LiveOVErdrive's consolidated build thread

Discussion in 'Luthiery, Modifications & Customizations' started by LiveOVErdrive, Nov 6, 2017.

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  1. LiveOVErdrive

    LiveOVErdrive CNC hack

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    I mean it's not a new concept but it's a new build. The bottom is shaped to sit on my lap how I like it to sit when I'm practicing.
     
    Last edited: Jun 5, 2018
  2. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Been posting designs on a few threads but here's a headless I'm working on.

    fan_headless_alt_2019-Jan-04_03-57-33AM-000_CustomizedView15939588316.png

    Tortoise pickguard. Some kind of dark fretboard. White block inlays. White fretboard binding. 25-26 inch fan.

    Its going to have 2 strat pickups and a third hidden under the pickup (not near the strings). There'll be some active electronics onboard that'll use the hum from that third coil to cancel the hum from the other two (but without the extra passive load of a stacked single coil).
     
    Last edited: Jan 3, 2019
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  3. KR250

    KR250 SS.org Regular

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    Really interesting pickup setup and cool design.... Would love to see how you wire it once complete. Planning to do a dual passive single coil setup soon and extra noise is definitely a concern.
     
  4. ThtOthrPrsn

    ThtOthrPrsn Unconventional

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    Too much goodness in one thread! I love that bevel and I can't wait to see how this headless turns out!
     
  5. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Thanks top. I actually plan on following through on this one so we might see some progress pics soon. And dare I say a video later.

    Sure thing. Here's a diagram:
    IMG_20190105_085410_1546700101119.jpg
    ERRATA: It says R2 = 1/2 * R1. It should read R2 = 2 * R1

    Pickups: 3 identical single coils. Use the negative lead of the "hidden" pickup. Hidden pickup should be away from the strings. Not even pointing at them. Mine is going in the control cavity.

    Cable sim: this is just a capacitor to ground to simulate a cable connected to a pickup, and give you the response you expect from a pickup. I'll use something between 500 and 1000 pF. This site has some great info on the interaction between the pickup and cable (though they are trying to sell you something) http://zerocapcable.com/?page_id=209

    Buffer: now that the passive interaction of cable and pickup is simulated, we do a unity gain buffer so we're not in high-impedance-land anymore. It is possible that this stage can be omitted without too much trouble, since the next stage is active also. I'll have to test.

    Noise cancel: this stage is two summing amplifiers - one for each of the "real" pickups. We sum the pickup signal with the negative noise signal from the hidden pickup. I plan to make the summing resistor for the hidden pickup a trim pot so I can dial in exactly the best noise cancelation.

    Selector: this is just a summing amplifier with a switch built into it. In the top position, only the neck pickup signal is connected so it acts as a simple unity gain amp (r1/r1). In the middle position, both signals are connected, but through r2 (I have it labeled incorrectly. R2 should be twice r1, not half). This makes it a summing amplifier that gives us the sum of the two signals, reduced by half (so we get roughly the same output level. Nice). Then the bridge position is the same as the neck position but for the bridge.

    Vol: this is a volume knob in the usual arrangement. I'll use a similar value to the other resistors in the circuit (20k probably. I have a lot of those). There is a clean buffer after it, to bring this higher impedance signal (because of the volume knob) to a low impedance signal.

    Output: the output jack. Got a nice low impedance signal that doesn't have any hum and doesn't care how long a cable you hook it up to (within reason)



    So that's how it works. If I drop the initial buffer stage, I should be able to fit this all on a little pcb with only 2 op amp chips on board. That'll be neat.

    Let me know if you have any questions.
     
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  6. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Oh, I'll also probably do a trim pot before the selector (or just change the resistor values in the selector of the neck pickup) so that the volume levels are balanced between the neck and bridge. Since I'm doing three identical pickups, the neck will probably be louder.
     
  7. LiveOVErdrive

    LiveOVErdrive CNC hack

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    I really just can't stay away from surf green.

    fan_headless_alt_2019-Jan-07_01-19-46AM-000_CustomizedView3721287355.png

    Still got some work to do on that pickguard shape but it is getting there.
     
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  8. Lemonbaby

    Lemonbaby SS.org Regular

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    Just out of pure interest: any reason you don't use a differential unity gain buffer for the first stage?
     
  9. LiveOVErdrive

    LiveOVErdrive CNC hack

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    You mean across both ends of the pickups or between the signal pickup and the noise cancel pickup?

    Can you do that with a single op amp? Is that just a diff amp? Definitely a good thing to look into. Would love to reduce my part count.
     
  10. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Actually I think the best thing to do is to use a single ended unity gain buffer for each pickup, then run all three into a differential amp (the two signals to the additive side with the selector switch arranged as before, and the positive end of the hidden coil to the subtractive side). Add the output buffer and I only need 5 op amps. Not bad.

    Or I could just buy two EMG SAs. But where's the fun in that? :)
     
  11. KnightBrolaire

    KnightBrolaire schadenfreude

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    so are you basically using the middle coil as a dummy coil to minimize noise?
     
  12. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Exactly. But actively buffered so it sounds (about) exactly like the bridge or neck alone, rather than like the cocked 2 or 4 position of a strat.
     
  13. KnightBrolaire

    KnightBrolaire schadenfreude

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    why not just use noiseless single coils? the lace ones are pretty good ime.
     
  14. LiveOVErdrive

    LiveOVErdrive CNC hack

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    Only because I've wanted to try this for a while. And I think it might sound pretty neat.
     
  15. LiveOVErdrive

    LiveOVErdrive CNC hack

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    On the other hand, I'm lying to myself if I say I like single coils more than hums.

    headless-2019-01-07.png

    EMG 81 + SA? Yeah I think that'll be okay.
     
  16. Defyantly

    Defyantly SS.org Regular

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    I'm really starting to dig the hum/s configuration! I say go for it!
     

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