First attempt at drawing a schematic...made it louder (Sound Clips Added)

[GGBB]

Jumper the input cap blend pot from wiper to whichever pin connects to C1.

[duck_arse]

"at that extreme", you have no resistance between the +9V and the collector of that transistor. the emitter of the transistor is connected to ground, so it will only take one big chord to turn on the transistor and - well, how much current can the battery supply, how much can the transistor stand?

next time, carefully take the pot to the point where "nothing happens" starts, switch off and measure the resistance of the pot at the wiper, and fit one value larger than that between the 9V and the wiper, would be the easy way to describe it. then, no matter how hard you crank to the extreme that pot, the resistance to supply won't go lower than your stopper value.

[patrick398]

"at that extreme", you have no resistance between the +9V and the collector of that transistor. the emitter of the transistor is connected to ground, so it will only take one big chord to turn on the transistor and - well, how much current can the battery supply, how much can the transistor stand?

next time, carefully take the pot to the point where "nothing happens" starts, switch off and measure the resistance of the pot at the wiper, and fit one value larger than that between the 9V and the wiper, would be the easy way to describe it. then, no matter how hard you crank to the extreme that pot, the resistance to supply won't go lower than your stopper value.

That's great thanks a lot. I'll definitely bare this in mind for next time!

Jumper the input cap blend pot from wiper to whichever pin connects to C1.

What's the purpose of this? I thought that the point at which the two caps meet becomes the output of the blend pot and then that's jumpered into the base of Q1...or have i confused myself?

[GGBB]

Jumper the input cap blend pot from wiper to whichever pin connects to C1.

What's the purpose of this? I thought that the point at which the two caps meet becomes the output of the blend pot and then that's jumpered into the base of Q1...or have i confused myself?

That's how it is "supposed" to be done (or is typically how you see it done), but technically there is nothing wrong with your approach - it's just different and some might say inferior.

It's not about the "output" of the caps, it's about the input.

You have a "pan" control between the caps. At either extreme you have no resistance before whichever cap. At the middle setting you have 62.5k resistance before both caps (most frequencies, lower frequencies up to 125k) which is 250k/2 || 250k/2. So as you adjust the control it varies the impedance at all frequencies, not just the low frequencies.

What you want is a cap blend control - a small cap with no resistance before it and a pot to gradually blend in a bigger cap to allow lower frequencies. So all that is being adjusted is the impedance to lower frequencies. Also - you'd probably want a smaller pot - say 100k.

[patrick398]

Jumper the input cap blend pot from wiper to whichever pin connects to C1.

What's the purpose of this? I thought that the point at which the two caps meet becomes the output of the blend pot and then that's jumpered into the base of Q1...or have i confused myself?

That's how it is "supposed" to be done (or is typically how you see it done), but technically there is nothing wrong with your approach - it's just different and some might say inferior.

It's not about the "output" of the caps, it's about the input.

You have a "pan" control between the caps. At either extreme you have no resistance before whichever cap. At the middle setting you have 62.5k resistance before both caps (most frequencies, lower frequencies up to 125k) which is 250k/2 || 250k/2. So as you adjust the control it varies the impedance at all frequencies, not just the low frequencies.

What you want is a cap blend control - a small cap with no resistance before it and a pot to gradually blend in a bigger cap to allow lower frequencies. So all that is being adjusted is the impedance to lower frequencies. Also - you'd probably want a smaller pot - say 100k.

Ok that makes sense, is that why it gets quieter in the middle and then really opens up at either extreme? So if i just add a jumper from wiper to Q1 base i'll get a more even sweep?
Thanks for your help

[GGBB]

Ok that makes sense, is that why it gets quieter in the middle and then really opens up at either extreme? So if i just add a jumper from wiper to Q1 base i'll get a more even sweep?

According to the schematic you posted, wiper to Q1 base will bypass the pot and both caps completely. You want wiper (middle lug) to whichever outer lug of the pot is connected to the smaller cap.

[patrick398]

Ahhhh ok gotcha!
Thanks!