Running an instrument through a turntable?

Discussion in 'Miscellaneous [BG]' started by Electricblue, Nov 23, 2013.

  1. Electricblue


    Feb 1, 2011
    Hi all! I picked up an old suitcase turntable from work, and I'm trying to run my guitar through it with no success.

    So far, I've removed everything I don't need so I'm left with the valvey gubbins, pots and a speaker. I cut the cables from the cartridge/needle and prodded the + with my finger and no buzzing is heard. Is there something I'm missing?

    This is the closest I can find on the internet:

  2. Do people do this or are you trying to recreate a dream here?
  3. FunkHead

    FunkHead Supporting Member

    Mar 10, 2007
    Stewartsville, NJ
    Have you tried connecting a guitar to it? It's two wires right? I would think that you should get some sound.
  4. look up RIAA equalization and you will find all turntables have a special EQ curve that limits its usefulness as a guitar amp. Have fun tinkering though it should be good for practicing (both the bass and electronics)

    You might need an active bass or a small pre-amp to match levels with the phonographs amplifier inputs.
  5. Fergie Fulton

    Fergie Fulton Gold Supporting Member

    Nov 22, 2008
    Retrovibe Artist rota
    If in working order you just strip out the two wire from the arm to the needle, expose the ends. Then take an old guitar lead cut of one end expose the wires. Then just twist then on to the exposed arm wires and all should work. Thats how i used to practice till i soldered an old female jack into it so i could practice with the record..
    The female socket just connected in to where i traced the arm wires back to,

    Problems are output valves and controlling the output, other than the input...expect blown speakers....thats why i gave up on mine in the end....well i say gave up...i got my a## kicked for breaking it and not allowed to use it when it got repaired.:)
  6. Electricblue


    Feb 1, 2011
    Well, I tried running a portable cd player's line out into the 2 wires, but nothing at all comes out. Both the vacuum tubes light up, and I can hear a slight crackle from the speaker sometimes but that's it.
  7. Unrepresented

    Unrepresented Something Borderline Offensive

    Jul 1, 2006
    San Diego, CA
    These are also the recommended steps for hot wiring any 1975-1982 Chrysler products.:|
  8. Did it function as a turntable before?
  9. Electricblue


    Feb 1, 2011
    I didn't test it as I didn't have any records to use. I couldn't resist pulling it apart :D I got it for a guitar amp project in the first place so I didn't give it a thought :atoz:
  10. bkbirge


    Jun 25, 2000
    Houston, TX
    Endorsing Artist: Steak n Shake
    I'd caution against messing around with this unless you know what you are doing. There is some lethal voltage/current associated with amps, tube or not.
  11. ahc


    Jul 31, 2009
    No. Virginia
    Back in the days of old (we're talkin 50 years ago) I did this. Same as Fergie Fulton did with the wires. If your "record player" / "phonograph" is working, this should work. A few years later I also "experimented" with using an RCA cartridge tape recorder as a preamp into my Ampeg BT-140 on a few gigs. That worked too, but didn't do much. :)

    To test the phonograph without a record, hook the stylus back up and run it over your finger. If it works, you'll hear a "brrraaaap" sorta sound. If you don't, the unit's not functional.
  12. Electricblue


    Feb 1, 2011
    I don't know if I'd want to plug my Strat in until I know it's safe :cool: the "ground" of the amp is actually neutral (blue wire in UK) so there's a good chance I would get cooked if it was faulty. There's no earth wire at all.


    Surely if the cd player didn't drive it, then my guitar wouldn't either?
  13. ahc


    Jul 31, 2009
    No. Virginia
    Well, we're past my pay grade now. The "finger test" would let you know if the unit works and shouldn't fry you. I'm saying to run your finger across the needle with the cartridge hooked up.
  14. This may very well be a "hot chassis" design. If that's the case. extreme caution is in order. Electrocution is a very real "hot chassis radio" for a further explanation.

    So aside from that issue, what we've got is an old record player with tubes in it. So people see a device with tubes and they go "aha! guitar amps have tubes! I can have me a guitar amp here! I'll just somehow connect a guitar and have the Tube Tone of the Gods!"

    Well, there's a couple of problems. First, a very old electronic device, like a 50+ year old record player, has some components that are very likely toast by now. Specifically, electrolytic capacitors; they dry up and fail, sometimes taking out other vital components with them when they are fired up. So before anything further is done, those components would require replacement--just to make a working record player.

    The second problem, though, is that this is a portable record player. Made to spin records and reproduce the sound from a stylus/cartridge, with limited volume, not to amplify a guitar signal. The functions are somewhat similar but yet very different. The EQ is going to be different. The internal speaker is going to be pretty poor for guitar use. And let's not forget the hot-chassis issue, if it is a hot chassis.

    I don't intend to throw a wet blanket on the fires of enthusiasm, but we've got to be realistic at the same time. Some knowledge of electronics and electronic repair will be required to get this into a usable guitar amp. It's possible, but here's what would be needed IMO:

    1) Get a schematic for what you've got. Figure out what all the components are that are shown on the schematic and get a idea what they do. You don't need a PhD-level understanding but you've got to know what a capacitor is and what it does, what a transformer is, etc.

    2) Compare your schematic to some of the simple guitar amps, like the Fender Champ or some of the simple Kalamazoo amps. Find one that's really close to what you've got.

    3) Now take what you've got and make it like the amp you've picked. You've got to replace electrolytic caps anyways, so make the power supply similar. Plate resistors should probably be changed, make them like your new design. Coupling caps probably require changing, so make them like your new design. Stick in a volume pot and tone pot like your chosen design.

    4) If it's a hot chassis, buy an isolation transformer for it.
  15. Tupac


    May 5, 2011
    I wish I knew jack **** about electronics.
  16. Hi.

    Good luck and be safe.

  17. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    I must agree - before trying to use it for another purpose, it would be prudent to make sure that it works at all and not assume it.

    The RIAA curve mentioned above boosts the highs when recording and cuts them on playback, so even if it worked, the sound will be very muddy.

    Just don't go poking around inside the tube amp. It is likely very cheap design and could have dangerous voltages in unexpected places.
  18. Electricblue


    Feb 1, 2011
    Well the whole chassis is connected to Neutral of the mains input, and that doesn't really give my much confidence. Maybe I should admit defeat then?
  19. A non earthed chassis is potentially lethal, by far the safest thing to do is to take it for recycling.