pucho812
Well-known member
Anyone know the mic input and the output transformers used in the ampex 351?
Looking for basic specs. Cj?
Looking for basic specs. Cj?
Ampex 351 transformers
- Thread starter pucho812
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Input xfmr is 1:14, and OT is described by Sowter as 5.55CT:1CT+1 or 15K/"600"+NFBpucho812 said:
Actually, the center tap on the main secondary is not strictly necessary, but the primary's is necessary because of the push-pull stage.
CJ
Well-known member
reading around on the net some people say that they used two inputs, a big one then a small Beyer that craps out at high level.
octal plug in with gold pins suggests Peerless, ratios might have been different, seeing 15: 1
someone suggests the UTC A-11 as a good substitute,
don't know about the output,
might have taken some 351 iron apart, hard to remember all the kills, got more meat on the plate as we speak,
octal plug in with gold pins suggests Peerless, ratios might have been different, seeing 15: 1
someone suggests the UTC A-11 as a good substitute,
don't know about the output,
might have taken some 351 iron apart, hard to remember all the kills, got more meat on the plate as we speak,
pucho812
Well-known member
Hmmmm. Food for thought
Adadan
Well-known member
I have a few 351 octal input transformers, generally two different part numbers, but both numbers have the same diagram on the side, showing a very typical dual primary, in series they call it "150-250 ohms," in parallel, they call it "30-50 ohms," and then a standard single secondary to grid. I haven't compared them, but 1:14 or 1:15 seems right.
Ampex definitely used Beyer inputs too, but I think for the super compact electronics, like the 354, PR-10, etc rather than 351?
I haven't removed the output transformers on mine, but I remembered reading that they measured with only so-so frequency response when tested without the feedback of the stock circuit. I'm not sure this is the link where I first read about it, but this is the first thing that came up from Google:
https://www.audioasylum.com/messages/tubediy/223149/ampex-351-output-transformer
By the way, Cinemag makes a repro of the output, too, and they describe it similar to Sowter, as 15k:600 plus tertiary. It's the CM-9600-T.
Ampex definitely used Beyer inputs too, but I think for the super compact electronics, like the 354, PR-10, etc rather than 351?
I haven't removed the output transformers on mine, but I remembered reading that they measured with only so-so frequency response when tested without the feedback of the stock circuit. I'm not sure this is the link where I first read about it, but this is the first thing that came up from Google:
https://www.audioasylum.com/messages/tubediy/223149/ampex-351-output-transformer
By the way, Cinemag makes a repro of the output, too, and they describe it similar to Sowter, as 15k:600 plus tertiary. It's the CM-9600-T.
