Page 1 of 1

ETI Sustain Fuzz

PostPosted: 12 Nov 2012, 22:15
by DrNomis
I just found this old article from Electronics Today International, this is for a Fuzz stompbox which gives three sounds, Sustain, Fuzz with Sustain, and Fuzz without Sustain, looks like an interesting design which doesn't follow all the usual commercial designs, so I though I would post it here in the Davidoff library for anyone interested, enjoy.... :thumbsup

Re: ETI Sustain Fuzz

PostPosted: 13 Nov 2012, 00:40
by mictester
There are three basic problems with the circuit as published and a couple of more subtle ones:

The input bias circuit using the LED is missing a 2.7 Volt zener diode in series with the LED, to give roughly 4.5 Volts at the non-inverting input to the op-amp. This is necessary to maximise the available headroom in the first stage.

(Originally it was designed without the tantalum caps everywhere, and the output of the op-amp had to be at the same standing voltage as the reference in the 570 - hence the low bias voltage).

The input impedance is too low for most guitars. The input bias resistors need to be 330k at least.

The output needs a buffer - just a single transistor emitter follower would do, but an op-amp is better - after the volume control, so the thing can drive long cables, and other devices can't load down the output signal.

It's pretty noisy by modern standards. It's well worth giving the input stage significant top boost, and then rolling it back off again at the end of the circuit. This also gives the option of a fairly wide-ranging tone control towards the output of the circuit.

Tantalum capacitors are a great choice where space is at a premium, but they're expensive, prone to heat damage (easy to short them internally if you overheat them while soldering), and they have a nasty tendency to explode when too high a voltage is applied. Modern miniature electrolytics are now available in similar sizes to the tantalum types, so it's best to use those.

The fuzz part of the circuit is crude - it's just a transistor stage with so much gain that the signal "hits the rails". This gives a particularly nasty kind of distortion - there are much more musical clipper circuits that can be put in that part.

The CMOS switching is OK, but there's little attention paid to the suppression of the distorted signal when trying to play "clean". A more sophisticated switching method is required.

I'll put an updated version up here shortly!

Re: ETI Sustain Fuzz

PostPosted: 13 Nov 2012, 03:26
by DrNomis
Hi Mictester,

I'm actually interested in building one, but don't know where I could get the NE571 or NE570 IC, I think my local Jaycar Electronics store stocks the other ICs though.... :thumbsup

Re: ETI Sustain Fuzz

PostPosted: 13 Nov 2012, 07:38
by mictester
DrNomis wrote:Hi Mictester,

I'm actually interested in building one, but don't know where I could get the NE571 or NE570 IC, I think my local Jaycar Electronics store stocks the other ICs though.... :thumbsup


I bought 20 NE571s from Futurlec recently. You can also get the SA571 (same thing) from On Semiconductor. You can get a free sample if you write to them on letter-headed notepaper!

I still occasionally build something similar to this, using two dual op-amps (input and output buffers and tone controls), two transistors for the fuzz circuit (using Big Muff-style stages) and the 571 for compression and expansion / envelope restoration. I still frequently use the 4066 for audio routing - just make sure that there's no DC offset from input to output, and you don't get and switching pops or clicks. I'll put up the modernised version of the shortly

Re: ETI Sustain Fuzz

PostPosted: 13 Nov 2012, 10:12
by DrNomis
Cheers Mictester, looks like I'll be doing some more online shopping soon then.... :thumbsup


I've just been reading through all the problems with the circuit design that you've mentioned, and looking at the schematic, I can see what you mean, as designed, the biasing of IC1 (CA3140) with the red Led connected as it is, I'm guessing that the DC voltage on pin 6 of IC1 will be something like the forward voltage-drop Led 1, or approximately 1.2V or so, if I remember my electronics theory correctly, apologies if I'm wrong, I can see why the addition of the Zener will solve that problem.... :thumbsup


It seems like a bit of a strange way to bias the input of an op amp, and I would have expected R1 and R2 to be 1M rather than 180k as specified.... :hmmm:

Re: ETI Sustain Fuzz

PostPosted: 16 Nov 2012, 00:01
by pinkjimiphoton
hi guys, i believe this circuit is the one in question?

http://www.hobbytron.com/GMDoubleFuzzBoxKit.html

http://www.gssteched.com/G-138P.html

http://experimentalistsanonymous.com/di ... 20Fuzz.pdf

EDIT for IDIOT:

lol...nope. just looked at the schem... ooops~~~ nice find, simon!

so...with the proper mods mictester, is this circuit worth actually messing with ?

the one i linked to is similar, and according to RG an ETI too. mah bad. ;)

Re: ETI Sustain Fuzz

PostPosted: 16 Nov 2012, 01:07
by mictester
The original with the 570 was designed by a friend of mine. He was a pretty good guitarist, and not a bad engineer. The design is flawed, but was pretty good for its day.

I have an updated version that I'll post here in the next few days.

Re: ETI Sustain Fuzz

PostPosted: 16 Nov 2012, 01:46
by pinkjimiphoton
cool, thanks brother :applause:

Re: ETI Sustain Fuzz

PostPosted: 17 Nov 2012, 08:58
by DrNomis
I was just wondering, is there a way to re-design the circuit so that it uses a couple of LM3080 ICs instead of the NE570 and NE571?, or is the LM3080 too noisy?..... :hmmm:

Re: ETI Sustain Fuzz

PostPosted: 22 Mar 2013, 00:55
by mictester
DrNomis wrote:I was just wondering, is there a way to re-design the circuit so that it uses a couple of LM3080 ICs instead of the NE570 and NE571?, or is the LM3080 too noisy?..... :hmmm:


The 3080 is a completely different beast. The 570 / 571 are both widely available, and are great for guitar effects. I've used them for compressors, limiters, sustainers (compressors with funny characteristics), pseudo "Aphex" (they generate second harmonic distortion quite musically if provoked), and even a stereo tremolo....

Re: ETI Sustain Fuzz

PostPosted: 22 Mar 2013, 07:55
by DrNomis
mictester wrote:
DrNomis wrote:I was just wondering, is there a way to re-design the circuit so that it uses a couple of LM3080 ICs instead of the NE570 and NE571?, or is the LM3080 too noisy?..... :hmmm:


The 3080 is a completely different beast. The 570 / 571 are both widely available, and are great for guitar effects. I've used them for compressors, limiters, sustainers (compressors with funny characteristics), pseudo "Aphex" (they generate second harmonic distortion quite musically if provoked), and even a stereo tremolo....



Interesting, I didn't think it was possible to generate second harmonic distortion from a 570/571 IC, the second harmonic distortion would be more "musical", since the generated harmonics are basically octaves of the fundamental, which would give a thicker and smoother sound, I'd be interested in playing around with the Aphex circuit..... :thumbsup

Re: ETI Sustain Fuzz

PostPosted: 23 Mar 2013, 11:36
by mictester
All you have to do is make the capacitor from either pin1 or 16 to ground about 10 times too small. Ordinarily, you'd have 1µ or 2µ2 to ground there. Put in 100n and you get nice second harmonic distortion!

The "Aphex" trick is to filter out a section of the midrange (normally centred on about 1 kHz) and apply the second harmonic distortion to just that portion of the audio and then mixing it back into the full range audio. It has the effect of making vocals sound "louder" (they're not - your ears are just being fooled), and it can make an overall mix sound "clearer"....

Re: ETI Sustain Fuzz

PostPosted: 24 Mar 2013, 15:26
by phatt
mictester wrote:All you have to do is make the capacitor from either pin1 or 16 to ground about 10 times too small. Ordinarily, you'd have 1µ or 2µ2 to ground there. Put in 100n and you get nice second harmonic distortion!

The "Aphex" trick is to filter out a section of the midrange (normally centred on about 1 kHz) and apply the second harmonic distortion to just that portion of the audio and then mixing it back into the full range audio. It has the effect of making vocals sound "louder" (they're not - your ears are just being fooled), and it can make an overall mix sound "clearer"....


Humm,, :hmmm: Ok lol,,, you got me wondering. So I take it that this trick would be well suited to voice?
I'm wishing to improve live vocal projection.
Phil.

Re: ETI Sustain Fuzz

PostPosted: 24 Mar 2013, 22:21
by mictester
phatt wrote:
mictester wrote:All you have to do is make the capacitor from either pin1 or 16 to ground about 10 times too small. Ordinarily, you'd have 1µ or 2µ2 to ground there. Put in 100n and you get nice second harmonic distortion!

The "Aphex" trick is to filter out a section of the midrange (normally centred on about 1 kHz) and apply the second harmonic distortion to just that portion of the audio and then mixing it back into the full range audio. It has the effect of making vocals sound "louder" (they're not - your ears are just being fooled), and it can make an overall mix sound "clearer"....


Humm,, :hmmm: Ok lol,,, you got me wondering. So I take it that this trick would be well suited to voice?
I'm wishing to improve live vocal projection.
Phil.


Aphex was invented for vocals. It really does make vocals stand out in a mix!

Re: ETI Sustain Fuzz

PostPosted: 25 Mar 2013, 04:35
by pinkjimiphoton
i think i dug up the schematics for the aphex a while ago, if i find it, i'll try and post it up...
my archive of schems is getting WAY outta hand!! :shock: :D

Re: ETI Sustain Fuzz

PostPosted: 18 Jun 2013, 23:10
by stupidsignup
Hi.. I'm new here
mictester : Did you ever produce an updated diagram for this?

I built one, what must be 30 years ago, and since I have the need for a fuzz box I got it out and to my surprise it still works (I used a few electrolytics in it and thought they might have died )
It sounds not too bad through my Mustang amp - certainly a very different sound from the Mustang dsp fuzz.
I'm wondering if I should have a fiddle and replace a few parts along the lines of what you suggest..
So reduce that capacitor to a tenth and add the zener.. anything else?

Thanks!

Re: ETI Sustain Fuzz

PostPosted: 30 Jun 2013, 11:34
by stupidsignup
Ok I gave the box a more thorough work out and while the sustain part has fairly good tone, the fuzz is thin, not tizzy-thin, but it's bland.
The sustain part is quite noisy too so I reckon it's for the scrap bin.

Re: ETI Sustain Fuzz

PostPosted: 30 Jun 2013, 13:24
by uncleboko
pinkjimiphoton wrote:i think i dug up the schematics for the aphex a while ago, if i find it, i'll try and post it up...
my archive of schems is getting WAY outta hand!! :shock: :D


Just google
aphex aural exciter schematic

Re: ETI Sustain Fuzz

PostPosted: 02 Jul 2013, 09:41
by DrNomis
Just thinking, maybe this particular design might be worth tinkering with to improve the Fuzz circuit so it's not bland sounding, possibly with some kind of tone circuit..... :hmmm:

Re: ETI Sustain Fuzz

PostPosted: 02 Jul 2013, 15:57
by pinkjimiphoton
or massively f'n with the cap values.

i am finding more and more that bigger caps mean a much meaner sounding pedal.

i built an EKI fuzz with my son... one of them 9.95 fuzz kits ya find on the net, comes with everything but the box.

so it had a .01 input cap, and a .001 output cap innit stock. two 2n3906's for trannys.
well it sounded ok but not great. pulled q2 out of it's socket, and tried a bunch of transistors...ujt, bjt's, fets, mosfets, pretty much every npn i had kicking around and also turned the damn things so they were flipped cuz sometimes the goddamn transistors sound backwards... and settled on a nice ge ac187 that just sounded great right or wrong. musta been one leaky son of a bitch, too. but it sounds great. loud. but weasily and thin.

mod time.
first we brought up the input cap, put a 100n chicklet there. now it had some distortion. still not great.
changed the output cap to 400n. now it has output, ass, and plenty of fuzz.
added a bias trimmer too, doesn't do much but let you find a sweet spot. done. boxed.

i mean, sometimes, ya gotta break the rules (or stuff) to find some cool shit.

sorry...morning bake, no coffee yet.. ;)