Sam Ash/AstroTone Fuzz

[DougH]

I got one of those cool pcb's from John Lyons, the ones that Andy designed. (It's very nice, great work btw. )

In anticipation of building it I finally got this thing breadboarded up this morning. This is a very cool fuzz! Very creamy! Even with a strat and a bright amp it is pretty smooth. And with the fuzz you get the subtle nuances of your picking coming through, pup selection changes the tone and etc. With humbuckers it has a weird overtone that is pretty unique. The tone control works as drawn in the schematic, but the way it is tuned it was kind of useless to me. It goes from a full bodied sound to a thin nasally tone that was too thin for my tastes. It's kind of like a stock BMP tone control turned all the way up.

I'm going to build mine with 2 grab bag npn's with hfe ~300 or so. I didn't have any .047's so I'm using .056's instead but the difference should be negligible. For the "attack" and "volume" pots I'm using linear tapers. I know that sounds strange but it really works a lot better that way. With audio tapers only the last 10% of "attack" added any fuzz and the volume had to be at 75% to get unity gain.

I'm also ditching the stock tone control. In it's place I'm subbing a variation on Joe Gagan's "pre" tone control. I'm running another .056uf in series with a 10k variable resistor (audio taper) which is all in parallel with the .056u output cap. So this adjusts bass content, similar conceptually to the stock control. Except this sounds much better and is in a useful range for me. This thing doesn't need highs rolled off or any adjustment to the high content AFAIC. But adjusting the bass can be useful.

One more thing. I've read comments here & there that this is just capable of "crunch" and great for rhythms and not for lead, etc. I beg to differ. This is not a super-duper high gain pedal but it definitely sounds like a "fuzz" and is great for leads. With the strat it really does get the Bolin sound. I highly recommend this one to all you fuzz lovers out there. Get the PCB because it makes it so simple. I'll post pics and etc when I finish my build.

[8mileshigh]

Good to know, my board is populated but still sitting on my monitor at home waiting to be soldered.  I wish I had more time to devote to building 

Thanks for the report
Chris

[Arn C.]

Doug,

   What did you use for diodes?   914's, 4148's, ge's?

Arn C.

[DougH]

Everything is stock except for what I noted in the post above.

[yeeshkul]

I built mine with Big Muff tone controll and it works pretty well (2x39k, 10n, 4n7, 100k lin pot). A nice one is to try LEDs in place of the silicon diodes - it - as we can assume - gives more loudness and less fuzz - more like a booster. Or skipping the diodes completely sounds pretty well too.

Arn: Any diodes should do the job. There is not any gain stage after the clipping, so the main difference is how loud the fuzz is gonna be:
Ge-quitet & fuzziest
Si-moderately loud & quite fuzzy
LED-quite loud and boosted
no diodes - KABOOOOOOOM!.

hehe

[DougH]

I tried LEDs and didn't notice a difference between that and no diodes. I quickly realized the "magic" of what I like about it is the diodes. Everything in it is balanced pretty nice- just enough gain, just enough clipping, no need for LPF, etc.

Nice and simple fuzz!

[yeeshkul]

right there is a small difference between LED and no diodes, but mainly - LEDs are flashing, which can be fun when they're fixed on the enclosure ... haha

[DougH]

Another thing I discovered that I forgot to mention:

There's another Sam Ash Fuzz schematic floating around that shows a 3.3M feedback resistor and an 820 ohm Re on the first stage. I tried this and it had barely any gain at all. I suspect the schematic is wrong, maybe an Re bypass cap was left off or something.

Also- I tried this with a 100 ohm Re and 22uf bypass cap and it didn't sound as good IMO. But I now realize the cap was not large enough, which may have accounted for the difference. I'm going to play with that some more. Having an emitter resistor is better for temperature stability and will help the sound to remain consistent.

[Arn C.]

Thanks Doug!

That is the schematic I had, I found the other one!

Arn C.

[yeeshkul]

The "other"  schematics come from here: http://dam.10.forumer.com/viewtopic.php?t=781
I don't think it must be completely necessarily wrong. Compare his piece with the long known one:

1. This piece was reverse-ingeneered for the new schematics


the mistake is most probably the 1k8 res in series leading to the output

2. Classic, long known piece

[DougH]

The "other"  schematics come from here: http://dam.10.forumer.com/viewtopic.php?t=781
I don't think it must be completely necessarily wrong. Compare his piece with the long known one:

1. This piece was reverse-ingeneered for the new schematics

Sorry, that's doesn't look like an 820 to me. It looks like a 10k...

edit: Also, if that truly is Re (doubtful if it's a 10k) it would need to be jumpered to match the classic schematic.

Another interesting twist is the "classic" photo (w/missing resistor) shows a 3.3M instead of 1M like the schematic.

[yeeshkul]

10k, you're right ... i red it from the other side i guess .. i does not have to be jumpered - look where the yellow cable is connected - first time right on the emitter, the second time after the res - it depends on the circuit board.
But what resistor can it be? near Q1? 

EDIT: i appologize, it woul have to be jumpered, you are right.

[Dragonfly]

note the connection location of the yellow wire...assuming that they didnt change wire colors like they do part values.

also - as noted in the third schematic, which evidently was traced from the lower unit, the 10k is on the input/gain pot.

some sam ash / astrotone schemes....

http://img.villagephotos.com/p/2008-7/1317397/AstrotoneSchm.jpg

http://img.villagephotos.com/p/2008-7/1317397/SAMASHFUZZ.gif

http://img.villagephotos.com/p/2008-7/1317397/samash000.jpg


Clear as mud.

[yeeshkul]

hehe, now it is clear, i overlooked the 10k at the input  and let my fantasy flow. Thanks Dragonfly.

[DougH]

Yeah, the 10k was in series with the input.

Without a better picture, pulling the wires out of the way, there's really no way of telling what's going on, just by using the photo.