JHS JAPAN FUZZ

[jaminjimlp]

Hey, new guy here... started building pedals a little over a year ago if you don't count one a kit I built from an electronics warehouse in 1992 lol... I searched the forum and didn't see anybody talking about this. It was a video JHS released about a month ago and he gave away the schematic for it in the video description (https://drive.google.com/file/d/1gYhKOddL0GHauRGQfZrUwQypvEwirMiw/view?usp=sharing) which I downloaded and proceeded to put together, when I got done it would not work I was like crap what did I do wrong... lol So I double and triple and quadruple checked everything, and then I remembered something on the TAYDA website about the fuzz face if you didn't want to use the PNP transistors that make the pedal positive ground you could use the NPN transistors and just swamp the polarity of the polarized caps and make it negative ground... so I FLIPPED them even though I was using PNP that were not geranium and voila it worked... doesn't sound too bad either... So I was just wondering if anyone else had tried this and what their results were. Here's the link to the video if you haven't seen it.

 

[Sturdag Lagernathy]

Do you have positive DC going to ground? -9vdc is your VCC (common collector voltage)..
It will work both ways, i.e, with a negative ground, just make sure you observe the correct polarities on, yup, transistors and electrolytics..

 

[Feral Feline]

Is it weird that the output is coming off the power supply ?

Usually it would come off between collector of Q2 and its 10k trim... I'm going to have to breadboard it, put the output on either side of that trimmer and see how the 10k trimmer affects the output when it's on the "wrong" side.

Weird not having an output cap. There are JFET boosts and what not that don't have an input cap, but none on output? Weird.

 

[Big Monk]

Is it weird that the output is coming off the power supply ?

It's NOT coming off the power supply though. It's coming off the junction of the 1k "Output" resistor and the trim.

Usually it would come off between collector of Q2 and its 10k trim... I'm going to have to breadboard it, put the output on either side of that trimmer and see how the 10k trimmer affects the output when it's on the "wrong" side.

This isn't right. Normal output on a two transistor English Fuzz comes off the OUTPUT cap, not off the collector of Q2:

Weird not having an output cap. There are JFET boosts and what not that don't have an input cap, but none on output? Weird.



View attachment 62463

I think the absence of the output cap is balanced by the larger Emitter cap.

 

[Feral Feline]

It's NOT coming off the power supply though. It's coming off the junction of the 1k "Output" resistor and the trim.



This isn't right. Normal output on a two transistor English Fuzz comes off the OUTPUT cap:

View attachment 62469

Thanks Big Monk. Didn't sleep last night, 6:30 am and I'm incoherent-posting on the forum.

Yes, not DIRECTLY off the power supply, but... as follows...

And Yes, output cap, but usually isn't the output cap off the Q2 collector between the 8k2? That's what my sleep-deprived brain is telling me most circuits are like that.


For example, if you ditched the tone control below, the 100n output cap is off the collector but after the 33k shoots the juice. Josh's "Japan Fuzz" has no output cap and is taking the output off the "wrong" side of the trimmer with only a 1k resistor between it and 9V.















Anyway, I'll rejoin the thread after I get some sleep, food, work. Hopefully in that order.

 

[Big Monk]

Yes, not DIRECTLY off the power supply, but... as follows...

And Yes, output cap, but usually isn't the output cap off the Q2 collector between the 8k2? That's what my sleep-deprived brain is telling me most circuits are like that.

This is the nominal setup for the classic Two Transistor English Fuzz:



If we redraw slightly, we see R2 and R3 form a fixed voltage divider, with the output taken to the output cap:



Here is how the JHS is setup, just without the output cap:



The main reason we want to have some sort of voltage divider on the output on this classic configuration is that there is a WHOPPING amount of signal gain in this two transistor fuzz circuit.

If we were to think about this for a second. Take the baseline 470 ohm value of R2 and increase it to 1.5k or so. Practically speaking, that's a MASSIVE increase in output volume. It can shift the unity from around 3:00 on the Fuzz Face Volume control to about 11:00.

When you crunch the numbers, it's only about a 10-20% increase in output "leaving" out of the voltage divider.

If you were to let the whole of the output signal leave Q2C unattenuated, you'd barely be able to crack the Volume control open before it was a complete chaotic nightmare.

For example, if you ditched the tone control below, the 100n output cap is off the collector but after the 33k shoots the juice. Josh's "Japan Fuzz" has no output cap and is taking the output off the "wrong" side of the trimmer with only a 1k resistor between it and 9V.


View attachment 62470

I would say that it's likely a design choice to have this circuit configured that way, i.e. the absence of the tone control would have probably triggered a change in how the output signal was handled.

 

[Robert]

I think the absence of the output cap is balanced by the larger Emitter cap.

That JHS circuit is going to have DC on the output.

 

[Big Monk]

That JHS circuit is going to have DC on the output.

Yup.

Scratchy, scratchy.

 

[Robert]

That isn't going to play well with a DC coupled JFET stage in the next pedal in the chain either.

But in that case I'd consider both circuits at fault.


I don't know what all the fuss is about this circuit though, I just see a Fuzz Face without the output coupling cap?

EDIT: and a "bright" cap

 

[Big Monk]

That isn't going to play well with a DC coupled JFET stage in the next pedal in the chain either.

But in that case I'd consider both circuits at fault.


I don't know what all the fuss is about this circuit though, I just see a Fuzz Face without the output coupling cap?

EDIT: and a "bright" cap

And a huge emitter cap, which would not be necessary if you had an output cap.

 

[Harry Klippton]

But JHS

 

[benny_profane]

So, you could blow up an amp with a leaky input cap with this guy, right?

EDIT: I mixed up thinking about topologies there. That's not a thing. Wouldn't potential adversely affect the bias though?

 

[Feral Feline]

Thanks again, @Big Monk. A lot clearer to me now.

I did look at Electrosmash's breakdown of the Fuzz Face and noticed the voltage divider aspect, but you've added clarity where Electrosmash could not.

Thanks also to @Robert.

 

[Big Monk]

Thanks again, @Big Monk. A lot clearer to me now.

I did look at Electrosmash's breakdown of the Fuzz Face and noticed the voltage divider aspect, but you've added clarity where Electrosmash could not.

Thanks also to @Robert.

I AM a Fuzz Face Whisperer (Self Proclaimed).

 

[jaminjimlp]

Do you have positive DC going to ground? -9vdc is your VCC (common collector voltage)..
It will work both ways, i.e, with a negative ground, just make sure you observe the correct polarities on, yup, transistors and electrolytics..

Yep sorry for the slow reply