Shure M67... gut it?

Hi Gang,
Just came across a freebie today in my travels, a Shure M67 mixer. I know people have cited them as useful and utilitarian, but I'm wondering what to do with mine. I gave it a quick go over and only channel 3 seems to be working right. Should I bother with fixing up the other channels, should I just leave it as is and use it when I need something trashy? Or should I just gut the damn thing and use the input tx's and vu meter elsewheres. Those input tx's don't look to impressive, they look rather like what's on the inside of a sm57. But if there's something I can do with them, I will. Maybe this would be a good time to jam together some of those Hampton jfet circuits and put the trashy tx on the front for kicks. Ideas?

Do you have a circuit for it? Or even some pics of the inside? Some of the 'crap' Shure mixers Ive seen have a cool looking transistor circuit running on pretty high rails that would probably sound good. Forget about how the transformers look, plug in and see what they sound like. You might need to recap it but show us some pics anyway...


M

[quote author="jrd"]Hi Gang,
Just came across a freebie today in my travels, a Shure M67 mixer. I know people have cited them as useful and utilitarian, but I'm wondering what to do with mine. I gave it a quick go over and only channel 3 seems to be working right. Should I bother with fixing up the other channels, should I just leave it as is and use it when I need something trashy? Or should I just gut the damn thing and use the input tx's and vu meter elsewheres. Those input tx's don't look to impressive, they look rather like what's on the inside of a sm57. But if there's something I can do with them, I will. Maybe this would be a good time to jam together some of those Hampton jfet circuits and put the trashy tx on the front for kicks. Ideas?[/quote]

The input trannies are just as unimpressive as they look. You might try turning them backwards and using them for DIs, though. And the VU meter is a real one, with the right ballistics.

The amplifier circuits are cheesy as hell, and overload if you look at them crooked.

Peace,
Paul

Just in case anyone was curious, some pics.

http://groupdiy.twin-x.com/thumbnails.php?album=137

These tx's look uninspiring. The VU meter is nice, and I think those knobs would look great for an 1176... It's days intact are numbered.

Ok, this isnt like the other ones ive seen!



M

Hey Paul, have you ever used those input xfmrs in another circuit besides the Shure? I'm just curious. I stripped the input xfmrs off a bunch of RCA-branded M67s before they went to the dumpster. I swept one on the bench with 200-ohm source/500k load and the frequency response was decent, but I haven't gotten 'round to trying them in an actual preamp circuit yet. I do recall that the saturation level at 20Hz was pretty low (something like 200 or 250mV).

JRD's photos show open cans on the input xfmrs on his M67. The M67s I stripped had covers on the bottoms of the cans, and at least one of the mixers had much different-looking cans (shorter and wider, and of cast material instead of sheet).

Yo Dave,
In case you missed it, you inspired me to throw together a BC-2B prototype.. there's pics in my photobucket thing, and a thread buried here somewhere. Should I bother with the adjustable gain modifications you proposed for the circuit once, or should I just jam one of your bridged-tees on the back end of it and call it a day?... I'm thinking my input tx is so beefy that an output attenuator might be all need?......

[quote author="NewYorkDave"]Hey Paul, have you ever used those input xfmrs in another circuit besides the Shure? I'm just curious. I stripped the input xfmrs off a bunch of RCA-branded M67s before they went to the dumpster. I swept one on the bench with 200-ohm source/500k load and the frequency response was decent, but I haven't gotten 'round to trying them in an actual preamp circuit yet. I do recall that the saturation level at 20Hz was pretty low (something like 200 or 250mV).[/quote]

No; I've looked inside several M67s but they weren't mine, so I couldn't strip things out. The low-frequency saturation level was indeed the deal-breaker when they were in the M67 -- of course, the preamp circuits were saturating too.

Peace,
Paul