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Radioshack Audio Output Transformer

Discussion in 'Pickups & Electronics [BG]' started by Omnipharious, Jan 6, 2012.

  1. So, I was going through some slightly old stuff from a person's house that they didn't want, the only real stuff I was interested in was a small toolbox with a bunch of junk in it- caps, resistors, and all that fun stuff- and I found one of these. RadioShack® Audio Output Transformer - RadioShack.com

    I'm sure that's what it is, because I was in Radioshack just a week prior to seeing it in the box, and it is exactly the same, and it's the same thing as on the site. A few years ago I remember seeing a thread on some other guitar/bass/circuitry type site about using one of these as a tone choke, but after hours of searching, I can't find it.

    Looking at it sitting on the flat casing, wires sticking up, from left to right on one side is a green, black, then blue wire; on the other side is a red wire on the left, nothing in the middle position, and a white on the right. Could I use this as a tone choke like on an EB-3 or such? I don't know much about transformers, and inductors and all that mumbo-jumbo, so you'll have to talk simple to me if you want to help.
  2. You would want to use a regular inductor for that.

    A transformer is multiple inductors coupled together, and in this case, nothing is known of the inductance. The only known specs are input and output impedance.
  3. Even if the values aren't known, is there a way of finding out which wires do what? Say, if I just wanted to put it in line and see what effect it had, could you tell me what wires to put where, or would I have to find out what is connected to what myself?
  4. Just use an Ohm meter to determine the primary and secondary windings.
  5. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Yes, you can use these for inductors in Varitone circuits. You want to use the primary, which is the higher resistance side (1K).

    There are better transformers to use, but these work OK.
  6. I'm not sure which side is the primary, but these were my readings. And I am a bit ignorant when it comes to reading ohmage, but I did look up a few things on how to read ohmage, and I got that there was zero resistance between the white and red wires, there was thirty ohms between either black and blue, or black and green, and there was sixty ohms between green and blue.
  7. BogeyBass

    BogeyBass Suspended

    Sep 14, 2010
    yep you found the input, the input side is three wires
    Blue Black Green

    Blue ,green is the input and black is center tap
    the DC resistance will be 70 ohms +/- 20%

    Output is 2 wires Red, White
    DC resistance .62 ohms +/- 20%

    the AC impedance at 1khz and 1volt is
    input 1K
    output 8ohms

    the freq response is about 300 to 10,000hz
  8. +1.

    If you want, you can try using the primary winding at it's center tap, to see what that does.
  9. Okay, I'm glad to see I could get such a simple thing right at least :)p), but how exactly would I do that? Wire it in place of a capacitor?
  10. BogeyBass

    BogeyBass Suspended

    Sep 14, 2010
    A couple of cool circuits floating around using that transformer

    I did a google search for radio shack audio transformer circuits

    and got a few things like am transmitters, voltage multipliers, audio line converters etc. spend some time fishing around.

    I think if you had 2 of them you could make a passive ring modulator. you have to use very low forward voltage diodes like germanium radio detector diodes.

    the coolest thing maybe would be a diy wah pedal, I thought I remember seeing that, and looked for it because they gave the value of the primary in inductance for the shack transformer.

    so connecting the blue green wires would give you close to 500mH inductor. Check here scroll down to "Building a Wah from Scratch" for more info and pics

    otherwise a basic filter can be made with a inductor and capacitor. Do a search for LC filter you should find something.
    for a tone circuit that rolls of the highs, search for
    LC low pass filter or Simple RC low pass filter

    its good to know the math to calculate but im sure their is many
    LC filter calculators floating around the net.

    V this is a basic first order or single pole lowpass LC filter


    if you dont know or understand the electrical symbols then use this
  11. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Here's a Varitone circuit using an inductor. It will be far more interesting than the LP filter.


    If you want to keep it simple, just use one cap, and you can use a pot instead of a switch like they did in the Gibson Ripper.


    It's the center control with the .1 µF cap, wired up like a tone control with the inductor between the cap and ground. That will give you a passive mid cut tone control. You can change caps to get different tones.
  12. I must be doing something wrong then. I only somewhat well understand what you're telling me, so I probably am. I kept the cap on the right lug of the pot, and connected the other leg of the cap to the green wire of the transformer, and the blue wire to the ground, and it sounded no different from how the cap sounded normally. I tried switching either of those wires with the black wire, I tried putting the transformer before the cap, and neither sounded different. I tried changing the cap, and doing all of those things with a few different caps, and the transformer still didn't seem to change the playing tone (it did seem like it made a bit of hum go away, but I forgot to reground the bridge when I put it back together this last time anyway, so there was a lot of hum to begin with).
  13. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
  14. Okay, I might in the future. I have been looking around, I wanted to try doing something very complicated, with a lot of controls, but I am way in over my head for this circuitry thing. I had already planned to go to school for it, but now I'm sticking to simple stuff until I learn some theory. I really just wanted to hear how it sounded, since I already had it, I didn't think the bass it was going in had too much midrange or anything.

    Thanks for all your help anyway guys, at least I learned a little bit.

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