[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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    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 MLP Vendor V.I.P. Member

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    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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    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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    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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