Marshall Electronics MXL 990 Stereo Upgrade Manual

Brand: Marshall Electronics

Model: MXL 990 Stereo

Type: Upgrade Manual

Marshall Electronics MXL 990 Stereo is a versatile microphone well-suited for a wide range of recording applications, from studio sessions to live performances. It features a large diaphragm condenser capsule with a cardioid polar pattern, providing excellent sensitivity and isolation. The MXL 990 Stereo also offers a switchable 10dB pad and a low-cut filter, allowing you to tailor the sound to your specific needs.

With its rugged construction and balanced XLR output, the MXL 990 Stereo is built to withstand the rigors of everyday use. It comes complete with a shock mount and a carrying case, making it easy to transport and set up.

Ribbon Microphone Upgrade for MXL 990

Microphone

TL;DR – 3D printed ribbon bracket, 3D printed transformer bracket for MXL 990

Mic, along with a Ribbon alignment jig for a www.diyribbonmic.com/parts ribbon

element.

My Journey

I’ve been a long time audio buff and musician, who has a little recording studio in my basement. It’s always fascinated

me how expensive “good” ribbon microphones were, yet their construction was terribly simple. If you traverse the web,

you’ll see I’m certainly not the first to go down this path of homemade Ribbon Mics. There are a number of good

resources out there on the series of tubes. But of course, I’d like to think I’m a little different, and you can be the judge

of that. My approach has been to use cheap microphone bodies and upgrade, rather than making a body from scratch.

This has some limitations with respect to the dimensions of the body, but I think it gives a much more professional look.

At the same time, you now have to convince someone that the guts in that MXL is a whole lot better than they might

think. But once they listen to it, I think they will be able to make that judgement themselves. In addition, with my new

3-D printer, I figured I could design and print anything I might need to help the process, and it seemed some tools and

jigs were missing from all of the other posts I had seen.

Starting with a Kit

What started this journey for me was running into Rick at www.diyribbonmic.com/parts (sadly, it was more than a year

before I could finally get the time to finish this project). I saw he had everything you need to make a Ribbon mic

element (motor), transformers and even a complete mic, along with an excellent set of instructions and videos. He was

very easy to communicate with, and I had numerous emails with him before I even bought the kit. But to save some time

and cash, I wanted to upfit an old MXL mic.

Being an engineer, the first thing I did immediately after ordering my kit, was to look how to improve what was already a

good thing. A couple of things immediately struck me. 1

was that no matter what, I knew full well I would need to

eventually re-ribbon the thing. And I wanted to make that process as easy as possible. And I wanted to be able assemble

and disassemble the mic cleanly. So I started to work on some 3-D Printed parts.

But before you get started you will need to hit Rick’s site at www.diyribbonmic.com/parts and buy the ribbon motor kit

and his OTA transformer. You will need an MXL 990 mic, and the 3-D printer files on thingiverse.

Why MXL Mics

In a word, they’re cheap, easy to find, and many folks buy them as part of their 1

studio equipment, to then end up

tossing them in the back of the closet somewhere as they move on to get better quality gear. So they are good

candidates for cannibalizing for upgrades. While ripping the inner layers of mesh out of the basket is a bit of a pain in

the butt, you can’t beat them as a nice mic body as a base for an upgrade. And they most often come with a decent

shock mount. I often find them used for less than $50 each on craigslist, and found 4 for $25 each. Sticking a quality

Ribbon Motor and Transformer into one, quickly turns them into sounding like a mic costing $1,000 or more.

is a Series

This is in fact the 1

in a series of Instructables, with adjoining 3-D printable files to either upgrade or entirely build a

Ribbon Microphone. Since it’s my first, I’m making it fairly detailed. The ones that follow won’t be as long.

This Instructable is to take a ribbon microphone element (motor) from Rick at www.diyribbonmic.com/parts along with

his OTA transformer and upgrade an MXL 990 using some 3-D printed fixtures and tools.

Over the coming months I will be offering up other Instructables. I have recently completed an upgrade for the MXL

R144 Ribbon Mic (Ultimately, I plan to build in a phantom powered preamp into this body), and will shortly be working

on similar upgrades to the MXL R80 Ribbon Mic. All this will ultimately culminate in an entirely 3-D printable Ribbon

microphone (active, with a Phantom powered preamp), which I also hope to CNC a metal motor. They will come in time.

Needing Some Tools (Here’s where some CAD skills and a 3D printer helped)

When I traversed the web, what seemed to be missing, were some tools that would make things much easier to deal

with ribbon prep, installation and the final build. And that’s what I wanted to accomplish in this Instructable. Some

things I realized would make things so much easier.

 Cutting Guides – Terribly simple, but really necessary. You need to cut the Ribbon straight and of a particular

width. So I fired up InDesign, and made a very simple cutting guide of parallel lines for different Ribbon Widths.

 Paper Ribbon Carrier – Again, a simple set of parallel lines 20mm apart to cut some parchment paper, to allow

you to fold it in half, and gently tuck your ribbon into it so you can corrugate it. Once you cut your ribbon, you

need some place to gently stow it, before you corrugate it.

 Plastic Tweezers – So much easier than toothpicks to move the ribbon around, although, you will still love to use

those toothpicks in some places

 Glass – Since I have a 3D printer, I always print on glass, and found it so much easier to cut the ribbon on glass.

tape down your ribbon cutting guide, then some parchment paper, then lay the foil on the parchment, and

top off with another layer of parchment paper. I also just used some picture frame glass.

 Ribbon Alignment Jig – This 3D Printed part is probably the single most important thing I made. Getting the

ribbon properly aligned and tensioned in the motor is really tough when you just lay the motor on your desk,

and try to do everything free hand. This jig allows you to place the Ribbon Motor in it, than drape the ribbon

element across it to more easily align it, and put tension on it. I used brass nuts, to hold the ribbon in place, and

used a toothpick to slide them (the brass nuts) around to align and tension the ribbon. The ribbon really needs

something to help keep it aligned. This really did the trick. Then tighten up the clamps to hold the ribbon in

place (one end 1

, make final adjustments, then the other end). If there was any one thing that I was happy

about, it was this jig. I literally was able to use my very 1

ribbon and got it done in like 5 minutes. I attribute it

to this tool. After working on some other ribbon motors, I came up with a simplified version. Both versions are

included for download and print.

 Ribbon Corrugator – In traversing the web, I learned that corrugations of 20 or so per inch were optimal. I tried

to 3D print some gears to that specification, but the teeth are just too fine for my 3D printer (a friend’s got an

SLA, I might hit him up). And again hitting the Internet and various Ribbon Mic sites, I came across a very simple

arts and craft corrugator, which works perfectly. I of course wanted to 3D print some fancy contraption for it,

but the simple device works just fine.

 3D Printed Ribbon Motor Mounting Bracket – Again, my biggest motivation here was to create a means to

allow the Ribbon Motor to be easily removed to be re-ribboned. This is what I ended up with. This is a little

recess in the bottom so the copper strip has room, and little channels in the back, so you can press fit the

positive wires in place.

 3D Printed Transformer Bracket – Again, rather than just use some stuffing to hold it in place, I wanted

something a little neater. So I came up with a similar looking bracket, where Rick’s OTA transformer slides into.

This rotates the transformer on its side so the 2 ribbon motor wires go up through the holes on the same side to

connect to the motor on the back. It also has a bit of a stand off, to move the transformer further away from

the motor, so the magnets don’t effect it as much. It makes wiring things up easier.

Part List

This is the list of parts used and where to get them

 Ribbon Motor Kit and OTA transformer from Rick, you don’t really need the full MXL 660 upgrade kit, as you will

use my 3-D printed parts, just email him for the two parts, he’ll hook you up.

o http://diyribbonmic.com

 3D printable ribbon fixture jig, motor bracket and transformer bracket

o You can get them from Rick as part of his kit (PLA, .02mm, 100% infill) or print them yourselves, getting

them from Thingiverse below.

 MXL 990 Upgrade - http://www.thingiverse.com/thing:1271932

 Just the Austin Ribbon Mic Alignment Jig - http://www.thingiverse.com/thing:1271926

 PDF of ribbon cutting guide and ribbon pocket cutting guide

 Ribbon Corrugator – Like I said, I was going to make a fancy ribbon corrugator, but this works very well as is.

Maybe later I’ll 3-D print something.

o http://www.amazon.com/gp/product/B0054G623Y?psc=1&redirect=true&ref_=oh_aui_detailpage_o02

_s00

 Connecting wire – I really like this wire, nice jacket, fine strands. Perfect for this purpose.

o http://www.amazon.com/gp/product/B00CUKSITS?psc=1&redirect=true&ref_=oh_aui_detailpage_o07_

s00

 Heat shrink tubing – just a couple of inches of 3/32” and 1/8”. I got this kit, which was great

o http://www.amazon.com/NTE-Heat-Shrink-Assorted-

Colors/dp/B000FIDTYG/ref=sr_1_15?s=industrial&ie=UTF8&qid=1451328474&sr=1-

15&keywords=3+32+heat+shrink

 Non-metallic tweezers – I love these and they are cheap. Very helpful in really being able to handle the ribbon

delicately. You can’t use your fingers, as the ribbon will stick to them.

o http://www.amazon.com/gp/product/B00HGAKMMI?psc=1&redirect=true&ref_=oh_aui_detailpage_o0

7_s00

 2 Brass nuts for the ribbon alignment jig

 1 inch piece of 3m double back foam tape

 Soldering Iron and Solder

 Heat Gun

 Wire cutters, long nose, jewelers screwdrivers and other basic tools, jewelers nut driver for the ribbon motor

 Thick cotton sock – OK, laugh now, but when you carry the mic around, and the wind going through it, and blows

the element out, then you’ll get a sock to cover it. Ribbon’s are delicate. You cough on it, its shot. Just walking

with it unprotected in your hand, with the air movement going over it, can stretch the ribbon. Think of it as the

condom for a mic. We’ll be removing some grille material for better frequency response, which makes it more

susceptible to wind. For me, I just happen to have some of these little nVidia bags for their 3D glasses, which fits

perfectly.

 Glass – From a picture frame will do

 Printer to print the PDFs out

 Parchment paper – Rick’s ribbon motor kit includes some decent ribbon material. If you want to go hog wild and

buy a sheet of 1.8 micron foil, it will set you back $25 plus shipping. Not a whole lot of difference, but I spent

the extra money. Hit the site below, then email them with what you want to buy, contrary to what the site says,

you only need to buy one sheet at a time. You then pay with PayPal, and they ship the next day. Good

company.

o http://www.lebowcompany.com/foils_list.htm#ALUMINUM

OK, Let’s Get Started

MXL Mic Disassembly

Basically, you just want to strip it down to where you only have the case, XLR connector and basket. The mic basket has

3 layers of grille material. You really want to remove the two interior layers

1. Unscrew the black base nut at the bottom of the mic. This is used to trap the non-shock mount, but also helps

hold the thing together.

2. Once that has been removed, you can then unscrew the upper and lower halves of the mic.

3. There are 2 screws that hold the basket to the metal plate. Unscrew those, and the basket will come loose,

revealing the condenser element.

4. Unscrew the condenser element, and cut the wires. Hang on to the element, as you will need that little solder

tab for a ground tab later.

5. Cut the wires for the XLR connector close to the circuit board, and remove the circuit board.

6. Loosen the screw that is holding the XLR connector in the body, and let it drop out. Desolder the + & - wires

from the XLR. You will also need to add a new chassis ground wire later.

7. Grille – OK, this is a little bit of work. The grille on the Mic has 3 layers. Now on one hand you can just leave it

alone, but it does impact the frequency response of the mic. Therefore, I suggest you remove the inner 2 layers.

This is a little tough, as the layers are soldered in a number of places. I used long nosed plyers and some long

necked wire cutters. But if you are patient, you can completely remove the 2 inner layers. One thing to point

out, is that in removing the inner layers, you may deform or pull down on the top of the mic grille. The ribbon

element has some tight tolerances. So make sure you take a screwdriver handle and push up on the inside of

the grille to again return the top to where it is curved out. You don’t want to have the top of the ribbon element

touch the grille, as it will short. Ultimately, if you don’t trust the clearance, you can use a piece of electrical tape.

Putting it Together

Let’s first get the Mic body prepped for the new ribbon motor (element)

1. You will need to drill 2 holes in the metal plate (that the condenser element was mounted to), to secure the 3D

printed ribbon element bracket and transformer holder. I would suggest that you use the transformer holder as

your guide. Place the transformer holder aligning it with the 4 large center holes in the plate, and use a punch

to mark your 2 drill holes. Drill to fit a 4-40 or similar size screw. Don’t forget to deburr.

2. Using a film of silicone seal on the bottom of each bracket, secure the brackets to the metal plate. I would

suggest screws going through the ribbon element bracket, with the nuts on the transformer side.

See that little Intent in the bottom there? See the little grooves in the back of the bracket? Those grooves

are for the plus (+) wires to sit into. This is the BACK of the MIC

Wiring it Up

3. Before you wire up the OTA transformer, you should test fit the transformer into the bracket, to make sure it’s

not TOO tight. You may need to use an Xacto blade to shave it a bit. But you do want it very snug.

4. Now you need to prep the OTA transformer. Solder a 6” black wire to the mic input – side, and TWO 8” red

wires to the mic input + side of the transformer. Then heat shrink. 3/32” heat shrink for the single wire, and the

1/8” heat shrink for the plus leads. Don’t make the heat shrink too long up the black or red wire, as you need

them to be pretty flexible close to the metal plate.

5. You will then want to wire the transformer up to the XLR connector. If you haven’t done so already, loosen the

screw for the XLR connect in the side of the mic body. The XLR connector should drop out the bottom of the mic

body.

6. The output wires of the OTA transformer are plenty long, in fact you can see if you might want to trim them a

bit. But I left mine alone.

7. Slide some heat shrink tubing up the transformer wires, and put the wires THROUGH THE MIC BODY

8. You need to run the wires through the mic body BEFORE you solder them to the XLR connector. Then solder the

red lead to the + pin, which is pin 2. Solder the black lead to the – pin, which is pin 3. Slide the heat shrink over

the pins, and shrink with a heat gun.

9. Now, while that XLR screw you loosened to drop the XLR connector out of the body should provide ground for

the mic body, I went ahead and soldered a ground wire, that I then connected to one of the mic body screws

just to be safe. It should look like this

10. Now twist the transformer output wires a bit. Insert the XLR connector back into the body, making sure you

properly align the connector with the key slot and tighten.

11. First check the orientation of the Mic brackets. Remember that little notch in the bottom of the ribbon element

bracket? See those little channels going up the bracket? Those are for the wire to sit in. That’s the BACK of the

mic. Take the red and black transformer input wires, and slide them through the hole in the back of the bracket.

Next put a little blob of silicone seal in the transformer bracket, and you will want to insert the transformer into

the bracket so the back of the transformer, with the 2 mic input wires face the back of the mic. Slide the

transformer in. It will be a tight fit. It’s supposed to be.

12. Next loosen the side screws on one of the metal arms on the bottom mic bracket, and slide the metal plate into

place. Twist the transformer wires a bit as you go. Then install the 2 screws to hold the metal plate in place, and

tighten up the side arm screws. This is actually where I connected the ground lead. I used one of the solder lugs

from the condenser element for the ground.

13. Now the black wire will be soldered to the bottom center of the ribbon element. What I did was pull the wire

back out, and trimmed, stripped and tinned it. The red wires will go up the channels on each side of the bracket,

and to the center top of the ribbon element. What I did was push them into the channels, sorted out where

center approximately was, and then trimmed, stripped and tinned them.

14. You are now ready to install the ribbon element.

Putting the Ribbon Element (Motor) together

15. Ribbon Motor – Follow Rick’s instructions (pages 9 through 13 of his instruction PDF) for building the motor.

Glue the two magnets in using the spacer, with the proper polarity. Remove the spacer when dry. HOWEVER,

do not solder the connection wires to the motor. You will solder the motor while it is in place. But you can tin

the copper. But remember to mark the back of the body with a nice red plus + sign to indicate the plus end of

the element. It will make things easier later.

16. Prep for dealing with the Ribbon using the cutting guide PDF

a. Use the ribbon pocket guide to 1

cut a number of pieces of parchment paper. This will create 20mm

wide strips. First cut a strip of parchment paper to be about 145mm wide. Tape the cutting guide onto

the piece of glass, and then tape the parchment paper on to the glass on one edge, and using a steel rule

(cork side up if it has it), using a brand new exacto or razor blade, cut them into strips. These will give

you 20mm wide strips, which are around 145mm long. Then fold them in half long ways. You will use

these as pockets to place the recently cut ribbons into them.

b. Select and cut the ribbon cutting guide. There are several difference sizes to choose from. The closer

the ribbon is to the magnets the better, but you don’t want the ribbon to actually touch the magnets.

While Rick suggests basically a 4.75mm wide ribbon, I’ve found that using the ribbon alignment jig, I was

easily able to keep the ribbon centered, and have been able to easily do 5mm and carefully 5.25mm

wide ribbons. So pick the ribbon cutting guide you want to try, and tape this to the glass.

c. Then tape a layer of parchment paper on top of this. Keep a spare layer of parchment trimmed to fit on

top, as you will want to put another layer on top of the foil before you cut it.

d. Make a 2

piece of glass with just parchment on it. You will use this to trim up the ribbon foil to a

smaller size.

17. Cutting the ribbon

a. Turn off all the fans, close the heater vent, put the dog outside, kill the cat (Geesh, OK, I like cats) close

the door. The slightest breeze will send the foil flying.

b. Put the surgical mask on.

c. OK Branch in process

i. If you are using Rick’s foil material, you can leave it in the thin parchment paper, as it cuts OK. If

you are using the foil from Lebow, I have found that when you cut the foil in the parchment they

provide, it sticks on the edges, and can tear the ribbon. So if you are using Lebow foil, I suggest

removing the foil from their parchment, and use kitchen parchment paper.

d. Bring the ribbon foil over the top of this 2

piece of glass, with only the parchment paper. You will

essentially want to gently and carefully use one of the tweezers to float the foil out onto the parchment

paper. But don’t manhandle the foil, it will tear. Carefully remove the ribbon foil, and slide it onto the

parchment paper. You don’t want it to fold either. Nice and smooth.

e. COVER IT WITH ANOTHER LAYER OF PARCHMENT

i. What I suggest is roughly cutting it into a section that 110mm tall (the length of the motor

element and some extra length for the ribbon alignment jig), by 55mm, which is a little wider

than my cutting guides.

ii. Using a fresh razor or Xacto and steel ruler (cork side up), cut the ribbon material.

iii. Take the extra ribbon material and put it back into its parchment and store.

f. Now take this glass, and bring it over to the other piece of glass with the cutting guide, and gently float

the foil you just cut onto the cutting guide, roughly aligning it with the cutting lines.

g. Tape a fresh piece of parchment paper on top of the foil.

h. Again using the steel rule cork side up, line up on the guide and cut several ribbons. While you might

not need them all, cutting multiple now, will save you material, as you will have to trim off that 1

edge

the next time you need it. So might as well cut some extras.

i. Using the cutting guides to cut your ribbon. I found that a 5mm wide ribbon works well.

i. Take the folded parchment pocket, and open it slightly, and slide/float the ribbon into the pocket using

the tweezers. Be very careful you don’t fold the ribbon, or catch an edge and tear it on the paper. Tuck

it into the pocket, and once in, tap the folded edge of the pocket on your desk, to have the ribbon be

straight along the folded edge. This is important, as when you go to crimp the ribbon, this will help it

stay straight, and easier to align in the motor.

18. Corrugating (Crimping) the Ribbon

a. Take the ribbon, in the carrier, and in a nice steady motion, while applying decent pressure on the two

gears, corrugate the ribbon.

19. Mounting the Ribbon

a. Have the Ribbon Alignment jig already printed.

b. Cut 4 pieces of 3m double back foam tape into squares about 5mm and put in the indentations of the

ribbon alignment jig. This holes the screws in place while you tighten them.

c. Taking an edge of the exacto, remove any sharp edge on motor bracket and clips, which will go against

the ribbon

d. Clean up the motor

i. Take some scotch tape and stick around the motor magnets to pick off any fine metal that the

magnets may have picked up.

ii. Clean with some alcohol (don’t use acetone, it will loosen the superglue)

e. Put the 4 screws used to hold the ribbon element brackets in. Then flip the jig upside down, and then

put the motor in, and flip back over. (so the screws don’t fall out when you put it in the jig)

f. I also cut a strip of paper about 50mm wide, to cover the motor, while I’m working on it, so for example,

when you are putting on the nuts to save the ribbon in case you drop one.

g. Put your mask back on.

h. Take the now corrugated ribbon carrier, and pry it open with your tweezers, so the ribbon can be easily

slid out. Bring it over top of the motor and alignment jig, and slide it out over the middle. Using a

combination of the tweezers and some toothpicks, center the ribbon in the opening of the motor. Use a

brass nut to hold one end of the ribbon in place. I found using the toothpick as a means to gently move

the brass nut around, to help center the ribbon. Then using the tweezers, center the ribbon on the

other end. Put a nut on top of that end and using the toothpicks, just ensure that the ribbon is primarily

centered. Then place the bracket on one end, gently press it down, and (here’s where I put that strip of

paper on top of the motor, to protect the ribbon if you drop a nut) install the 2 nuts on the one end.

Make sure that end of the ribbon is centered before you finish tightening it. Once the ribbon has been

clamped in, there’s no going back, you can’t remove the cover without tearing the ribbon. Once the one

end of the ribbon is secure, use a toothpick to move the nut on the one free end, and center the ribbon,

while sliding it back to put tension on the ribbon.

i. You want enough tension to where the ribbon looks straight across the motor. You don’t want

it to sag. But you also don’t want too much tension, to where you are stretching out the

corrugations. You want to see the corrugations.

i. Put the cover on the other end, and install and tighten up the nuts.

20. You’re done. All you need to do is install the element.

21. First, everything you do from this point is slow and gentle. You don’t want to trash the ribbon element you just

installed. I’d still keep the surgical mask on, to keep you from breathing directly on the ribbon.

22. Gently remove the Ribbon Element from the holder. You can pull off the excess ribbon from the ends.

23. Look for that + mark that you made on the back of the ribbon element. That’s the top. Gently slide the ribbon

element into the bracket. The copper strips will be in the back, and the plus is top.

24. Carefully solder the minus (-) lead to the bottom. What I found was that some hemostats I had laying around

were pretty non-magnetic, and helped hold it in place.

25. Then press the red plus (+) leads into the channels, and solder both to the top of the element.

26. My element stayed put just fine. But if you are worried about vibration noise, you can use a little dab of silicone

seal on the top corners or a rubber band across the top to hold it in place.

27. Grab the mesh basket, and slide the element inside and secure the basket with the 2 screws.

28. Now grab the bottom of the mic body and screw it onto the bracket. Then the black nut.

29. Done.

30. Grab a cable, hook it up to your preamp, audio interface or mixer, and give it a try. NO PHANTOM Power. You

will need to turn the gain up pretty high. What I recommend is to put an inline preamp close to the ribbon mic,

so it has some gain before it gets to the mixer. A phantom powered in line preamp is perfect, because you can

plug it right into the bottom of the mic. I suggest that you get one of the following

a. Rick’s Ribbon Mic Preamp from www.diyribbonmic.com/parts

b. Cloudlifter CL-1 - http://cloudmicrophones.com/products/cloudlifter-cl-1/

c. Triton Audio FETHEAD -

http://tritonaudio.com/index.php?sectionid=4&option=com_content&task=category&id=17&Itemid=33

i. This is what I’m going to get for the short run, until I can get an in mic body phantom powered

preamp

Overall, I’ve been really impressed with the purity of the sound. It sounds great. I like that this let’s me quickly and

easily re-ribbon when needed, and the alignment jig really makes installing a new ribbon a snap. I hope you have as

much fun with this as I did.

Marshall Electronics MXL 990 Stereo Upgrade Manual

Marshall Electronics MXL 990 Stereo Upgrade Manual

Marshall Electronics MXL 990 Stereo Upgrade Manual

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