First Time Racking Questions

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heatwalk

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Oct 17, 2020
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14
Hi All,

After building a small foundation to stand on regarding electronics and my desire to learn and do more growing, I'd like to begin trying my hand at racking some preamps. While the PM1000 project has been on my radar for a long time, long before I even started my dive into the tech world, I'm sure I'll do it at some point but as of late I've been more interested finding some other module with less extensive documentation (so long as I have a schematic). My thought here is that it could be a better learning experience - instead of following step by step guides, it would force me to research and figure some stuff out on my own, study, and better understand the circuit. While that means more room for mistakes, with that comes more room to grow and learn and apply what I pick up to further endeavors. Maybe the end result won't be as versatile in the studio as the PM1000, but the PM1000 will always be there for a rainy day, and I'm sure I'll be able to build it.

With this being said, here are some potential options I'm considering right now. Weighing my options, inevitably I'll just need to pull the trigger on something to establish the project and set a goal for myself that I can work towards, but would like to hear the thoughts of others.

Gates M-6034 Broadcast Pre -
An affordable but unknown preamp with darkhorse potential? I can't find much about these beyond their tech specs and schematic in old product guides. Maybe the lack of talk about them indicates they aren't that great, unless someone on here knows anything about them to counter my assumption? A search showed that someone was selling a few of these at one point here but no further info. I know that while Gates tube stuff is coveted the solid state stuff doesn't seem to carry that rep and broadcast gear seems to be regarded as hit or miss regarding musical application. With the lack of information on how these sound and being germanium, maybe they're cool but if there a bigger chance they are a bust? If I rack them and they work then the project is a success regardless, but if the sound isn't what I'm after, is there room to experiment with swapping parts? I'll have to add an output transformer regardless, but knowing the rep germanium has, could I try experimenting with swapping out different silicon equivalents? While I know they don't operate under the same conditions so you can't 1 for 1 swap, elsewhere someone was suggesting that in the early days of transitioning to silicon, swapping them out while doubling the resistor emitter could get you in the ballpark of proper biasing conditions - does this hold somewhat true?

ADM Input Modules. Seem to have a great rep for their API sound and value for which you can get them. Don't think I'd being going wrong this way.

EAG Mic Preamp or Stereo Line Amp
That vintage eastern european appeal.... I guess the downside would be the language barrier on the manuals, but a schematic is a schematic at the end of the day so should be able to fare ok in that sense. A stereo line amp actually has some appeal here for me as well cause I could use something to throw on the 2-bus right now, and I'd have the added benefit of not needing to build phantom and saving that for next time. Saw these go up on reverb before and thought they sounded pretty nice when I listened to a demo video, so thought I could give it a go. As an added bonus, with a line amp I wouldn't have to worry about supplying phantom so the PSU could be simpler.

Beyond options and looking toward the work entailed, in a general sense, it seems the bulk of the work in a racking project stems from building the PSU to the conditions the module needs, the rest stems from switching, recapping, pad/input/output level control, etc. If the PSU is the bulk of the work, is trying to design and build my own a good or bad idea vs using a kit (JLM, FiveFish, MeanWell)? As I want this to be a learning process in which I can start to grasp what is going on under the hood and apply it elsewhere, I was thinking going through the process on my own with a simple PSU be a good experience that sets me up for success in the future? Nothing against the kits as they are well regarded, but for the sake of project I don't mind doing some homework and studying in the name of improving my theory, even if its more difficult and will take longer. Safety being a concern here, as long as I'm triple checking wiring, connections, checking my design with more experienced people, and following safety protocol, is this a bad idea? I just think it would be pretty satisfying for it to come together as a product of my own design, even if beyond this project I choose to use kits.

Any thoughts would be appreciated, thanks.
 

mjrippe

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I racked a pair of similar Gates cards many years ago (GATES Discrete Microphone Preamps). Mine had output transformers though. Sounded good, simple, easy to understand.

I also just sold my ADM preamp and eq to a member here as raw modules. They really do sound nice and are high quality (Grayhill switches, transformers, DOA in the preamp, etc.). More complex power requirements and lots of connections you may or may not use!

There are plenty of plans for power supplies around, or just build off the datasheets for linear regulator supplies.
 

heatwalk

Member
Joined
Oct 17, 2020
Messages
14
Thanks for the input. Just hooking up an external 30V PSU seems pretty convenient especially if I was to go for a simple no phantom approach and simply mount a two of these in a chassis like you did. Maybe taking most of the challenge out of it, but keeps the project simple and cost effective so maybe there less of a reason to mess with an internal PSU in this case? For providing the -30V the card wants, would that mean +30 from the PSU hooks up to GND on the module and 0V connects to the -30V connector?

I've now also spotted some Teac M301 input modules for the same price. I'm a fan of the teac/tascam sound so heavily considering those as well now. Seems to be more info floating around on them as well as a thread here about racking them so might be a safer and more versatile bet with more room to experiment on and have more fun. Trying to repurpose the buss buttons, testing out different op amps, toying with the eq, etc.
 

mjrippe

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I don't know the Teac modules personally, but they might be a nice midpoint between too simple (Gates) and too complex (ADM).
 

MidnightArrakis

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HEY!!! Perhaps I may be able to help you out in one way or another!!! My expertise is in the designing of electronic equipment by only working with finished schematics!!! In addition, I am also pretty good at taking circuit boards and then do a "Reverse-Engineer" project on them so they can be replicated as "new" again!!! I have done that already with some API circuit boards for a guy in Florida that was restoring a 1974 API mixing console and I have also done that for a defense contractor who needed some "new" circuit boards that were originally hand-designed in 1979!!! And, believe it or not, these "ancient" PCB's were for use inside of > fighter jets!!! < I thought that that was pretty cool!!!

I myself had an opportunity once to purchase a pair of "bare and unpopulated" circuit boards of the ALLISON Research "Gain-Brain" compressor/limiter. I "Reverse-Engineered" the bare PCB so I had my own set of artwork films and I then had a dozen new PCB's fabricated so I could create a bunch of "Stereo Gain-Brains" in a 1U rack-chassis. I even have one sitting just behind my left-shoulder here as I write this message!!!

If you are looking to have and/or use a bunch of the GATES M-6034 preamps, I took a look at that PCB and I could easily replicate that for you. So, if you buy one and send it to me, I can then provide you with all of the data files you would need to fabricate a couple of dozen or a couple of hundred of them!!! Not only that, but similar to what I had done for the 1979 PCB for the defense contractor, not only did I "Reverse Engineer" the PCB, but I had also - converted - all of the "Thru-Hole" components to "Surface-Mount" types, which could open up a whole new world on what you are looking to do. Take a look at this link to see some of my equipment designs:

Some Of My Equipment & Systems Designs

By "Re-Engineering" the GATES M-6034 preamp, I could at least fit 8-channels or maybe even 16-channels, into a 1U rack-chassis. A 2U chassis max!!! There are a bunch of choices for power-supplies to select from, but the main criteria will be what your total load current will be. And, that will depend upon how you end up packaging or using the circuit cards in your system. Not only that, but as an example (i.e. "food for thought"), if I were to "Reverse-Engineer" the GATES M-6034 card which would provide me with its basic schematic and components data, I could then design a - single - large PCB which would not only contain all 8 or 16-channels of preamps, but also their power-supply, any LED's, gain controls and everything else all in a 1U rack-chassis!!! Do you see where I am going with this? I could even design this to be a "kit" that you would assemble yourself, if that is what you are looking to accomplish!!! Cool, huh?

Anyway.....this is my 2-cents worth!!!

JBW

/
 

Whoops

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I have 2 ADM modules for sale,
a Mic input module (input transformer, discreet opamp and output transformer) and also an EQ module.

Send me a message if you're interested
 

heatwalk

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Oct 17, 2020
Messages
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Thanks for the offers guys. After giving it more thought I ended up going with the Teac to try out. Thats a pretty generous offer JBW but a little above what I'm trying to get myself into as I start out but I don't doubt it would be a really cool project. Your other work looks really impressive.
 

MidnightArrakis

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Sep 25, 2015
Messages
106
I racked a pair of similar Gates cards many years ago (GATES Discrete Microphone Preamps). Mine had output transformers though. Sounded good, simple, easy to understand.

I also just sold my ADM preamp and eq to a member here as raw modules. They really do sound nice and are high quality (Grayhill switches, transformers, DOA in the preamp, etc.). More complex power requirements and lots of connections you may or may not use!

There are plenty of plans for power supplies around, or just build off the datasheets for linear regulator supplies.
Would you happen to know the - entire and exact - Part Number of the audio input transformer (i.e. 814-????)? If possible, could you take some photos of the transformer "all of the way around" the unit in order to capture all of the printed details on it? THANKS!!!

Based upon what "Heatwalk" was looking to do, I went ahead and contacted TRIAD Magnetics about this transformer and ended up communicating with the president of TRIAD!!! WOW!!! I certainly wasn't expecting THAT!!! Anyway, I forwarded to him whatever online photos of this GATES M-6034 preamp card I could find and he put his Tech Support people onto tracking down this ancient transformer. Long story short.....the Tech Support got back with me letting me know that they had no record of that transformer!!! To say the least, I was rather shocked to hear that as I would have thought product information like that would be certainly archived on some kind of corporate level. But, no.....

In any case, I was told that the company needs to see - all - of the information printed around and on the transformer in order for them to know what direction to go in looking for this transformer in their back records. And....."YES!!!", I did mention the "GATES Radio M-6034" mic-preamp card and any other information that I could come up with that I felt would be useful to them.

Let me know, OK??? THANKS!!!

JBW

/
 

mjrippe

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Hi JBW,

I no longer have those preamps, so photos are not possible. However the attached document has a Gates part number in the parts list and another number on the schematic. Perhaps that will help?

Mike
 

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  • GATES - M6034 Mic Pre-Amplifier Manual.pdf
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MidnightArrakis

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Messages
106
Hi JBW,

I no longer have those preamps, so photos are not possible. However the attached document has a Gates part number in the parts list and another number on the schematic. Perhaps that will help?

Mike
THANKS!!! I will forward your document to TRIAD and see if it will help them in any way, but I am certainly NOT going to hold my breath!!! There just isn't enough readable information in Heatwalk's photos to discern what the exact P/N is for the transformer and the GATES P/N in the document is of no value.

I guess this is yet another instance to chalk up to "Another Mystery Of Life" and hope that one day it can be solved. THANKS!!!

JBW

/
 

mjrippe

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Messages
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THANKS!!! I will forward your document to TRIAD and see if it will help them in any way, but I am certainly NOT going to hold my breath!!! There just isn't enough readable information in Heatwalk's photos to discern what the exact P/N is for the transformer and the GATES P/N in the document is of no value.

I guess this is yet another instance to chalk up to "Another Mystery Of Life" and hope that one day it can be solved. THANKS!!!

JBW

/
I found some more pics on my drive. Gates 814-3486-001, Triad/Utrad 4824, date code 7044.
 

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  • Gates 814-3486a.jpg
    Gates 814-3486a.jpg
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  • Gates 814-3486b.jpg
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MidnightArrakis

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And this is where I got the photos from - an ebay seller who still has this piece for sale!
THANKS!!! I will forward your photos to TRIAD Transformers and see if they are of any help in identifying these old transformers. THANKS AGAIN!!!

JBW

/
 

mjrippe

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THANKS!!! I will forward your photos to TRIAD Transformers and see if they are of any help in identifying these old transformers. THANKS AGAIN!!!

JBW

/
You are welcome! It is not my item on ebay, but at that price you could even purchase it and send it to Triad so they could reverse-engineer it.

Mike
 

MidnightArrakis

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Messages
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You are welcome! It is not my item on ebay, but at that price you could even purchase it and send it to Triad so they could reverse-engineer it.

Mike
THANKS, AGAIN!!! -- I downloaded some of the other photos that seemed to offer various tidbits of information about the transformer and.....for some God unknown reason.....I also went ahead and placed a bid on the damn thing!!! So, I guess that I'll just have to "wait and see" what happens there. THANKS!!!
 
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