DIY MC Step Up Transformer

specialidiot

Break Glass, Smoke Lucky
I've been curious about moving coil cartridges, and when the PX-3 I bought a couple of months back came with one, I started getting serious about it.

I came across several projects involving Altec microphone transformers, seems that they are a great fit if you wire them up "backwards", so I watched ebay until I found the pair that I wanted.

Here's a site I like a lot, and the schematic shown as well as several examples of other transformers are shown: http://members.myactv.net/~je2a3/mic-mcstep-up.htm

Here are the parts involved, first the chassis, perf board, 8 pin sockets and RCA jacks.
stepup1.jpg


Here's the pair of Altec 15095-A transformers
stepup2.jpg


The ugly side, all wired up.
stepup3.jpg


And the completed project. I totally horked up the cover so I'm going to fab one out of flat plastic and apply some veneer to it one of these days.
stepup4.jpg


And it works perfectly. I have my Yamaha MC-705 dialed in and playing my Pink Floyd DSOM 30th Anniversary disc right now.
 
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Very nice! :thmbsp:

Have you got a ground lug on that thing?

I'll have to shoot some pics of the one I built... :D
 
Here's the one I put together. Funny that we ended up using the same enclosure, huh? :D

I haven't had a chance to test it yet - the cart I got won't physically fit on my stupid Linn Akito arm! So I'm building a tonearm from things I find around the house.

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It's a Vampire lug, I got it from Parts Connexion but I bet you could find it elsewhere, too.
 
Inspirational work here! :thmbsp:

I started getting seriously interested in these things just some weeks ago, after getting the GT-2000 TT and finding an AT-33ML/OCC MC cart to use on it. Since then, I've been looking at every microphone and mic-related device I see in the government surplus place in recent visits, hoping to find some good mic transformers to use in just such a project. I have an okay Denon SUT to use in the meantime, but hope to improve on it by using one the "famed" vintage microphone transformers. I might eventually just buy the transformers online, but I'm giving myself some time to try to 'score' a pair, first.

I wish I had known about this use for these transformers, twenty years ago. I'm sure I could have picked up a number of them by now, for relative peanuts. Oh, well...better late than never, and they aren't really that expensive, considering what they do and how rare they have become.

Thanks again for showing those pics. It's motivational!
 
Thanks Arkay. This was a nice little project for a rainy afternoon.

And you are right about their value as a DIY project. I've found commercial versions at 6 to 10 times what I've put into mine. I'm fairly impressed by the Yammie MC-705, so now I'm wondering what else is out there.....
 
Very nice work here, guys:music:

Your workmanship is superb. In fact more 'pro' inside and outside than the vintage Nagatron "Z-coupler" shown below. This one went 'dead' about two weeks ago. When I opened it, I found loose wires hanging without solder from the rca's tags:scratch2: I re-soldered them and all is OK again.

I have some active dc step up devices but I love my SUTs.

tripod
 
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Nice work, Jeff and Nate. Jeff, I'll be machining some aluminum in the next week. If you want a cover made, give me a shout.
 
Damn, you guys are inspiriing!!

I had to do the same thing, but my trannys are still sitting loose in a rat's nest of wires. Sounds fine, looks like crap :D

One thing I've been messing with is that my trannys have an option for dual impedance inputs and I'm trying to figure out how to wire a switch to take advantage of that. That ans the fact that the pins on them are about 1/8" long and as big as cartridge pins, which is why there's headshell wires connecting them. I took a pic, but it turned out fuzzy; too dark behind the amps. I'll reshoot it later.

Here's the wiring of the output schematics. Maybe you guys can help me figure out how to wire a switch??

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Nice work, Jeff and Nate. Jeff, I'll be machining some aluminum in the next week. If you want a cover made, give me a shout.
Hey Lance, you may have just opened a can of worms... I'll have to talk to you sometime about what you can do.
 
Very nice work here, guys:music:

Your workmanship is superb. In fact more 'pro' inside and outside than the vintage Nagatron "Z-coupler" shown below. This one went 'dead' about two weeks ago. When I opened it, I found loose wires hanging without solder from the rca's tags:scratch2: I re-soldered them and all is OK again.

I have some active dc step up devices but I love my SUTs.

tripod
That's a good-looking device there, tripod. Nice that you were able to resurrect it. :yes:
 
Here's the wiring of the output schematics. Maybe you guys can help me figure out how to wire a switch??

Check out the JE Labs link in my OP, there's an example for switchable impedance.

I didn't have the link there when I first posted, I thought I should include it because its full of info.
 
Nice work Jeff.

These Altec transformers make great step-ups in the right surroundings - my favorite low-cost way to do this.
 
Nice work Jeff.

These Altec transformers make great step-ups in the right surroundings - my favorite low-cost way to do this.

Thank you sir, I'm looking forward to the MC world!

No problem, Nate. BTW, I have a couple of things for you.

Sounds good, if you don't have my Email addy, send me a PM.

I have your addy.... I need to get this sketched out and scanned for you.

Thanks!
 
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