BMP tone control question, how to implement?

[Barcode80]

so, i want to tack the BMP tone control onto a firestarter OD that i'm building but i'm not sure how to do it. does the output of the circuit that would normally go to the volume lug 3 get moved to the junction of the 4000pF cap and the 39k resistor, then the wiper of the tone pot goes to lug 3 of the volume pot? am i seeing this correctly? HELP!   

[tcobretti]

In place of the output cap and volume pot, use this:

[Barcode80]

okay, i'll give that a shot! thanks!

[Barcode80]

could you have a look at the pcb i made up for that and check me a bit for errors before i print it up?

http://aronnelson.com/gallery/album120/BMPToneSectionLayout

[tcobretti]

I've had a few drinks, but all I see is that you omitted the 39k resistor that goes from Lug 1 of the tone pot to ground.

Otherwise it looks good to me.

[Barcode80]

okay, i think i fixed it, could you have one more look 

[brett]

Hi
regarding this schemo.



While the general principles are ok, I can suggest a couple of changes.

Firstly, the BMP tone section is quite sensitive to loading. This isn't discussed much, so it's no surprise that it's not considered.  Instead of a 100k resistor to ground on the base of the transistor, it would be better to have 220k (or even 330k).

To compensate for that change, you'll want a 1M resistor from the base to supply (instead of 470k).

Also, the gain is high without any reason. It's a lot more than necessary to compensate for losses. So try a collector resistor of 22k and an emitter resistor of 4.7k.  The collector voltage should be 4 to 7 volts with these resistor values.  These resistors make the output impedance a bit high, but you'll be ok as long as the volume pot is a large value (100k and up).

Just my 2c worth.

[Barcode80]

okay, i'll try your changes out. fortunately, no pcb changes needed for any of that

[tcobretti]

The layout looks good to me.