Modding a Big Muff to Boost Treble???

[Minion]

Hi Folks, I just finnished building a Big Muff (Discrete version) from TonePad and I noticed that all I hear is Bass and absolutely no High end, so I was wondering what Caps I should switch and what Value to change the Tone controll to have more Trebble or less Bass??

I tried changeing C10 from 470pf to 220pf but it didn"t have much effect, I"m thinking maybe I should change C12 from 0.1uF to something smaller like 0.05uF...Is this the correct Cap to change?? Or is Maybe C12 the one to change??

I used different Transistors (2n3904 instead of 2n5088) if that means anything, and 1n914 Diodes and added a 10uF Filter cap but everything else is the same as in the Layout.....

Thanx a Lot

[Dragonfly]

Hi Folks, I just finnished building a Big Muff (Discrete version) from TonePad and I noticed that all I hear is Bass and absolutely no High end, so I was wondering what Caps I should switch and what Value to change the Tone controll to have more Trebble or less Bass??

It sounds like there is something wrong with your build, in which case a "mod" is not needed, but debugging. A BMP should have plenty of high end, especially when the tone control is up.

Check the "Debugging" thread thats stickied at the top of this forum, gather the info, and post it here, and we can probably help out.   

[Minion]

Well I don"t really think there is anything wrong because it does work it is just all Low end, The tone controll works but it just gives more low end when turned up ( I thought it should give more High end when turned up but it is the opposite and my wireing is exactly as in the PDF)

Actually I have just done a Bit more research and It seems to suggest that a LOT of poeple think there is too much bass in the Big Muff, It says to change the 1uF Caps for 0.1uF to get more High end, Like doing the Triangle or Green Mods....I will try those first and report back to tell if they helped.....

Thanx

[MartyMart]

One end of the BMPI tone control is "Fat n bassy" the other is "thin n trebbly" so you must
have a problem here.
In General, using 1uf's is too much for me also, a combo of 1/2 1uf and 1/2 0.1 is nice, but
my last one I used all 0.22uf's and like that a lot.
Worth trying out but fix the TC first

[Minion]

Well Maybe I am looseing some high end through Cable Capacitance?? I tried useing all of the Correct Values for everything as in the Layout includeing the Tone controll and I get very simular Voltages on the Transistor pins as in the Layout and the Tone controll works, It just goes from very Bassy to extremely bassy.....all of My resistor Values are within 5%-10% of the Values in the Layout if not exactly correct and I etched my own PCB and there are no problems with it nor are there any Bad solder joints, the only real changes from the layout are the Transistors are different (2N3904 VS 2N5088) but have the Same Pinout and many of the same perameters.....

I"ll change the 1uF for .5 or .1uF Caps and see how that sounds and if it doesn"t help I"ll try bypassing the Tone controll.....

Thanx

[jonathan perez]

Well Maybe I am looseing some high end through Cable Capacitance??

no....just....no...

I tried useing all of the Correct Values for everything as in the Layout includeing the Tone controll and I get very simular Voltages on the Transistor pins as in the Layout and the Tone controll works, It just goes from very Bassy to extremely bassy.....all of My resistor Values are within 5%-10% of the Values in the Layout if not exactly correct and I etched my own PCB and there are no problems with it nor are there any Bad solder joints, the only real changes from the layout are the Transistors are different (2N3904 VS 2N5088) but have the Same Pinout and many of the same perameters.....

I"ll change the 1uF for .5 or .1uF Caps and see how that sounds and if it doesn"t help I"ll try bypassing the Tone controll.....

Thanx

sure, you used good resistors and soldered well...but fact of the matter is that you may have the wrong values in the wrong place. the tone control shouldnt be adding bass as you turn to the right...sure its a bassy unit, but it shouldnt be adding bass as you turn up the tone control. so yes, there is a problem with your circuit.

[jlullo]

i built the triangle version from tonepad, and like these guys are saying, mine can go from way bassy to WAYYYY trebley.... so there is definitely and issue with yours

[Processaurus]

hi, i agree, it sounds like something isn't right.  Analog stuff is funny, it can still work in some fashion even with major errors in a circuit.  Catching the ones that just make it not sound so great are the trickiest.

My guess as to why the tonestack isn't working is either a) R18 isn't connected to ground, b) c10 is shorted, or c) the tone pot is a really wrong value, or isn't wired correctly (my best guess there).
The combination of a series capacitor (C10) and a resistor to ground (R18) make a hi pass filter, ie. the lows are cut but the highs get to pass.  The tone knob pans between that hi pass filter, and a lo pass filter (made the opposite way, with a series resistor and a cap to ground).  When the tone is panned to the hi pass side, it should be rolling off frequencies below 1kHz, so, when its working, there will be plenty o treble, and no bass.  There are some articles at muzique.com about the big muff tone stack if you are interested.

[Minion]

Well I checked the my Layout against the PDF one and all Values are correct for the Tone stack and it is Wired up exactly as shown in the Layout , Maybe the Layout has a Mistake??

[Dragonfly]

Well I checked the my Layout against the PDF one and all Values are correct for the Tone stack and it is Wired up exactly as shown in the Layout , Maybe the Layout has a Mistake??

Lots of people have built successfully from that layout, so I tend to doubt it.

I would use a DMM to check the values on the parts around the tonestack. Also, you might use a jumper to "bypass" the tonestack, just to verify that its where the issue is.

Many times people will accidentally do things like mix up a 100K resistor with a 10K...thats where a DMM helps, as you can verify "actual" values.

Also, like I mentioned in the first reply, read the debugging thread. It will have additional ideas for you.