Not by the cap on my shin-ei, shin, shin....

[Mark Hammer]

Looking over the schems of several fuzzes today, I noticed an interesting opportunity for modding.  Take a look at the Orpheum Fuzz here:

....the Fuzz-Rite here:

...and the Shin-Ei FY-2 here:

On each of these, you will see two resistors in series from V+ to the collector of Q2.  In the Fuzz Rite and Orpheum, there is a cap from the junction of those two resistors to ground.  But on the FY-2 the cap straddles the first resistor.

If I understand the role of that cap (and please correct me if I am wrong), it plays a role in governing the extent to which the transistor can "pull" current from the supply at various frequencies.  If I do understand this, then the cap to ground arrangement in the Fuzz-Rite and Orpheum rolls off some of the high end fizz, via the sort of lowpass-filter arrangement that the 100k and cap form.  In contrast, the FY-2 provides an "express lane" for higher frequencies by straddling the 100k.

I'm going to go out on a limb here, and suggest that there are perhaps a couple of mods one could do to these fuzzes with this little network.

1) Wire up a toggle switch for one end of the cap so that the end NOT tied to the junction of the two resistors can either go to V+ or to ground.

2) Wire up a 2nd toggle to add 1 or 2 other caps in parallel with the one shown in the schematic.  E.g., the FY-2 has a .047uf cap.  Make it .022 and add another .022, or a .047uf in parallel, using a 3-position toggle.  IN tandem with the gnd/V+ switch, that yields 6 tonal/voicing possibilities.

3) If the cap and 1st series resistor form a sort of filter network, then we could make it variable by using a variant on the SWTC.  Let's change the 100k+47k series pair to 22k+100kpot+27k.  The 22k goes to one outside lug on the pot, and the other outside lug goes to the 27k.  The wiper of that pot goes to the cap, which in turn goes either to V+ or to ground.  The total series resistance of the resistors and pot remains constant, but what changes is the amount of resistance on each side of the pot wiper.  That pot, plus a gnd/V+ switch for the cap should provide a wide range of tones.

Whaddya think?

[John Lyons]

Ahh...3 fun little nasty fuzzies that I like!
Both arrangements cut high end. The 100K in parallel with the cap to +v has
more effect with the values chosen. The variable high cut 22k/100k/27k
sounds interesting. I wonder how much different that would be than the usual
SWTC?
Good ideas Mark!

[analogguru]

From an AC point of view a battery is a short for AC-signals, therefore I cant´t see a big difference - the cap goes to V+ which itself is shorted to ground (for AC-signals), therefore the cap is "grounded" too in the FY-2.

analogguru

[Mark Hammer]

I'll try and do the experiment later tonight after work, but does the cap to ground sound identical to the cap to V+?

[analogguru]

I'll try and do the experiment later tonight after work, but does the cap to ground sound identical to the cap to V+?

Imagine that the battery is like a 1.000µF capacitor.  Now the 1.000µF capacitor is in series to ground with the 47nF capacitor.  That´s the difference.... are you able to hear this difference ?

analogguru

[LucifersTrip]

I just finished tweaking a breadboarded Orpheum. That cap reduced the shrill high end when I hit the high E string.
I have no fizz with or without the cap.

I'm modding it by simply repacing the 47K with a 50K pot. The closer you get to 0k, the more it turns into a bumblebee...and it doesn't gate.

[Mark Hammer]

Why, thank you!

I started building one last night, and got most of the way through, but shut down to watch a movie (the amazing 2003 documentary "Festival Express": http://www.imdb.com/title/tt0372279/ ).

Mine uses a 100k pot for adjusting fuzz intensity (I wanted bigger contrast between dirty and cleaner), a 100k pot for adjusting the "bumblebee" quality (though I have V+->22k->100k->27k->collector, such that the cap/collector resistance never drops below 27k), and a 1k variable scoop pot, in addition to the volume pot.  So, 4 controls overall.

Based on your comments, I look forward to finishing wiring it up tonight.

[LucifersTrip]

Why, thank you!

I started building one last night, and got most of the way through, but shut down to watch a movie (the amazing 2003 documentary "Festival Express": http://www.imdb.com/title/tt0372279/ ).

great flick...worth it for the drunken Joplin/Garcia jam alone.

Mine uses a 100k pot for adjusting fuzz intensity (I wanted bigger contrast between dirty and cleaner), a 100k pot for adjusting the "bumblebee" quality (though I have V+->22k->100k->27k->collector, such that the cap/collector resistance never drops below 27k), and a 1k variable scoop pot, in addition to the volume pot.  So, 4 controls overall.

I believe the one you're working on is the SI one.
http://tonebender.webs.com/orpheum-SILICON.GIF

I built this:
http://tonebender.webs.com/orpheum%20-%20GE.GIF
[scheme's missing the .1 cap at the junction of the 47's]

I replaced the 47K from the Q2 C with the 50K pot. Raising above 50K did hardly anything.  Changing the 47K from (-) did nothing cool.

On a side note, this has to be the most flexible fuzz I've built for Q2. I used something around 120 hfe for Q1, but Q2 could be anything from the low teens (sounded great with 17 hfe 2n1499) through hfe  ~100-120. After hfe ~60-80, it just increased  hum, increased treble with a little loss of fuzz...and was getting more harsh on the high strings. I settled for a switch between two: 2n1499 hfe~24 and 2n404 hfe ~50

I even got decent fuzz when I put the many trans [not the super low gain ones] in the wrong way, flipping E & C

Where's your 1K pot?

Based on your comments, I look forward to finishing wiring it up tonight.

have a blast

[Mark Hammer]

Actually, I made the booster-stage enhanced Companion (FY-2) fuzz that JD Sleep has over at GGG. ( http://www.generalguitargadgets.com/projects/73-fuzz-tones/89-shin-ei-companion-fuzz )

I used a trio of 2SC945 transistors that had hfe readings between 295 and 310.  More than enough bees in that hive.  Using a 100k Fuzz pot instead of the standard 50k yields a broader contrast between "cleaner" and "dirtier" fuzzes.   You may like it, or maybe not.

The FY-2 has the cap going between the resistor junction and V+.  So my added control essentially varies the resistance in parallel with the cap, and the resistance between the cap+parallel and the Q2 collector.  Within the range I'm using (and my cap-to-Q2-collector resistance doesn't go as low as yours....though I may change that), the added control could be described as introducing more and less "body".  The variable scoop does too, but in a different way. 

Using the GGG diagram as a reference point, when R9 is bigger and R4 smaller, the sound gets thinner.  And as R4 gets bigger and R9 smaller, the sound gets fuller.  I'm not trying it out very loud or with large speakers so there may be a broader change than I suspect, and than might be apparent with 12" speakers.  I may try out some other cap values.

Overall, I think a 4-knob FY-2 makes for a decent fuzz with a broad range of tones.  I think I might recommend still using the 100k "body" pot, but maybe reducing R4 to 15k or 18k, and raising R9 to 33k.  Making the variable scoop pot 2k for a broader range of adjustment, instead of 1k, is probably a good idea too.

If one is going to implement the "body" control on an Orpheum or Fuzz-Rite, instead of an FY-2, then it becomes a 3-knob fuzz, by virtue of omitting the adjustable midscoop filter.

[LucifersTrip]

Thanx for the info. I'll consider that for the next one.

Actually, I just finished a Shin-Ei a few weeks ago & it's a killer!
http://fuzzcentral.ssguitar.com/schematics/shineify2schematic.gif

I made mine a 4 knobber, also. I left out the volume pot and wired it at 100%. I used 2SC536 that had hfe 280+
http://www.futurlec.com/cgi-bin/search/qty_price.cgi?part_no=2SC536

I left the fuzz pot untouched.

I replaced your R9 with a 100K pot and it does exactly as you said. Lowering the resistance boosts volume and adds a thickness...a bit more bass response.

But the killer was replacing your R5 & R6 with a 50K & 100K respectively. Man, you can now get a full range from the original to ear-killing [2 friends complained of ringing in their ears] metallic fuzz...and you can get a sh*tload of more volume, too.

So, all 4 knobs control tone. You'll never get board...

[Mark Hammer]

I had pondered monkeying with the location of the midscoop, but declined to.  If I install that, my own instinct would be to replace the 10k/15k (R5/R6) with a trimpot, again wired SWTC style, to move the scoop around.  A 10k trimpot with 5k1 on the "input" side, and 10k on the "output" side, will permit shifting the bottom side of the midscoop around without disturbing the treble/bass balance too much.  I like having control, but I don't like my pedals to be too cluttered on the panel.  But I can see the appeal of wanting to play with the scoop.

I finally settled on replacing the R9/R4 pair on the circuit with V+ -> 33k -> 100k -> 18k -> Q2 collector.  That provides a nice usable range of adjustment that yields audible differences.  I might tinker with the cap value, but I think I'm happy with the way the control performs at the moment.

Since you are in the mood to play with the tone, consider this.  The .001uf cap in the tone circuit, provides a path for the higehr frequencies to bypass the lowpass filter formed by R5/C7.  It is that combination of highpass and lowpass that produces the midscoop.  If you make the .001uf cap larger in value you let more upper mids through.  make it smaller and only the mosquitos can pass unaffected.

So....consider replacing the .001uf cap with, oh let's say a .0033uf and a 680pf unit.  Both caps terminate with R6, but each of them is tied to an outside lug of a 10-25k linear pot on the other end.  the wiper of that pot goes to the junction of R5 and the Fuzz control.  Rotate it fully in one direction, and the 680pf cap becomes your "bypass" cap, letting less treble through.  Rotate it fully the other way, and 3300pf becomes the bypass cap, letting more upper mids through.  Positions in between adjusts how much of the treble and upper mids are mixed in with the R5/R6/C7 path.

[glops]

Exciting to see new mods for my favorite fuzz.  I will definitely breadboard some of these new ideas since I love this circuit so much.  Thanks for the further
exploration and new ideas guys.

I have built 6 of these in the last year. A couple for friends and a couple for strangers and have gotten a great response from the users.

I have been building them with the boost stage on the back end the only way I can get it to sound great is to drop the base/collector feedback resistor
on Q2 to 220-470k.   For some reason I have to do this WHEN I have the boost stage added.  I also use a 25k for the fuzz pot and a 5k for the variable
mid scoop.  Can't wait to try these mods!

- Richard

[LucifersTrip]

I had pondered monkeying with the location of the midscoop, but declined to.  If I install that, my own instinct would be to replace the 10k/15k (R5/R6) with a trimpot, again wired SWTC style, to move the scoop around.  A 10k trimpot with 5k1 on the "input" side, and 10k on the "output" side, will permit shifting the bottom side of the midscoop around without disturbing the treble/bass balance too much.  I like having control, but I don't like my pedals to be too cluttered on the panel.  But I can see the appeal of wanting to play with the scoop.

Exactly, In most occasions I try to limit myself to 3-4 knobs and 1-2 switches max. In this case, I dropped the volume pot since the  R5 /R6 combo greatly effects the volume.  Remember, I can still dial R5/R6 in to get the original tone.

I finally settled on replacing the R9/R4 pair on the circuit with V+ -> 33k -> 100k -> 18k -> Q2 collector.  That provides a nice usable range of adjustment that yields audible differences.  I might tinker with the cap value, but I think I'm happy with the way the control performs at the moment.

Since you are in the mood to play with the tone, consider this.  The .001uf cap in the tone circuit, provides a path for the higehr frequencies to bypass the lowpass filter formed by R5/C7.  It is that combination of highpass and lowpass that produces the midscoop.  If you make the .001uf cap larger in value you let more upper mids through.  make it smaller and only the mosquitos can pass unaffected.

So....consider replacing the .001uf cap with, oh let's say a .0033uf and a 680pf unit.  Both caps terminate with R6, but each of them is tied to an outside lug of a 10-25k linear pot on the other end.  the wiper of that pot goes to the junction of R5 and the Fuzz control.  Rotate it fully in one direction, and the 680pf cap becomes your "bypass" cap, letting less treble through.  Rotate it fully the other way, and 3300pf becomes the bypass cap, letting more upper mids through.  Positions in between adjusts how much of the treble and upper mids are mixed in with the R5/R6/C7 path.

That's definitely something I considered. Coming from a background in circuit bending, I do try different values for all components.
I realized that many times I can get very similar results to switching caps by just adjusting the low/mid/high on my amp.  Since in most cases it's just as easy and costly [a .29 spdt switch] and has much more effect on the overall sound, I've been switching between transistors instead....which is what I did with the Orpheum.

On a side note, I just checked the C voltages for the 2 trans I used. The hfe 24 one read -4.7v and the other with hfe ~50 read -.6v. The -.6v is the hotter one.