Astrotone layout?

[charriman]

Guys looking to build an astrotone/Sam ash fuzz boxx. I found 3 layouts on this site 2 vero and a PCB layout to etch. I'm more interested in the vero but one of the 2 has a couple of stand up resistors that are not labeled as to what the value is. The other shows a dpdt switch wired in that I'm assuming is the bypass. So 2 questions.
Which one would you suggest I tackle?
Also,  what trannies should I use?  Run of the mill 3904s?

Thanks!

[midwayfair]

3904 is probably a good choice. BC transistors in the B range and 2N5088 will also be fine and are low noise.

This reminds me that this is a fuzz box I never got around to soldering up ... thaaaaaanks ....

Best thing to do to figure out those standing resistors is to compare the schematic with what's missing. A layout's not a schematic.

[nocentelli]

IvIark's vero over at tagboardeffects.blogspot.co.uk  is excellent as always. He also has a 3pdt wiring layout and power layout.

I would highly recommend considering trying analogman's mod to increase the bass and get a bit more gain, you can still dial in the original tone.

[charriman]

Nocentelli, would this one be it?
http://tagboardeffects.blogspot.co.uk/2012/10/astro-tone-fuzz.html?m=1

What are the analogman mods?

[midwayfair]

Here's a perfboard layout with a "better" tone control. It will be less prone to loading issues with pedals that follow because it keeps the output impedance steady (instead of dropping it below 1K in the analogman version) and it has more range, going from actual full bass (rather than a ridiculous cutoff of over 300Hz) to about the same thinness of the original.

[LucifersTrip]

Guys looking to build an astrotone/Sam ash fuzz boxx. I found 3 layouts on this site 2 vero and a PCB layout to etch. I'm more interested in the vero but one of the 2 has a couple of stand up resistors that are not labeled as to what the value is.

I saved this pic when I built the last one...

Also,  what trannies should I use?  Run of the mill 3904s?

I always wind up with ones in the 200-300 range. Here are working voltages so you have some idea what you're shooting for:



Just remember, this is really not a fuzz...it's closer to a distortion. It's very cool, but don't expect any real nastiness.

[nocentelli]

Here's a perfboard layout with a "better" tone control. It will be less prone to loading issues with pedals that follow because it keeps the output impedance steady (instead of dropping it below 1K in the analogman version) and it has more range, going from actual full bass (rather than a ridiculous cutoff of over 300Hz) to about the same thinness of the original.

I like the idea of a blend for the tone control, but aren't the 220n and 10n caps reversed in that layout? It apppears the larger bass cap is permanently connected, whilst the smaller cap is blended in parallel.

[midwayfair]

Here's a perfboard layout with a "better" tone control. It will be less prone to loading issues with pedals that follow because it keeps the output impedance steady (instead of dropping it below 1K in the analogman version) and it has more range, going from actual full bass (rather than a ridiculous cutoff of over 300Hz) to about the same thinness of the original.

I like the idea of a blend for the tone control, but aren't the 220n and 10n caps reversed in that layout? It apppears the larger bass cap is permanently connected, whilst the smaller cap is blended in parallel.

Thanks for catching that! I'll fix it as soon as possible.

Also, LT's right ... this is an Electra distortion with an output buffer and tone control.

[Gus]

A sim showing a higher beta hfe transistor for the stages
Adding R8 allows R6 3.3meg(feedback/DC bias) to be the same value as in the schematic LucifersTrip posted and keep the collector voltage about the same
R8 can be adjusted to give 4.98VDC at Q1, a fixed resistor and a trim potentiometer would be something to try

[PRR]

> higher beta hfe transistor

It's really not fussy. (The old guys were not stupid.) For half-B+ bias, R6 should be about hFE bigger than R1, BUT if it is off it will self-correct quite well.

We don't need half-B+ at Q1 collector to get big 3v swings. D1 D2 will clip at 0.6V.

So Q1 collector only has to be significantly more than 0.6V away from either rail. 2V to 7V is plenty good.

hFE may be from 50 to 840 and it'll do what it's supposed to do. (To infinity with Gus' 680K mod.)

Q2 same only more so, since it is unity-gain.

[Gus]

LucifersTrip was nice enought to post collector voltages.  Also the open loop gain is higher when the collector is closer to ground (saturation)
So the DC voltages matter somewhat for how well the C to B resistor closes the loop and sets the gain with the input volume and what is before the input.