Astrotone - Fuzz  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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LucifersTrip
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Post by LucifersTrip »

jrod wrote:Hey LT
The original transistors were 2N3565.

sounds cool...I'll update the schematic

thanx

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Post by theehman »

the one I reverse-engineered had 2N3566.
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Post by jrod »

theehman wrote:the one I reverse-engineered had 2N3566.
Cool! Good to know!

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LucifersTrip
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Post by LucifersTrip »

theehman wrote:the one I reverse-engineered had 2N3566.
sounds good...I'll add that to the schematic, too.

when you reverse engineered it, what did the diodes turn out to be?

thanx

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Post by theehman »

LucifersTrip wrote:
theehman wrote:the one I reverse-engineered had 2N3566.
sounds good...I'll add that to the schematic, too.

when you reverse engineered it, what did the diodes turn out to be?

thanx
Sorry, I didn't note that at the time.
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Post by mat033 »

mat033 wrote:Here
If anybody's intrested, I've just built this and it works perfectly.
Sounds great BTW!

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Post by Thaxt »

Those green ceramic caps look exactly like the ones in my 1970 BMP. Maybe they were a large lot/ grab bag staple around the NY vicinity @ the time. The Big Muff Pi, Sam Ash Fuzz & Astrotone are NY vintage.

They appear to have a waxy coating on them (on the board of my Big Muff). Soldering with those early ceramic caps often produced a melting of this coating, glistened, like melting wax. In any case, ceramics do make for a different sound.

I notice on the ebay pic of recent that one of the gain resistors is a 3.3Meg.

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Post by Blues1911 »

Well I've improved an existing schematic with Analogman specs, adding a DPDT for switching between the classic and the bigger input-output capacitors couple.
I've checked it many times and it seems basically correct, but please double-check it by yourself in any case of use - hope to verify it as soon as possible, and to update this post:
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Post by Blues1911 »

UPDATE: this layout can be considered VERIFIED, full working and great sounding. The switch is a great point of versatility, allowing to cut bass on darker amps or (viceversa) to add more fatness on bright amps, and more, the tone knob still allow to rectify it with precision; I've tried it in the "fat" mode on my 1959HW with '68 specs. and it sounds like a charm: rich, fat and rounded.

It could be a good idea to add a 47uf or a 100uF electrolytic cap in parallel with power input and ground, with function of power supply hiss/noise filtering... I haven't thought to place it in the layout nor when I built my own, but I'm sure it can be quite useful (and it requires just one or two more columns on the right, so still allowing the placement of the veroboard in a standard 1590B box).

Enjoy! :)
Blues1911 wrote:Well I've improved an existing schematic with Analogman specs, adding a DPDT for switching between the classic and the bigger input-output capacitors couple.
I've checked it many times and it seems basically correct, but please double-check it by yourself in any case of use - hope to verify it as soon as possible, and to update this post:
Image

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Post by kinski »

Ok, this is possibly one of my favorite fuzz/od pedals ever. I mostly love the low gain settings on this thing.

However, I'm bummed that Im getting some white noise under the fuzz sound when engaged. Adding more gain does not increase the amount of white noise. Its can be easily heard with gain at 9 o' clock and volume at unity.

I tried adding a electrolytic. Positive to DC power lug and negative to DC ground. This did not help at all.

Is this just the nature of this circuit or am I the only one with this problem? Its not a problem at all in loud situations, but in quieter ones, its pretty noticeable. However, if I run the Astrotone INTO any other od/distortion, the white noise becomes unbearable!

Any thoughts?

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Post by Seiche »

possible faulty ground connection? check all the wiring, etc. Did you do it on vero? If so, check between the traces, trace cuts, etc.

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Post by Blues1911 »

kinski wrote:I'm bummed that Im getting some white noise under the fuzz sound when engaged. Adding more gain does not increase the amount of white noise. Its can be easily heard with gain at 9 o' clock and volume at unity.

I tried adding a electrolytic. Positive to DC power lug and negative to DC ground. This did not help at all.

Is this just the nature of this circuit or am I the only one with this problem? Its not a problem at all in loud situations, but in quieter ones, its pretty noticeable. However, if I run the Astrotone INTO any other od/distortion, the white noise becomes unbearable!

Any thoughts?
Just try wiring Attack 1 to ground. I apologise for forgetting to specify it among the notes in appendix to the layout, hope to add it as soon as possible and re-load the complete layout... hope this can be useful in the meantime.

In any case, it's really a great od-fuzz for a Les Paul. It easily became my favourite pedal with the combination Les Paul 1958 and the Marshall 1959HW which I've modified to '68 specifications: thick and sustained, it cleans perfectly lowering the volumes... absolutely a classic set-and-forget fuzz in the best '60s and early '70s tradition, no doubt about it.

The bass cut switch isn't so useful, in truth, but it remains a nice option for obtaining a sort of "small radio" fuzz effect which can be really tasty in some circumstances... and anyway more is better than less, isn't it? :D

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Post by charriman »

what transistors are you guys using for this?

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Post by theehman »

charriman wrote:what transistors are you guys using for this?
I use 2N3566.
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Post by mictester »

mat033 wrote:
mat033 wrote:Here
If anybody's intrested, I've just built this and it works perfectly.
Sounds great BTW!
Either the 47µ or the power leads are the wrong way around!
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Post by astrobass »

Built one of these with 2N3904s, and it sounds good, except the tone control sucks. Bypassing it sounds good, but I wanted to experiment with other ways to control tone. Tried inserting a BMP tone control modified to provide mid hump rather than mid scoop before/after the diodes, didn't get anything good either way.

Going to use a blend cap on input and a level control and call it a day I think, unless I really get a bug up my ass and put in that BMP tone control after the circuit followed by a gain recovery stage.

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Post by Nocentelli »

astrobass wrote:...the tone control sucks.
The "Analogman" mod (replacing the 1k8 that leads to the tone pot with a 470 ohm) works quite well to improve matters. Or have you tried it?
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Post by allesz »

Hallo, this is not a favourite circuit of mine: I experimented with it only a little on the breadboard... but never boxed it.
About the tone control the best results are swapping the 1,8 K resistor with a 10 or 22 nF capacitor.

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Post by astrobass »

Nocentelli wrote:
astrobass wrote:...the tone control sucks.
The "Analogman" mod (replacing the 1k8 that leads to the tone pot with a 470 ohm) works quite well to improve matters. Or have you tried it?
I tried it, but still didn't find any use to the tone pot. There was some position, either all the way forward or all the way back (can't remember, it's been a few weeks since I played with this one), and it got better with the 470 ohm resistor as opposed to the larger resistor, but there was still limited value to actually using the tone control. It's been put on the back burner for now, but I'll probably resurrect it sometime soon. I've got a gutted enclosure from a Yamaha Overdrive with 3 holes in it for knobs and tonnes of space inside, so I'll probably actually go ahead with that BMP tone control + gain recovery.

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Post by astrobass »

I will say though, that it DOES sound nice with a Les Paul. Boring with my Strat, great with a Les Paul. The opposite of most of the fuzz pedals I've put together.

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