Clandestine Issues

[Pedal_man86]

Built the Clandestine Preamp, works okay for the most part but I'm having a few issues.

1) The volume has a slight drop once the pot is turned all the way up
2) Not much, if any, difference between the mid and the dark settings.
3) The bias voltage seems a little strange, the lowest voltage I have is 12 Volt with the trim pot all the way down. Should I swap the transistor?

I saw another thread where other people had these issues, so is it a design flaw with the circuit, does the pedal it's based off of behave this way, and can these issues be fixed?

 

[mkstewartesq]

Built the Clandestine Preamp, works okay for the most part but I'm having a few issues.

1) The volume has a slight drop once the pot is turned all the way up
2) Not much, if any, difference between the mid and the dark settings.
3) The bias voltage seems a little strange, the lowest voltage I have is 12 Volt with the trim pot all the way down. Should I swap the transistor?

I saw another thread where other people had these issues, so is it a design flaw with the circuit, does the pedal it's based off of behave this way, and can these issues be fixed?

That volume drop is exactly how the original Chase tone pedal works. From the documentation for that pedal, you’ll see that the last portion of the knob turn actually decreases in volume.:

• VOLUME CONTROL- Wired just like an original EP3 for Amazing Versatility!
  • FULL COUNTER-CLOCKWISE = NO SIGNAL
  • 10 to 11 0’clock = UNITY GAIN (Depends upon EQ Setting)
  • 1 to 2 o’clock = 3dBs+ MAXIMUM OUTPUT BOOST
  • 3 to 5 o’clock = 1dB or 2dBs with FLAT EQ just like a worn, vintage Echoplex
• Chase Tone® Exclusive 3-Way EQ 1970s Era EP3 Mini-Toggle Switch!
• Early 1970s = BRIGHT
• Late 1970s = DARK
• Hybrid Early & Late = MID”

As far as your voltage, normally people shoot for around 12 V (although that is normally around the middle of the trim in my experience) but if you’re hitting 12 V, you should be just about right.

Mike

EDIT to add – I can tell a difference between the three EQ settings, although it’s not super dramatic. But note that when you turn the knob all the way up, in addition to the volume drop, the EQ becomes flat and so the switch isn’t going to function or make any difference during that last part of the turn.