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Old 17th April 2004, 08:12 PM   #11
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You're the one that brought up the output transformer without mentioning an input transformer.

So ... do you only design output transformers?

Sorry Frank. I'm just being nasty. I know full well what you were saying. I respect you for your ballz.
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Old 17th April 2004, 08:50 PM   #12
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You might want to check out this link:

http://recordist.com/ampex/apxschem.html

Scroll down to the MR-70 record/Play amplifier. There are also drawing s for 50 and 60 dB mic pre mods for theses things.

Its a highly regarded amplifier for R-R machines and I understand that one of the reasons its been becoming increasingly scares is its popularity as a mic Pre.

-Dave
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Old 18th April 2004, 06:07 AM   #13
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ChocolateMotor,

I agree that building a tube mic preamp is a bold endeavor, especially if you've never built a tube amp before, let alone a preamp. I started down that path myself and a couple of years went by before I had a solidly reliable unit.

Of course, there are easier paths -- if you can find a kit, that would be a great way to start. Definitely check out the Gyraf project. Also, for a copy of just about every mic preamp schematic known to human kind, you can go to Pat's Tube Schematics

And there's also a version of the Altec 1566 that I think you can buy in kit form.

Lastly, a guy named Greg Norman who works for Steve Albini's Electrical Audio studios here in Chicago modified the classic Ampex 350 electronics into mic preamps. The report is available here.

Hope that helps. Good luck!!

E. Lectreau
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Old 18th April 2004, 07:21 AM   #14
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Hello electronaut. I looked at "Pat's Tube Schematics", and although he beats his drum hard, I didn't see anything that made me think "gosh, that's clever, I'll have to try that". I'll probably be rained on for saying it, but most of the "engineers" in the music industry would be flummoxed by Kirchoff or Thevenin, let alone anything more complex.

Once Chocolatemotor gives some details of what he needs, we might be able to move on from mere speculation.
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Old 18th April 2004, 04:01 PM   #15
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Quote:
Originally posted by EC8010
Hello electronaut. I looked at "Pat's Tube Schematics", and although he beats his drum hard, I didn't see anything that made me think "gosh, that's clever, I'll have to try that". I'll probably be rained on for saying it, but most of the "engineers" in the music industry would be flummoxed by Kirchoff or Thevenin, let alone anything more complex.

Once Chocolatemotor gives some details of what he needs, we might be able to move on from mere speculation.
Well, I referred ChocolateMotor to Pat's Tube Schematics not because of how good or bad of an engineer Pat might be, but because he might be a good resource for schematics, especially if ChocolateMotor has a favorite preamp he might want to start with or something.

You are right about Pat beating his drum hard -- I guess I usually ignore those things and didn't take much notice, frankly.
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Old 19th April 2004, 01:21 AM   #16
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I think I can count on one hand the number of recording engineers I know of who are also Electrical Engineers. Perhaps on one finger (no not that one) because I donít think George Massenburg finished his degree. Tom Scholtz however may be the only MIT grad with more than one platinum album.

Likewise here at DIY we see some who are great EE and knowledgeable about audio as well as practitioners who also do a fine job.

I guess Im not to sure I understand what your getting at.

I posted this link:
http://recordist.com/ampex/apxschem.html
because it has virtually every schematic for Ampex tape rec/play amps.
I think the MR-70 was the tube RC amp for the AG-350.
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Old 19th April 2004, 11:01 PM   #17
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The MR 70 was the last vacuum tube model audio tape recorder Ampex made, and used nuvistors.
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Old 19th April 2004, 11:26 PM   #18
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Quote:
Originally posted by Da5id4Vz
I guess I'm not too sure I understand what you're getting at.
I don't have a problem with studio operators preferring one piece of kit over another. Microphones are certainly different, and you need to select the right tool for the job. What I do have a problem with is when they start thinking they can fiddle with the insides of electronics and make design choices without having any knowledge of the engineering involved. Those older designs were carefully thought through by chaps with slide rules. Admittedly, their designs can often be improved by substituting modern components, but only if you understand what the original designers were doing in the first place. Thus, I find a lot of modern non-engneering-based tub-thumping rather insulting.

EC8010: Grumpy dyed-in-the-wool engineer who has listened at both ends of the chain.
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Old 20th April 2004, 01:16 AM   #19
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Well Said.
Back in the old days when I was still in "the business" I found that moderate success was often built on image and attitude. The truly talented could make a living without such grand posturing.

Tub Thumping! Boy doesnít that say it well.

I suppose for my part I should go back and read the mans article to see what he's all about. After all I have declared myself an MR-70 fan.

-Dave
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Old 20th April 2004, 01:48 AM   #20
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Quote:
Originally posted by thoriated
The MR 70 was the last vacuum tube model audio tape recorder Ampex made, and used nuvistors.
Yes, I noticed that (6CW7). And as they're so small, it just cries out to be hung from the back of the microphone - allowing sensible signals to travel to the desk.

Will we ever hear from Chocolatemotor?
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