Modern slo

[Sensei Tim]

Building this one



For whatever reason I can’t get the volume above unity gain at 9V and at 18v it squeals like a pig.

I don’t remember having problems like this when I build one before, but that was 2-3 years ago and I don’t remember all of the details

[Sensei Tim]

So i've been messing with this some more and discovered a few things.

looking at the linked schematic, there is a mistake in the power section.

The voltage divider at R21/R22 is wrong.  with a 24k/33k divider you will not get 4.5V out with a 9V supply. it should be 24k/24k or 33k/33k.  This will give an improper pull up voltage going into Q2 and Q4.

This is correct in the "original" shown above, but in this one:



the values are incorrect.  the offenders in question are the 24k resistor above and to the left of Q2 and the 33k immediately to the right of q2.