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Fishman Blackstack Soundhole Pick Up - Double Stacked Humbucker

I have contacted Fishman to ask what vol pot and or tone pot I would use with this humbucker. I want to mount the pots on the guitar, and they said that any humbucker circuit would do and probably a 500k pot. (Actually it depends somewhat on the impedances of the pickup coils, but Fishman sent me a Seymour Duncan diagram!)

I found a circuit for a Fishman Neo-D single coil which showed a 20K pot volume but Fishman advised to use a 250k pot!

So which equipment do I need, and, more importantly, how do I wire it?

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  • Hi Kevin. Welcome to the site. I've taken the liberty of rewriting your question to conform to site rules. Asking how to accomplish a task is encouraged, but requests for resources are considered off topic. If you feel I've misrepresented your intentions, please let me know, and I'll remove my changes. (You may also do so yourself by click on the "edited (time) ago" link and then clicking the "rollback" link.)
    – Aaron
    Sep 23 at 21:51
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    I’m confused about this question. Fishman told you to use a 500k Ohm pot for your Fishman pickup, right? If so, how does that not answer your question? Sep 23 at 22:11
  • @ToddWilcox I think this is my fault when I edited the question. I believe the underlying issue is how to do the wiring. I've re-edited, but you might double-check me by looking at the question as originally written.
    – Aaron
    Sep 23 at 22:22
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    @Aaron yes, but it seems Fishman provided also a wiring diagram to the OP, so it's unclear what else is there to answer. Sep 23 at 22:24

2 Answers 2

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I have wired a few acoustic guitars for pickups over the years, probably in search of my own Beatles J160E setup.

I would recommend the 250K pots to you.

Either that, or mount the Fishman Blackstack as is is designed to be mounted (without volume and tone controls), and adjust your tone on the amp or mixer.

For volume control, there are many quality volume pedals. I recommend the Ernie Ball JPJR Volume Pedal with built in (easy to see) tuner onboard.

Great item. Good luck with this project!

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  • It should be noted that a volume pedal should also use a 250kΩ (or other in similar range) pot, rather than 25kΩ. Sep 23 at 22:21
  • I may have erred in editing the original question. I believe the core issue was the wiring. I've edited the question to reflect. FYI in case that changes your answer.
    – Aaron
    Sep 23 at 22:23
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Pickup and pot essentially form a sort of low pass filter. The higher the resistance is on the pot the higher the cut point will be (as the increased resistance of the coil at higher frequency is less significant).

So generally you’ll have that a higher resistance on the pots will result in more overtones being preserved in your signal, while a lower resistance pot will sound "warmer" by taking way such overtones.

Some things to keep in mind: Humbuckers do cause high frequency loss by themselves, so often they are paired with higher resistance potentiometers. As acoustic guitar will necessarily have some dampening on the strings, which affects high frequencies more than low frequencies. So you should expect less high frequency output in the first place.

Also if you add a tone pot circuit you are increasing this high frequency loss. With tone and volume pot each 500kΩ at "pass through" this will thus look like 500kΩ + 500kΩ in parallel to ground, which results in a resistance of 1 / (1/500 + 1/500) kΩ = 500/2 kΩ = 250kΩ. Thus if you plan to use a volume + tone circuit it is reasonable to use twice the resistance you’d go for else.

Also the tone pot will allow you to add a low pass at your liking, so you might want to go for brighter to have the option.

So it makes sense that the single coil diagram as 250kΩ, while for the humbucker you might use 500kΩ. When adding tone you might even think about getting 1000kΩ (or 1 MΩ), especially if the pickup is already rather dark on the acoustic guitar.

If you want to you can test this out during the installation: Simply get yourself a pair of resistors at 250kΩ, 500kΩ and 1MΩ (these are very cheap, also you can probably ask any electronics repair workshop for some spare resistors (if not you can also just buy 250kΩ resistors and put them in series to get the higher values. Or just buy 1MΩ and put them in parallel to get lower values. Or whatever). Then bridge two resistors to ground (maybe add a capacitor for one to make it really realistic, if you leave out the capacitor you could also just use single resistors at 125kΩ, 250kΩ, 500kΩ). This should then simulate the behaviour with both pots turned all the way up without having to buy multiple more expensive capacitors. If this sounds too bright or harsh for you, go for a lower resistance, if it is too dark go higher.

Now: What do you need, and how do you wire it? You need the pickup. I’m assuming you know which cable of your pickup is hot and which is ground. You need two pots, probably 500kΩ, maybe also 1MΩ, depending on whether you like the sound. Make sure these pots scales logarithmically and not linearly, because else you’d get the most action in the lowest portion of the pot (our hearing is not linear!). Get a small capacitor of a size of your liking (10-22nF, the higher the capacity the lower the cut frequency, so more treble cut). In fact, get multiple capacitors, then you can try some options. You need a socket. And you need wire. If you get wire in two colors you can color code ground and hot phase.

The socket has two connectors, one that goes to the tip and one that goes to the shaft of the jack. The shaft will be ground!

So first thing: The ground of the socket should be connected to the ground of the pickup, the case of each potentiometer and the third pin of the volume potentiometer. The second pin of the tone pot should be connected to ground through the capacitor.

The hot cable of the pickup should be connected in parallel to the first pin of both volume and tone pot. The second pin of the volume pot should be connected to the tip connector of the socket.

This is something like the usual way of how to wire these things, but there are alternatives.

You will also need to think about where you are going to mount the socket and the pots. This should be done in a place you can reach through the soundhole, and if you have potentiometers in a place you can reach well. You will need a drill for installing these. Assemble the circuit outside of the guitar and then try to install everything through the soundhole.

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  • Thanks for this very comprehensive and informative answer - giving an insight into why both Fishman and Baggs like their pickups to go straight through to the external preamp - Im modifying a new Martin SC13e and being the animal i am i have fitted it with a ToneWoodAmp. Yesterday that was, a very anxious business but the sound is amazing being a mix of the straight acoustic tone of the guitar (quite loud as its a Martin) and the TWA output, both sounds coming through the soundhole and the rest of the guitar body and the mix varied by the piezo volume of the built in preamp. Thanks once again
    – Kevin
    yesterday
  • @Kevin Nice! Btw the sound does not really come from the sound hole but mostly from the top. The top can be seen as a membrane, transferring vibrations to the air. That’s the reason by semi-acoustics with plywood tops offer significantly less sound than one with a good fir or cedar top.
    – Lazy
    yesterday

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