Sam Ash Astrotone Fuzz build - low volume and strings flubbing

[Dinosaur_Sr]

Hi Guys,

I've just recently built my first full scratch pedal (ie: not from a kit) and after a few hiccups I finally got it working, the trouble is that it's not very loud and it kind of flubs when I hit the strings hard. The volume is slightly less than my clean volume even with the knob all the way up, I presumed it wasn't going to be super loud but this can't be right. The flubbiness is really bugging me too, I've tried switching the orientation of the diodes, tried numerous different transistors, it's always the same. I've tried a couple of batteries, the current one in there is reading 7.5v but it started out at around 8.5 and the problem was still there then. If anyone can offer any advice it would be extremely gratefully received.

I followed this schematic:
http://pedalparts.co.uk/wp-content/uploads/2013/02/AstroTone.pdf

Here are my voltages, apologies if I've got these ass backwards, I'm very much a noob.

Q1
e = 0
b = 0.4
c = 1.9

Q2
e = 0.9
b = 0.8
c = 0

[nocentelli]

Q2 looks wrong straight away: the emitter should be grounded and therefore 0v - Unless you have it in backwards, or have recorded these voltages backwards?

[nocentelli]

My bad - It's Q1 that's grounded emitter, Q2 seems to be a buffer: However, it should have a +9v connection direct to the collector so Q2c should be at 9v (or whatever your battery reads - p'raps get a new one?).

[LucifersTrip]

R1 is different on the early version, but here's some working voltages from the last one I built:



9.6V supply

     E   B   C
Q1 0, .58, 4.98
Q2 1.32, 1.93. 9.6

If I remember right, the transistors were in the 200-300 hfe range.  It's not a super loud fuzz, but does reach unity when turned up.

[Dinosaur_Sr]

Hey guys, thanks for the assistance!

That schematic definitely helped as the one I was using didn't have the 9v going to the 22k resistor, I hooked it up on my board and the pedal is now much louder and isn't farting any more!

[Dinosaur_Sr]

After a bit more tinkering I've found that there's still something going wrong in there somewhere, it's now much louder than before but there's a slight volume drop when I hit the strings harder and the tone and attack knobs cut the volume if I turn them down between 1 - 2 

[PRR]

Did you find and fix this?

> Q2  c = 0 (should be +9V)

[Dinosaur_Sr]

I changed a few things around by combining the two schematics, separated r2 and r3 and moved a couple of connection points, I seem to be getting roughly correct voltages now, except Q1 C is getting 2.2v. I wasn't able to fully test it as it was late when I finished, but I think it's sounding better, however there is still some kind of string volume issue, like the notes won't sustain for long and the signal weakens when I hit the strings. If I put a 3.3m resistor in r1 would that help?

[Dinosaur_Sr]

OK, got it all going nicely now and it sounds amazing but it's VERY trebly! I need to darken this thing up a bit, the schematic says that you can replace c1 and c4 with 470n caps but I don't have any of those, I do have more 47n's, knowing that you can stack caps would adding a second 47 on top of c1 and c4 do any good?

[Dinosaur_Sr]

I've just come across Mark Hammer's "Stupidly Wonderful Tone Control" and it sounds like this is what I need to add to tame the wild treble, I'm having some difficulty working out how I would go about adding it to my circuit though, would any of you happen to have a diagram?

[allesz]

Hallo Dinosaur, and welcome.

My two cents: put a cap (10nF - 22nF - 47nF) in place of R6. If you don't have 22nF you can use two 47nF in series.

If you would like to try bigger input and output caps you can solder another 47nf in parallel of c1, c2, c3 and c4... and see what happens.

[Dinosaur_Sr]

Beautiful, I had a 22n and put that in, it sounds incredible now, thank you!

[allesz]

Incredible? Woha thank you but...

Now it sounds incredible, tomorrow you will start thinking about some mods... in a couple of weeks (maybe a month) you will be addicted; it's really bad, try to stay away of all this s**t if you can. Talk to your parents/relatives/girlfriend/wife to get some support.