Does this schematic look good?

[Ben Lyman]

It's my own Ge fuzz creation, borrowing of course from many other sources, thanks Gus for the awesome tone stack!
Anyway, it sounds great on my breadboard but I want to know if any of you can spot any redundancies, overkill, important missing parts or improvements that can be made.
I created it through a lot of trial and error so a lot of changes were made along the way and this is where I ended up liking it.
(I just realized I forgot the 1M pulldown resistor in my drawing but I would not (hopefully) forget to include it in the soldering stage.
Also, let me know if any or all of it looks familiar to you 
Thanks!

[Derringer]

looks good Ben

One of the longest lasting pedals on my board is a MKII variant. They are open to lots of fun mods and just sound good!

The 0.1uF from emitter to ground on Q3 is a new one for me ... suppose you're always getting some top-end boost that way even with the 1k gain rolled all the way down. Cool.

Diodes are silicon?

Is everything biasing up nicely for you? No need for trim pots?

[Cozybuilder]

It's my own Ge fuzz creation, borrowing of course from many other sources, thanks Gus for the awesome tone stack!
Anyway, it sounds great on my breadboard but I want to know if any of you can spot any redundancies, overkill, important missing parts or improvements that can be made.
I created it through a lot of trial and error so a lot of changes were made along the way and this is where I ended up liking it.
(I just realized I forgot the 1M pulldown resistor in my drawing but I would not (hopefully) forget to include it in the soldering stage.
Also, let me know if any or all of it looks familiar to you 
Thanks!

Just curious why you have the voltage divider for Q1C? Essentially its 10K to C, 100K C to ground, which would give approximately 8.2V with 9V on the rail. Are you simply trying to attenuate the signal by 50%? If you want signal attenuation, you might consider a DC isolated pot instead.

[Ben Lyman]

...The 0.1uF from emitter to ground on Q3 is a new one for me ... suppose you're always getting some top end boost...

Diodes are silicon?

Is everything biasing up nicely for you? No need for trim pots?

I really don't know what I'm doing here but yes, the lowest gain setting sounded better to me with that .01 cap there, it made an otherwise muddy, unusable tone into a great sounding crunchy, rhythm-like or bluesy OD lead tone.

Diodes are still being swapped around a bit but I'm mostly liking the HP Motorola Si diodes from the surpluss store score.

I haven't even checked voltages because it just sounds perfect and I haven't even moved it back up off the floor to work on it in a couple days. If I get time later I'll check it out and see where it's at. No need for trimmers yet, Q2 and Q3 were dialed in using Joe Davissons FF calculator according to the gains I measured.

Just curious why you have the voltage divider for Q1C? Essentially its 10K to C, 100K C to ground, which would give approximately 8.2V with 9V on the rail. Are you simply trying to attenuate the signal by 50%? If you want signal attenuation, you might consider a DC isolated pot instead.

Thanks Russ, that is one of the things I was hoping to get advice on. Like I said, I don't know what I'm doing here but it sounds good so I'm afraid to experiment further without some guidance. After I used Joe Davissons FF calculator, I added a Ge volume booster stage in front (Q1) based on the EHX LPB-1. It added the right amount of boost when the pot was about 1/2 way so, not knowing anything else to do, I took out the (100k) pot and put in two (51k) resistors.
Is there a better way to achieve the same goal without using a pot? I really don't want four knobs on this box, I'm always hesitant to do even 3 knobs on anything 😬

[Derringer]

nothing wrong with attenuating the signal there. I did pretty much the same thing in my mk2 design 

Do you have a multimeter handy that you can check the voltage of the collector from the 1st transistor?

If it's somewhere between 3 and 6 volts, and it sounds good to you, I'd think you're good to go.
Otherwise, you might want to add a capacitor between the collector and the 51K resistor to isolate the DC voltage to the collector, re-measure it and then mess with either the 10K resistor or the 390R resistor (or both) to get that voltage somewhere between 3 and 6 volts ... 4.5 volts being the ideal clean boost voltage.

I've had experiences where, I breadboard everything, it sounds great with whatever biasing arrangement I made, then I build it, play it for a week and all of a sudden start noticing some gating or cutoff that I hadn't notice before.

[Kipper4]

You're a lucky guy Ben with these two guys on it and Gus too. Like the tones stack.
Watching and waiting a sample maybe?

[Ben Lyman]

...you might want to add a capacitor between the collector and the 51K resistor to isolate the DC voltage to the collector, re-measure it and then mess with either the 10K resistor or the 390R resistor (or both) to get that voltage somewhere between 3 and 6 volts ...

Yes, I have a DMM so I will look into that ASAP. I honestly didn't even know that I had all that stuff laid out like that until I inspected it to draw up the schematic. If I decide to adjust the voltage to Q1, is that 4.7uF ok right there or should I just move it in between the Q1c and 51k?

You're a lucky guy Ben with these two guys on it and Gus too. Like the tones stack.
Watching and waiting a sample maybe?

Yes indeed, I feel SO lucky to be getting help from any and everyone at this forum! I'll try to make a short video later.

[Keppy]

Cool design! I'd normally expect a coupling cap between Q1C and the 51k series resistor, but the voltage at Q1C will be dominated by the 10k to 9v and the CE resistance (10kish) rather than the 102k to ground so I don't see it screwing up the biasing. If it sounds good, box it up.

... except your 4.7uF cap is backwards. Q2B should sit at .3v or so, while the other end of that cap should have 2-3v at idle (Q1 collecter at 4.5v-ish divided in half by 51k resistors). Sometimes electrolytics can get leaky (or generally behave oddly) if they're reversed, so flip it on the breadboard and make sure it sounds the same with that cap inserted correctly. You really shouldn't leave an electrolytic reversed, so hopefully none of the sound you like is caused by a badly-behaving cap.

[Ben Lyman]

...I'd normally expect a coupling cap between Q1C and the 51k series resistor...

...your 4.7uF cap is backwards...

Thanks Keppy, fixed the 4.7uF and still love the sound... so that's the good news, I like the way it sounds... here's the bad news:
EDIT- New readings with 9v wall adapter:
Q1
   c. 1.41
   b. 0.49
   e. 0.32

Q2
   c. 0.73
   b. 0.11
   e. 0.00

Q3
   c. 5.96
   b. 0.73
   e. 0.56 

any suggestions? box it up because I like it? 🤔

[Keppy]

The posted schematic cannot produce the numbers shown. For example, Q2C is shown connected directly to Q3B, but you recorded them as different readings. Also, Q3B is above E, which shouldn't be possible, although I say that with little confidence because I haven't spent a ton of time experimenting with (potentially) leaky germanium transistors.

Whatever. The voltage feedback biasing maintains itself pretty well, so as long as Q3 collector is reasonable (it is), Q2 and Q3 should be fine.

Q1 is biased pretty hot, which should make it pretty asymmetrical, and lack of headroom in that stage doesn't matter much with all the gain behind it. That should be fine as well.

The only REAL problem I see is making sure you build what's actually on the breadboard. I say, double- and triple-check your schematic against what's on the breadboard to make sure you got it right. Then box it. Then play it a lot, because it sounds great!

[Ben Lyman]

The posted schematic cannot produce the numbers shown. For example, Q2C is shown connected directly to Q3B, but you recorded them as different readings. Also, Q3B is above E, which shouldn't be possible...

You're right, thanks! I think I was just careless when I did that. See my new readings above, they are all a little different because I used a one-spot instead of a battery but I'm pretty sure they are accurate this time.

[Ben Lyman]

I got the transistors from these boards I pulled from a 1967 Ampex Procamp processing amplifier.
It's loaded with Ge Texas Instruments and Philco transistors, about half PNP and half NPN. Lots of Ge diodes too, those sounded great but I think my mysterious HP/Motorola Si diodes sound a little better in this circuit.

[duck_arse]

what is that flying saucer on the heatsink, and what is the "stat-tran" directly above the double-twirled diode? another trivia Q?

[Cozybuilder]

Overall I think its looking good. If you can up the voltages on Q1 to (C= 3 to 5V) and (B= 1 to 2V), and for Q2C to about 1.5V, leaving Q3C about 4-6 V, I think you'd be real happy.

Which transistors did you wind up using?

[Gus]

look at Q2 collector note R10 VR2.
http://moosapotamus.net/ideas/acoustic-360-bass-fuzz/#more-263
and http://www.diystompboxes.com/smfforum/index.php?topic=105024.msg944241#msg944241

I think the decay control is something to experiment with

[Ben Lyman]

what is that flying saucer on the heatsink, and what is the "stat-tran" directly above the double-twirled diode? another trivia Q?

I dunno about the "Stat Tran" Duck.
Printed on it is:
PULSE ENG. PE-1983 .5MH,1:1:1 STAT-TRAN PAT NO. 2,885,643 6333P
It has 3 legs at each end, numbered (on the board) 1,3,5 and 2,4,6

The Flying Saucer is a solid gold Philco 2N600 protected by an elaborate heat sink/roll cage and gold leads insulated with clear plastic tubes.

Overall I think its looking good. If you can up the voltages on Q1 to (C= 3 to 5V) and (B= 1 to 2V), and for Q2C to about 1.5V, leaving Q3C about 4-6 V, I think you'd be real happy.

Which transistors did you wind up using?

Thanks Russ, any trick to upping the voltage? Maybe adjust my whack-a-doo voltage divider 51k to ground?
I swapped Q1 out with some others, sound didn't change but I got some new voltage readings:

Q1
   c 2.89
   b 0.39
   e 0.24
Q2
   c 0.80
   b 0.12
   e 0.00
Q3
   c 5.47
   b 0.80
   e 0.65

They are all Texas Inst. 2n1304 npn

look at Q2 collector note R10 VR2.
http://moosapotamus.net/ideas/acoustic-360-bass-fuzz/#more-263
and http://www.diystompboxes.com/smfforum/index.php?topic=105024.msg944241#msg944241

I think the decay control is something to experiment with

Thanks again Gus, I will look into that. I would rather not add anymore knobs to this and I really love that tone stack so I think 3 knobs only on this one.
I wonder if an internal trim pot would be a good place for the gate control?

The only other thing I am wondering about is power filtering. The little 1nF cap seems to lower some of the noise but I was considering a very small resistor in series with the +9v right before or after the protection diode. Any thoughts on that?

[Cozybuilder]

Ben- I'd try getting rid of that voltage divider first, this is easily done by just sticking a cap between Q1C and the first 51K, leaving the rest leading to Q2B as is, {or stick a 100K trimmer (or pot) in place with the wiper to the 4u7, and adjust to your liking, replace with a pair of resistors that are close to whatever that pot setting divides out to, or leave the trimmer (pot) in place}. The next thing is to up the 47K from ground to Q1B to about 100K. Measure- you should be closer on Q1 B and C.

Q2, I'd try 39K on the collector- that should get you closer to 1.5V, or even 33K.

[Derringer]

sounds pretty righteous in your clip!

Is there any ducking when you hit the strings hard? If not, I think you're pretty good.
If you have a 1K trim pot, you might want to try that in place of your 390r resistor on the emitter or Q1 and see if you can dial the voltage from its collector up to that 3v ~ 6V range. You could do the same think with a 10K trimmer in place of the 10K collector. That way, once you box it up and temperature changes, which changes the gain on those GE trannies, you have something you can compensate with. Might as well do a 10K trimmer in place of the 8k2 resistor as well if you're up for it.

I wouldn't mess with the 51K/51K voltage divider. I think that's part of the mojo you have going here.
The small cap from Q2e is a nice mod ... gives that real nice top end boost as heard in the clip. Leave it in.

I like to put a small resistor (100r ~ 330r) in series with the input voltage before the first filter cap just to make a proper low pass filter.
I honestly don't know if the polarity protection diode offers any resistance to do this function or not.
Keep in mind that series resistor, and the protection diode, do drop your V+ voltage a bit but probably not enough to lose the grand fidelity on a fuzzed out signal 

(entered this as Cozy was typing. So you have some options.  Lots of cooks in this kitchen)

[PRR]

> what is the "stat-tran"

Google and a good eye are your friends.

American Ultraminiature Component Parts Data 1965-66: Pergamon Electronics

Pulse transformers. Essentially zero use in audio.

[Ben Lyman]

Ben- I'd try getting rid of that voltage divider first...

I wouldn't mess with the 51K/51K voltage divider...

Okay, when I get a chance, I will try all of the above and see if the voltages come up without changing the sound.
I got a little ducking when I ran my FF into it wide open, but FF as a clean(ish) boost worked fine, added some presence and sustain, easy feedback. Otherwise seems to work properly all on it's own. 

...by just sticking a cap between Q1C and the first 51K, leaving the rest leading to Q2B as is...

If I do this, what is a good cap to use? My original layout did have a .1uF right there (I think) or maybe it was .01uF

I like to put a small resistor (100r ~ 330r) in series with the input voltage before the first filter cap...

I had a 100r in there too but it I didn't notice it doing anything and then I was concerned about the low voltages so I pulled it. Maybe If I can get the volts up, I can put it back in... or even a 330r