixing consoles provide only simple equal-

ization for individual channels. If your console has chan-

nel inserts, you can patch your graphic equalizer into a

channel that’s being used for something important and

use it to tailor the sound of this channel exactly the way

you want.

Large Room Equalization

Large rooms tend to suffer from multiple reflec-

tions with long time delays, long reverberation times, and

“ring-modes”, all of which lead to reduced intelligibility

and a generally “muddy” sound. As sound travels long

distances through the air, high frequencies are attenuated

more than low frequencies. In general, large rooms ben-

efit from some low frequency roll-off, high frequency

boost, and attenuation of ring mode frequencies. As in

the case of feedback control, a graphic equalizer can help

reduce an isolated ring-mode or two, but a tunable nar-

row-band equalizer such as a parametric is more effec-

tive here.

8.2 COMPRESSOR/LIMITER APPLICATIONS

As the functional name implies, a compressor/

limiter can be divided into two basic categories, limiting

and compressing. When used as a protective device to

prevent audio levels from overloading systems such as

tape recorders, power amplifiers, speakers, or transmit-

ters, it is generally referred to as a limiter.

It may also be used to create special effects and

unusual sounds for recording and musical performance

by deliberately reducing the dynamic range of a signal,

creating a much louder or fuller sounding signal without

increasing the loudness peaks, in which case it is referred

to as a compressor.

The Limiter As A Protective Device

The DPX-100 compressor/limiter section pro-

vides fast and accurate gain control for the prevention of

sound system overload due to unexpected transients.

Sound system distortion is usually the result of amplifi-

ers running out of power, in which case nice round wave-

forms turn into harsh sounding squared-off waveforms.

Looking at it from the perspective of the speaker dia-

phragm, this means that, whereas in normal operation the

diaphragm is required to accelerate, slow down, smoothly

change direction, and accelerate again, distorted opera-

tion requires an instant acceleration, instant stop, a change

of direction, and instant acceleration again.

Since speaker diaphragms are subject to the laws

of physics, they won’t take this kind of punishment for

long. The diaphragm may shatter, or its voice coil may

overheat. In addition to the damaged caused by sustained

overload, the speaker may also be damaged by occasional,

one-shot high level overload, for example, the sound of a

microphone falling face-first onto a hardwood floor. Even

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

if this type of transient doesn’t destroy a speaker outright,

it may damage the speaker surround in such a way as to

cause mechanical abrasion and future failure.

Alternatives For Sound Installations

To install a compressor/limiter in a sound sys-

tem using a passive crossover, insert it between your mix-

ing console output and the power amplifier input. For

systems using electronic crossovers, there are two ways

to use a compressor/limiter. It may be inserted between

the mixer output and the crossover input, in which case it

will act on the entire audio frequency spectrum. Alter-

nately, if the limiter is inserted between an output of the

electric crossover and the input of a power amp, it will

only affect a specific band of frequencies.

Recording

The Ashly limiter can be used to prevent tape

saturation in analog recording. Also, with modern trends

toward inexpensive digital recording, it remains neces-

sary to protect against input overload. With digital re-

cording, the information stored on tape, hard disk, optical

disk, etc., is either a 1 or 0, so actual signal level on the

tape is not the concern it is with analog recordings, in

fact it is not even a user controllable parameter. What is

of concern however, is the signal level applied to the A-D

(analog to digital) converters. If clipping occurs at the

converter input stage, the resulting distortion is most un-

pleasant, and will be recorded digitally as if they were

part of the original audio signal, forever mixed with the

audio. To prevent converter distortion while preserving

the extended dynamic range of digital recording, look up

the max input level of your recorder/converter and set up

the limiter as follows:

1. Set Gain to 0.

2. Set Threshold to 2-3 dB below max converter

input.

3. Set Ratio to 10.

4. Set Attack to 2 mS.

5. Set Release to .2 Sec.

6. Set Output level to 0.

If you are exceeding threshold frequently, your

input signal is probably too high and should be turned

down. Of course, every situation is different, so experi-

mentation before final recording is always a good idea,

but this is a good starting point.

To obtain a gentler limiting action at the expense

of some dynamic range, decrease the threshold to -15 and

the ratio to 3-5. This is also a good starting point for

analog recording.

Broadcasting

Compression has long been used as a

tool to make an audio signal appear louder. A

good example is in broadcasting, where com-

peting stations with identical transmitters and power at-

tempt to sound louder than each other. Since they are all

restricted with respect to maximum audio level (modula-

tion), their best tactic is to squeeze the dynamic range of

their programs to just a few dB. The audio output level

of the station virtually never changes, and the listener

perceives this continuous high-level sound as being louder

than the same material in an uncompressed form. Although

both compressed and uncompressed programs reach the

same peak levels, the compressed signal stays near peak

level more of the time, and thus sounds louder. This tech-

nique makes the broadcast more intelligible over ambi-

ent noise, and increases the geographical area over which

the broadcast is audible to the listener. Additionally, this

compression technique is extremely useful for FM and

infrared transmission systems for the hearing impaired.

8.3 Special Effects

Compression For Feedback Control

A common ritual in sound system set-up is equal-

izing the room to remove feedback. This is generally

accomplished by turning up system gain to purposely in-

duce feedback, searching for the center frequency of the

feedback, and then equalizing at that frequency to remove

the feedback. Once this frequency has been cut, system

gain is again increased to induce another feedback point,

and the whole procedure is repeated until the engineer is

satisfied that the significant problem frequencies have

been corrected. The major problem with this approach is

that the feedback can easily get out control, and the engi-

neer ends up dashing back and forth between the mixer

volume controls and the equalizer controls, while every-

one in the room plugs their ears and prays it will end

soon. The Ashly DPX-100 can turn this procedure into a

fast, painless job, eliminating loud feedback levels and

the possibility of speaker or ear damage.

Procedure:

1. Set up the DPX-100 limiter controls

as follows:

a. Output level control to -20dB.

b. Input Gain control to 0dB.

c. Threshold control to -30dB.

d. Ratio control to infinity (∞)

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

e. Attack time to 5mS.

f. Release time to 1 Sec.

g. Limit switch IN

2. Using a 1/3 octave (31 band) or parametric

equalizer, set the EQ controls to a flat setting, and if the

equalizer has an overall volume control, boost it by 10 to

15 dB.

3. Open up several microphone input channels

to a normal operating level, with typical EQ settings, and

turn the console master fader up to a louder than normal

setting. At this point, the system should be well into feed-

back, but the room volume will be constant due to the

action of the limiter. You can listen to the feedback at

any level you like by simply varying the limiter output

level control, although below a certain monitoring level,

the feedback will stop.

4. Try to determine the feedback frequency, and

then equalize it by adjusting the center frequency, band-

width, and boost/cut controls of your parametric equal-

izer. (Note: a graphic equalizer can also be used, although

with less accuracy.) After eliminating the problem fre-

quency, try to further define it by sharpening up the band-

width, reattacking the frequency control, and making the

cut shallower, if possible.

5. As soon as the first feedback frequency has

been removed, the compressor/limiter will automatically

bring up system gain until another feedback point is in-

duced. Repeat the equalization procedure until it becomes

impossible to distinguish individual, predominant feed-

back frequencies.

6. Write down EQ marks for safekeeping if nec-

essary, and return all mixer, EQ master gain, and com-

pressor/limiter gain controls to normal operational

settings.

Altering the Texture of Musical Instruments

It would be impossible to mention here all the

ways that compression is used to create new sounds with

familiar instruments. Some typical uses are:

1. Creating a “fatter” kick drum or snare sound.

2. “Thickening” acoustic guitars.

3. Adding punch and sustain to electric bass or

guitar.

In general, use a gentle compression ratio, say

4:1, with a 10 mS attack time, 0.1 Sec. release time, and

a low enough threshold to cause 6 to 10dB of Gain Re-

duction. Try using this effect to help bring out a lead

vocal or instrumental solo in a cluttered mix. The com-

pressor is also a great corrective tool when working with

singers whose own dynamic control is less than perfect.

A little compression helps to keep their quieter lines from

becoming buried in the mix. Experimentation is highly

recommended.

Voice-Over Compression (“Ducking”)

The compressor/limiter can be used to automati-

cally reduce music to a background level when an an-

nouncer is speaking. In this scheme, only the music signal

is actually gain-reduced by the limiter. However, the de-

tector is connected to respond to an announcer’s voice

instead of the music’s peaks. Voice-Over compression

assumes you are already using some sort of mixer to com-

bine the music and mic signals. Use the direct out (send)

of the mic channel to feed the detector input on the CLX

unit. Note: Be sure to use a mono plug for the CLX

detector input. Then use the Threshold and Ratio con-

trols to determine when and by how much the announcer’s

voice affects the music level.

De-Essing

A special type of saturation problem often en-

countered in recording is the sibilant (Ssss) sound of the

human voice. High frequency, sibilant sounds can reach

very high energy levels, so that a voice that is otherwise

undistorted breaks up on the esses, producing a raspy, un-

desirable sound. With analog recording to magnetic tape,

high frequencies tend to saturate the tape sooner, and com-

bined with the internal high frequency boost (record pre-

emphasis) on standard tape decks, the need to control

sibilants becomes apparent.

The solution is frequency-dependent limiting,

which is easily accomplished with the DPX-100. By in-

serting an equalizer into the Detector Patch point and

boosting the equalizer at high frequencies in the vicinity

of the sibilant, the limiter’s detector circuit becomes more

sensitive to this particular range of frequencies, and so

will limit the bothersome sibilants more than other fre-

quencies.

Realize that this technique is very different from

simple equalization. Equalizing a sibilant vocal by cut-

ting high frequencies would result in a loss of important

high frequency information at all times, whereas de-essing

has no effect whatsoever on the signal except at the in-

stant of the sibilant. At that moment, the Ashly limiter

will reduce overall gain. Frequency response is unaf-

fected, and the sibilant is controlled.

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

9. DESIGN THEORY

Graphic Equalizers: The Basics

While most graphic equalizers look very much

the same, there are several important differences in the

circuitry used to implement various designs.

Perhaps the major differences are in the filters.

Some equalizers use a filter made of a capacitor, an in-

ductor, and a resistor, or “RLC” filter. The advantage

here is simplicity, but the real disadvantage is the induc-

tor itself. An inductor is a coil of wire with a core of

some sort. Inductors are susceptible to hum fields and

they are large and expensive.

Other equalizers use the same basic approach, but

replace the inductor with a “simulated inductor”, which

is actually a circuit comprised of an amplifier, a capaci-

tor, and a couple of resistors. This adds parts but is less

expensive than a real inductor. The problem with this

approach is that simulation is less than ideal; it produces

an inductor with high resistive loss resulting in poor curve

shape when used in a filter.

Another problem with “RLC” designs is that large

capacitors must be used for the lower frequency filters,

limiting the choice to large, expensive non-polar types or

electrolytic capacitors with poor audio performance. Also,

when this filter type is combined with a potentiometer to

adjust the equalization, the resistance of this pot affects

the “Q” of the filter so that a little equalization produces

a much broader curve than a lot of equalization.

The other filter approach is a true bandpass fil-

ter. This can be made with no inductors and more practi-

cal sized capacitors; the “Q” is easily set and remains

constant, and the parts count is reasonable. there are sev-

eral types of bandpass filters suitable for this job. Ashly

uses a “Q” enhanced Wein-bridge filter. Because it is a

symmetrical design using matched tuning components,

the “Q” is easily set and is very stable.

In designing a graphic equalizer, a selection of

filter sharpness must be made. More sharpness (higher

Q) produces less filter overlap and tighter control over an

individual band, but also causes ripple in the frequency

response when many filters are boost or cut together to

produce a flat response. We feel that the graphic

equalizer’s primary use is for “voicing” and tone control,

and have set our filter sharpness to produce a maximum

of 1dB ripple.

The summing system in a graphic equalizer is

also important. Since there are a number of filters which

combine to produce the overall response, it is important

that the filters not interact (they WILL overlap, but the

response of one filter should not modify the response of

another). Ashly uses an “interleaved” summing system

where every other filter uses the same summing amplifier

so that adjacent filters never share the same drive and

feedback signals. This allows the filters to maintain their

natural response.

Compressor/Limiters: The Need For Gain Control

The human ear excels in its ability to detect an

extremely wide range of loudness levels, from the quiet-

est whisper to roar of a jumbo jet. When we attempt to

reproduce this dynamic range, by means of amplifiers,

tape recorders, CD players, or radio transmitters, we run

into one of the fundamental limitations of these electronic

media: limited dynamic range. Amplifier dynamic range

is quite good, and is adequate for most musical program

material. However, some types of audio equipment, such

as cassette tape recorders, have a very narrow useful dy-

namic range.

What is it that compromises the dynamic range

of this equipment? The useful operating region of a piece

of audio equipment is squeezed in between noise and dis-

tortion. As program level decreases, it approaches what

is known as the “noise floor”, and if the volume of the

program material goes lower still, it is engulfed by the

noise. The noise floor, or minimum constant noise level,

will consist of hiss, hum, transistor noise, tape hiss, buzz

and whatever noises are inherent in the medium. When

the program level is considerably higher than the noise

floor, our hearing masks the noise, and it is not a prob-

lem. However, when listening to very quiet sections of a

program for example, a pause between movements of a

string quartet the noise can become very bothersome.

At the other end of the loudness spectrum, the

limitation on dynamic range is usually distortion, either

in the form of amplifier overload, tape saturation, or A to

D clipping. In most transistorized equipment, the transi-

tion from clean, undistorted operation to severe distor-

tion is very abrupt. Therefore, it is common practice to

operate a piece of equipment at a level that is somewhat

below the distortion point, leaving a margin of safety for

unexpected, transient volume peaks in the music. This

safety margin is known as headroom, and may range from

10 to 25 dB. Lowering our standard operating level to

leave ourselves some headroom helps prevent distortion,

but at the same time it moves our average program level

closer to the noise floor, thereby compromising signal-

to-noise performance. It becomes apparent that to get most

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

dynamic spectrum will be pushed toward the “middle”.

This is quite different from simple limiting, where only

loud peaks are subjected to gain reduction. More than

anything else, it is this double-ended effect which dis-

tinguishes compression from limiting. Compression is

further differentiated from limiting by careful selection

of attack and release times. When limiting is employed

to protect an audio system against transient volume peaks

and possible overload, attack time is usually set as fast

as possible, consistent with distortion-free performance.

Release time would also be relatively short, so that the

output signal would be restored to normal as quickly as

possible after the transient.

Compression is frequently used to keep over-

all signal level within a specific dynamic range, and

for this application, slower attack and release times

are usually chosen. This approach is analogous to our

manual gain riding example, where our operator is fad-

ing the music up and down to keep it fairly constant,

but is doing it slowly enough so that the listener is un-

aware that the gain is being altered.

Voltage Controlled Amplifiers

Early VCA’s were based on vacuum tubes with

a “remote cutoff” characteristic. The tube would sim-

ply change its gain in response to a changing bias volt-

age. Tubes developed for this purpose did an excellent

job, in fact they could exceed the noise and distortion

performance of today’s best solid state VCA’s. Unfor-

tunately, they also had some serious disadvantages pe-

culiar to tubes - change of gain and matching as aging

took place, heat, microphonics, high cost, and the need

for both high-voltage and filament power supplies.

Over the years the need for good, low-cost,

solid state VCA brought about many innovative ap-

proaches. A good example is the electro-optical at-

tenuator where a photocell is used as one leg of a

potentiometer. Since the photocell behaves as a true

resistor, distortion and noise are very low. Unfortu-

nately, the response time of photocells is slow and un-

predictable so their use in a fast peak-limiter is really

not feasible. Also, the matching between units is very

poor so that stereo tracking is not possible without te-

dious hand-matching of photocells.

Another approach uses a field-effect transis-

tor (FET) as a variable resistor. Here, at least, the re-

sponse time is fast (in the nanosecond range), but

matching between units is still poor, requiring hand

matching for stereo. An additional problem is that a

FET will only act as a pure resistor with very small

signals applied so it is necessary to attenuate an input

out of an audio system, you have to keep your standard

operating level as high as possible without risking distor-

tion.

GAIN RIDING

One solution to the noise vs. distortion trade-off

is to keep your hand on the level control and manually

adjust gain to suit the program. Indeed, there are times

when this approach is entirely satisfactory. However, in

most types of music there are instantaneous, short dura-

tion volume peaks, or transients, which would be difficult

to anticipate and impossible to respond to with manual

gain riding, you simply could not bring the level down

fast enough. In many situations, this can present real prob-

lems. For example, in recording, an extra burst of enthu-

siasm from a lead singer might overload the capabilities

of your recording tape, causing ragged distortion and ne-

cessitating another take. In sound reinforcement, a sud-

den burst of energy through the system can blow fuses or

even damage loudspeakers.

In addition to the problem of response time with

manual gain riding, it also requires your constant atten-

tion, which takes you away from more important jobs. The

need for a fast-acting, reliable, automatic gain control is

answered by limiters and compressors.

WHAT COMPRESSORS AND LIMITERS DO

LIMITING

In any musical program are constant changes in

loudness. It is the job of a limiter to detect when the vol-

ume has exceeded a predetermined maximum safe level,

and to then turn down the volume. When the incoming

signal returns to its original level, the limiter should re-

spond by restoring the gain to normal. Thus, when the

level is within a specified “safe” range, the limiter has no

effect. When an occasional peak occurs, the limiter re-

sponds. This situation is completely analogous to manual

gain riding, except that it occurs faster and more consis-

tently.

COMPRESSION

A very significant difference in dynamic range is

achieved simply by changing the relationship between nomi-

nal signal level and threshold, as a result of either increas-

ing the GAIN and/or decreasing the THRESHOLD control.

The most interesting effect to be noted, however, is seen by

comparing the original input signal with the output signal.

The quietest portions of the original signal will be effec-

tively increased in volume while the loudest portions of the

original signal will be decreased. In effect, both ends of the

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

signal before the gain control FET and then amplify it

again. Of course this results in less than ideal noise per-

formance and imposes a frustrating trade-off: less noise

= more distortion.

A number of VCA’s based on the exponential volt-

age-current characteristic of a bipolar junction transistor

have been used. One of the most common is called a

“transconductance amplifier”. Using the inherent match-

ing obtained by integrated circuit technology, these de-

vices have very predictable control characteristics.

Tracking within 1dB over a 40dB range is common. Not

only do the control characteristics match well from unit

to unit, but they can easily be made exponential (loga-

rithmic) so that even increments of control voltage pro-

duce even increments of gain change in decibels. The

response time is also very fast.

The problem with simple transconductance am-

plifiers is that, like FET VCA’s, they can handle only very

small signals so the noise performance is poor. A num-

ber of linearizing circuits have been devised to minimize

this problem, but even the best transconductance amplifi-

ers have an equivalent input noise of about -80dBv, which

compares poorly to straight linear amplifiers.

The best analog compromise to date is the “class

AB current ratio multiplier.” Early implementation of

this circuit used two matched pairs of transistors, one pair

of NPN’s and one pair of PNP’s. The problem here is

that excellent matched integrated NPN pairs were avail-

able, but integrated PNP’s were not. The PNP’s had to be

hand-tested and matched. Careful trimming was neces-

sary for low distortion and even minor temperature

changes made re-trimming necessary because of differ-

ing characteristics between the two types.

The Ashly VCA

The Ashly VCA is an integrated current ratio mul-

tiplier circuit. It has low noise (-90dBv), low distortion

(.05%), excellent response time and tracking and does

not suffer from thermal drift. The noise and distortion

are at state-of-the-art levels and the circuit is consistent

in mass production with minimal trimming and no hand-

selection of transistors.

Detectors

It would seem that, of the two components in a

compressor/limiter, the VCA is the more critical since the

audio passes through it and the detector only provides it

with a control voltage. Experience showed us that both are

crucial to the overall sound and that, if anything, the

detector’s performance is the harder to judge by conven-

tional measuring techniques. While the VCA is doing its

job if it has low noise and distortion, the detector must con-

stantly adjust the gain of the audio path in a manner which

keeps the level under control while sounding acceptable to

the listener. This constantly changing gain is a dynamic

action, while conventional audio measurements like noise

and distortion checks are Static (at a constant level). We

became painfully aware of this problem with some of our

earlier limiter prototypes which measured fine and sounded

terrible. This led us to use a purely subjective approach in

the design of the detector - we did a lot of listening to de-

termine what sounded good and what didn’t.

Two important features emerged from this re-

search:

1. We designed the detector to let the attack and

release times speed up as more and more limiting occurs.

The compression ratio also increases. This lets us main-

tain peaks fairly close to a constant ceiling level, but al-

lows the illusion of increasing loudness as input level

increases, thereby preventing complete loss of dynamics

when limiting.

2. We incorporate a double release time constant.

When release time was set slow with a single time con-

stant, transients such as mic “pops” caused a quick re-

duction in gain and a slow fade-up, making the action of

the limiter very obvious. With the double time constant,

release from gain reduction after a brief transient is al-

ways fast, with a slower release after a sustained over-

drive.

When choosing a compressor/limiter, you can see

that it is very important to listen to it in your particular

application and see that it sounds the way you want. There

are lots of these devices with seemingly excellent specs

which sound very different with real program material

applied to them.

Peak Or RMS

There are several ways of looking at a signal to

determine its level. A peak detector looks at the maxi-

mum voltage a signal reaches regardless of it’s waveform,

while an RMS (root mean square) detector looks at the

energy in a signal regardless of the short term voltage

levels. This makes a peak detector the correct choice for

preventing clipping, overmodulation, or tape saturation,

while an RMS detector can be used to restrict material to

a given loudness. When an RMS limiter is used to pre-

vent clipping, the result is unpredictable. For instance, a

flute and a snare drum which are limited to the same RMS

level might have peak levels as much as 30dB apart! Use

peak limiters to prevent clipping.

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

10. BLOCK DIAGRAM

11. Equalizer Troubleshooting Tips

No Audio Output

Check AC power - is the pilot light on?

Check in/out connections - are they reversed?

Are you sure you have an input signal?

EQ Controls Do Nothing

Is the master EQ switch in?

The lowest and highest frequency sliders may be

beyond the range of the program material or speakers and

may produce little or no audible effect.

Peak Light Flashes or Stays On All the Time

If the peak light flashes, the signal level to the

equalizer is too high. Turn down the gain. If it is on all

the time, disconnect the input and output cables. If it is

still on, the unit must be returned for service.

Distorted Sound

This will only be caused by too much

signal which will show on the Clip LED. If the

LED is not flashing, there is an overload some-

where else in the signal path. Adjust the rela-

tive gain of each component in your chain to

keep everything at a comfortable level.

Excessive Hum or Noise

Hum will usually be caused by a ground

loop between components. Try using the sug-

gested balanced input and output hook-ups if the

other pieces of equipment used in conjunction

with your equalizer have balanced inputs and

outputs.

Noise (excessive hiss) can be caused by

insufficient drive signal. Make sure you are send-

ing a nominal 0 dBu line level signal to the

equalizer. Most noise problems occur because

gain is applied to audio signals too late in the

chain. For best performance, apply gain to in-

dividual source signals as early as possible, like

at the mixer input preamp section. As gain in-

creases, it also boosts the noise content of that

signal. Any cumulative noise built up in a mixed

signal will only be increased by using an equal-

izer as a gain device, so make every attempt to

operate the equalizer with as little gain as pos-

sible.

Note: Unshielded cables, improperly wired con-

nectors, and cables with broken strands of wire are very

common problems. Use quality cables with quality, cor-

rectly wired connectors.

11.1 Compressor/Limiter Troubleshooting Tips

No Output

Check AC power. Is the power switch on? Check

input and output connections - are they reversed? Are

you sure you have an input signal?

Controls Have No Effect

Is the limiter in/out switch in? Perhaps the ratio

control is set too low to produce an audible effect or the

input level is below threshold. Is the threshold LED light-

ing up? If not, lower the threshold setting or increase the

gain. Do not expect to hear any effect when the input

level is below threshold, since the unit is simply a linear

amplifier at those levels.

CHAIN

LIMITER

EQ OUTPUT

EQ In/OutHPF In/Out

6dB/15dB

15 BAND EQ

SIG

GAIN

HPF

CHANNEL

INSERT

DETECTOR

CLIP

IN/OUT

GAIN REDUCTION DISPLAY

THRESHOLD

RELEASE

ATTACK

RATIO

CIRCUIT

DETECTOR

INPUT

GAIN

LEVEL

OUTPUT

INPUT/OUTPUT METERS

VCA

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

When Using Heavy Compression, Background Noise

Is Noticeable During Quiet Sections Of The Program

As defined in the section on compression, quiet

program material is effectively made louder while loud

peaks are made quieter. When the program source is thus

raised in volume, its noise floor is also raised in volume

by a proportionate amount. This is not a defect in the

compressor/limiter, but an unavoidable side effect of the

gain altering process. If the noise becomes a problem,

the solutions are to either decrease noise at the program

source, or use less compression.

Excessive Hum Or Noise

Hum is often caused by a “ground loop” between

components. Try using the suggested balanced input and

output hookups if the other pieces of equipment used in

conjunction with the DPX-100 have balanced inputs and

outputs. Noise can also be caused by insufficient drive

levels. Make sure you are sending a nominal 0 dBV line

level signal to the unit.

12. WARRANTY INFORMATION

Thank you for your expression of confidence in

Ashly products. The unit you have just purchased is pro-

tected by a five-year warranty. To establish the warranty,

be sure to fill out and mail the warranty card attached to

your product. Fill out the information below for your

records.

Model Number ______________________________

Serial Number ______________________________

Dealer _____________________________________

Date of Purchase ____________________________

13. SPECIFICATIONS

EQ:

Input Type . . . . . . . . . . . . . . . . Active Balanced

Impedance . . . . . . . . . . . . . . . . 20KΩ Balanced

10KΩ Unbalanced

Max. Level . . . . . . . . . . . . . . . . +23dBu

Input Connectors . . . . . . . . . . 1/4" Phone Jack, XLR

Output Type . . . . . . . . . . . . . . . Pseudo-Balanced

Impedance . . . . . . . . . . . . . . . . 200Ω Balanced

100Ω Unbalanced

Max Level . . . . . . . . . . . . . . . . +23dBu

Output Connectors . . . . . . . . . 1/4" Phone Jack, XLR

Frequency Response . . . . . . . . ±.25dB 20Hz-20kHz

THD (20Hz-20KHz) . . . . . . . . <.01%@+20dBu

IM Distortion (SMPTE) . . . . . <.01%@+20dBu

Output Noise (20Hz-20KHz) . <-100dBu

Gain Control . . . . . . . . . . . . . . −∞ to +6dB

(EQ in, all faders flat,

20Hz-20KHz)

Filter Type . . . . . . . . . . . . . . . . Constant Q/Wein Bridge

Bandwidth . . . . . . . . . . . . . . . . 2/3 octave

Tolerance . . . . . . . . . . . . . . . . . ±3%

Range . . . . . . . . . . . . . . . . . . . . ±6 or ±15dB

Subsonic Filter . . . . . . . . . . . . 18dB/octave @20Hz

Compressor/Limiter:

Gain:

. . . . . . . . . . . . . . . . . . ±15dB

Ratio:

. . . . . . . . . . . . . . . . . . 2:1 →

∞

Attack Time: . . . . . . . . . . . .

200µS-20mS

Release Time: . . . . . . . . . . .

100mS-3Sec

Output:

. . . . . . . . . . . . . . . . . . -

∞

to +18dB

Maximum Input Level: . . . .

+23dBu

Maximum Output Level: . .

+23dBu

Input Impedance: . . . . . . . .

20KΩ balanced

Output Impedance: . . . . . . .

200Ω

Pseudo-Balanced

Frequency Response: . . . . .

±0.2dB 20Hz-20KHz

Distortion: . . . . . . . . . . . . . .

<.01% THD, 0dBu, 1KHz

<0.15% THD, +15dBu,

20Hz-20KHz

Output Hum and Noise: . . .

<-95dBu

DPX-100 Power Requirements:

93VAC-120VAC, 50-60Hz, 10W

Size and Shipping Weight:

19"L x 1.75"H x 6"D (8 lbs.)

Note: 0dBu = 0.775 Vrms

Pseudo-Balanced Output has balanced output impedance

with single ended signal.

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

14. DIMENSIONS

Dimensional Drawing for DPX-100

0.10

6.00

17.00

1.25

1.75

0.75"

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

15. SCHEMATICS

1 2 3 4 5 6 78

7654321

APPROVED: Dw

Size

Drawn B

Rev.

S:\En

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\CLIENT98\1551\10s1551c-1.Sch

10S1551

DPX-100 MINI-EQ + COMPRESSOR/LIMITER

James B Franks

Sheet # of

847 Holt Road

Webster, NY 14580-9103

Phone: Fax:

(716) 872-0010

(716) 872-0739

Print Date

3-May-2002

11:44:50

A->B @ 157%

47P3151

47P1030

47P1295

U1B

4560

U2B

4560

100

10.0K

27P

C64

47U

R6 10.0K

VR1

B10K

22K

4.7K

22K

27P

R10

15K

1N4148

R11

R12

4.7K

R13

R14

300K

VR7

50K

Ec+

1 8

V-

V+

Ec+

GND

Ec-

U18

52P2150

-18

+18

-18

U2A

4560

R15

15K

27P

C65

47U

47P3151

R16

U1A

4560

U3B

4560

VR2

B100K

C66

47U

R17

9.76K

R18

R19

100K

R20

100K

5pF

C6747U

R21

10K

R22 4.99K

R23

3.3K

R24

47K

R25

150K

R26

10K

R27

10K

U3A

4560

1N4148

U4B

4560

D15

1N0754

1N4148

SW1A

45P2600

-18

2N4125

R28

100

VR3

A10K

U4A

4560

-18

VR4

A1MEG

R29

100K

C79

1.5U

C80

1.5U

R30

68K

R31

3.3K

2N4123

+18

R32

R33

VR5

C10K

C68

47U

R34

10K

U5B

4560

VR6

B10K

R35

10K

R36

820

R37 12K

27P

C69

47U

R38

10K

1N4148

OUTPUT METER

PEAK BUS 1

INPUT METER

PEAK BUS 1

GAIN METER

THRES

OUTPUT

BALANCED

INPUT

GAIN +/- 15db

DETECTOR

TIP = INPUT

RING = SEND

SYMMETRY

ADJUST

THRESHOLD

(-20db MIN +41.4db MAX)

OUTPUT

(+17.0db MAX)

LIMIT

OUT

RATIO

ATTACK

RELEASE

TO EVEN

TO ODD

FILTERS

10s1551c-2.SCH

PEAK BUS 1

PEAK BUS 2

THRES

SIG

GAIN METER

INPUT METER

OUTPUT METER

PWR SUPPLY + METERS

10s1551c-3.SCH

REVISION HISTORY

10s1551RV.SCH

47P3151

47P1295

U6A

4560

R39

10.0K

R40

10.0K

R41

10.0K

27P

R42

10.0K

BALANCED

INPUT

C70

47U

R43

10K

47P3151

47P1030

R44

100

R45

100

U23A

4560

C71

47U

R46

10K

OUTPUT

1N4148

PEAK BUS 2

.1U

C10

.1U

C11

.1U

R47

62K

R48

470K

R49

22K

U23B

4560

SW8A

45P2600

OUT

C72

47U

R50

15K

R51

20K

VR8

R52

30K

C12

27P

U7B

2043

U8B

2043

U8A

2043

U7A

2043

U9A

4560

R53

10K

R54

10K

R55

10K

1N4148

C73

47u

SW3B

45P2600

R56

20K

R57

390K

C74

47U

R5820K

PEAK BUS FLTR

R59

2.2M

R60

10K

R61

10K

R62

10K

C13 27P

C14 27P

C15 27P

T2 T3

R63

10K

R64

10K

SW2B

45P2600

R65

2.55K

R66

8.2K

TO ODD

U9B

4560

SW2A

45P2600

R67

2.55K

R68

8.2K

TO EVEN

PEAK BUS FLTR

SIG

SW5A

45P2000

C16

.1U

HPF

EQ SWITCH

RANGE SWITCH

IN +/- 6 dB

OUT +/- 15 dB

EQ GAIN

20 Hz HPF 18dB

/OCT.

COMPRESSOR/LIMITER

CASCADE

OUT

OUT OUT

U6B

4560

R17610K

R177

10K

SW5B

45P2000

D53

1N4148

PEAK BUS 1

JP18

JP18/2

JP17

JP17/2

JP16

JP16/2

J20/2A

J20A

J20G

J20/2G

J20/2B

J20/2E

J20/2D

J20/2C

J20B

J20C

J20E

J20D

+18

-18-18

+18

PEAK BUS FLTRPEAK BUS 2

JP20JP19 JP20/2JP19/2

FILTER BOARD

(ALONG WITH SHEET 2)

JP21/2

JP21

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

1 2 3 4 5 6 78

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APPROVED: Dw

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Drawn B

Rev.

S:\En

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\CLIENT98\1551\10s1551c-2.SCH

10S1551

DPX-100 MINI-EQ + COMPRESSOR/LIMITER

James B Franks

Sheet # of

847 Holt Road

Webster, NY 14580-9103

Phone: Fax:

(716) 872-0010

(716) 872-0739

Print Date

3-May-2002

11:43:56

A->B @ 157%

TO EVEN

TO ODD

U10B

4560

R69

4.7K

R70

63.4K

R71

63.4K

R72

7.87K

R73

10.0K

C17

.1u

C18

.1u

TO ODD

U12B

4560

R74

4.7K

R75

9.76K

R76

9.76K

R77

7.87K

R78

10.0K

C19

.1u

C20

.1u

TO ODD

U14B

4560

R79

4.7K

R80

15.8K

R81

15.8K

R82

7.87K

R83

10.0K

C21

.01u

C22

.01u

TO ODD

U16B

4560

R84

4.7K

R85

2.55K

R86

2.55K

R87

7.87K

R88

10.0K

C23

.01u

C24

.01u

TO ODD

U10A

4560

R89

4.7K

R90

39.2K

R91

39.2K

R92

7.87K

R93

10.0K

C25

.1u

C26

.1u

TO EVEN

U12A

4560

R94

4.7K

R95

63.4K

R96

63.4K

R97

7.87K

R98

10.0K

C27

.01u

C28

.01u

TO EVEN

U14A

4560

R99

4.7K

R100

9.76K

R101

9.76K

R102

7.87K

R103

10.0K

C29

.01u

C30

.01u

TO EVEN

U16A

4560

R104

4.7K

R105

1.58K

R106

1.58K

R107

7.87K

R108

10.0K

C31

.01u

C32

.01u

TO EVEN

U11B

4560

R109

4.7K

R110

25.5K

R111

25.5K

R112

7.87K

R113

10.0K

C33

.1u

C34

.1u

TO ODD

U13B

4560

R114

4.7K

R115

39.2K

R116

39.2K

R117

7.87K

R118

10.0K

C35

.01u

C36

.01u

TO ODD

U15B

4560

R119

4.7K

R120

6.34K

R121

6.34K

R122

7.87K

R123

10.0K

C37

.01u

C38

.01u

TO ODD

U17B

4560

R124

4.7K

R125

976

R126

976

R127

7.87K

R128

10.0K

C39

.01u

C40

.01u

TO ODD

U11A

4560

R129

4.7K

R130

15.8K

R131

15.8K

R132

7.87K

R133

10.0K

C41

.1u

C42

.1u

TO EVEN

U13A

4560

R134

4.7K

R135

25.5K

R136

25.5K

R137

7.87K

R138

10.0K

C43

.01u

C44

.01u

TO EVEN

U15A

4560

R139

4.7K

R140

3.92K

R141

3.92K

R142

7.87K

R143

10.0K

C45

.01u

C46

.01u

TO EVEN

25 Hz 40 Hz 63 Hz 100 Hz

160 Hz 250 Hz

1 KHz 1.6 KHz

6.3 KHz 10 KHz

400 Hz 630 Hz

2.5 KHz 4 KHz

16 KHz

VR21

VR17

VR13

VR9

VR11

VR15

VR19

VR23

VR22

VR18

VR14

VR10

VR12

VR16

VR20

JP24

JP24/2

JP25/2

JP25

JP27/2

JP27

JP28/2

JP28

JP32/2

JP32

JP36/2

JP36

JP35/2

JP35

JP39/2

JP39

JP38/2

JP38

JP37/2

JP37

JP33/2

JP33

JP34/2

JP34

JP29/2

JP29

JP30/2

JP30

JP31/2

JP31

JP26

JP26/2

U17A

4560

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

1 2 3 4 5 6 78

7654321

APPROVED: Dw

Size

Drawn B

Rev.

S:\En

ineerin

\CLIENT98\1551\10s1551c-3.SCH

10S1551

DPX-100 MINI-EQ + COMPRESSOR/LIMITER

James B Franks

Sheet # of

847 Holt Road

Webster, NY 14580-9103

Phone: Fax:

(716) 872-0010

(716) 872-0739

Print Date

3-May-2002

11:42:28

A->B @ 157%

PEAK BUS 1

PEAK BUS 2

THRES

SIG

GAIN METER

INPUT METER

OUTPUT METER

out

SW6

45P1501

out

SW7

45P1501

J10

47P1413

D19

1N4003

D20

1N4003

D21

1N4003

D22

1N4003

C85

1000u

C86

1000u

Out

U19

7818

Out

U20

7918

D23

1N4003

C81

1.5u

C82

1.5u

D24

1N4003

D25

1N4003

-18

C47

.1U 100V

C48

.1U

C49

.1U

R144

1.5K

+18

J11

KEYSTONE

1/2 AGC

110VAC 220VAC

2 11

3 10

51P7308

R145

10K

R146

3.3K

D16

1N754

D10

1N270

C50

220P

2N4125

C51

.1U

+18

+18-2

VCC +

FOR IC 5

R147

1.5K

SW1B

45P2600

D26

LIMITER(G)

D27

POWER(Y)

+18

OUT

2N4123

R148

390K

R149

2.4K

R150

62K

C52

.1U

D28

+20(R)

R151

1.5K

PEAK BUS 1

SIG IN

MODE

RLO

RHI

REF ADJ

V+

V-

REF OUT

LED10

LED9

LED8

LED7

LED6

LED5

LED4

LED3

LED2

LED1

LM3915

U21

LM3915

D29

+6(Y)

D30

+3(Y)

D31

0(Y)

D32

-3(G)

D33

-6(G)

D34

-9(G)

D35

-12(G)

D36

-15(G)

D37

-18(G)

D38

-21(G)

+18

J13/2A

J13/2B

J13/2C

J13/2D

J13/2F

J13/2G

J13/2E

J13/2H

J13A

J13B

J13C

J13D

J13F

J13G

J13E

J13H

SW4A

45P2600

INPUT METER

OUTPUT METER

-18

+18 +18

-18

R152

4.7K

D17

1N964

-18

+18

R153

2.4K

R154

2.4K

8 4

U5A

4560

D11

1N4148

D12

1N4148

R155

R156

100K

R157

100K

C83

1.5U

OUT

METER SELECT

OUTPUT LEVEL (db)

2N4125

2N4123

R158

560

R159

15K

R160

100K

R161

1.5K

D13

1N4148

D14

1N4148

C84

1.5U

C76

47U

D39

(Y)

+18

THRES

SIG IN

MODE

RLO

RHI

REF ADJ

V+

V-

REF OUT

LED10

LED9

LED8

LED7

LED6

LED5

LED4

LED3

LED2

LED1

LM3914

U22

LM3914

D40

-20(R)

D41

-18(R)

D42

-16(R)

D43

-14(R)

D44

-12(R)

D45

-10(R)

D46

-8(R)

D47

-6(R)

D48

-4(R)

D49

-2(R)

+18

J14A

J14B

J14C

J14D

J14F

J14G

J14E

J14H

J14/2A

J14/2B

J14/2C

J14/2D

J14/2F

J14/2G

J14/2E

J14/2H

GAIN METER

-18-18

-18 -18

+18+18

+18

R162

4.7K

D18

1N964

-18

R163

4.7K

R164

13V

GAIN REDUCTION (db)

C53

.1U

C54

.1U

C55

.1U

C56

.1U

C57

.1U

C58

.1U

C59

.1U

C60

.1U

C61

.1U

C62

.1U

Q10

2N4123

Q11

2N4123

Q12

2N4123

2N4125

D50

CLIP(R)

R165

1.5K

R166

62K

R167

390K

R168

2.4K

+18

C63

.1U

PEAK BUS 2

C77

47U

R169

63.4K

R170

3.92K

R171

R172

1.58K

2N4125

R173

19.6K

R174

1.5K

D51

SIG(G)

-18

+18

C78

47U

SIG

J12

KEYSTONE

J15

KEYSTONE

COMPRESSOR/LIMITER METERS

EQ METERS

+19 dBu

-20dBu

D52

1N4003

J16

KEYSTONE

J17

KEYSTONE

J18

KEYSTONE

J19

KEYSTONE

-18

+18-2

J21

KEYSTONE

Printed in USA 05/02 DPX100 -0

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter

ASHLY AUDIO INC. 847 Holt Road Webster, NY 14580-9103

Phone: (585) 872-0010 Fax: (585 872-0739

Toll Free (800) 828-6308 Internet: www.ashly.com

Ashly DPX-100 User manual

Brand: Ashly

Model: DPX-100

Category: Audio equalizers

Type: User manual

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Ashly DPX-100 User manual

Ashly DPX-100 User manual

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