High pass filter at the end of Big Muff circut?

[stonerbox]

Hi Folks!

I'm ashamed that my second thread is yet again all about asking for help, but I need it bad.

I'm modding my Big Muff Pi NYC (Ec3003) beyond this world! It now has the ability to create a fairly large varieties of "fuzzsounds". My goal was to take a pedal with not so much variety and turn it into a pedal with more fuzz types to mix and choose from.  

Here is a short list of the types:

1. From gentel to harsh Nintendo-squarewave-ish
2."Boosted" more fuzzier big muff sound
3. Super creamy, "singing", smooth and thick fuzz.
4. A Unicord Superfuzz style of sound, does not sound as good as the original, but pretty close.
5. And  at last the basic Big muff sound.


Back to the question:
I have been reading tons and of tons of threads on the topic high pass filters, active and passive. I have also tried to add several different version between the C2 and the first lug of the volume knob (as seen on the pic) but with no success.. all I get are either another "volume knob" or just a lowpass filter.  
I was able to add a presence filter/lowpass at the end of the circuit (on the  volume knob), but adding a high pass is a real bummer.



I know that a high pass is supposed to be a low pass with the capacitor and the resistor (and in this case the variable resistor) swapped places.
I may have been connecting some of the cables wrong, but I doubt it.


The filters I have tired to add:
1
http://www.muzique.com/schem/filter.htm
2

3

[John Lyons]

The first pic you posted is a low pass filter.
The second is high pass.
With the stock tone BMP control turned to the treble side is a high pass filter.
A cap in series with the signal and a small resistor to ground will create a high pass filter.
.002 and 22K is what the maestro fuzz tone and others use.
You can play with the Duncan Tone Stack Calculator turned to the treble side to fool around with
different values.
http://www.duncanamps.com/tsc/

[stonerbox]

Thanks for your reply, I´ll give it a try.

Oh and your right it is a low pass, my bad.

[Suicufnoc]

I don't see why you'd want another high pass on a Muff?  With the tone all the way up, you're getting lot more of the high-passed signal than the low-passed signal as it it.
But then I am a low-pass freak.  I love to tame harshness, possibly to a fault

[John Lyons]

I don't see why you'd want another high pass on a Muff?

Depends on what you're doing with it.
Crank it up to the high pass side and add a ton of reverb and
out come the lava lamps...either than or a showdown at high noon. 

[roseblood11]

Another interesting version would be a James tonestack instead of the Big Muff tone control.
"Nocentelli" posted a vero layout over at the other forum, I made it a bit smaller, it fits into a 1590B now:

[stonerbox]

I don't see why you'd want another high pass on a Muff?  With the tone all the way up, you're getting lot more of the high-passed signal than the low-passed signal as it it.
But then I am a low-pass freak.  I love to tame harshness, possibly to a fault

I also love to tame the harshness in fuzz. A smooth, big and fuzzy low end is definitely my thing. But in order to get a good clean tone on my Laney pro tube lead head I need to crank the preamp up, then when you add the fuzz into the signal the bass get enormous and the mids and some of the important highs gets lost. The thing is also that when I engage some of the modes the tonestack are bypassed.

Another interesting version would be a James tonestack instead of the Big Muff tone control.
"Nocentelli" posted a vero layout over at the other forum, I made it a bit smaller, it fits into a 1590B now:

Not exactly what I need now, nonetheless interesting!

[stonerbox]

Okay, I think I'm going crazy. I have been on this for days and it is just not working... I'm able to filter out some of the lower frequencies but when I dial the knob to full at any direction the signal goes straight out to the ground= no sound.

Could somebody explain what is going on here:

[John Lyons]

There should be no connection to ground in that filter pictured.
WHat you have there is a resistor paralleled with a cap.
Usually a fairly larger resistor with a fairly small cap.
The resistor blocks a lot of signal and the cap lets signal past.
Since the cap is small the signal getting though is small...er, small in frequency.
Meaning high pass. The resistor is a variable one so as you make the resitance smaller
more signal comes though the resistor and that signal isn't filtered through the cap so it's full
range Highs/mids/lows. Big resistance means more comes through the small cap which = more high end
or less low end (same thing).



When the resistance is lowered you get more un affected signal back.
The other way to do it is with cap in series with the signal and the resistor/pot to ground.
For example a .02 cap to in line and a 100k pot to ground. The output is the junction of the right side of the cap
and the top of the pot. Make the resistance smaller and you get a bass cut. Larger and it's more full range.

[stonerbox]

Many thanks for the in depth explanation, it helpt me a lot.

[stonerbox]

It works, finally! Thanks again for taking the time explaining John.  

Strange thing though (or maybe not?), when I add the filter somewhere "inside" the circuit it acts as an low pass but when I add it between the output cable and the output jack tip it does the job I want. The obvious problem that arises then is of course that the HPF is not bypassed when the pedal is disengaged.

hm... I need to figure this out somehow.

[John Lyons]

Put it in last, right before the volume pot.
Though, generally the resistor to ground version is used there.
When you use is somewhere inside the circuit you may not notice
the high pass setting as much as the full range setting.
It should not cut treble either way. You'l notice it cleans up the
bass more as a "feel" or clarity control when used after Q1 or Q2.
This gets you a more distortion like sound...

[stonerbox]

I've tried that, I put it at the end right before the volume pot (tapping the signal from C2 negative to the volume pots first lug) and at that position it acts as an LPF. My only reasonable explanation for this is that the problem could be cause by the already connected LPF/"presence control" that sits on top of the volume pot, or maybe not?


Thanks for helping the noob!


edit: I used the cap in series and pot to ground.

[John Lyons]

Can you post a schematic of what you have going right now?

[frequencycentral]

There's also the AMZ Dual (Big Muff) Tone Control:

http://www.muzique.com/lab/atone.htm

[stonerbox]

Here you have it:

I forgot to write "Q4" next to the transistor.

I removed the LPF that was connected to on top of the volume pot, but when I add the HPF as shown on the schematic it still acts as and LPF.  
This HPF only works when I put it in the output signal after the volume pot. Why?.. Beats me?

[stonerbox]

Just noticed that when the volume knob is set at full (5-6 o'clock) the high pass does not affect the signal that much, it only cuts some of the higher frequencies.
When I backed down the volume knob  to  3-4 o'clock it does the job very well.

[John Lyons]

Remove the connection from the top of the vol pot and the right of the 1uf cap.
Make the 1uf cap .047 (may need to make it smaller or switch between two caps)
You have one too many connection there. 

[stonerbox]

haha, I probably do.    Thank you for all the help!
Oh by the way, I love your work man! Cheers!

[PRR]