Pepper Spray (Troubleshooting Questions)

[4stringphuzz]

I just finished up my Pepper Spray build last night. Overall, I think it sounds good, but there are a few things I had questions on.

1) The output of the stock 1N695 diodes seems kind of low. Both the "Harm" and "Balance" pots have to be full on, before the signal reaches close to unity gain. Even then, it's still probably just slightly below unity. I used Red LED's as the second diode pair option, and there isn't a problem there. It's plenty loud on that setting. Is this the way that the stock setting is supposed to sound? Some other threads in the Madbean forum say yes, or perhaps, but I can't tell for sure.

2) On the LED diode pairs, only the LED in position D3 is visibly lighting up. The LED in D4 isn't lighting at all. I've checked both LED's individually (they're fine), tried different pairs, and still nothing for the LED in D4. I ended up using a water clear red LED for D4, and it gets the SLIGHTEST bit of signal through it, but I know it still isn't right.

3) As far as I can tell, both transistors are oriented properly according to the build guide. Here's the strange thing, the voltages on the transistors are much closer to the "Albini" version values than the stock values. The pedal is built completely to standard specs though.

4) Finally, I can't really notice any difference in texture/clipping symmetry when I change the trimpot value. Should it be pretty drastic/noticeable?

https://imgur.com/7IsTn3L
https://imgur.com/3z9tNin

Any help or insight with these issues would be greatly appreciated. Thanks!

[Bret608]

Hi there--I've built both the stock and Albini and can hopefully help out. The main thing I notice right away is that you did in fact build this to the Albini specs. The only place I can see the stock values on the build doc are in the parentheses on the schematic. Also, it looks like you have one of your LEDs backwards. It looks like the flat side of the LED in D4 is facing the same way as the one in D3. Flip D4 around if I'm right and you should be good to go. One thing to note though is LEDs used for clipping will not always light, but in this case they probably will once you fix that.

As far as the volume issue on the 1n695s goes, that 10k trimmer may actually help you here--the main thing you'd notice is things getting louder as you turn that up (i.e. going more asymmetrical). I agree this circuit is not the loudest--my Albini build hits unity at about 2:00 on the balance pot with the stock 4.7k resistor (about halfway up on your trimmer). One other thing would be to double check you don't have those two pots switched. I hope this all helps!

[WormBoy]

The output will be limited in an absolute sense by the clipping diodes, irrespective of the input volume. Whether that feels like unity gain or not depends on the pickups in your guitar (and whatever other pedal that is doing something volume-wise between the guitar and the circuit). So it depends on what you think is 'normal' with your setup. With Ge diodes, output will be low. Not so much of a problem if you're using old-fashioned passive single coils, since it will generally feel louder with the volume on the pedal up. But for humbuckers and active stuff, you'd be easily wanting more volume than what's available in the pedal, I'd wager.

[4stringphuzz]

Hi,

Thanks for the input on my issues. I did go back to look at the build doc, and I realized that the B.O.M is in fact for the 'Albini' version. It makes sense now. Is the stock version drastically different than the 'Albini' version (like, in a good way)? I was considering changing the resistor/cap values in question to make the build a tad more aggressive. Also, would any of those value changes affect the output volume favorably?

1) It looks like LED in D4 is in fact backwards, so I'll de-solder and reverse it. Hopefully that should fix the problem
2) It looks like the pot values are correct for the controls (A50K Balance and A100K Harmonics). I even tried an A100K pot for Balance, hoping it would boost the output a little extra, but there wasn't much of a difference, so I put back the original.

I'll report back if there are still any issues. Thanks again!

[WormBoy]

Also, would any of those value changes affect the output volume favorably?

No, volume will be completely determined by the clipping threshold of the diodes (up to a certain point of course). To raise volume, you need to raise the clipping threshold (which also changes the sound) or add a booster. Raising the threshold can be done by using a different diode type, stacking diodes, or adding some resistance in series with the diodes. As Bret608 already noted: the asymmetry trimmer should increase volume some, even though it is on just one diode. All changes to the clipping section will change the sound of the pedal, for better or worse.

[matmosphere]

I will second the point about this not being a loud circuit. My build has unity gain maybe around 3 o'clock. From hearing Albini talk about it, I thought it was going to be the loudest, craziest pedal ever. At least mine didn't turn out that way, but it does sound cool.

From what I've read Albini uses his with everything dimed. It isn't that it makes things louder, just more gnarly sounding.

I think pinkphotonjimi made a cool video we're he was experimented with a similar circuit to see how different chamges effect the sound. I think it was basically a percolator but with parts that are easier to source.