Pot on input of Fuzz Face

[phillip]

I've recently been experimenting with the Fuzz Face again, which included the addition of a pot on the input (ala the Fulltone '69), which would allow a preset of the "guitar volume turned down" effect.  The 50KB, which is shown in the Fulltone '69 schematics, doesn't seem to have much effect on the sound right away when compared to the guitar's volume control, which does change the sound of the Fuzz Face right there in the first bit of its rotation.

I'm thinking that it might need to be a larger value, like 100KB, so that the resistance increases faster than in the 50KB, or using a 50KC (reverse audio) pot so that the resistance increases faster early in the pots rotation.  Problem is...I haven't seen a 50KC pot anywhere!  I do have plenty of 100KB pots to experiment with though.

Any ideas?

Phillip

[RGW]

Hey Erik,
I tried it with both 50K and 100K pots (linears and logs) and to be honest it is always a "subtle" effect.

With the 100K naturally you get more attenuation when the resistance is dialed in all the way, but overall the gain never drops like it does with your guitars volume knob or with the input pot set up ala Joe Gagan's mod (which is essentially the same as the Fulltone 69 set up except the 1 lug on the input pot is grounded).

So the "parallel" input gain set up works more drastically, but I like the "series" input gain pot better.

To my ears it is very subtle but adding the series resistance really softens the attack and is much more useful to me.

But as far as different values of series input gain control pots, it always reamins a "subtle" control to my ears.

take care,
Robbie

[Lonestarjohnny]

Rob 1 out of an old Fender amp, they all had 1 in them, that is on the S/F - B/F amps, Just Joken about robbin 1, Stewart-Macdonald did list a 50K ra pot, I don't think I have ever seen a mini-pot listed anywhere though.
JD

[phillip]

Thanks guys.  I bet the pot on the input would work a lot better wired as a voltage divider instead of a series resistor.  I'll have to use a 100K pot and wire it up that way instead.

Robbie, who's Erik?

Phillip

[J Gagan]

I always come back to the magic 250k for this function.never tried the voltage divider thing, will have to give it a go

I set the FF type circuit up pretty hot with a high gain Ge for Q2 and a 47uf to ground at Q2 (adjust Q2 bias accordingly). Si for Q1

I used to sub in a 2k resistor to ground in place of the fuzz pot, but lately I like the added versatility of using a 1k ( or 500 ohm ) pot to parrallel the aforementioned 47uf alongside a 2.2 uf. To my ears, this gives a more musical effect to the traditional fuzz control on the FF
see circ:
http://www.ampage.org/sounds/files/ezfacemodgain.jpg

[RGW]

Robbie, who's Erik?
Phillip

Uh...Erik was the guy I sent an email to right before I posted my reply...lol.

Gotta keep the names straight, too much bouncing around in the old head today...lol.

But in ref to the input pot: wired as a voltage divider you will definitely notice it functions better as an "input gain control", but to my ears it sounds virtually just like rolling your guitars volume knob up and down. Essentially it is doing the same thing. So you have your guitars volume knob and a pot on the fuzz face doing the same thing. But if you want to have a "pre-set gain" on the pedal and leave your guitars volume knob up then this would be beneficial.

I tried the input pot both series and parallel and even with the pot turned up all the way for max gain (lugs 3 and 2 shorted) you can hear a difference when making and breaking the ground on lug 1 to make it series or parallel . The load of the 100K pot on the input of the Fuzz Face makes a difference (be it a small one maybe since the input impedance is low to begin with). The series sounds a hair thicker when at max gain.  


Try it and let me know what you think, I am curious to see if you have the same opinions. Maybe a try 250K, I think Joe Gagan used that value (not sure though).  

I love the Fuzz Face circuit when it comes to tinkering.


take care,
Robbie

[J Gagan]

ha. looks like Robbie was typing at the same time as me.

to  be more clear, I experimented extensively with values of input gain pot, 250k was always my fave.  but that might be influenced by my preference for the high gain FF setup

[phillip]

Nice to see you back, Joe!  Didn't you use a voltage divider arrangement for "PreGain" on the Easyface?  Lug 3 takes the input signal, the wiper arm is connected to the base of Q2, and lug 1 is grounded.

With that setup, it would work just like the guitar's volume control, especially if you used a 250KA pot.

The series resistor is quite a subtle effect, but it also has the effect of helping to prevent RF interference in the circuit if you turn it up just a bit, so that it's only at 1K or so.

Phillip

[J Gagan]

oh yeah voltage divider. right. I was thinking of it a different way.

[Ben N]

Wouldn't that really load down your signal--like having two volume controls on your guitar, or halving the value of the volume pot (assuming the FF is unbuffered & first in line)?

[J Gagan]

Wouldn't that really load down your signal--like having two volume controls on your guitar, or halving the value of the volume pot (assuming the FF is unbuffered & first in line)?

yes, but it doesn't hurt the tone much at all. try an a/b test, you will hear a slight difference between 250k full up vs.bypassed.

i used to use a  250k switched pot to do this ( GT fuzz)

[Kleber AG]

Nice to see you here Joe!
http://www.ampage.org/sounds/files/ezfacemodgain.jpg
In this schem, the pre-gain control conects straight to Q1 base, but I remember when I tried this kind of arrangement I had problems with Q1 bias because of the pre-gain, so I just moved it right to the input before the first cap...

Is it just me? Well I may have done some mistake... Does anyone had some experience with this?

(((uhmmm, I think it's because I was using PNP "negative" ground)))

Kleber AG

[phillip]

In my Fuzz Face I have it before the input cap also.  The signal goes into lug 1, the wiper is connected to the input cap, and lug 3 is left unconnected.  I haven't tried it with the pot after the input cap.

Phillip

[J Gagan]

that is correct. the cap is better after the pot

i can no longer log into the ampage site to update the schems (?)

[Kleber AG]

Hey Joe, I love your circuits, I remember I tried the bronto but with silicon piggbacked transistors  and I liked it very much...

Please, If you don't mind could you post new(or corrected) schems here in the "schematics 2" section?

That would be great! And we miss you here Joe... Have you seen the "Piggbacking transistor" thread? For fuzz styles circuits?

Kleber AG

[J Gagan]

no prob posting the most current versions
I have a few new babies to spread around also , but they are on paper , not digital yet
I don't have a webpage per se.
does the schematics 2 section have a way to download them directly?

Yes, I saw the piggybacking thing ( cool trick). I messed with it a little , but need to spend a little more time with it

[Kleber AG]

wow,  new babies!!!

Yeah, I think that the schematics 2 is open to post schems, but I don't know how. I'm sure someone can help you here on how to post there (anyone?)

Could someone help here?
Thanks
Kleber AG

[phillip]

no prob posting the most current versions
I have a few new babies to spread around also , but they are on paper , not digital yet
I don't have a webpage per se.
does the schematics 2 section have a way to download them directly?

Yes, I saw the piggybacking thing ( cool trick). I messed with it a little , but need to spend a little more time with it

Joe, I can post your schematics at Fuzz Central if you'd like.  That way if you wanted to update one all you'd have to do is email me the newest vesion and I'd post it up.

Phillip