First project: Fuzz Shin-ei Companion clone

[SamuelD]

Hello everyone. I'm new in this forum and in this world of DIY pedals. I've made a Big muff PI clone (with effect layout schematics) last week and now I wanna make a Fuzz Shin-ei for the bass of my band. Why the Shin-ei? Because we love the sound of that bass in "Exit music (for a film)" from Radiohead.

I have a pretty basic understanding of electronics (I'm a physicist) but I don't really know very much in pedals electronics.

Well, I based my project on this schematics, without the tone bypass. I see on the effect layout blogpost that he added a boost at the end of the circuit (because the sound is very low on the original). Apparently, the booster is based on the LPB-1.
Also I decided to add a potentiometer to control the tone a little bit, so i modified a little bit the tone part (I based that modif from the big muff tone controller part). After that modification, the second pin of the tone potentiometer were linked directly into the third pin of the volume (before the boost part) and I didn't like that. So I change the position of the volume pot to move it at the end of the circuit.

Well, in the end, my circuit look like this. With in red the modification from the original pedal. I tested it, it works ! But I have some questions.

• First of all, is there any big flaws in the schematics?
• Moving the volume in the end could change something?


• When I change the tone part, I don't change the resistor's values, so I have:
  
  
  
  • R14 = 10K
  • R 8 = 15K
  • C12 = 100n
  • C5 = 1n
  • pot = 100KA
  Should I change the values ? Maybe using a potentiometer that large change too much the original tone?
• Using 100K pot instead of 50K is a really bad idea?
• For the R16, using 2M instead of 2M2 is a big deal? Same thing with the 1M2, where I use 1M5 resistor. I didn't really hear a modification of the sound. But I don't know the purpose of these resistors.
• I tested the circuit on an experimental breadboard and there's a lot on noise. I used a lot of crocowire and I thing it's the main cause (I even hear the radio). Is there a method to know if a circuit is noisy or not?
• Last question! Do you have any references, books, articles or so, to learn the electronics applying to audio effects?

Maybe I asked too much questions at once, sorry for that. And thanks to reading my post.

Link to check the hear of the current state of the pedal: http://www.zenocyne.com/ressources/test_fuzz_shin_custom.mp3

[Mark Hammer]

I've made probably a half-dozen or more of these, changing this part or that to achieve different outcomes.  So, a few things to consider.

1) The need for a gain-recovery stage after the tone-section comes from there being too much passive loss in the tone-section.  If you insert a 2k-5k variable resistance between ground and what you labelled C12 in your drawing, you can vary the mids and lift the scoop, giving a throatier tone and getting more volume.  The Big Muff-style tone-stack you drew WILL work, but it will also lose enough signal level that it makes the gain-recovery stage obligatory.  Simply lifting the mids gives a surprising amount of volume-boost.

2) What you show as C6 (47nf) in your drawing limits the bottom end.  That gives the signature thinner sound of the FY-2.  If you would like a fuller sound, omit that cap, or make it switchable.

3) The changes to the collector-base resistors you indicated should not change the sound appreciably (which you indicate seems to be true at first glance).

4) On mine, I wire the Fuzz control as a "pan-pot".  So, one outside lug goes to C10, and the other goes to C11, with the pot wiper going to the tone stack.  *I* like the degree of tonal variation it gives, but it's a matter of taste.  If you can, try it out and see if it aligns with your tastes/needs.

5)  I've always been able to use 2SC536 transistors for my builds, but they don't seem to be particularly special, so one could probably use 2N3904s, paying attention to pinout differences.

6) The tone section uses a fixed lowpass (R14/C12) corner frequency, but it doesn't NEED to be fixed.  The stock drawing shows a 10k in series with 15k, and a cap to ground from their junction.  If one replaces that 25k with 3k3, a 10k pot, and 12k, in that order, with the outside lugs of the pot going to their respective fixed resistor, and the wiper going to the cap to ground, you end up with a variable lowpass whose corner frequency can shift from 120hz to 480hz (stock is around 160hz).  Used in tandem with the mid-lift control described in #1 gives a fair amount of tonal flexibility.

[SamuelD]

Ok, I've learnt a lot from your post. I've checked the theory about the RC filter and I've found the 1/2piRC formulae. Thanks!

So, as far as I understand it, There's two filters. A LPF at 159hz with that 10k res and 100nf cap, and a HPF at 10,61kHz with the 1nf cap and 15k res. So in the end, the frequency between 160hz and 10 600hz are filtered. Something like a "well" shaped filter, right?

I'll try the variable filter. I don't have a 10k pot right know, but I'll try something else ('cause now I know how these things works).

I ommit the C6 and yeah, the sound is a little bit more "large". Thanks.

I've also checked the Fuzz pot with the wiper on the tone stack input, it feels a lot more aggresive with a wider range. I'll check that with the new tone.

Is the type of transistor really matter?

[Mark Hammer]

As far as I can tell, anything with an hfe of around 230-250 will provide the expected sound.  In my experience, Q1 does not have to be any different than Q2.

The 15k is really there to balance the level of the lows and highs, and does not form part of the high-pass filter.  The 1nf cap lets more than 10khz+ pass.

[abc1234]

I wanna make a Fuzz Shin-ei for the bass of my band. Why the Shin-ei? Because we love the sound of that bass in "Exit music (for a film)" from Radiohead.

Maybe I've missed it, but nobody has mentioned increasing the values of the caps.

The 47nf are OK for the low end of a bass, but the 2.2nf and 3.3nf are not.

If I recall correctly, increasing the 3.3nf (e.g. to 100nf, 1uf, etc.) improves the low end immensely.

If you're still at the breadboarding stage, I'd also recommend testing increasing the caps at the bases of the two transistors from 47nf, although that might also bring with it more compression and saturation, which is counterproductive when trying to hear more low end.

The 1nf (labelled C8 on your schematic) between Q1's collector and base rolls off high frequencies; a slight increase (e.g. to 2nf, 4nf, etc.) might allow more low end to be heard without affecting the characteristic FY-2 sound too much.

BTW, that sawtooth bass fuzz sound on 'Exit Music' doesn't sound like it was made with the FY-2 alone, but instead an FY-2 doubled with a clean/slightly overdriven bass. (That's why the recording has a good amount of not just low end, but low end clarity.)

So if I were to trying to nail that sound 100%, I'd try a stock FY-2 (plus boost on the output), but add a clean blend with a low pass on the high mids and its own vol and overdrive controls.

If I wanted to get close but have my own sound, I'd do what you're currently doing or consider Devi Ever's Ruiner.

[Pepeu Dias]

I've made probably a half-dozen or more of these, changing this part or that to achieve different outcomes.  So, a few things to consider.

1) The need for a gain-recovery stage after the tone-section comes from there being too much passive loss in the tone-section.  If you insert a 2k-5k variable resistance between ground and what you labelled C12 in your drawing, you can vary the mids and lift the scoop, giving a throatier tone and getting more volume.  The Big Muff-style tone-stack you drew WILL work, but it will also lose enough signal level that it makes the gain-recovery stage obligatory.  Simply lifting the mids gives a surprising amount of volume-boost.

2) What you show as C6 (47nf) in your drawing limits the bottom end.  That gives the signature thinner sound of the FY-2.  If you would like a fuller sound, omit that cap, or make it switchable.

3) The changes to the collector-base resistors you indicated should not change the sound appreciably (which you indicate seems to be true at first glance).

4) On mine, I wire the Fuzz control as a "pan-pot".  So, one outside lug goes to C10, and the other goes to C11, with the pot wiper going to the tone stack.  *I* like the degree of tonal variation it gives, but it's a matter of taste.  If you can, try it out and see if it aligns with your tastes/needs.

5)  I've always been able to use 2SC536 transistors for my builds, but they don't seem to be particularly special, so one could probably use 2N3904s, paying attention to pinout differences.

6) The tone section uses a fixed lowpass (R14/C12) corner frequency, but it doesn't NEED to be fixed.  The stock drawing shows a 10k in series with 15k, and a cap to ground from their junction.  If one replaces that 25k with 3k3, a 10k pot, and 12k, in that order, with the outside lugs of the pot going to their respective fixed resistor, and the wiper going to the cap to ground, you end up with a variable lowpass whose corner frequency can shift from 120hz to 480hz (stock is around 160hz).  Used in tandem with the mid-lift control described in #1 gives a fair amount of tonal flexibility.

Hello!

I guess understood the explanation and I did the schematic. If it seems correct, I will be very happy! Thank you

[Mark Hammer]

Yes, that is correct.  I think you'll like the tonal possibilities.  It does not change the basic quality of the fuzz, but changes what you get to hear of it.