Mr Green Genes (Son of...)

[mybud]

Build Rating

5.00 star(s)

This seems to be pretty popular round these parts, judging by the plethora of associated build reports. Nice to come back to the familiar territory of a PPCB board after some detours elsewhere. A quick build by my standards and I copped out of drilling/finishing by repurposing a Tayda 4-hole enclosure that was previously home to a General Tso.

I used standup polystyrene caps for the 250 and 470pFs called for, as you see, and for symmetry used something similar for the 100nF power filter cap. I have absolutely no reason to believe that this makes any difference to the toan, but hell's bells, why not?

I winged the biasing, set Q2 and Q3 as close to 4V as I could get and then biased Q1 more or less by ear. I wanted the dirt to come in a little later in the pot's travel (say 11am) and this seems to work. FWIW I measured 7V or so on Q1. Naturally, this might be 'wrong' and YMMV, depending on what you want to get from the pedal.



The name puns on 'Son of' in my usual puerile fashion.

I regret to say I didn't find anything particularly outstanding about the pedal toan-wise. It's serviceable if a mite pedestrian IMHO but once again don't let my sense of 'mildly meh' deter you from taking it on. It might be just what you're after, after all.

I notice that it tends to hum when anything ground-related gets too close (my hand, in this case), suggesting I need to work on sanding off some paint where the jacks meet the enclosure. At least this confirms the ground loop theory as in my hand providing an alternative pathway to ground, or so I surmise.

Thanks for reading and much success in your builds.

 

[mattdrago]

I just came across your post and thought I'd give some insight into that noise issue you described.

Just in case you weren't already aware, polystyrene capacitors are known for being delicate little flowers that love to find any excuse to make noise in a circuit. Of course I'm exaggerating, but if you've ever used them in a large diaphragm tube condenser mic then you'd see where I'm coming from. They are extremely susceptible to microphonics as well as RF noise and to make matters worse, it seems like most polystyrenes still in production today don't have any marking to indicate which side is the outside foil connection. Basically it has to do with the construction of the capacitor itself and the wire lead for the outside foil is meant to be connected closest to circuit ground to minimize any stray noise that could be picked up. When that side is connected to your circuit ground It sort of creates it's own internal shield to help block that noise, but that's typically only of great importance if it's a more critical part of the design that needs high precision and high stability.

Anyway, what I do think might be contributing to your noise issue is having them mounted upright without any additional reinforcement to help dampen vibrations. Anytime I use a polystyrene no matter what the application may be I make sure to have them laying down flat and to use a strong adhesive to lock that capacitor in it's place so it won't ever budge. I'll say again, this is based on what I've seen with high fidelity vacuum tube mics that have a much lower noise floor than an electric guitar's signal running through a pedalboard, so it might not actually have a noticeable effect on the pedal either way. Just in case though, maybe try tapping on the enclosure when the effect is engaged and see if you hear anything. Since you said that the hum manifested just by being in proximity of the pedal, I feel like you'd hear some noise if you tapped on the pedal while it's active. If that's the case and you don't want to swap those caps out completely, glue those suckers down and then test it again to see if it got a little less noisy. I hope this helps!

 

[mybud]

I just came across your post and thought I'd give some insight into that noise issue you described.

Just in case you weren't already aware, polystyrene capacitors are known for being delicate little flowers that love to find any excuse to make noise in a circuit. Of course I'm exaggerating, but if you've ever used them in a large diaphragm tube condenser mic then you'd see where I'm coming from. They are extremely susceptible to microphonics as well as RF noise and to make matters worse, it seems like most polystyrenes still in production today don't have any marking to indicate which side is the outside foil connection. Basically it has to do with the construction of the capacitor itself and the wire lead for the outside foil is meant to be connected closest to circuit ground to minimize any stray noise that could be picked up. When that side is connected to your circuit ground It sort of creates it's own internal shield to help block that noise, but that's typically only of great importance if it's a more critical part of the design that needs high precision and high stability.

Anyway, what I do think might be contributing to your noise issue is having them mounted upright without any additional reinforcement to help dampen vibrations. Anytime I use a polystyrene no matter what the application may be I make sure to have them laying down flat and to use a strong adhesive to lock that capacitor in it's place so it won't ever budge. I'll say again, this is based on what I've seen with high fidelity vacuum tube mics that have a much lower noise floor than an electric guitar's signal running through a pedalboard, so it might not actually have a noticeable effect on the pedal either way. Just in case though, maybe try tapping on the enclosure when the effect is engaged and see if you hear anything. Since you said that the hum manifested just by being in proximity of the pedal, I feel like you'd hear some noise if you tapped on the pedal while it's active. If that's the case and you don't want to swap those caps out completely, glue those suckers down and then test it again to see if it got a little less noisy. I hope this helps!

Thanks for the detailed comments, Matt. Much appreciated.

 

[mattdrago]

Thanks for the detailed comments, Matt. Much appreciated.

I'm always happy to provide insight if someone might find it useful! I literally just stumbled across your post because I've had the PCB for this for over a year and forgot about it, then I found it again and thought I'd see what kind of mods people made to it on the forums. Those polystyrenes were the only thing that stood out to me in your assembly as being potential causes of the noise issues because everything else looks solid and well done

Polystyrene capacitors are one of those parts that I see more and more in audiophile builds and I wonder if it's because people tend to focus on the advantages it can bring while also forgetting about the disadvantages that caused it to be phased out of production in the first place. As long as you take the necessary precautions to minimize vibrations and RF signals from bringing noise into the circuit, you typically will be fine using polystyrene capacitors wherever you see fit! Definitely let me know if you get around to opening this pedal up again and checking for microphonics like I described, I'm interested to hear the results. Solving problems is what I do for work and for fun anyway lol

 

[mybud]

Thanks again, Matt. I’ll have a close look at the build tomorrow and get back to you.