Best place to add a BMP tone stack or active eq to a Fatpants pre

[hoyager]

Does anyone know a good place in the circuit to add this sort of thing?

Cheers
Andy

[jkokura]

Breadboard both of them, and then use a wire to try 'tapping' it into both of them. My suspicion is that you'll have to play with some values on some things. I would try before C4 (100nF cap).

Jacob

[stecykmi]

typically you need a gain stage after passive filter section like the BMP. don't be too surprised if you have unusually low output.

[hoyager]

Cheers

I imagine the volume drop wouldn't be a problem in the fatpants because it is a booster anyway?

[jkokura]

Might not be, but I still suggest the breadboard. It's a simple test to jump it in and out to see the difference. Ic my breadboard wasn't being used, I might do it myself.

Jacob

[hoyager]

So just before the output?

I've got 3 fatpants boards to build so I might socket the various caps instead, I've modded one already but it was pure experminentation. I found C1 had a big effect on the tone too, is that another possible spot for a tone control?

The breadboard is still a mystery to me but I have some coming with the hope of making a few different LPF's and the tone control

[madbean]

A passive tone stack should be fine without recovery on the FP. There's enough output that I don't think you will suffer greatly for it. Best guess would be to do the BMP in place of the volume pot. Get your tonestack where you want it, then connect the wiper of the 100kB tone pot to lug3 of the 100kB volume pot for the FP.

[hoyager]

Awesome, thanks man

That tone stack calculator is the s**t

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

[gtr2]

Awesome, thanks man

That tone stack calculator is the s**t

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

It would be great to have a sticky to links like this!

[hoyager]

I've done this tone control and its behaving exactly how I'd hoped, except there *is* quite a volume drop.



Signal is on the white wire and goes to lug 3 of the pot (100kb) and goes back to the board from lug 2. Ground is connected by the green and purple from the other side of the cap from lug 1

I've found bridging lug 3 and 2, brings some volume back but the tone control is very mild after that.

Also removed R4 (47k) which makes it slightly louder again.

Now its pretty much at unity but its function as a booster has definitely gone...

The tone control is supposed to take away 8 - 10db at 12 oclock with the freq at both ends only minus 2 when the control is full up or full down

Does this seem correct? Is there anything anyone can see which is out of place, or just plain wrong??

cheers
andy

ps what looks like a 220n in C3 was just an experiment..

[bigmufffuzzwizz]

Hmm well thats not good at all. I've never added this mod before so I don't have much experience with it but yesterday in class we were talking about db/wattage/power related topics. Not sure if it applies to this but with amplifiers the difference between a 50watt and 100watt is something like 3db change in volume. If it works the same, 8-10db could be a big change like what your describing. I'm curious, what layout are you using?

[jkokura]

Because tone controls are generally passive, there needs to be a makeup gain stage after it. The volume loss you're desribing is pretty major. You could fix it by building in a simple jfet gain stage to follow the tone control.

Take a look at a tubescreamer, or a big muff schematic and you'll see the tone control is followed by one more gain stage to reamplify the signal after you've filtered it with the tone control.

Does that make sense?

Jacob

[bigmufffuzzwizz]

Because tone controls are generally passive, there needs to be a makeup gain stage after it. The volume loss you're desribing is pretty major. You could fix it by building in a simple jfet gain stage to follow the tone control.

Take a look at a tubescreamer, or a big muff schematic and you'll see the tone control is followed by one more gain stage to reamplify the signal after you've filtered it with the tone control.

Does that make sense?

Jacob

Time to get your vero/perfboard out!! 

[hoyager]

Sorry I am tripppin, when bypassed the pedal is def quieter, so it is boosting but with the gain on full though and the tone control semi bypassed as described.

I'll remove the jumper to see.

The tone control on the pot is using this guide

http://www.beavisaudio.com/techpages/BigMuffToneControl/

with component values found from using the tone stack calculator further up the page

Could I put the tone control before the gain stage on the Fatpants? Also is there another cap or component which the whole signal passes through, other than C4, where the tone could go?

In and out in place of C2 maybe? would the pot need to be grounded in that case?

Sorry one more, would changing the resistor at the input R1 100k to a lower value raise the input level?

te choice
Andy

I'll post some audio soon, hopefully a video with an actual guitarist..