[Technical ?] Tube Phono amp Conversion

Discussion in 'The Squawk Box' started by bblooz, Nov 25, 2016.

  1. bblooz

    bblooz Senior Member

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    Oct 8, 2014
    This has been sitting in my project (s) pile for a while. I pulled an amp chassis out of an old (I'm guessing late '50s-early '60s phonograph record player with the thoughts of making a little combo amp someday. It has a 5Y3 rectifier, two el84 output tubes, two 12AX7s, a6AN8 and a 6AV6. It looks like the 12AX7s are the main pre-amp stage for the phono inputs, and a mic input going through the 6AV6, and the 6AN8 appears to handle the phase-inversion to the output stage. There are 4, and 8, ohm taps on the output transformer. There is a schematic, but it's on buff colored paper. I'll try to scan it and post a picture later.

    My question is, would this work for a guitar amp, and has anyone had experience doing this, and how did it work out?
  2. Soul Tramp

    Soul Tramp Speaker Snob V.I.P. Member MLP Vendor

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    Jul 19, 2012
    I've done things similar. You'll have an impedance mismatch between the guitar pickup and the phono input. As well, the tone stack won't be right.

    Best to design a new preamp.
  3. MooCheng

    MooCheng Senior Member

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    Sep 2, 2013
    the phono stage may have RIAA equalisation to compensate for the uneven frequency response of records, probably would need some tweeking to get a response curve useful for guitar
  4. Paragon

    Paragon Senior Member

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    Apr 10, 2008
    You can surely rework what you have there or start from scratch.. Lots of potential being able to handle 4 preamp tubes. I would think it would be best to rework it, assuming the transformers are good. You will want to change the 7-pin socket to a 9-pin and give you more flexibility (step drill bits work best for that - I got a cheap set from harbor freight.. just use some light oil or wd-40 and they work just fine)

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