Foxx Select-a-fuzz.

[Gus]

Are the parts values from a traced select-a-fuzz or is this still a guess?

It does sound good

Are you getting any oscillation from the circuit with the heavy fuzz setting and humbuckers at full guitar volume? (R11 connection at R5, R6)?

I am not a fan of about 1/2 supply voltage at a FF like distortion 2nd collector.

[bluebunny]

Nice noise.  Nice PJs.   

[digi2t]

Are the parts values from a traced select-a-fuzz or is this still a guess?

It does sound good

Are you getting any oscillation from the circuit with the heavy fuzz setting and humbuckers at full guitar volume? (R11 connection at R5, R6)?

I am not a fan of about 1/2 supply voltage at a FF like distortion 2nd collector.

Guess. Here are the values that you had sent me;



It wasn't performing like it does now. Your sim was actually rather poor in the sustain department.

No oscillation whatsoever. The 1n cap across Q1 takes care of that, and the high end still has lots of spank. The 12K/332 cap combo reacts like a drive control. Using a cap bigger than 2u2 makes it sound really mushy, hence the 3K3/2u2 combo.

Nice noise.  Nice PJs.   

Muchos gracias hefe!

[bmsiddall]

Greetings from Australia.

First of all, great to see you back on deck Digi2t!

Secondly, have built this with mixed results.  It's fuzzing but single note leads show a consistent octave down and lack thickness. Ironically I'd be very pleased if this was another harmonic perc build!    Voltages in the fuzz face section are close (Q1 1.43, 0.65, 0, Q2 5.3, 1.43, 0.76), but the collector on Q3 reads about 4.5v with the fuzz pot set halfway.

Regarding Q3, i've thrown some values into the guitar science simulator (http://www.guitarscience.net/calcs/cecbmf.htm).  Inputs- Hfe 150, Vcc 8.65v (measured), Vc 4.5v, Rc 12K, Rb2 8.3k (39K//(1/2 x 10k pot + 5k6).  These values calculate Rb1 at 47K, which is right on the money from the schem.  Substituting the posted Vc of 1.96v, Rb1 calculates out at 16k.  So not sure if the posted values are ok or if I've made an error?

I'll need to break out the audio probe to see where the octave is being generated, but I'm wondering about the single diode on the output.  I seem to recall reading a comment about asymmetrical clipping potentially resulting in an octave, so could this be an issue?  Has anyone seen an unwanted octave on a fuzz face build before?

Cheers,
Brett

[digi2t]

Greetings from Australia.

First of all, great to see you back on deck Digi2t!

Secondly, have built this with mixed results.  It's fuzzing but single note leads show a consistent octave down and lack thickness. Ironically I'd be very pleased if this was another harmonic perc build!    Voltages in the fuzz face section are close (Q1 1.43, 0.65, 0, Q2 5.3, 1.43, 0.76), but the collector on Q3 reads about 4.5v with the fuzz pot set halfway.

Regarding Q3, i've thrown some values into the guitar science simulator (http://www.guitarscience.net/calcs/cecbmf.htm).  Inputs- Hfe 150, Vcc 8.65v (measured), Vc 4.5v, Rc 12K, Rb2 8.3k (39K//(1/2 x 10k pot + 5k6).  These values calculate Rb1 at 47K, which is right on the money from the schem.  Substituting the posted Vc of 1.96v, Rb1 calculates out at 16k.  So not sure if the posted values are ok or if I've made an error?

I'll need to break out the audio probe to see where the octave is being generated, but I'm wondering about the single diode on the output.  I seem to recall reading a comment about asymmetrical clipping potentially resulting in an octave, so could this be an issue?  Has anyone seen an unwanted octave on a fuzz face build before?

Cheers,
Brett

Thanks Brett. Good to be amoung the living.

If I may ask, which schematic are you drawing on, mine or Gus'?

[bmsiddall]

I used yours.

Cheers,
Brett

[digi2t]

With the transistors I've listed on the schematic, same resistor values, I range between 1.8 and 2.2 volts at the collector.

Mind you, this is a very fussy circuit when it comes to transistors. It just doesn't seem to like the run of the mill 2N3904, or worse yet, 2N5088. I've tried BC108's and 2N3700 in here as well, and the results were not stellar. The 2N2222A's were just... OK. Just. The 2N2219 or 2N3903 are really nice, but the 2N3965 2N3569's are the cat's ass. Don't know why, but the ear candy is there. 2N3903 is a nose hair behind in second place, followed by the 2N2219 a quarter length back. Of course... those are my ears.

[bmsiddall]

Deleted

[Ben N]

You had me confused there--some of the posts in the thread have subbed 2N3965 for 2N3569 -- but that wouldn't work at all, now would it? But a glance at the schematic set me straight. It's the NPN one. 
It's all cool--I get a touch of dyslexia now and again, too. But Dino and Brett--you might want to edit above to keep from leading the flock astray.
I note for purposes of the conversation that Small Bear lists hfe for the 2N3569 as 60-150. Fairchild's and Central Semi's datasheets say 100-300. And, FWIW, my stash of 2N3904s tend to test at the high end of its spec range for hfe, or even slightly, above. So maybe low gain really is the key.

[digi2t]

 Oups! Yes... dyslexia indeed! I've corrected my offending post.

[bmsiddall]

i win- have deleted my offending post