Retro Channel - The Fuzz

marshmellow · Post by **marshmellow** » 05 Mar 2012, 12:21

Consider the circuit verified (the layout of course was never in doubt

):

I built two, they sound consistent with what I hear in clips/videos.
Maybe I would bias a little bit different, but that is up to taste I guess.

sinner · Post by **sinner** » 23 May 2012, 09:03

My take

roseblood11 · Post by **roseblood11** » 23 May 2012, 10:47

This is my built, I used my small vero layout (see p.3)

: rbf.jpg (57.8 KiB) Viewed 3056 times

Lawnchair · Post by **Lawnchair** » 23 May 2012, 14:00

roseblood11 wrote:This is my built, I used my small vero layout (see p.3)
rbf.jpg

Haha always the best graphics roseblood!

IvIark · Post by **IvIark** » 03 Aug 2012, 07:15

Another vero layout:

induction · Post by **induction** » 13 Jun 2013, 17:49

I was inspired by IvIark's Fuzz (Sur)Face layout, and the Retro-Channel Fuzz with a proprietary fuzz chip, I mean Tonebender MkII with a CA3046, was next on my list, so I bought an SMD cap and resistor kit (size 1206) and came up with a hybrid SMD/thru-hole vero layout for this puppy. For the most part I followed marshmellow's schem, but made a few minor mods after breadboarding:
- R9: 100k -> 33k
- C4: 100p -> 47p
- Pin 7: Can go directly to ground, or through antiparallel diodes (choice of Si or Ge) via on/on/on DPDT. (Thanks to mictester for the idea.) Compared to stock, the Ge diodes give a slightly fuzzier/less muscular tone - a nice but subtle variation in texture, possibly too subtle to be noticed in a band context. The Si diodes give a splatty, gated sound (reminiscent of mis-biased fuzz face) that I also like a lot.

The result is fairly compact:

The full layout picture shows both sides of the board at once and is kind of ugly, but it's useful for designing and double-checking the layout. Individually, each side is pretty neatly laid out.

The layout is verified by me and sounds great. Here's my build:

I didn't use any shielded wire this time, but with a battery or regulated adapter it's dead quiet.

Notes:
- I didn't have any 620R resistors, so the layout uses a 470R and 150R in series.
- SMD components in parallel is ridiculously simple. Just stack them. My kit didn't come with 18k resistors, so I stacked a 100k and a 22k.
- The trace cuts underneath SMD components need to be smaller than I tend to get with a drill bit. I ended up using a razor blade and a needle file, but I'm still looking for a better solution, and I'm open to suggestions. I experimented on some scrap vero with the Dremel diamond wheel that I use to cut my boards, but the diameter is too big and I always ended up unintentionally cutting the neighboring tracks.
- The SMD connections are not centered on holes, so you can fit them anywhere you like and the thru-hole parts on the other side won't get in the way.
- This should have been obvious before I built it, but wasn't: Solder all the SMD before anything else. It's much easier that way. If both pads have solder on them already, you have to heat both leads simultaneously to make the SMD lay flat. It's possible to do, but it's tricky and the component wants to stick to the iron tip and move around. It's easier to just solder one side and then the other. If the SMD is soldered on both leads, heating up the track for a nearby thru-hole component won't push it out of place. My next hybrid build will be neater and faster.
- As so many of you know already, hand-soldering SMD is not as hard as it sounds, as long as you use a fine-point tip. In many ways its easier than thru-hole. This build turned out so well that I plan to incorporate SMD in all my vero layouts from now on. The layouts come out much smaller and neater. Layouts are also easier to do when I don't have to customize them to fit my caps, which I get from a surplus store and are all different shapes and sizes.
- On/on/on DPDT's come in two configurations. Double-check yours with a DMM, and reverse the jumper if necessary.
- After building this, I realized that the diode selection could be done with a on/off/on DPDT, which might be easier for some people to find. Here's the alternative switch arrangement:

: alt_switch.png (14.42 KiB) Viewed 2632 times

This should work as long as D4 and D5 have higher Vf than D6 and D7, respectively.

roseblood11 · Post by **roseblood11** » 13 Jun 2013, 18:46

Well, it's 13*11 holes, my layout for through-hole components is 16*11. Is it really worth the effort?

induction · Post by **induction** » 13 Jun 2013, 19:02

I'm not sure I understand the question. It wasn't any more effort than a purely thru-hole build.

JustinFun · Post by **JustinFun** » 14 Jun 2013, 06:02

induction wrote:I'm not sure I understand the question. It wasn't any more effort than a purely thru-hole build.

I build mostly smd now and agree with this - the components are way cheaper, and it's a lot quicker to build - no leads to clip or (if you're etching a pcb) holes to drill!

Come on in, the water's lovely...

mganzer · Post by **mganzer** » 19 Jun 2013, 12:08

Hi guys;
Maybe is stupid questions but i appreciate any help...
I'm try to figure out what part of schematic is the clipping stage and how put some diodes to have an enhanced octave effect with a dpdt switch.

And

how i can reduce the gain in first stage or all stages? maybe a capacitor (range 100-200pf?) between base and collector of the transistor in array work?

Maybe its sound like a bulls*** but i like more subtle effect of fuzz.
Thanks

IvIark · Post by **IvIark** » 19 Jun 2013, 18:21

induction wrote: The layout is verified by me and sounds great. Here's my build:

[ Image ]

[ Image ]

Very cool, love it!

induction · Post by **induction** » 19 Jun 2013, 20:34

mganzer wrote:Hi guys;
Maybe is stupid questions but i appreciate any help...
I'm try to figure out what part of schematic is the clipping stage and how put some diodes to have an enhanced octave effect with a dpdt switch.

And

how i can reduce the gain in first stage or all stages? maybe a capacitor (range 100-200pf?) between base and collector of the transistor in array work?

Maybe its sound like a bulls*** but i like more subtle effect of fuzz.
Thanks

Yes, mictester recommended these mods (but I can't find those posts anymore for some reason).

The diodes go from Q2 emitter (pin 7) to ground and are included in my layout above. Mictester recommended germanium, and I like the way they sound, but the difference is very subtle. With silicon diodes, the effect is way more noticeable, but I wouldn't call it octave.

To reduce the gain in the first stage, I'm tempted to say add a 1k resistor from pin 3 to ground. I wouldn't mind if someone verified that for me, though. I have a tendency to think I know what I'm doing when I don't.

Maybe the other two gain stages can be reduced in a similar way? Q2: add 1k (or more) to ground (or to diode pair) from pin 7. Q3: increase the 680R on pin 10 to 1k or 1.5k. You'll have to experiment to see if it does what you want it to.

mictester · Post by **mictester** » 19 Jun 2013, 23:25

This seems a strange request - it's already pretty low gain. If you want to reduce it further, change the 100k feedback resistor between stages 2 and 3. The quickest way to try this is to just tack another 100k in parallel with the one that's already there (that gives you 50k). This will reduce the gain in the distorting part of the circuit.

The transistor array was chosen as a way of getting fairly low Hfe silicon transistors cheaply, as most modern transistors have much higher gains.

mganzer · Post by **mganzer** » 20 Jun 2013, 00:42

IvIark wrote: I have a tendency to think I know what I'm doing when I don't.

I'm too. unfortunately.

I build one already. Works very well but give as gift for my brother.
Another build, another approach. IS a strange request but i'm trying to figure out what component do what.
The trick with cap between base and collector will smooth the effect? If yes, what the good values to breadboarding?. Maybe i cause a misunderstanding of what i looking for...

In fact i want to smooth the fuzz effect, enhance overtones/octaves/harmonics, put something like a presence control and add a buffer after.
Maybe i'm just want too much...

Ali7887 · Post by **Ali7887** » 04 Jun 2021, 14:07

Anyone has "byoc large beaver Ram's Head" layout?

soggybag · Post by **soggybag** » 25 Mar 2023, 17:04

I just built one of these, sounds great. I’m wondering if there is something that could be done with the extra transistors?

To be honest I’m not sure if there are any extra transistors. Looks like Q1 and Q5 are used to create a bias for the input of Q2. But I’m not sure how it actually works or if this could be replaced to free up one or both of these. Q1 collector would need to go to ground since it’s connected to the substrate.

Retro Channel - The Fuzz [traced]