I have the Q5 drain adjusted to 4.5V (1/2 of the input voltage) And I have built several of these and never had this issue.
I have a problem wth a BSIAB2's sound cutting out when you hit a note really hard. This issue does not happen as long as I keep the drive pot to about 25%. The sound later slowly comes back, and comes back slower as the drive pot is increased above 25%.
This circuit worked great for several months, then when I moved the parts to a PCB from a veroboard it started doing this only at 100% drive settings. Now, this happens at 25% of drive or higher.
So it looks like a component is failing, but I'm not sure which one of C3, C7, Q3 or Q4. Anyone have a problem like this?
Did you adjust Q5 just based on the 4.5V (D) setting or did you also trust what you were hearing? I didn't really pay attention to the Q5 values as much as I relied on my ears.
I once had somewhat similiar problems caused by a faulty drive pot, so you might wanna check that...
Quote from: MihkelI once had somewhat similiar problems caused by a faulty drive pot, so you might wanna check that...
Yep, THAT WAS IT! Thanks. :D
I generally don't suspect resistors and pots - thinking that these are usually a catastrophic failures - but not so in this case. I replaced the drive pot and it's doing fine now.
What a strange situation. I had reused this pot and I think either the DC screwed it up when I was doing some prototyping or I got something inside of it that is shorting it out a 25% rotation. Anyone else seen DC current screw up a pot?
Quote from: powerplayjDid you adjust Q5 just based on the 4.5V (D) setting or did you also trust what you were hearing? I didn't really pay attention to the Q5 values as much as I relied on my ears.
Thanks, generally I would tweak the voltage a bit once I got it working just right, having the voltage just a little off sounds better to me - it is kind of a tune by ear thing.