Hipster Fuzz Osilation..

[hammerheadmusicman]

Hi guys, as per the rules Brian laid out.,

(1) Hipster Fuzz
(2) oscillates like crazy except when the fuzz is on a very low setting..
(3) Have Changed C2 to 47pf, seems a little better (will try a 100pf later when I have been to the local electronics shop)
(4) No subs have been made


All parts are correctly orientated, all wiring is where it should be.

I have used 2n3904's and they are biased a 4.5v, with the voltage lower it does seem to oscillate less.

Also I have been at it with an audio probe, and it seems like something hinky is going on with C5, one end sound really 'fat' and one sounds really 'thin'

Thanks for any help:)

George

[hammerheadmusicman]

OK... So i have put 100pf in, and it no longer oscilates.. but it does give off a painfully high pitched squeal when the fuzz is up high?? the fuzz sounds killer except for the squeal. one step forward...

[midwayfair]

when the fuzz is up high??

1) Does this occur only when it's wide open, or in, say, the last 1/4 turn of the fuzz pot? Does it stop squealing if you change your guitar volume? Is it like a microphonic squeal or like a "TV left on" super high-pitched squeal?

2) How loud is the pedal, and are you sure it's not your guitar feeding back? I know it sounds silly, but this could actually be what's going on.

C5 is functioning as normal. It's your output cap ... the AC protection cap on your probe is probably a different size.

[hammerheadmusicman]

It's not the guitar feeding back, it does it with the amp even really quiet. It squeals when it wide open, and when you turn the guitar volume down it changes pitch (ish). It is almost ear-drum bleeding territory!

[midwayfair]

It's not the guitar feeding back, it does it with the amp even really quiet. It squeals when it wide open, and when you turn the guitar volume down it changes pitch (ish). It is almost ear-drum bleeding territory!

If you're okay with not having the very last notch on the fuzz knob, you could put a very small (e.g. 47R) resistor in series with lug2 of the fuzz pot. It'll limit the minimum resistance shorted to ground through the 22uF cap.

I guess triple check all your parts values and orientation, too.

[hammerheadmusicman]

Have just had another look, it is doing some strange things..

1) when the fuzz pot is 'wide open' it has bucket loads of fuzz, bubba shrill whining noise..

2) when the you turn the fuzz pot down say 10% around 70% of the fuzz drops off, and the whining noises dissapears.

3) the whining noise is less when the bias pot is wide open..

If I were to ut a 47R resistor across the fuzz pot, I'd loose most of the effect :/

[midwayfair]

If I were to ut a 47R resistor across the fuzz pot, I'd loose most of the effect :/

Not across the pot, which reduce the pot to a ~40Ohm pot (and result in a great deal more distortion) in series with lug 2. This puts 47 ohms of resistance between the emitter and the 22uF cap. At minimum fuzz, there will be 1.04K resistance between the cap and the emitter (instead of just 1K), and an maximum fuzz there will be 47Ohms between the emitter and the cap, with 1K to ground. It essentially prevents the pot from maxing out. You could also put the 47R between lug 3 and the board, it has much the same effect, but it'll be different at minimum fuzz.

[mgwhit]

I'd like to see some clear pictures of the board.

[hammerheadmusicman]

Hi guys,

Pics of front and back of board

[hammerheadmusicman]

Back...

[mgwhit]

Thanks!  Looks good.  You might want to try substituting the transistors.  I would recommend breadboarding the circuit first so you know you've got good parts, or use sockets on the PCB.  This is a weird one.  Good luck!

Edit: Oh, what else is in your signal chain, and what pickups are you using?

[hammerheadmusicman]

Just had a quick test again (as loud as you can at 10 at night!) and something strange happened..

You asked a question about pickups, which sparked off something in my brain, I tested it with my strat (the one I was using before custom shop relic 61 - CS pickups) the squeal was there.. I switch to my Parker fly deluxe (humbuckers), and low and behold, noise is gone (ill have to have a louder test tomorrow, and see what's what) also I didn't try it coil tapped, so ill try that too. Btw I'm playing through a Dr Z Maz 18rvb head and cab.


What do you guys make of this? Do you think I could be a 60 cycle hum problem, I'm lead to believe this as it didn't happen with the buckers... I do have a power conditioner kit which I am yet to build up, which would be fairly useful at this point!

I suppose my next question is, if it is that, how do I fix it?

[greyscales]

I actually had a problem similar to this the other day when I built up a Fuzz Face with 2n3904s. I tried a range of ceramic caps from 47p to 470p. Originally I had left it empty, and got squeal when it was wide open. 47p knocked it down a bit. 100p was almost there. 220p was perfect.

I would try to get a range and see which is best for you. It's one of those values it wouldn't hurt to socket.

[hammerheadmusicman]

Thanks I've tried the stock 10pf,  47pf, and 100pf, I don't have a 220 to hand I don't think.
I have a 470pf though, I'll whip that in and see what it does. 

Mgwhit - forgot to say nothing else in the signal chain whatsoever, haven't boxed it yet either, 'build it, rock it, box it' (learned that the hard way on a previous tubescreamer project!!

Thanks again dudes. I'll keep you posted

[angrykoko]

Mine does the same thing, I tried different transistor types, changed the ceramic cap value too but didnt help.  Been meaning to look at it again to see if I could solve it.

When it's whining, mess with your guitars tone knob + volume.. I get some wicked cool 70's Sci-Fi sounds out of mine