A somewhat different fuzz

[Gus]

If you want to use a lower beta transistor you might need to adjust R4 for a lower collector voltage.  A 2n2222 sims at just over 5VDC with R4 at 1meg however if you reduce R4 value it changes the gain control interaction with the circuit. It might sound OK

I set this circuit up for higher beta hfe transistors for a more just drop in the transistor and don't worry about biasing.
For more output you could try 1n400Xs or 4 1N4148s(2 and 2) or two about 1.5 drop LEDs the 10K in series with the diodes can be adjusted up and down.  The  cap in series with the clipping diodes can be adjusted down in value for more bass.

A circuit design can be a set of compromises.  This circuit was a two higher hfe transistor, two control somewhat different way to set the gain in a fuzz circuit.  I tried to get the gain stages to increase in gain at the same time in a musical way (both gain and high and low pass filters).   Higher hfe beta silicon transistors can sound nice in fuzzes and distortion.

[Davelectro]

Thanks. I'll go with a pair of 2N5088.

[pinkjimiphoton]

went back in, turned out i'd swapped pins 1 and 2 on the volume pot/. 

huge improvement. also made the leads shorter, and grounded the volume pots to star ground (it's in a plastic enclosure) and added a "shield" connected to ground to cover the bottom of the circuit inside the plastic box. believe it or not, it works. it's quiet enough to gig with now.

[tubegeek]

So I notice that R2 and R10 have been 0, 10 or 100 ohms depending on the specific build (Gus with 100 in the first place, 0 on thge build, jimi with 10 ohms on his build.)

What would be the difference that you'd expect? Is it a biasing choice or is it a choice based on the desired degenerative feedback (I think that's what those R's will do, right? Like a cathode R on a tube?)

Working on a little PCB layout for this.

-j

[pinkjimiphoton]

to me, yeah i think of it like a cathode in a tube.

[tubegeek]

I drew up a PCB layout. NOT BUILT/NOT VERIFIED YET!

I'll try and etch it over the weekend and report back. Any corrections/comments much appreciated.

The pdf linked below has 5 views: copper side 3x life size, correct orientation for toner transfer; component side 3x life size, correct orientation for reading or for glue-on;  component side 1x life size, correct orientation for toner transfer, 6-up; component side 1x life size, correct orientation for reading or for glue-on, 6-up; copper 1x life size, correct orientation for toner transfer, 6-up.

https://dl.dropboxusercontent.com/u/4722178/asdf%20circuit%20board%20views.pdf

EDIT: I revised the pdf.

[tubegeek]

This was a very good etching experience - I gave up on sticker paper and plunked down 13 bucks for 250 sheets of H-P Presentation Paper, which has been recommended by some of the folks here. This worked quite well, take a look.

This is what it looked like after etching, with the toner still attached. You can see my spot repairs made with a Staedtler Lumicolor pen, the choice of such luminaries as Mark Hammer and Salvador Dali:



This is what the board looked like after I stripped off the toner (you are looking at the cleaned-off copper side, backlit):




This is my best etch ever by far - the detail is far better than I've ever achieved. Both the negative-space lettering and the copper lettering are very well detailed - that letting is very tiny. The whole (double ) board is 3" x 4" to give you a sense.

Score one for H-P Presentation Paper.

In a frustrating turn of events, I'm having trouble finding where I put my Dremel - as soon as I do I can start populating these boards!

Anybody know where it is?

[mth5044]

Nice looking PCB! Glad I saw this as I was about to make one and share it on OSHPark.

[tubegeek]

Nice looking PCB! Glad I saw this as I was about to make one and share it on OSHPark.

Thanks! You may want to wait until I find my Dremel, test & verify the board, but I - think - I did it right (famous last words.)

[pinkjimiphoton]

that looks awesome... love the vintage trippy vibe!!

[tubegeek]

Found the Dremel! So I've made some progress: almost ready to test - maybe tonight?

Gus: Hfe of 270 seem OK? I am using some 2N2222's or perhaps a different number, they came in a Rat Shack Pack and I can't read the numbers without my loupe. I'm using 500K linear for the Gain control. 10 ohms for the emitter resistors. I had to jumper the Zener diode spot because I don't have one. The closest I could get to 330 pF in my parts stash was 220 pF. Otherwise, everything is as drawn in your schematic.

Seem likely to work?

One board is just drilled, one drilled/stuffed/soldered:


And, the stuffed board wired to jacks etc.:



Hoping to play a little bit tonight after everybody goes to sleep - we'll see.

[pinkjimiphoton]

ummm,.. the 390 pf is part of the guitar sim. the circuit starts at the input, the junction of r18 and c2.

all the stuff before that point to the left should not be on the board, it's to show the guitar's interaction with the circuit, and it may not work with all that stuff on there.

hfe of 270 should be fine, in this higher gain is better. socket. cut up a 6 or 8 pin ic socket if you need to.

by zener do you mean the diode clipper between b and c of q2? you can't jumper that , it will become the equivalent of shorting c and b together, tho the cap may help. the diodes there are what make this thing fuzz, if you take them out you'll most likely have a booster.

any diodes should work, even led's, which should be louder and give a nice bit of compression.

500k gain pot is fine.  anything from 100k to 1meg will probably work there. i used 500k if memory serves.

so... i don't know if it will work with all the stuff in front of the circuit, but pretty sure you need the diodes, and not a jumper.

if it doesn't work, try connecting your input to the node i mentioned, and putting led's or something in for the diode clipper. i think it's an open circuit without them, and a short circuit jumpered.

may be wrong...

[tubegeek]

ummm,.. the 390 pf is part of the guitar sim. the circuit starts at the input, the junction of r18 and c2.

I hear that bro. I'm looking at the schematic Gus posted in message #29 (just after your vero layout in this thread) - there's a 330 pF from B to C of Q2 adding a little extra NFB for stability at high freqs I suppose...

The Zener I mentioned is shown in that drawing too - it's up by the battery, reverse battery protection I think?

all the stuff before that point to the left should not be on the board, it's to show the guitar's interaction with the circuit, and it may not work with all that stuff on there.

Check. I'm not using that section from the first schematic. Check Gus' second schematic out. I'm starting where you say - at the "input" marker.

hfe of 270 should be fine, in this higher gain is better. socket. cut up a 6 or 8 pin ic socket if you need to.

Check. I did socket, momma didn't raise no fool, except my brother.

by zener do you mean the diode clipper between b and c of q2? you can't jumper that , it will become the equivalent of shorting c and b together, tho the cap may help. the diodes there are what make this thing fuzz, if you take them out you'll most likely have a booster.

any diodes should work, even led's, which should be louder and give a nice bit of compression.

Check. I have the 2 antiparallel 2n4148's, those are all set.

500k gain pot is fine.  anything from 100k to 1meg will probably work there. i used 500k if memory serves.

Check.

so... i don't know if it will work with all the stuff in front of the circuit, but pretty sure you need the diodes, and not a jumper.

if it doesn't work, try connecting your input to the node i mentioned, and putting led's or something in for the diode clipper. i think it's an open circuit without them, and a short circuit jumpered.

may be wrong...

You might be, but I agree with you! Thank you for the confirmation on the 270 Hfe and the 500K pot, I will get some time to play tomorrow afternoon, I'll check in with my results then.

[pinkjimiphoton]

must have missed the other schematic. my memory blows these days. cof cof...

yah, if it was up by the filter cap with cathode to + and anode to ground, just leave it out.

other than that, you should be good to go.

i think you're gonna love it.

[tubegeek]

i think you're gonna love it.

I'm itching to try it but sleep & work are getting in the way....
Thanks for chiming in and keep crossed fingers....

[Gus]

a link for the diode
http://www.fairchildsemi.com/ds/1N/1N5818.pdf

You could  jumper the emitters to ground, 10 ohms does little

500K should work

What are the collector voltages to ground with the 2n2222s you have?

[mth5044]

EDIT: Under revision

[tubegeek]

a link for the diode
http://www.fairchildsemi.com/ds/1N/1N5818.pdf

Aha! A schottky, not a Zener - I have something around here that will be close enough... thanks.

What are the collector voltages to ground with the 2n2222s you have?

Will let you know in a short while, thanks for the help!

[Gus]

I made a board as well if anyone is interested. The unsymmetricalness of the diodes is killing me, but what are ya gonna do. Schematic and board:




It's $7.60 for each order (3x) of boards. It's 1.39" x 1.10". I've never done the share thing before... this should be a link to it.

http://oshpark.com/shared_projects/GUCh5dyf

Also NOT VERIFIED!!! Except by Eagle, who says 'yeah sure'.

I grounded the emitters and you are missing an important 10K

[Gus]

thats not what I built