Old Shure Mic Mixers I got for 20 bucks

hereonmars

hereonmars

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Howdy,

A while back, a guy had a few of these listed and let me take them all for 20 bucks. I figured there may be some sort of cool project I could use them for, and 20 bucks wasn't a lot. Maybe some sort of analog summing or vintage-y mic pre type of project? I did some searching around and couldn't find much, other than people just saying they're "meh." In the end, I may just recycle them if the juice ain't worth the squeeze.

I attached the user guide with schematic from Shure.
 

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Probably some useful parts if you're into keeping junk around and scrounging parts.

If not, I'd pay shipping if you want to send em to my house!

Definitely try them for yourself before you chuck em. The internet says pretty much all my gear is trash, and I still manage to have a lot of fun with it.
 
It is totally a vibe mic pre, have used them a number of times, bought and sold a couple of them. Needs to be the right source/song for it. Did doubled vocals for an alternative rock song through it, really dirtied them up and filled it out. Let me see if I can find the song, it was done pre-streaming and not sure it has been uploaded.
 
Cascade two inputs to 1 output for a variable dirt pre. Curious the trace/wire and pull the signal off of the channel 1 gain pot(1 or 3, whichever isn't going to ground) and feed it back to the input of channel 2 transformer(yellow green(to ground)).
Do the same thing for channels 3-4.
You should be able to drive it to carrying degrees of dirt, depending on the two gain pot positions, hopefully saturating the cheap transformers some. You could probably add some switched clipping diodes to channels 2 and 4 of you want.

You could repurpose a transformer and take the output of stage two through a transformer and install an out XLR at the former channel 2 input. Note that they use the same transformer but inverted for output.
Steal a transformer from another unit and repurpose T5 and you can have a stereo pre. Or try one of the 42MT mouser transformers . Note, that should be mic to instrument level out, depending on which side of the output transformer you use. So you'll likely need some more gain down the line. The "high" out is supposed to be line level-ish. These were meant to combine 4 mics down to one XLR level for input into another mixers mic in.

There's a lot of things that could be done to turn these into a little dirt supplier.

Everything after the gain trimmer is the summing amp. It's just a single gain stage for the mic amp.
 
Erik S said:
Probably some useful parts if you're into keeping junk around and scrounging parts.

If not, I'd pay shipping if you want to send em to my house!

Definitely try them for yourself before you chuck em. The internet says pretty much all my gear is trash, and I still manage to have a lot of fun with it.
Click to expand...
I will let you know! I'll get them out and mess around with them. I have 4, I know I definitely don't need that many.
 
CheapSuitG said:
It is totally a vibe mic pre, have used them a number of times, bought and sold a couple of them. Needs to be the right source/song for it. Did doubled vocals for an alternative rock song through it, really dirtied them up and filled it out. Let me see if I can find the song, it was done pre-streaming and not sure it has been uploaded.
Click to expand...
awesome, thank you. I would love to hear it.
 
jwin615 said:
Cascade two inputs to 1 output for a variable dirt pre. Curious the trace/wire and pull the signal off of the channel 1 gain pot(1 or 3, whichever isn't going to ground) and feed it back to the input of channel 2 transformer(yellow green(to ground)).
Do the same thing for channels 3-4.
You should be able to drive it to carrying degrees of dirt, depending on the two gain pot positions, hopefully saturating the cheap transformers some. You could probably add some switched clipping diodes to channels 2 and 4 of you want.

You could repurpose a transformer and take the output of stage two through a transformer and install an out XLR at the former channel 2 input. Note that they use the same transformer but inverted for output.
Steal a transformer from another unit and repurpose T5 and you can have a stereo pre. Or try one of the 42MT mouser transformers . Note, that should be mic to instrument level out, depending on which side of the output transformer you use. So you'll likely need some more gain down the line. The "high" out is supposed to be line level-ish. These were meant to combine 4 mics down to one XLR level for input into another mixers mic in.

There's a lot of things that could be done to turn these into a little dirt supplier.

Everything after the gain trimmer is the summing amp. It's just a single gain stage for the mic amp.
Click to expand...
thank you! It's all above my head, but I can understand all of that!
 
Erik S said:
Probably some useful parts if you're into keeping junk around and scrounging parts.

If not, I'd pay shipping if you want to send em to my house!

Definitely try them for yourself before you chuck em. The internet says pretty much all my gear is trash, and I still manage to have a lot of fun with it.
Click to expand...
question for you and all, when you're plugging in an ancient piece of gear like this, do you take any precautions? Or is it pretty reasonable that it I won't get the crap shocked out of me? I don't even have it open, just plugging it in and gonna plug a mic into it, then run it into my interface to see if it makes sound.
 
hereonmars said:
thank you! It's all above my head, but I can understand all of that!
Click to expand...
Disclaimer being in have no idea how well that will work or how it will sound. But if I had $5iah invested in them, that's what I would try. At least at first glance. Also if I had one, I'd swap out C20 C21C22 for new caps and upping the voltage rating. Maybe add a 100n in parallel to C22.
Also. Check your DC voltages and make sure nothing is wacky.

You could also mod one where each of the 4 channels is different. Socket the Q1 transistor and try some Ge, maybe some hard clipping diodes thrown in around R20/21/22/23 on another channel. For clippers, you'll want to swap/bias the Q1 stage to get you a hot enough output to actually clip. I think between C9 and R20 would be ideal. C9 would block DC but you want to clip before the attenuation of R20. Even then, pretty low signal. Could squeeze a muffin crumb or lpb-1 and some clippers in there though. 11.8vdc should play pretty happy with simple transistor boosts
🤔 What if you put a different fuzz on 3 channels? You'll probably want to temper the output waaaay down of each fuzz circuit.
Is there room internally to mount 3 PCBs to the lid? IIRC, there's a decent amount of room in these. PPCB boards may be too big but if there's vertical clearance, I bet some of the smaller madbean and effectslayouts boards will fit.
Just spit balling.
 
hereonmars said:
question for you and all, when you're plugging in an ancient piece of gear like this, do you take any precautions? Or is it pretty reasonable that it I won't get the crap shocked out of me? I don't even have it open, just plugging it in and gonna plug a mic into it, then run it into my interface to see if it makes sound.
Click to expand...
First power up of ancient tube amps, there are some reasonable precautions to look into, but something like those mic mixers I’d just send it personally.

Maybe I’d pop the case open and look for obvious burnt, leaking, damaged components, but If the power cord seems to be intact I’d probably just plug it in and see what happens.
 
hereonmars said:
question for you and all, when you're plugging in an ancient piece of gear like this, do you take any precautions? Or is it pretty reasonable that it I won't get the crap shocked out of me? I don't even have it open, just plugging it in and gonna plug a mic into it, then run it into my interface to see if it makes sound.
Click to expand...
Take a look at C20-22 in particular
I wouldn't replace them regardless but if they're not visibly swollen/leaking, an initial power up should be fine. Worst case they pop.
You could turn the switch on and plug it in for a quarter second a couple of times if you want.
If the power cable isn't grounded, mide the little big spade
 
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