Help identifying coupling caps

megatrav

megatrav

Well-known member
I have 2 Citrus Press (JHS Pulp n Peel) boards from Effects Layouts.
I am going to build one as stock but I would like to build the other as a the “Lime Aid” version.

Josh Scott mentioned on a Facebook post that the only difference is the coupling caps.

I know that increasing the value will allow more bass through.

So, I need some help identifying which are the coupling caps

IMG_4964.jpeg
 
C1, C4 and a maybe C2
Increasing would let more bass pass
Decreasing C7 and C9 would restrict the bass.
Not sure what the Lime Aid is, more/less bass
You'll want to do the math on any filters these caps are part of as well.
 
You could tweak the filter in the feedback loop of IC1B as well as I don't think it's doing anything.
 
jwin615 said:
You could tweak the filter in the feedback loop of IC1B as well as I don't think it's doing anything.
Click to expand...
Isn’t that network necessary for the compressor to work properly? I’m not familiar with compression circuits.
 
jwin615 said:
What's the audible difference between the two JHS pedals?
We just don't know the objective...
Click to expand...
I haven’t played the Lime Aid but in my experience, the PulpnN Peel cut off is around 80-100hz
I’d like to get it lower for sure
 
With the stock values on the clean path, virtually nothing is being filtered. Adding more bass signal to the comp path would most likely negatively affect the performance of the comp (i.e., lower frequency guitar signals can have a higher amplitude, causing an imbalance in the detection circuit).

I’m inclined to think this is a hacky approach wherein a different topology would be better suited. I’ve found VCA comps to handle low tunings/bass much better than optical or JFET comps—the latter typically relying on clean blend to retain low end attack without overwhelming the frequency balance.
 
The Orange Squeezer is a half-wave rectifier (the diode splits the signal in two), feed-back design.

Some people do love the Orange Squeezer on bass, but stock it does actually cut some low end (which can be a good thing if your signal is a swampy mudbog).

I'd play with C1, the stock input is 47n, and increase it to 56n and keep increasing it, 68n, 82n up to 100n maybe 120n or even 220n until I find the Goldilocks' cap.

However, IIRC the circuit clips the initial transient which is exasperated by hitting it with more gain which is what bass freqs have and do, gain up and muddy things up. The transient will briefly clip before the compression kicks in, so the OS has a naturally higher noise floor and grit to it.

John "Midway Fair" Patton uses a NE5532 for the op-amp instead of the 4558, and says it's a little quieter which may help mitigate an increased input-cap's distorting things down the line. Try Patton's NE5532, but also try TL072, Burr Brown, TI RC4559, TLC2272. Having said that, some people still prefer the 4558.

Further Noise-Reduction:
JFETS 2N5457: Use quality Fairchild (try BF245B, 2N5458, MPF102). The MPF102/J113 may be better for bass (slightly less gain).​
TANTALUM and/or XICON caps​

DIODES: find the right Fv diode, 0.25–0.35 : 1N100 is unobtanium, so find a Schottky diode with the correct Fv — Schottky 1N5817; flaunt 'm if you got'm VD1210-Ge,
 1n40 Ge, 1N34A... 1N60P Schottky work-a-like of the 1N60 Ge... Russian D9 types... BAT4x ...1N4148...​
​

Next up, I'd play with C4 (also 47n, stock), since it's directly inputting signal to the op-amp I'd be even more careful and lean towards increasing it less than the input cap. For this one I'm just stabbing away in the dark hoping I hit the right target.



Here's the BASSification suggestions from DIY Doyen Mark Hammer and A Colman:

1) Change output cap from 4.7µF to 1µF — [YES! Counter-intuitive, I know, but I forget the explanation why]​
2) Change bleed-cap from 4.7µf to 10µF. [cap connected to the diode, in this case C8]​
3) Decrease feedback resistor from 220k to 200k. [R10, should help reduce distortion]​

MORE BASSIFICATION:
mods too subtle (OS modded for bass player):

Orange Squeezer based the GGG layout, with some minor modifications. I used trimpots instead of resistors for R2, R9, R11 and R12 so I could control the ratio, gain, attack and release (respectively).

I should mention that I added a 27nF cap from the output to ground to kill the hiss. At half volume (about 2k on the 10kA pot) it should be damping frequencies above 3kHz. Guitarists might cringe at that figure, but my friend was looking for a more old-school vibe for bass so that should be just fine.
Click to expand...

More fiddling with CAPs:
Add 51p parallel with R10​
Add 100p across pins 1 and 3 of output pot​


FURTHER READING:
https://www.diystompboxes.com/smfforum/index.php?topic=105710.0 VERY GOOD BIAS SETTING INFO HERE!

RG KEEN:: https://www.diystompboxes.com/smfforum/index.php?topic=54308.0
The Technology of the Orange Squeezer
Copyright 2007 R.G. Keen




Oh, there is one more thing: the transistors do NOT need to be matched.
 
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