PigeonFX Supa Fuzz

[m3gan00b]

So after hearing the sounds and learning the lore of the Marshall Supa Fuzz/Mk I/Mk II TBs (and tripping over a pair of OC81s and an OC81D), I decided I'd like to build one as I don't exactly have the cash for the real thing. Thankfully, I found the PigeonFX site with their etched PCBs and kits that needed the transistors that I so happened to have.

I'm no electrical engineer by any stretch, but I've had some luck in the past with simple guitar/pedal/amp repairs, building simple AB switches etc., so I figured if I just followed the guide I found (posted below), how hard could it be?



Well, hard enough to reach out to the forums and see if any of y'all have built this kit, and if there's any inherent problems with that layout that you know of. Discovered from doing some research that one builder needed to change the polarity of the 9V clip to accommodate PNP transistors, so I took that into account.

Populating the board wasn't the problem, but when I got to the jacks/switch/pots, that's where the confusion started.

Anybody built one before and have any tips? Sorry for the noob post (hence my handle), I'm just trying my hand at something new!   Thank you!

[m3gan00b]

...though I gotta say, those OC81s are making Mexican radio sound pretty sweet thru a bassman 4x10

[Taylor]

Here's a diagram for wiring a bypass switch:

http://www.premierguitar.com/Stream/StreamImage.aspx?Mode=News&Image_ID=C3D5E99E-DDB2-4F2B-8E25-24030207684F&Image_Type=image

But, if you're really unsure about things (and we all start that way) you might want to just wire it up straight to the jacks to make sure the effect is working correctly before you add in the switching. A germanium fuzz is not the easiest first build, because of the many variables involved.

All of the little triangles made of three horizontal lines indicate ground. You need to connect these all together, and to the ground tab on each audio jack and the ground jack. Then you connect the tip of the input jack where it says input, the tip of the output to "output" and the power to where it says "9vdc."

If the circuit is not designed for PNPs, then just plopping them in upside-down and reversing the power is, I gather, one of those things that sometimes works and sometimes doesn't. This is a good time for me to point you to geofex.com. There's a ton of great info there, including some on this topic.

[LucifersTrip]

Anybody built one before and have any tips? Sorry for the noob post (hence my handle), I'm just trying my hand at something new!   Thank you!

I just dug out my notes on the Supa Fuzz. This DAM post was the most helpful. The moderator is a master of TB MKII/ Supa Fuzz:

http://dam.10.forumer.com/viewtopic.php?t=779&highlight=collector+voltage
his post regarding gains and Q3 collector voltage:

====================
On vintage units it varies from around -7.6V - -8.9V.
Even seen em with 9.1V! I take measurements with Zinc Carbon batteries which are around 9.6 Volts when fresh. The original batteries used in the MKII's and its variants were PP4's (Eveready 226) which also read high at around the 9.6V level.
Hfe levels are usually higher also. For example my '67 Supa Fuzz measurements...

Q1 - 174
Q2 - 208
Q3 - 194
====================

I wrote a bunch of build reports as I was experimenting, but this is the final one:

I'm finally done (well, at least this build) and thanx to DAM's 200 hfe recommendation, I will barely have to make any change. It is absolutely killer with the 47K reduced to 36K...that's all.

I furthered my leakage tests with a much more controlled experiment. I substituted transistors with the same number (2SB459), almost same hfe, but different leakage...into each of the 3 slots. If you are going for straight out smooth saturated screaming fuzz, then low leakage won out in all cases. If you want a more lower gain, dirty, gated fuzz, then throw a higher leakage one into Q2. In Q1 a higher leakage reduced treble, sharpness, a little volume, and gave it a little fatter sound (not needed with 10uf input cap). In Q3, it reduced the overall attack.

In my previous version I had hfe 186, 193, 213 respectively ...but I upped the ante on the screaming fuzz by increasing Q1 further and keeping the leakage low. So, my final version is hfe 244, 193, 213 ...all leak under 150uF

If I want to get some gating, I can raise the C voltage on Q3 to around -8.3V. This way, you'll have a gate along with a rich, saturated fuzz. I can also get it to gate by lowering the voltage to around -2v, but the tone is way too thin and wimpy. If you want the gate to by dirty (with not nearly as much rich saturated fuzz) simply increase the leakage of Q2.

I like monster fuzz, so I'm going with low leak hfe 244, 193, 213 and a trim/cutoff on Q3 collector to give me from -6v to -8.5v

If I was going to mod it, I'd just put in a switch to alternate between a high and low leakage Q2. That way I could have everything: rich saturated fuzz, a dirtier low gain tone and gating with both.

[m3gan00b]

@LucifersTrip - Thanks for the info! Have been curious about transistor placement, and appreciate the info. @Taylor - Thanks for the link! Though I'm using a DPDT switch as I want to stay relatively true to the original. That being said, when I do finally give up and get a 3PDT and throw in an LED I'll know where to go.

I guess the real issue I'm having is with the offboard wiring, knowing where the circuit input/output are...I know they're labeled on that image I posted, however the indicated output location isn't on my PCB? Everything else is identical, just that one spot. Hmm...

Anybody have one of these that they've built that they'd be willing to take pictures of/draw/describe?

Thanks!

[LucifersTrip]

I guess the real issue I'm having is with the offboard wiring, knowing where the circuit input/output are...

Anybody have one of these that they've built that they'd be willing to take pictures of/draw/describe?

Thanks!

according to the Pigeon site, it is a replica...so, this would be a great time to not make one of the oldest beginner mistakes...not learning how to read a schematic.

you should be able to find all wiring points with a little studying...and I'm sure someone will answer again if you get stumped. remember, a schematic is basically nothing more than straight line connections between components.



good luck

[m3gan00b]

Thank you for all the helpful info! I've checked out my circuit with that schematic, took the switch out of the equation and followed the pot/jack instructions to the tee, and I'm getting glorious, wonderful, amazing...clean signal that doesn't seem to be affected at all by the pots. Head scratching commencing now...

[m3gan00b]

Update: After tinkering I'm not getting radio anymore, just great thick fuzz, however only when I run a wire from the input sleeve to the collector of Q1 and another from ring to ring on both jacks??? That and the pots don't control much except for a high pitched screeching noise that comes when a full on note or chord arent being played? Bizarre but rewarding and extremely interesting! Any tips? Thank you!

[Taylor]

If your jacks have ring connections, they are stereo jacks, which you don't need and will complicate things while you learn how to wire an effect. When you plug a mono cable into a stereo jack, the ring and sleeve are shorted together. The sleeves of the two jacks should already have been connected to each other and to all the other grounds. Did you wire things up as I explained earlier? Can you post a photo of your build?

Sounds like everything after Q1 is working at least sort-of. So build an audio probe, and probe all the points from the input jack through to Q1 and find where your signal is not getting through.

[m3gan00b]

 Hi Taylor, I did indeed wire things up with just the jacks, no switch, with a stereo in and mono out as I've come to believe is what to do. I'll post photos in a bit when I get within reach of a decent camera. Will also try the audio probe to find out which pesky joint/component is causing the issue and see what I come up with.

Thank you for your help!!

[m3gan00b]

Here's a few pictures so far...
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/m3gan00b_3.JPG
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/m3gan00b_2.JPG
http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/m3gan00b_1.JPG

[m3gan00b]

Update: I've gone thru with a multimeter and all the components seem to check out except the Input>10uF cap. Could it be a dead cap/bum solder joint? hmm..

[Taylor]

It looks like you've got some strange wiring going on. You need to connect the sleeve of your output jack (it's the connection closest to where the plug goes into the jack) to all the other grounds.

Also, maybe the photo is a weird angle but it looks like you have wired your battery to the input jack's tip, so the input from your guitar is just being shorted to 9v. What wiring diagram are you following? You need to connect the sleeve to ground here, the battery to the ring (the center tab of your jack) and the tip to the input of the circuit.

[m3gan00b]

It works! Allllllmost! The sound is great, the volume control works, however the fuzz pot doesn't seem to do anything to the signal...any other dumb n00b mistakes you can think of?

Thank you so much for your help!

[LucifersTrip]

first guess is too obvious, which is probably why noone replied yet...if the fuzz sounds good and the fuzz pot does nothing, it's either a bad pot or the wiring is off

[m3gan00b]

Checked , checked and checked again, the wiring is as it should be according to the schematic, and I'm using a brand new pot. As well the volume pot works in the opposite direction? So weird

[Taylor]

Checked , checked and checked again, the wiring is as it should be according to the schematic, and I'm using a brand new pot. As well the volume pot works in the opposite direction? So weird

This means you have the wires for lugs 1 and 3 (the outer lugs of the pot) backwards. Switch them and it will work the right way. As for your fuzz pot, I know it's tough on the ego, but if the wiring was right and the solder joints were all good, and you had the correct parts in the right spots, then it would be working. That it isn't is evidence that one of those elements is not in place.

Check with your multimeter that every connection in that area is correctly connecting to the thing to which it's supposed to connect, that your transistor is in the right way, and that you have the right parts values (the pot and the capacitor).

[m3gan00b]

Hahah no worries about my ego, I left that at the door when I started this thing! I know it's probably some simple thing I've switched around. Thanks again for your help, I'll check the pots again as per your advice and hopefully we'll be off to the races

[m3gan00b]

Flipped 1 & 3 on Level and voila, it works. Thank you!!! Attack still didn't do anything, so I swapped for good measure, same deal...fuzz, yes. Volume, yes. Fuzz control, nope

[m3gan00b]

Many moons later...picked it back up, stripped it down to the PCB and off board parts, built it again, still scratching my head. One wire on the switch I haven't got a clue as to where it goes. Was passing signal before with no switch, sounded lovely too, but obviously the ability to turn on and off would be a plus!

Looking at the image below, does anything jump out? Besides the mystery wire?

Thank you!!