Jordan - Bosstone [schematic]

[JVanDe7]

Oh and I'm talking about your amp's gain, not volume.

[JVanDe7]

I have way too much volume on tap. What's the best way to fix this?

My volume pot is usable from OFF to 12 o'clock (halfway) but after that it just mushes everything up. Sorry I can't explain it with more detail but it basically "maxes out" too early, and turning it any higher up from there doesn't do much, just makes the problem worse.

Should I change the value of the pot? I used a 10K pot for volume (here's the layout I used, only difference is I made input cap switchable .022/.1)

[Liquitone]

if your volumepot is linear most of the usefull volume is bunched up at the first half of the pot's rotation,. a logaritmic pot should fix that problem

[JVanDe7]

Thanks! I'm not sure if I used log or linear but I'll take a peek once I get home from work. That makes sense, much appreciated.

[JVanDe7]

Sure enough. The layout didn't specify so I just used a linear 10k. Thanks for helping me spot the error! I'll get a log pot in there ASAP and then I shall have a nice smooooooth taper!!

[JVanDe7]

UPDATE: replaced the linear taper 10k volume pot with a log/audio taper one and it fixed the issue. Thanks again!

[Liquitone]

your welcome,. I'm glad it helped

[Chris Brown]

here's a video demo of my build.... Check it out: http://youtu.be/-m6-8F8ju4o

I used [this layout] which is the nashville circuit but I swapped the input and output caps for .1uf... it does a really cool octave thing as the notes sustain... Killer fuzz!

Thanks for all the info you guys posted here!

[Chris Brown]

here's a video demo of my build.... Check it out: http://youtu.be/-m6-8F8ju4o

I used [this layout] which is the nashville circuit but I swapped the input and output caps for .1uf... it does a really cool octave thing as the notes sustain... Killer fuzz!

Thanks for all the info you guys posted here!

just figured out the youtube link thing....

Link

[d rock]

I built one of these not too long ago and it is one of my all time favorite fuzzes. I put in switchable input caps but with I would of just put them on a pot to blend the two. Oh well. Used a 2N3904 for the Si and a Russian Mp16b for the germanium. Sounds way better than expected.

Can anyone elaborate on why this sounds so much different than a fuzz face? Very similar in schematic but sounds a good bit different. I'm sure the NPN/PNP combo has something to do with it but what is going on with the voltage dividers and capacitor to ground by the input stage?

[Nocentelli]

Can anyone elaborate on why this sounds so much different than a fuzz face? Very similar in schematic but sounds a good bit different. I'm sure the NPN/PNP combo has something to do with it but what is going on with the voltage dividers and capacitor to ground by the input stage?

I don't know if the circuits are that similar, other than being two-transistor fuzzes. To my eye, the bosstone looks like Q1 is a discrete, high gain boost circuit, a bit like the first transistor of a big muff or EHX LPB-1 booster (biased with two base resistors and a collector resistor on Q1, but running at max gain with a grounded emitter instead of a resistor/resistor+cap to ground), which then goes through a buffer formed by Q2. The heavily boosted, buffered guitar signal then has hard clipping applied with the diodes.

The fuzzface is a bit different because it has the two transistors used a single boost/fuzz stage, and no diode clipping: There is a different style of base biasing of Q1 (via feedback from Q2's emitter) so the way clipping reacts to absolute guitar input level is going to be different. There is a long and detailed explanation of this at [url=rgkeen's technology of the fuzzface]http://www.geofex.com/article_folders/fuzzface/fffram.htm[/url]

[d rock]

Can anyone elaborate on why this sounds so much different than a fuzz face? Very similar in schematic but sounds a good bit different. I'm sure the NPN/PNP combo has something to do with it but what is going on with the voltage dividers and capacitor to ground by the input stage?

I don't know if the circuits are that similar, other than being two-transistor fuzzes. To my eye, the bosstone looks like Q1 is a discrete, high gain boost circuit, a bit like the first transistor of a big muff or EHX LPB-1 booster (biased with two base resistors and a collector resistor on Q1, but running at max gain with a grounded emitter instead of a resistor/resistor+cap to ground), which then goes through a buffer formed by Q2. The heavily boosted, buffered guitar signal then has hard clipping applied with the diodes.

The fuzzface is a bit different because it has the two transistors used a single boost/fuzz stage, and no diode clipping: There is a different style of base biasing of Q1 (via feedback from Q2's emitter) so the way clipping reacts to absolute guitar input level is going to be different. There is a long and detailed explanation of this at [url=rgkeen's technology of the fuzzface]http://www.geofex.com/article_folders/fuzzface/fffram.htm[/url]

Some great info here. I now see the fuzz face is way different in design so thanks for pointing that out. Are you sure that the bosstone is just a boost and buffer with clipping diodes? The version I build I excluded the diodes for a more open sound and it is still super fuzzy. I did use a low gain germ transistor in the 2nd stage so I was assuming that was where I was getting all the fuzz, just sending a hot signal into that old leaky germ. Any thoughts on that?

[Nocentelli]

Q1 is definitely not a "clean" boost, it is running at a very high gain level and will distort the signal before it hits the clippers. I actually had a play around with it on the breadboard after posting yesterday (I was chiefly interested in the way Q1 collector is connected to the +9v via the Q2 emitter resistor) and whilst doing this, I removed the clippers to reveal the pleasing distortion you mention. I still think Q2 is set up exactly like any pnp buffer like this one below, but instead of using the two 470k resistors to bias the base, the Q2 in the Bosstone gets it's Vref direct from the Q1 collector since it is DC-coupled (i.e. no DC-blocking coupling capacitor):



One thing I did notice was that the signal out direct from Q1 is: a) less distorted, and b) lower output level than the output of the buffer. I think this maybe because the Q1 stage is overloading the buffer (providing more distortion), and the buffer is maybe altering the output impedance so there is less loading leading to a higher perceived output. Maybe others can chime in here, because I'm not at all certain.

[d rock]

Still trying to figure out the second PNP stage of this one. I've been playing around with it on the breadboard and what I get more than anything is just texture. Not much difference in gain but you do get some germanium character. Going to play around with the resistor values a little because since I am isolating Q2 i'm not exactly sure what the voltage of the base should be without Q1 feeding it.