Simulating cable capacitance...?

Joben Magooch

Well-known member
Just kind of randomly came to me, so this might not be particularly well thought through, but I'm wondering if anyone's come up with a simple way to try simulating different cable capacitances?

Reason I'm asking...I recently rewired my whole rig with Mogami 2314 cable, which is 33.5 pf/ft. Previously, it had been wired up with Mogami 2319, which I believe comes in at 47.5 pf/ft.

Since doing that re-wire I have noticed everything is quite a bit brighter than before. I guess this is to be expected with lower capacitance cable but it seems like a more pronounced difference than I'd expect from ~14 pf/ft. I've only got about 20 feet of patch cable throughout my board, so I suppose I could simply say I've now got ~280pf less capacitance across the whole board?

Anyways, I suspect there are more variables than just that at play, but it got me thinking that it would be interesting to whip up some sort of simple box to test out simulating different cable capacitances. As I understand it capacitance basically serves as a low-pass filter so I would think some sort of simple adjustable capacitor in-line would serve a similar effect? I'm kind of thinking of something akin to a "decade box" but don't really have any more than just that nebulous idea. Not exactly sure how to wire that up, nor am I sure what kind of math would be required to know how much capacitance to add to the path. For instance, as above, if 20 feet of 2314 would have a total capacitance of 670pf and 20 feet of 2319 would have a total capacitance of 950pf, then would simply adding a ~280pf cap more or less provide the same capacitance-tone as though it were still wired up with 2319?

I'm thinking of a passive device here as I don't really need/want anything lower capacitance than I already have but I guess with some sort of active box you could go that way, too.
 
Jack Orman's "Guitar Pickup Simulator" article describes a technique to emulate a passive guitar pickup and includes a cable capacitance element. I've built out a couple to see how they behave on a pedalboard. I was quite pleased with the learning experience and outcome. Both are passive and require no power. The schematics are from Jack Orman's article in the link from Muzique above.

Based on your questions and the info in that article, adding the capacitive difference in your updated wiring should do the trick. Just swap out the existing cap value in the schematic for the difference you're looking for in your situation. You may or may not want to use the transformer. Try it and see.

FuzzBuckers_Done.jpg FuzzBucker_Vero_1-Knob2.jpg FuzzBucker_1-Knob_Schem.png FuzzBucker_2-Knob_Schem.png
 
Not being of any use here, but you reminded me of the first time I tried a "boutique cable" many years ago. I was very sceptical that a cable would make any difference to how my guitar sounded but I was floored when I heard the difference. Maybe my existing cable was truly knackered but I was ashamed how much difference I could hear! And now, all these years later here I am building my own pedals and talking of the differences between clipping diode types.

It's a slippery slope...
 
Just kind of randomly came to me, so this might not be particularly well thought through, but I'm wondering if anyone's come up with a simple way to try simulating different cable capacitances?
Sure, Linear Technology did that many years ago. It's called LTSpice. ;)

When I design onboard preamps I usually do try to factor in cable capacitance, but once you start measuring things and looking at the bigger picture it kind of becomes less and less simple, IME.
 
Jack Orman's "Guitar Pickup Simulator" article describes a technique to emulate a passive guitar pickup and includes a cable capacitance element. I've built out a couple to see how they behave on a pedalboard. I was quite pleased with the learning experience and outcome. Both are passive and require no power. The schematics are from Jack Orman's article in the link from Muzique above.

Based on your questions and the info in that article, adding the capacitive difference in your updated wiring should do the trick. Just swap out the existing cap value in the schematic for the difference you're looking for in your situation. You may or may not want to use the transformer. Try it and see.

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Love the graphics on both your Fuzz Buckers.

Been meaning to build myself a buffer buster (Fuzz Bucker) and I see yours have no bypass switch. I was thinking of making mine with a loop to isolate the problem pedal and leave it on in the loop on and just switch it in/out of the chain via the loop/buffer-buster.

What are the pros & cons to having the Fuzz Bucker always on?
 
Love the graphics on both your Fuzz Buckers.

Been meaning to build myself a buffer buster (Fuzz Bucker) and I see yours have no bypass switch. I was thinking of making mine with a loop to isolate the problem pedal and leave it on in the loop on and just switch it in/out of the chain via the loop/buffer-buster.

What are the pros & cons to having the Fuzz Bucker always on?
IMO . . . the Guitar Pickup Simulator (FuzzBucker) is utility circuit for impedance & capacitance correction. So where there is a guitar volume control sensitive pedal after it, that volume control sensitivity is retained. So there's a 'pro'. A 'con' would be if for some reason that impedance and capacitance correction is not needed. They well in front of buffered wah pedals too.

After learning of Jack's Guitar Pickup Sim, I started building them directly into my fuzz face (and other volume control sensitive circuits) projects.
PUFF_02_Gutshot.jpg
 
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