ATI Technologies P1000 Operating And Maintenance Manual

Brand: ATI Technologies

Model: P1000

Category: Musical Equipment

Type: Operating And Maintenance Manual

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P1000

STEREO TURNTABLE AMPLIFIER

OPERATING AND MAINTENANCE MANUAL

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GENERAL

A turntable preamplifier is a deceptively simple device and has been the subject

of an amazing amount of poor design. The seemingly simple matter of attaching

a high capacitance load (in the form of the RIAA feedback network) onto a

preamp stage which does not have adequate current drive capacity, guarantees

Slew Rate Distortion, Transient Intermodulation Distortion, rising high frequency

harmonic distortion and probably a few other distortions we haven’t named as

yet. This problem is common to almost all existing preamps.

A second common fault is designing too much gain into the input equalized state

to compensate for a mediocre noise figure in the following output stage with the

result that the input headroom is severely limited. Since groove stylus velocities

of digitally mastered and direct disc recordings exceed 50 cm/sex peaks regularly

with even greater dynamic range expected in the future, a high output cartridge

can readily strain the typical 80 mV maximum input limit of typical preamps.

ATI has eliminated these two problems by use of a new integrated circuit

developed for the European professional audio market and recently made

available to the US market through two major manufacturers. This chip

incorporates a low noise input stage designed for use with the low source

impedances typical of phono cartridges. In addition, this chip has an output

stage free of crossover distortion and of sufficient current swing capability to

drive 600 ohm loads to full supple voltage. An inherent slew rate capability of 13

volts per microsecond, a 50 KHz gain bandwidth product and 100 db open loop

gain make this chip an ideal device for audio applications.

Excellent low noise performance in both input and output stages allows to the

MicroAmp to operate at reduced input stage gain yielding an input swing

capability of almost 1 V p-p at 1 KHz while preserving excellent noise

performance. The high Push Pull output capability allows the first stage to drive

the RIAA equalization network with ease and without slew rate limiting to

degrade high frequency performance. The high open loop gain provides 46 db

loop gain for 200 to 1 distortion reduction even below 50 Hz where the equalized

stage is operating at maximum gain.

The high output also allows the output stage to drive the load directly on through

a simple 1:1 isolating transformer. ATI proves three models of each MicroAmp;

Transformer outputs for high RF field environments. A balanced, differential

output stage version (bridge circuit) is also available. It is suitable for low RF

environments where balanced output lines are required for hum rejection in long

runs and the minor performance degradations of an output transformer are not

desired. In addition a simpler, lower cost single ended output model with full 600

ohm drive capability is designed for use for short runs in low RF environments.

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Another design consideration is the presence of large low frequency input

signals, which originate in record warp and seismic pickup from people walking,

bumping studio desks etc. The signals are strongest in the neighborhood of the

cartridge/tone arm resonant frequency, typically 6 to 10 Hz. In studio

applications these signals can overload subsequent amplifiers, overdrive limiters

and damage loudspeakers. Previous attempts at Rumble Filters noticeably roll

off low frequency audio when operated and therefore must remain switched out

of the circuit most of the time.

The MicroAmp incorporates an active two pole, subsonic filter bridged around the

RIAA equalization network. The Q of this filter is designed to allow the

preamplifiers response to follow the RIAA curve precisely to approximately 28 hz,

drop only 3 db at 20 hz then plunge quickly to –18 db at 10 hz and achieve

approximately 30 db rejection at 6 hz. Thus, excellent subsonic rejection is

attained without low frequency degradation. Hi Boost and Hi Cut switches are

included.

Our power supply incorporates a couple of unique regulation devices called

zener diodes. In contrast to most fancy three terminal IC regulators these

devices will live through line transients and simultaneously protect your

expensive circuitry.

INSTALLATION

MOUNTING

Your MicroAmp may be desk mounted on its suction cup feet and left out for

everyone to see since it is so pretty. If you want to keep knob twirlers away, you

can bury it inside your turntable cabinet using the two angle brackets provided.

Place them at diagonal corners under the lower cover mounting screws. Avoid

magnetic fields from the turntable motor. Make sure your cartridge leads reach

the preamp before permanently mounting.

Rack Mounting Kits are available. P/N 20021-501 mounts a single MicroAmp.

P/N 20024-501 mounts two MicroAmps side by side in 1 ¾” vertical rack space.

WIRING

The third wire ground can cause a ground loop with your station ground. If you

are sure your station ground will provide adequate protection to personnel in

case of an AC line short to the chassis, a 3 to 2 AC line adapter can be used to

isolate the power line ground. We recommend that the adapter be removed and

the power line ground reconnected prior to any service work requiring removal of

the station ground connection from the MicroAmp chassis.

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The four inch copper strap which you are, of course, using for your station

ground is not going to fit around the #6 chassis ground screw on the MicroAmp

rear panel. Run strap to within a few inches of the chassis and jump to the

chassis ground with shield braid. Connect the tone arm ground lead to the same

point (or any other place that works better).

Plug cartridge leads into the phono jacks. Convention is white for left channel,

red or black for right channel.

Output wiring is indicated on the rear panel label. HI outputs are in phase with

each other and are in phase with the input signal. Transformer output

MicroAmps (1000-1) may have either HI or LO outputs grounded (but not both).

Single Ended Output MicroAmp (P100-3) has the Lo output internally grounded.

Do not ground the HI output as this shorts the output.

CAUTION

Balanced differential output MicroAmps (P1000-2) has active drivers for both HI

and LO output terminals. Do not ground either HI or LO terminals. To drive an

unbalanced (one side grounded) load connect it between HI and GND terminals

and let the LO terminal float. Two separate 600 ohm unbalanced loads can be

driven from each output without interaction by connecting one between HI and

GND and the other from LO to GND. The two loads thus driven will be out of

phase with each other. Individual grounds are provided for left and right outputs.

ADJUSTMENTS

The MicroAmp has sufficient gain and output capability to overdrive some

console inputs particularly those providing preamps for high level input channels.

Two o’clock on the level pot will provide +8 dBm for 0 VU (5 cm/sec) recording

level with typical cartridges providing 1 mv/cm/sec, 12 o’clock is approximately 0

dBm, 10 o’clock is approximately –10 dBm output. Operation with the MicroAmp

pot below 10 o’clock degrades noise performance and a fixed attenuator pad

should be placed between MicroAmp and output and console input to allow

operation around two o’clock.

MAINTENANCE NOTES

Power supply voltages are + and – 20 VDC nominal, dropping to +\- VDC under

full output. Maximum allowable voltages are +\- 22 VDC (limited by IC). If

zeners are replaced remove A1, A2, and A3 ICs and check output voltage before

plugging ICs back into the circuit. Remove power when inserting or removing

ICs.

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IC output DC voltages (no signal conditions) should measure OVDC +\- .5 VDC.

Significant deviation indicates IC or circuit problem. Measurable DC difference

between +\- amplifier inputs (other than due to meter loading) indicates IC failure.

MODIFICATIONS

230 VAC OPERATION

Your MicroAmp is wired for 115 VAC 50/60 Hz operations unless otherwise

requested at the time of ordering. It can be modified for 230 VAC use by

removing the Power transformer primary jumpers W1 and W3 and inserting a

jumper in the W2 holes.

150 OHM OUTPUT IMPEDANCE

Transformers output MicroAmps are converted to drive 150 ohm audio lines by

removing jumpers W4 and W5 located adjacent to output transformers T3 and T2

respectively. Insert two new jumpers for each output transformer between the

original jumper terminals and the empty terminals immediately adjacent to and in

line with the original terminals in order to parallel the secondary windings.

Balanced differential output and single ended output MicroAmps will drive 150

ohm loads without modification but will current limit before full supply swing is

reached.

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TECHNICAL SPECIFICATIONS

MODELS

P1000-1 DUAL/STEREO TRANSFORMER

OUTPUTS

P1000-2 DUAL/STEREO BALANCED

DIFFERENTIAL OUTPUTS

OUTPUT CLIPPING LEVEL +22 dBm (P1000-1-3)

+26 dBm (P1000-2)

DISTORTION @ +20 dBm OUTPUT

P1000-1: .2% 30 Hz to 20000 Hz

P1000-2: .05% 20 Hz TO 20000 Hz

EQUIVALENT INPUT NOISE SHORTED INPUT, .5 MICROVOLTS RMS.

Cartridge Input, .8 micovolts, RMS.

1000 ohms + .5 Hz

SIGNAL TO NOISE RATIO 80 db unweighted, ref. 10mVrms, 1 KHz

20 KHz bandwidth

FREQUENCY RESPONSE RIAA Curve +\- .25 db, 30 to 20000 Hz.

INPUT SENSITIVITY Adjustable, 1.0 mVrms at 1 KHz for +8 dBm

output

INPUT OVERLOAD 320 mVrms at 1 KHz.

INPUT IMPEDANCE 47K ohms and 220 pf.

SUBSONIC WARP AND ARM -3 db max @ 20 Hz

RESONANCE FILTER -18 db @ 10 Hz.

HI CUT SWITCH -3 db @ 10 kHz

HI BOOST SWITCH +3 db @ 10 kHz

SYSTEM SLEW RATE 13 V/Microsecond

POWER REQUIREMENTS 115/230 VAC +\- 10%

47-63 Hz.

8 ½” W X 1 ¾” H X 7” D, 2 ½ lbs.

ATI Technologies P1000 Operating And Maintenance Manual

Brand: ATI Technologies

Model: P1000

Category: Musical Equipment

Type: Operating And Maintenance Manual

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ATI Technologies P1000 Operating And Maintenance Manual

ATI Technologies P1000 Operating And Maintenance Manual

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