Can you match a Ge Fuzz Face tone with Si transistors?

[Grunfeld]

I apologize if this topic has been beaten to death at this point, but I couldn't find anything conclusive on this.

I've built two fuzz pedals, one germanium and one silicon (these two for anyone interested)
https://aionfx.com/app/files/docs/solaris_documentation.pdf
https://aionfx.com/app/files/docs/epsilon_documentation.pdf

Ideally I'd like to match the tone of the Ge one with the Si one if possible due to the reliability of Si obviously.
I've been trying a 2N3903 in Q1 and then various 2N3904s and 2n2222s in Q2 from batches of 20 each.
However, all the combinations I've tried, while they don't sound bad by any means, they lack the smoothness of the Ge transistors and end up sounding more brittle.

Is it even possible to get Si transistors to sound like Ge ones? I've read people claiming that the only thing that matters is the hFE of the transistors and other people claiming that the only thing that matters is getting that 1.5 ratio between Q1 and Q2. Should I just accept the differences between Si and Ge and stick my Ge fuzz in the freezer? 

[EBK]

It really depends on what you mean by "match".
Can you make a 100% accurate clone of a particular Ge fuzz with magic Si transistors?  Probably not.
Can you make something that reasonably captures many of the qualities you like about a Ge fuzz using Si transistors? Probably yes.
Pinkjimiphoton made a couple projects that aimed for this:  the Stupid Face and the Photon Face, combined into the Schizoid Face.  Search for those, or wait until I dig up a link.....

[Grunfeld]

It really depends on what you mean by "match".
Can you make a 100% accurate clone of a particular Ge fuzz with magic Si transistors?  Probably not.
Can you make something that reasonably captures many of the qualities you like about a Ge fuzz using Si transistors? Probably yes.
Pinkjimiphoton made a couple projects that aimed for this:  the Stupid Face and the Photon Face, combined into the Schizoid Face.  Search for those, or wait until I dig up a link.....

Obviously it's going to come down to something pretty subjective. I don't think I can explain it any other way than I already did. The Ge fuzz has a certain smoothness that I'd like to achieve with the Si one, but haven't been able to.

[EBK]

Let's jump straight to PJP's results, then you can go back and dig further if you like what you hear:
https://www.diystompboxes.com/smfforum/index.php?topic=117221.msg1088312#msg1088312

[mozz]

Also try 100pf caps across the C-B junction of both transistors.

[Grunfeld]

Let's jump straight to PJP's results, then you can go back and dig further if you like what you hear:
https://www.diystompboxes.com/smfforum/index.php?topic=117221.msg1088312#msg1088312

Thanks! I'm kinda new to this so there's a few things I'm not understanding. On the very layout the volume pot is wired to the output which I don't understand.
Also how would I adapt the very layout to forgo the bicolour LEDs and also just use a single toggle switch for the different modes?

[EBK]

The layout uses a 3PDT switch.  If you want to skip the LED switching, just use a DPDT switch instead and ignore the LED connections.

The output of the circuit comes from the center lug of the volume pot.  That is the only output.  I'm bot sure I understand the question....

[Grunfeld]

The layout uses a 3PDT switch.  If you want to skip the LED switching, just use a DPDT switch instead and ignore the LED connections.

The output of the circuit comes from the center lug of the volume pot.  That is the only output.  I'm bot sure I understand the question....

The way I'm understanding it is that the output from the volume pot is wired directly to the output jack. Is that correct?

[EBK]

Not exactly.  Jimi omitted the usual bypass footswitch wiring.  The toggle only switches between the Stupid Face and Photon Face modes.  You'll need a separate 3PDT foot switch for turning the pedal off/on.  The volume pot circuit output would normally go to the footswitch. 

[Grunfeld]

Not exactly.  Jimi omitted the usual bypass footswitch wiring.  The toggle only switches between the Stupid Face and Photon Face modes.  You'll need a separate 3PDT foot switch for turning the pedal off/on.  The volume pot circuit output would normally go to the footswitch.

Oh yeah I see that now.

I'm actually thinking of trying to arrange this on perfboard instead of stripboard. Do you have any tips for that? I suppose I could just take the stripboard layout and manually forge the links where the tracks are, but I feel like there's a better way to do it.

[EBK]

For perfboard, I'd try to physically lay things out in the same general arrangement as they are drawn in the schematic.  Spread things out a bit, unless you are aiming to put this in a 1590A. 

Also, use sockets for the transistors.  You may want to audition different ones to see what sounds best ti you.

[Grunfeld]

For perfboard, I'd try to physically lay things out in the same general arrangement as they are drawn in the schematic.  Spread things out a bit, unless you are aiming to put this in a 1590A. 

Also, use sockets for the transistors.  You may want to audition different ones to see what sounds best ti you.

Yeah sockets are a given.

Would it make sense to include the power section on the board or do a separate board?

[antonis]

Also try 100pf caps across the C-B junction of both transistors.

@Grunfeld: Don't overtake what mozz said..
(although, I'd start from 47pF..)

[Grunfeld]

Also try 100pf caps across the C-B junction of both transistors.

@Grunfeld: Don't overtake what mozz said..
(although, I'd start from 47pF..)

I'll give that a try for sure.

[mozz]

Yeah, 47pf-51pf-68pf-82pf-100pf, something in that range. A lot of old crappy germanium transistors will measure somewhere about 50pf.

[pacealot]

This is also why Mac and several others around here recommend trying power transistors with a high(er) internal capacitance, like the BD237, BD175 and others. I've had good results with BD237s in several germanium-adapted circuits, though I've yet to try them specifically in an FF....

[Kevin Mitchell]

Will these mods make the transistors as temperature sensitive as GE?
Let's say you have a classic Ge fuzz face and a *simulated* Si version. You've tailored it at your soldering bench for Si to sound identical to a Ge unit, perhaps discernable. But once you bring those pedals out under the sun for your outdoors gig, the Ge will sound way different while the Si may retain more of it's character from your bench testing.

The mojo of a classic fuzz is derived from it's imperfections. So the effort to "match" these imperfections are subjected to the environment. Perhaps you could whip up a line of seasonal fuzz pedals to emulate these operating conditions.

Just my thoughts on the subject. Carry on 

[EBK]

For perfboard, I'd try to physically lay things out in the same general arrangement as they are drawn in the schematic.  Spread things out a bit, unless you are aiming to put this in a 1590A. 

Also, use sockets for the transistors.  You may want to audition different ones to see what sounds best ti you.

Yeah sockets are a given.

Would it make sense to include the power section on the board or do a separate board?

Yeah do the power section on the same board.  Keeps it simpler.  Mind your ground connections though. Transistors will happily amplify noise if arranged to do so.  (I get in trouble for saying things like this.  )

[Grunfeld]

Will these mods make the transistors as temperature sensitive as GE?
Let's say you have a classic Ge fuzz face and a *simulated* Si version. You've tailored it at your soldering bench for Si to sound identical to a Ge unit, perhaps discernable. But once you bring those pedals out under the sun for your outdoors gig, the Ge will sound way different while the Si may retain more of it's character from your bench testing.

The mojo of a classic fuzz is derived from it's imperfections. So the effort to "match" these imperfections are subjected to the environment. Perhaps you could whip up a line of seasonal fuzz pedals to emulate these operating conditions.

Just my thoughts on the subject. Carry on 

I don't know about you but my express goal is to avoid the temperature sensitivity of Ge transistors by using Si, but emulating their tonal characteristics.

[Grunfeld]

For perfboard, I'd try to physically lay things out in the same general arrangement as they are drawn in the schematic.  Spread things out a bit, unless you are aiming to put this in a 1590A. 

Also, use sockets for the transistors.  You may want to audition different ones to see what sounds best ti you.

Yeah sockets are a given.

Would it make sense to include the power section on the board or do a separate board?

Yeah do the power section on the same board.  Keeps it simpler.  Mind your ground connections though. Transistors will happily amplify noise if arranged to do so.  (I get in trouble for saying things like this.  )

On a slightly unrelated note, can you swap out electrolytic capacitors for tantalum? Seeing as tantalums aren't polarized.