Rat - Increase Volume?

[reubenreub]

So I've been playing around with the Rat circuit a bunch lately and have found I really like the sound with germanium clippers. The only thing is, it drops the volume quite a bit with how hard it's clipping.

Would it be possible to tweak things around a bit with the JFET buffer to instead act as a bit of a boost? Something like a 22k resistor or a 50k trim in between the 9v and the drain (to achieve ~4.5v) and connect the 1uf to the drain as seen below. Would there be any problems with doing this or unintended consequences? I do have this mocked up on a breadboard and am happy with the extra volume but I feel like I'm missing something here.... Any insight is appreciated!

 

[Nostradoomus]

If you have enough spare GE diodes try to double them up in series on your breadboard. The volume just might be back where you want it to be.

 

[reubenreub]

If you have enough spare GE diodes try to double them up in series on your breadboard. The volume just might be back where you want it to be.

But that's not as much fun! ? haha

Mostly I'm just curious if I'm on to something and if this is a correct way to turn a buffer into a boost.

 

[Nostradoomus]

I wouldn’t really mess with the output buffer as a source of volume, that’s not really the point of it. If you mess with the output impedance enough the next pedal in your chain won’t want to play nice.

Basic Buffers

Basic buffer circuits for use with guitar effects pedals.

www.muzique.com

 

[zgrav]

.... don't create a situation where you need to tack on another buffer after your first buffer...

 

[phi1]

I think it could work fine, check out the JHS morning glory schematic, which has a jfet boost to end the circuit very similar to your drawing. Maybe test out that portion of the circuit with a bread board to see if it has a big effect on down stream effects.

 

[Nostradoomus]

Yeah by all means experiment with it!

 

[Chuck D. Bones]

Getting the bias correct on that JFET may be a bit tricky because they have a wide spec for VP. Before you make the mod, measure the source voltage in-circuit. If it's higher than 3V, then you won't have any headroom once you add the drain resistor. You need a JFET with low VP, like the J201 or PF5102. Don't worry about output impedance, that's dominated by the VOLUME pot. The resistor values in your sketch will give approx 2x gain. You might want to go a little higher, maybe 3x. Once you get the right JFET, try 10K on the drain and 3.3K on the source. Test it out on a breadboard first to select the JFET and dial in the resistors.

 

[reubenreub]

Thanks for all of the responses! I have definitely been doing lots of experimenting on this and have been learning a lot in the process. I actually did use a PF5102 instead and have been getting some nice volume bumps to go along with it. I'm still tweaking how much gain I actually want out of it but am really liking where this is heading. Almost thinking I might do something similar for something like the Harmonic Percolator or other things which I'm looking for a bit more volume on.