Component tolerances are a bitch

[SillyOctpuss]

Just finished testing a new pcb before boxing it up. Thought it didn't sound quite as I was expecting so plugged in a vero build I'd completed before ordering the pcb and the vero build hammered it. The midrange was more present, there were more harmonics and it just generally sounded better.

It's clear they're both the same circuit and I could get them reasonably close but the vero build just... sounds better.

I like to build new circuits on vero if I think I might make value changes or mod it. I don't like adding a bunch of sockets to final builds for my pedalboard and vero is also really easy to desolder and mod as needed. I like pcbs for final builds for neatness and I suppose just neatness really.

I've been though the schematic and both builds to make sure I haven't put in an incorrect value or that the vero layout and pcb layout are different. Everything checks out so the only difference is component tolerances. I've got two choices now, either build another one and hope it sounds closer to the vero or try and remove the sockets and tidy up the vero then put it in an enclosure.

 

[Humbug]

Is this a transistor circuit? If so, make doubly sure that the bias conditions etc are identical between the two.

 

[SillyOctpuss]

Is this a transistor circuit? If so, make doubly sure that the bias conditions etc are identical between the two.

Yes it's transistor based but the bias is bang on in both circuits. The only differences I can find are layout and component tolerances. The hfe of the transistors is the same too.

 

[Humbug]

Yes it's transistor based but the bias is bang on in both circuits. The only differences I can find are layout and component tolerances. The hfe of the transistors is the same too.

That sucks. Next on the "easy" list is checking if any potentiometers in the circuit are giving you the same resistance values for a given position and in total. If they do, I can't think of anything other than taking apart both, measuring all the components individually and comparing them.

I'll assume the pcb itself is well laid out.

 

[SillyOctpuss]

That sucks. Next on the "easy" list is checking if any potentiometers in the circuit are giving you the same resistance values for a given position and in total. If they do, I can't think of anything other than taking apart both, measuring all the components individually and comparing them.

I'll assume the pcb itself is well laid out.

Yeah the pots are pretty close but it doesn't matter where they're set on either pedal, the vero build just has more mids and generally sounds a bit better. I think I'm just going to remove the sockets from the vero build, tidy up the wiring and put it in an enclosure.

 

[Eagle]

This is why Dumble clones don’t sound as good as real ones. Alex could hear the amp and go back in to it swapping components until it was just perfect for the specific person it was built for.
I’ve played a few and even talked to him in the 90s he was obsessed and would really only engage with you if he decided he liked you. I must have caught him in a good mood. He was hot and cold with a college of mine at the time.
In guitars I meter everything before I use it.

 

[SillyOctpuss]

In guitars I meter everything before I use it.

I do that with pedals too. I don't want the hassle of looking for parts with the wrong value or put of spec when something doesn't work properly later.

 

[SillyOctpuss]

Had a theory and swopped a few parts. Just lifted a pad and a trace on the last one so after I harvest the transistors this board is going in the bin.

I honestly don't remember the last time I lifted a pad or a trace. Balls