JFET Vulcan with BMP tone

[blues123]

Hi,

Just breadboarded Joe's JFET Vulcan with a few alterations:
Bypass caps on stages 1 & 2 changed to .33u
Bypass cap on stage 3 removed
Voltage divider at output removed and replaced with BMP tone stack/control
Very pleased with the results and now have a lower gain tubey sounding overdrive with tone variations.

My issue is this:
After performing these alterations, I find that I am having to have the Volume at very near full to get unity gain.
Not a major problem, but I would like more output (obviously the tone stack and change to caps has reduced it somewhat).

What would be the easiest/best way to increase output?
Would a change of o/p pot do it without altering the sound?
Do I need an extra stage after tone, if so what would you guys suggest?

I don't want to alter the tone as I am very happy with it (I just want more Vol).

Any help appreciated, as I am still very much a novice!!

By the way, thanks Joe, this is a great sounding circuit..

[Khas Evets]

If you could show us the schematic with your changes, it would make it easier to make suggestions.

[blues123]

Here is the link to the schematic on Joe's page (didn't think it right to post it here)

http://www.diystompboxes.com/analogalchemy/pedals/jfetvulcan.html

These are the changes:
Stage 1 & 2 caps to ground from source both changed to .33u (was 1u)
Stage 3 cap to ground from source removed altogether (was 1u)
Voltage divider before output (2 x 470k resistors) removed and replaced by BMP tone stack top one on page below:

http://www.muzique.com/lab/tone3.htm

Hope this helps

[blues123]

Anybody??

[Skreddy]

One thing I would suggest is replace the 39k and 22k resistors in the BMP tone stack with 33k's (both).  It will even out the bass and treble sides of the output curve and give you a little bit more volume too.

Another way to increase gain and volume is to put back that last bypass cap.  But since you don't want it so heavy, just put either a pot (trimpot maybe) or a fixed resistor inline with it to simulate a pot at roughly 1/2 turn.  F'rinstance, 10k in series with a 1u cap. 

If you decide you need a volume-recovery stage after the tone stack, there are a plethora of single-transistor designs to choose from.  How about the BMP's very own volume-recovery stage, though?  I like it.

[MartyMart]

One thing I would suggest is replace the 39k and 22k resistors in the BMP tone stack with 33k's (both).  It will even out the bass and treble sides of the output curve and give you a little bit more volume too.
How about the BMP's very own volume-recovery stage, though?  I like it.

Yup, used that trick a few times and it does work very well too !!

MM.

[pyrop]

Hi.
Between stages 2 & 3 there is a 470k resistor, Maybe try lowering its value.
Try using 390k or 330k etc.
Or maybe use a 470k/500k trimpot & adjust to suit.
Worth a try.

pyrop

[blues123]

Thanks for your replies guys.

I will give it a try.

[WGTP]

There is a tone stack on one of Joe's other circuits that has different values than a BMP, and had less loss when I simmed it.  You might try that.