Big Muff tone stack, help?

[fuzzjunk1e]

Alright - I built a GGG green russian muff clone. I want to make it more Hoof-like. I changed the diodes to LED's and replaced Q2 and Q3 with germanium trannies. It's sounding fantastic and much more Hoof-like than it did with stock values/parts.

The one thing I'm having trouble with is the tone stack. Anyone care to give any helpful tips on trying to duplicate the Hoof tone stack? The main problem I'm having is that there's too much treble there even when the tone knob is totally CCW. It's definitely wired up correctly. CW is treble and CCW is bass, but it seems like CCW just adds bass freqs without cutting treble, whereas (from the two 3-knob Hoofs I've owned in the past) the Hoof seems to be more bassy/muffled when you have the tone knob set low.

I don't mind having a 3-knob Hoof-ish muff but I'd also be open to adding the Shift knob if anyone has any good info on that. I tried the AMZ presence/body mod and didn't really like the results though, so I switched it back to "stock".

Thanks!

[fuzzjunk1e]

http://www.kitrae.net/music/big_muff_guts.html

This is the best page I know of for Muff tweaking. It tells you what all of the parts do and which way to adjust them, etc. So I know which parts I'm looking to change - just wondering if anyone can suggest some Hoof-like values? I don't have it breadboarded so it would be a real pain in the ass to keep soldering/desoldering and playing guess and check.

[moose23]

Duncan tone Stack Calculator will give you plots for different values in the Muff tone stack. Also as far as I know the Hoof has flat mids too.

http://www.duncanamps.com/tsc/

[John Lyons]

If there is still too much treble with the tone knob full CCW then something is wrong.
The tone pot pans between a high pass and low pass filter.
At full CCW you should have a steep low pass signal with not much treble.
Check your layout again, there has got to be a solder bridge or miswire. It happens...

[fuzzjunk1e]

I have both the high pass and low pass resistor at 39K right now. Stock value was 20k and 22k. The low pass cap is stock at .01uF and the high pass cap was changed from .0039uF to .0047uF
The mid scoop is mostly flattened out and it sounds great but yeah, when turning the tone knob CCW from full CW, it gets more bassy and less trebly until about 9 or 10 o clock and then the treble comes back in during that last bit (8 o clock, 7 o clock) as I travel to full CCW. Very weird. I don't recall it doing that previously (built this pedal a year or two ago, just recently started trying to tune it to sound more like a Hoof)

I've built dozens of pedals but as you mentioned, mistakes do happen. I'll give it a look to see if I can spot the issue. It's on a GGG board though, not vero (like many of my builds), so there is less chance of error but still always a possibility...

[fuzzjunk1e]

Couldn't spot any errors. I replaced the b100k tone pot just in case it was somehow causing the issue. Nope. Still doing it. It sounds good, so it isn't a problem, but I seem to recall a Big Muff is supposed to be basically treble-less when the tone control is fully CCW. Like a blanket over your amp. I'm not getting that at all. Maybe my low pass cap is jacked up? I don't know - the lows are there for sure, but so are the highs. Why would that be?

Also, does it matter than my high pass cap was ceramic when "stock", but now it's a Mallory film cap? I figure it might change the tone a bit (ceramic cap vs film) but that wouldn't cause this excessive treble at low tone settings would it?

[fuzzjunk1e]

When it was stock, the tone control worked very well. Once I made the change from diodes to red LED's for clipping, that's when it seems to have started. Maybe it's related? Or maybe I dicked something else up while I was in there changing things...

[John Lyons]

The tone network is isolated from the things you mention.
Changing the resistors in the tone section may have been when it happened.
Do you have an audio probe?
They are something you will use all the time. Dirt simple to make...This way
you can hear what each half of the tone knob is doing.

[Jero]

Do you have an audio probe?
They are something you will use all the time. Dirt simple to make...This way
you can hear what each half of the tone knob is doing.

Mind explaining? I thought audio probes usually just bleeped, or didn't bleep...the hear what each half of the tone knob is doing interests me.

[moose23]

You're thinking of the continuity test mode of a multimeter, audio probe is connected to you amp so you on hear what's happening/not happening at different points of the circuit. Great for finding exactly where any problems are in a circuit. you still need a guitar or a tone generator running into the pedal too, I use an oscillator for this part.

I use one like this:



and here's what's in it:

[Jero]

You're thinking of the continuity test mode of a multimeter, audio probe is connected to you amp so you on hear what's happening/not happening at different points of the circuit. Great for finding exactly where any problems are in a circuit.

You're right, thanks! That makes much more sense. I'm going to make one of those today, but use a male jack so I can plug it directly in.

[John Lyons]

I made one in a small box with a volume pot between the cap and input tip.
This way I can attenuate the signal if need be without reaching for the amp.
I used an old meter probe so I can get into the small areas easily.
It's really handy to go though a whole pedal or amp and here what each stage is doing
and once you find where the signal stops or sounds wrong then you found your bad area.

[moose23]

That sounds like a good idea, nice one John.

[fuzzjunk1e]

Cool thanks man. I got some help from the fine folks at freestompboxes.org and they think it sounds like a cold solder joint. I'm going to check all my joints first but I'll be back if that doesn't fix it...