BISIAB II - love it but feedback problem

[vince76]

I recently built a BSIAB II. I etched a board starting from that found on GGG.
I really love the effect but I have huge feedback problems. I cannot turn the drive and volume knobs more than half way up.
Used all components as showed in the partlist. Searching on the forum I found that it was better to use shielded wire for input and output and ground one side of the shield, but no luck. Anyone experiencing this problem??

Thank you, V

[elshiftos]

It could be a problem with the layout. With high gain pedals you have to be very careful to keep the input wires away from the output, otherwise feedback or other tone colouring issues can occur. Screening the input can help - give it a go!

[vince76]

the layout has been used by others and didn't reported these problems.
I used screen cable for input and for output wires. and kept them away.
the feedback point seems to be reached later if I cut treble in some way.
any suggestions?

[vince76]

I noticed that if I set the trim pot to have higher voltage on Q5 drain the feedback reduces a lot. The fact is that a "good" setting require 6.9 Volts on Q5 drain, and I'm not sure if I like the sound.

V.

[tackleberry]

When I built my BSIAB2 off the schematic and layout off GGG. I didnt have any feedback at high volume but it didnt sound very good the distortion sputtered. I just couldnt get the pin voltages specified not even close to what it said. I later found another schematic of the same pedal. It had trimpots on the drains of Q2 and 4 once I figured a way to engineer em in and got the voltages right it worked really well. Many seem to have success with the GGG plans or the various others out there without those trimpots.