Another NPN Fuzz Face Question (...and yes, I searched.)

[ayayay!]

This is for a JH-2 Classic Fuzz.  It's apparent the electro caps are oriented differently on the NPN versions of the Fuzz Face.  Why is that?  (I'm not finding any hints in the search, or geofex's TTOTFF.)  Does this have something to do with the negative ground wiring for the different versions?  I'm ignorant to the knowledge of negative grounding. 

What specifically confuses me is the 2.2uf input cap having the neg side on the input.  Why is that?  I've seen 3 of these schems saying this.   Also the gain 22uf cap on NPN versions is oriented opposite the PNP versions.

I'm sure this has been covered ad nauseum, but I need your knowledge on the matter.  Thanks! 

***Ooh, one more question:  Does the protection diode have to be a zener?  I used one, but wouldn't a 1n4001 suffice?  What's the reasoning behind using a zener?  ***

Here's one version:  http://www.schematicheaven.com/effects/hendrix_fuzzface.pdf   

[Gus]

Did AG give permission for the schematic to be shown in your post?

Use a meter set to DC volts for an answer to your question.  You are asking a very basic question about electrolyic caps in circuits.

[ayayay!]

Did AG give permission for the schematic to be shown in your post? 

Who is AG?  I see nothing in either schem that says not to, but I'll yank it.  If someone posted it and caused me to inadvertently post via 3rd part, I apologize.   

Use a meter set to DC volts for an answer to your question.  You are asking a very basic question about electrolyic caps in circuits.

Wow.  That really didn't answer any of my questions.  It never fails that I'm greeted with this kind of answer for asking legitimate questions. 
And of course, I'm the bad guy because I'm going to ask again:  "It's apparent the electro caps are oriented differently on the NPN versions of the Fuzz Face. Why is that?  (I'm not finding any hints in the search, or geofex's TTOTFF.)  Does this have something to do with the negative ground wiring for the different versions?  I'm ignorant to the knowledge of negative grounding. 

What specifically confuses me is the 2.2uf input cap having the neg side on the input.  Why is that?  I've seen 3 of these schems saying this.   Also the gain 22uf cap on NPN versions is oriented opposite the PNP versions.

I'm sure this has been covered ad nauseum, but I need your knowledge on the matter.  Thanks! "

I dunno, if I'm the only guy left on the forum that has questions, I guess I'll leave.

[Gus]

Take the meter and measure across the caps.

Links are OK. 

You don't know who AG is? (AnalogGuru)  Check out ....

This site is DIY,  I did give a kind of answer but you would need to measure, or ask why does the sticky about what to do when it does not work ask to take voltage measurements.  Now this being the web you might have misunderstood my post.  If you took measurements, you would note the +cap side is more positive than the -cap side(the base is about .6vdc higher than the emitter in Si transistor in this circuit) why does a cap have + and - markings?

[caress]

pnp fuzzfaces are wired with positive ground, npn negative ground - because of this it is necessary to flip the orientation of your polarized caps, diodes, etc.
you would do the same on other pnp -> npn conversions and vice versa on npn -> pnp conversions...

[ayayay!]

Thank you guys.  Makes perfect sense now. 

But Gus, I'm afraid you missed MY point, which was not only to educate myself, but several of the lurkers here that are too afraid to ask questions. 

The effect works.  I never said it didn't.  I apologize if I gave that impression, but I didn't think I did.  So the sticky wouldn't help me really in that case. 

Can either of you guys point me towards a good read-up on the subject? 

Thanks!   

[grapefruit]

Not much to read on this. Electro caps are polarised, so you always put the + terminal to the side that is going to be highest voltage. In the case of the NPN fuzz face one side of all the electro caps is effectively connected to ground and the other side is connected to a positive voltage, so the - terminal on the cap goes to ground.

Maybe transistor biasing would be a useful thing to read so you can understand what the voltages will be.

Stew.

[bumblebee]

Did AG give permission for the schematic to be shown in your post?

AG wouldn't care one bit about using his schema online, Infact he promotes using his schematics because they are correct.

[ayayay!]

so you always put the + terminal to the side that is going to be highest voltage.

That is what I was looking for.  I know about biasing transistors, but I haven't encountered the caps in this orientation before.  And like I said, this effect works. 

I always assumed (wrongly, I can see) that the negative side of any polarized cap must have the input enter on the positive side.  Clearly this depends on what you call "input"    Yuh learn something new every day. 

[grapefruit]

Yes, the cap is blocking DC voltage so the + terminal goes to whatever side has the highest DC voltage. It doesn't make any difference wether it is the signal input or output.

Stew.

[petemoore]

  RG just recently wrote on this..
  Capacitors should never be reverse polarized, even for a moment.
  So basically you need to know what you're subjecting the cap to in each placement, what potentials will be present in that position, and the difference between + and - on the cap, that it never include reverse polarization.
  Thats easy in  -gnd. circuit. Ground will always be the most negative node in the circuit. Input and output caps will be lower voltage on the 'outsides' of the DC blocking capacitors -lCapl+circuit+lCapl-, the active portion of the circuit [B/C/E..etc.] measuring these will show + readings, the 'inside' of the circuit is +ish.
  Caps can be placed in positions which swing + and - with the signal, iwcase non-polarized capacitors would be required.    
  In almost all cases, follow the schematic, there is no substitube for measuring the voltages, the show makes great note taking fodder, tells DC polarities.

[ayayay!]

Hey could you help me with something else?  In the last 5% of the gain pot travel, everything suddenly gets super bright, and I mean in a hard cut-off kind of way.  It sounds good actually, but when dialing back down I lose the brightness and like I said it's SUPER apparent.  Once I hit about 30 ohms on the gain pot, it's all downhill from there.  No smooth taper, it's like a hi-cut button is being pressed. 

Here's what I don't get:  I'm using 2n5088s, which sound great (remember, this is the NPN build...) I tried 2n5089s, MPSA18s & 2n3904s.  They all have vastly different gain structure, but all do the exact same thing with the travel of the gain pot.  So my thought was, "bad pot."  But after replacing the 1K Lin pot, the same thing still occurs.

So then I figured maybe the polarized caps got hit in reverse somehow.  Nope.  Replaced those (2.2uf &22uf) and the same thing still happens. 

What am I missing? 

[ayayay!]

bump

[grapefruit]

Probably should start a new thread for this...

I'm not too familiar with that circuit, but you could try adding a series resistance (27 ohms??) to the pot (between the pot and Q2,68k,47pF), or increasing the 22uF cap, or a combination of both...

Maybe new MPSA18 are higher gain than they used to be.

Stew.

[ayayay!]

Probably should start a new thread for this...

I'm not too familiar with that circuit, but you could try adding a series resistance (27 ohms??) to the pot (between the pot and Q2,68k,47pF), or increasing the 22uF cap, or a combination of both...

Maybe new MPSA18 are higher gain than they used to be.

Stew.

I started a new one just a few minutes before you posted this response, but thank you.  http://www.diystompboxes.com/smfforum/index.php?topic=74704.0