Can a 6x5 drive PP 6V6 guitar amp

Discussion in 'Glowing Bottle Tube Amp Forum' started by Still54, May 4, 2020.

  1. Still54

    Still54 TDPRI Member

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    Looking for advice as to whether a 6X5 can support the current draw of a push pull 6v6.

    I have this crazy vision to make something unusal with an old Packard 6V car radio and a power transformer that I pulled from a Webster Chicago 2010 reel to reel

    The Webster 2010 (schematic below) drove PP 6v6 with the 6x5 and the transformer that I have. But is 210v on the 6V6 plates going to be high enough for the guitar amp?

    The tubes for the amp will be (2)6v6 driven by a 6SQ7 PI, driven by a 6SK7 pentode preamp on channel 1 and a 6SQ7 triod Preamp on channel 2. This is the setup in the packard radio, and I think it would be cool with these tubes as a guitar amp. I calculate the Webster 2010 pulls 90ma HV for plates which is about what the guitar amp tube set would draw.

    0504201130.jpg
     
  2. Nandrewjackson

    Nandrewjackson TDPRI Member

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    Sure sounds like an interesting project. Seems like you've found your answer in the schematic that shows the combination of those preamp and power tubes. As for *how* to combine the 2, yikes. I wouldn't trust hardly any original component in an old tube car stereo, aside from transformers, and sockets. So with that in mind, I'd say a total scratch build.

    To literally incorporate the car radio chassis into a larger chassis and head box (or combo cabinet) does sound neat.

    Please keep us informed about any progress.
     
  3. dkevin

    dkevin Tele-Meister

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    Hmmmmm......
     

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  4. Wally

    Wally Telefied Ad Free Member

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    Dkevin, I knew I had seen a 6X5 in at least one amp that has crossed my path, but I could not bring that amp to mind. Good find.
     
  5. Dacious

    Dacious Poster Extraordinaire

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    My first 5E3 had a 6X4 which is the octal version. Borderline if I recall.

    You could run a pair. That would give enough current.
     
  6. zook

    zook Friend of Leo's

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    The 6X4 is a seven pin tube, a 6X5 is an octal
     
  7. Nickfl

    Nickfl Tele-Afflicted

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    The 6x5 datasheet says 70ma, which is kind of low for push pull 6v6. They also have a reputation for catastrophically shorting and killing PTs according to the radio forums. You could use backup diodes and fuses to protect it though.

    I think the real issue is the low plate voltage, 210v is real low for class AB 6v6 operation. I've never run push pull low like that, but IME, single ended gets unpleasant if its much below 300v so I would expect it to be an issue with push pull even more so.

    Looks like you've got a 220v HT winding, so you should be able to get 300v or so with a solid state rectifier. I'd do that and maybe base the amp on something with similar B+ from the early tweed era. A Harvard does pretty well at just over 300v.
     
  8. dkevin

    dkevin Tele-Meister

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    If you've ever heard or played through a Silvertone 1333, it has that low voltage grind. When I saw "6X5" I immediately thought of all the early Silvertone tweedish amps that use the 6X5.
     
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  9. Wally

    Wally Telefied Ad Free Member

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    Dkevin, I have owned one Md. 1333 and can support your observations...very rich ‘Lo res’ cleans and a great overdrive to my ear. The amp had original tubes in it and is still operating as far as I know. I recapped it and gave it proper service...great little Silvertone amp,imho.
     
  10. mndean

    mndean Tele-Meister

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    Yes, with a caveat. Those radios (Zenith mostly) did tend to drive the 6X5 hard. Also, there are later versions of the tube which don't seem to have the problem the original had (all scuttlebutt I picked up, I've never worked on one). I haven't heard of issues with the Silvertones, so I guess its a matter of whether anyone wants to take the chance or not. Never heard of issues with the mini 6X4, but it seems some are still afraid of it.
     
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