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Thread: Buying and inductor to make a varitone

  1. #1
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    Buying and inductor to make a varitone

    Hi everybody!!!

    Just a little question. Could anybody tell me where I can buy and inductor to build a varitone?

    Thanks a lot in advance.

    Iván

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    I don't know the value of the vari-tone inductor, but Torres Engineering offers a vari-tone kit for $15.95. If the inductor you need is a 1.5 henri, you can get it for $4.95 with the "Torres Famous Midrange Kit". If you find a better source for these, would you please post it?

  3. #3
    Pickup Maker David Schwab's Avatar
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    You can get inductors from any electronics part suppliers, like mouser, digikey, jameco, etc.

    You can also use audio transformers. The one from RadioShack works ok.
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein

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    Found one

    Hi,

    Thanks a lot for your help. I found this one in Mouser (I believe is the one Dan Torres uses to build his varitones):

    42TL021

    Will that be fine? The thing has six legs...to be honest I don´t know what to do with so many of them. Has any of you any idea of how to connect this?

    Thanks,

    Iván

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    The data sheet is on the link you provided. There is a center tapped primary, and a center tapped secondary. Either use the entire primary, or the entire secondary, and never mind the center taps.

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    Quote Originally Posted by ivanmax View Post
    Hi,

    Thanks a lot for your help. I found this one in Mouser (I believe is the one Dan Torres uses to build his varitones):

    42TL021

    Will that be fine? The thing has six legs...to be honest I don´t know what to do with so many of them. Has any of you any idea of how to connect this?

    Thanks,

    Iván
    That transformer has a 3:1 turns ratio; thus, the inductance of the secondary is 1/9 that of the primary. Using half the primary would give you 1/4 the inductance of the whole primary. The inductance of the whole primary is probably about 1 Henry. I am just guessing that based on the 300 Hz low frequency spec and the primary impedance (4K). Probably you want to use the whole primary.

  7. #7
    Pickup Maker David Schwab's Avatar
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    In the book Electronics Projects for Musicians, Craig Anderton uses Mouser part 42TM-019 for the inductor. He uses the whole primary, and also has a switch at the tap for half the primary.

    The inductor in the Gibson L6-S was a 1/4" steel bolt, with three washer and a nut! They wound two coils between the washers so it was humbucking.

    I have the specs around somewhere, but it isn't hard to make.
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein

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    Although I've used these things for years, my understanding of them is a little foggy. If I were using a 1.5h inductor, a .033uf capacitor, and a 250k pot, which component (or combination thereof) would determine the frequency of the cut? Which would determine the depth? I don't have a strong background in math. If someone could explain it in layman's terms it would be greatly appreciated.

  9. #9
    Pickup Maker David Schwab's Avatar
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    I found this one on the 'net somewhere. This is for a standard Gibson 6-position Varitone:

    Position 1--> off
    Position 2--> -5db at 1950hz
    Position 3--> -12db at 1100hz
    Position 4--> -16db at 620hz
    Position 5--> -18.5db at 360hz
    Position 6--> -21db at 120hz

    Position 5 used a .03 cap.

    The L-6S guitar used a pot instead of a switch, and a .01 cap.
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein

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    Just bought a Torres one

    Hi,

    Well, I have just bought a Torres kit to make a varitone. When I got it I will post the value of the inductor here. Actually I believe he uses a small transformer.

    Regards and thanks,

    Iván

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    Old Timer RedHouse's Avatar
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    Quote Originally Posted by ivanmax View Post
    Hi,

    Well, I have just bought a Torres kit to make a varitone. When I got it I will post the value of the inductor here. Actually I believe he uses a small transformer.

    Regards and thanks,

    Iván
    So what did it turn out to be?

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    Transformer

    Hi,

    It is a small transformer with the following writing on its body:

    TL021-R

    You can find these ones in Mouser.

    Regards,

    Iván

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    I measured a Radio Shack miniature output transformer (10K/8ohms) and the primary came out to .8H @ 1KHz. At 120Hz = 2.1H. Obviously, it will vary with frequency, but for anything in the right range, the cap used with the inductor is the part to experiment with. I'm using this set-up with a Telecaster in the neck position, approximating the Varitone 'Position 4'.
    The middle position = neck only and the back = Broadcaster Blender (Lollar CC set). Cool, cool, cool.....

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    Quote Originally Posted by thumbs View Post
    Although I've used these things for years, my understanding of them is a little foggy. If I were using a 1.5h inductor, a .033uf capacitor, and a 250k pot, which component (or combination thereof) would determine the frequency of the cut? Which would determine the depth? I don't have a strong background in math. If someone could explain it in layman's terms it would be greatly appreciated.
    Sorry to raise a dead thread, but I couldn't help myself because this question needed to be answered. The capacitor wired in series with the inductor creates a resonant frequency of a certain value. THe equation is

    ƒ=1/ 2π(√CI)

    where ƒ is the frequency, C is capacitance, and I is inductance. you can go to Wolfram|Alpha
    and search "resonant frequency" for a calculator that will allow you to determine your various noth filters based on your inductor and whichever capacitors you choose. In order to vary the depth of the notch, wire the whole thing up to the tone control as if it was a single capacitor instead of a wad of components. Turning your tone control should vary the depth of the notch.

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    dovedescending, thank you for your post and the link. I've built a number of these filters either "by ear" or by copying someone elses design. It will be fun to try again, going for a specific result.

    thanks again'

    thumbs

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    Varitone inductor

    The original varitone circuit appeared in the Gibson ES355 Stereo in the early sixties. The value was 7 Henrys. The ones that everybody is using to make varitones are too low in inductance and the DCR is too high so they don't have the notch depth that the original Gibson circuit had. I'm an electronic engineer and had a company wind some custom for me a few years ago. I still have one or two left somewhere but I can't remember who the vendor was. I'm going to check with some of the makers of power torroids adn will post a source if I find one.

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    rjb
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    Zombie transformers?

    Quote Originally Posted by dovedescending View Post
    Sorry to raise a dead thread...
    This may be a redundant post; it didn't show up for a while after I thought I submitted it the first time. I don't know forum etiquette regarding old threads, or whether anyone will see this, but here goes:

    Can someone tell me if this shielded inductor would work for the Varitone application? It would be going into an Epi Dot (can't shield the control cavity if there is none).

    429-7202-RC Xicon Audio & Signal Transformers

    Thanks.

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    We've been discussing the value of the chokes here and in another thread, this week I just measured a pair of chokes in a 1966 ES-355 Stereo.

    They both measured in at 15.5-16 H and measured about 760 ohms. This was completely removed from the circuit.

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    Quote Originally Posted by 52 Bill View Post
    We've been discussing the value of the chokes here and in another thread, this week I just measured a pair of chokes in a 1966 ES-355 Stereo.

    They both measured in at 15.5-16 H and measured about 760 ohms. This was completely removed from the circuit.
    What did the core look like? did you happen to take a pic?

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    The chokes are encased in metal cans that are soldered closed. Then the two cans are soldered to a small "U"-channel that screws down in the space beneath the bridge pickup.

    Although I did think about it, as the guitar was not mine, I didn't want to try and unsolder the cans or open them either.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by RedHouse View Post
    What did the core look like? did you happen to take a pic?
    Here's the inductor from the Ripper (L9-S) bass which was also used in the L6-S guitar. It's made from a steel bolt, some washers and a nut!

    ripper-wiringbig.jpg
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein

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    Old Timer RedHouse's Avatar
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    I remember that pic David, thanks again.

    I was wondering if the "quality" improved with the ES series varitone (if you know what I mean).

  23. #23
    hpj
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    Sorry to reply to such an old thread... but did you ever find out how to build the inductor for the Gibson L6-S? I have bought a Torres, but would much rather make one myself. Thanks for whatever help you can give me.

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    Radioshack

    First post here,
    Which Radioshack transformer would work as an inductor for a mid-cut? I'm having trouble finding anywhere that sells inductors(especially large ones), and would like to not have to pay shipping.

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    Note on XIRCON Inductors

    Hi there, just a quick note on the cheap Xircon transformers: i used one of the TL series (i.e., with a small IE14 core) in a Varitone of an Epiphone EB3. They are driven into (iron) saturation, at least if the circuit is undamped, especially if the notch frequency is low. Well, an efficient method to build a passive fuzz, but that's not what i intended. I did not try the larger TM-series, but if i was to build a varitone a 2nd time i would use that.

    Beate

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    What about the Xircon 429-series shielded and epoxy encapsulated cubes? Wouldn't these be better for guitar applications?

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    bea
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    Larger EI-19 core, otherwise similar specs. Chances are good they are better suited - i did not try until now.

    BTW: core saturation affects low frequencies earlier than higher ones. So a bass is more demanding in this respect than a guitar.

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    Very interesting, bea. Do you mean the 429 series have iron load as well or no? I'm using a Bill Lawrence Q-filter as inductor with a cap and pot for variable mid cut. This setup has worked well with no audible distortions on guitar(1.8H) and bass(3.0H) but I'm hoping to source a common part for future projects.

  30. #30
    bea
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    Like every other transformer it can be driven into saturation. I do not dare to judge wether this larger transformer is sufficent (but there are success stories, especially in this forum). So it might be worth to give it a try.

    Currently i am considering to make the bass active, mainly in order to decouple the two pickups - the low impedance mudbucker dampens the bridge PU too much if both are run parallel. Given that, a PI-Filter (like that of the AMZ tone control, possibly passive) would be a more useful alternative adding much more versatility to the instrument than a passive notch filter.

    Beate

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    Maybe I'll try one of each series for future projects, they're not terribly expensive parts. I'd tip you off about using resistors in series with each pickup for a decoupling effect except that mudbucker is some monster in terms of inductance. The trick works pretty well on lower impedance pickups, though. David Schwab will have a thing of two to say about individual buffer circuits btw, he's a big fan of them.

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    hpj
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    Making my own inductor...

    Since this thread seems active again I wonder if maybe someone has an answer for me. Can someone describe how I'd go about building my own inductor for an L6-S? Like wire spec, # turns, core diameter, etc. Someone earlier that it was simple to make... I'd like to give it a try.

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    Pickup Maker David Schwab's Avatar
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    Quote Originally Posted by hpj View Post
    Since this thread seems active again I wonder if maybe someone has an answer for me. Can someone describe how I'd go about building my own inductor for an L6-S? Like wire spec, # turns, core diameter, etc. Someone earlier that it was simple to make... I'd like to give it a try.
    If you look at the photo I posted of the L9-S Ripper bass, you can see that the inductor for that and the L6-S is a 1/4" steel bolt, a nut and three washers. I know someone that rewound one, but unfortunately he didn't keep notes. I'd think if you look up info on winding wah pedal inductors, it should follow suite as far as wire gauge. The L6-S inductor was wired up as a humbucker with the two halves separated by the middle washer.
    It would be possible to describe everything scientifically, but it would make no sense; it would be without meaning, as if you described a Beethoven symphony as a variation of wave pressure. — Albert Einstein

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    Quote Originally Posted by bea View Post
    Larger EI-19 core, otherwise similar specs. Chances are good they are better suited - i did not try until now.

    BTW: core saturation affects low frequencies earlier than higher ones. So a bass is more demanding in this respect than a guitar.
    would the TU series with the EI-24 core be even better for bass? http://www.mouser.com/catalog/specsheets/XC-600133.pdf

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    bea
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    Yes, probably, but possibly also no - have a look at the frequency response: it looks as if the core had pretty large losses at low frequencies. The size might also be a problem. At least in the Epiphone EB-3 it will be difficult to fit into the instrument without woodworking.

    My impression from the circuitry: it sounds totally different from an active notch filter and inferior, just dark and nothing else. The impedance of the circuitry outside the notch is too low and damps the pickups too much. Hence the inductivity must be chosen significantly larger than the 1.5 H i used. I recall the Gibsen themselves used L=8H, didn't they?

    BTW: larger inductivity means less current through the circuitry and less tendency toward saturation.

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