Tube Playback, Recording Amplifier for Reel Tape Recorder

I am engaged in the restoration of "Electronics 004", the Russian clone of the Revox A-700. Wonderful mechanics, and not very successful sound circuitry. I am looking for a circuit on the lamps of a playback amplifier, recording amplifier for playback at a speed of 15 ips, 2 tracks, with correction of NAB and CCIR. There is a set of heads from Revox A-77.
I think to make a separate unit, so there are no restrictions on the lamps and dimensions. In the playback amplifier, I think to use a pentode at the input. Type EF86, 6AU6 .. for example, the output is either a pentode in the triode mode of type EL84, or a triode, for example 6N6P. But I don’t have an understanding of the recording amplifier yet.
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I have a book at father's book called "Grabadores de cinta" (Tape recorders) from a well known engineer here in Argentina, Julio Rueda. I can scan or photograph some pages of the book for you, but the text is in Spanish. Although the formulaes are understandables. But, for legal issues I will not post them here. Send me an email to lw1dseATgmailDOTcom or lw1dseATyahooDOT com, and the next week I possibly are sending this stuff. Unfortunatelly the book isn't available in the net.


Paid Member
2003-06-12 7:04 pm
Maine USA


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I found this, an old scanned article. here you have an example:

Thank you very much)

However, to me the playback amplifier of the G36 doesn´t sound very good. But what do you expect from three ECC83 in row ;)

I absolutely agree with you.

The playback amplifier for the tape recorder is essentially the same RIAA corrector. Accordingly, with the recalculated correction. The next question is matching the Revox A-77 playback head with a playback amplifier.
I do not have enough knowledge and information to do this myself. Electronics is a pleasant hobby for me.
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I built my own playback amplifier in exact the same way by using a good RIAA stage and changing the time constants. Just changed the triode input stage to EF86 pentode.

Using also an A77 playback head in my G36 I´m getting exactly the frequency response I wanted.

The A77 head does the same as the G36 head. Just 6dB less output voltage.

Best regards,