BSIAB2 Tone control question

[tungngruv]

I really love Ed G's BSIAB2. The only thing that I would like to change (for my rig) is the tone control. I never seem to have the tone control under the half way position. With my setup, it almost sounds like a blanket being placed over the speakers. I also tried the mod of removing the .002uf's (made them switchable in or out) but they really sound good on my amp leaving them in the circuit. Has anyone here had that tone control experience? I guess ideally what I'm looking for is to somehow spread the last half of the tone control (12:00 to max) over the entire range of the tone pot. Any ideas? Other than that, I totally agree that this is truly one of THE OD/Distortions available, commercial or home made. Thanks in advance for any ideas.

[John Lyons]

Tony

Check out the thread (should still be on the first page here...) about BSIAB2 mid modifications.
You can get Duncans tone stack calculator and plug in the values of the tone control there and see what you can do about that tone pot values.
The circuit is basically a modified big muff tone control.
Try different values for the tone pot and see what you come up with. it's a pretty fun little program.
I want to put in a mid control a la Jack orman's AMZ Presence control (which is also lnked above) which gives a good amount more mids as it flattens out the mid cut in the original circuit.


John

[tungngruv]

Thanks John, just what I was looking for.

[Ed G.]

I'd also recommend plugging the values in the Duncan tonestack sim. Try stock, then plug in the BSIAB values, it has pretty flat mids.
Don't let this discourage you, but I think the AMZ Presence Control mod might not work well with my values, mainly because the mids are flat. I remember simming it in and being discouraged from trying it.
I'm always trying out different things on one of my pedals, and I seem to gravitate back to the stock values.
I'd love to hear of anybody's mods, I'd like to clean up the sound in the upper mids.

[John Lyons]

Ed, you are correct. The curve of the BSIAB is flat in the mids, with a good wide bump in the low end around 100hz.
For some reason I was thinking tghe curve was closer to the Big muff values...

Here's the stock BSIAB2 curve





Here is what the AMZ presence curve looks like (roughly as there is no 3.3K off the "body" control)



Sorry for the cunfusion!


Tony, I tried a few configurations in Duncan's tone stack calculator and it seems that in order to get less of a high cut with the BSIAB set up you end up shifting the curve and messing with the low end and low mids. Personally I like the deep high cut on tap with the stock set up, for maximum variety...  So I guess I'm back to  the original set up with this one. It does sound great!  Thanks ed!

John

[tungngruv]

Thanks John. I feel like I should be paying you guys for this kind of tech support!!

[ubersam]

Instead of the stock tone control, I used a 3-knob tone stack with Marshallesque values. I have never built the BSIAB with the stock tone control so I can't compare, but I really like the 3-knob ts. The circuit seem to have more than enough highs that I prefer to keep the treble control at around 9:00.

[John Lyons]

Ed.
If you come back to this thread can I pick your brain?  In another thread "Mojotron" sugested making the .068 cap (C2) between the drain and gate of Q1, Q2 larger for more mid response, and also the same cap (C7) for Q3 , Q4.
Do you have any thoughts on what this does or if it works? I don't doubt Mojotrons advice, I just was curious if you did this or if there were any pitfalls etc etc.

Ubersam

Here's what the Marshall Type Tone control curve looks like. The mids are scooped pretty much all the time...

[ubersam]

...
Ubersam

Here's what the Marshall Type Tone control curve looks like. The mids are scooped pretty much all the time...

http://www.mrdwab.com/john/BSIABmarshallcurve.jpg

Thanks. I used different values in some of the places because I did not have the exact ones as in the Duncan TSC example. I plugged in the values I used in the Duncan TSC and got this:


The mids do seem to be scooped all the time, but there is still enough for me. I did make some substitutions because I did not have the right parts. All the 22nF caps were subbedwith 27nF, the 68nF with a 74nF (27nF+47nF), the 1uf subbed with a 1.2uF, the drive pot was subbed with a A1M pot. I did not have any 2N5457s so I used all J201s, which is probably why my BSIAB is a bit hissy at higher gain settings. Even with all the substitutions, I think it still sounds great. One of my buddies said it sounded "mean".

[Ed G.]

I shied away from a 3-knob tone stack because I wanted something simple. I suspect that the bass knob would be useless as I'd probably have it all the way on '10' all the time.
If I were to put in a 3-band tone control, I'd either have an active one or I'd consider the marshall guvnor/daddy-o one. I used to have a Daddy-O and I liked the tone control a lot.
The tone stack curve looks nice, a little mid dip is not always a bad thing.
Changing out the .068 for something larger will give more bass and low mids, but it could get muddy. I wanted a tight, aggressive sound. Fets get muddy fast if you don't trim them down early. If you don't, you won't get a very amp-like response. It's a delicate balancing act to get the right amount of grind and keeping enough headroom to make it 'breathe'

[John Lyons]

Ok, thanks Ed for the cap change info reguarding mids and lows. I figured you would know!
There is a good amount of low end anyway so I'll keep things to the original values.
The Marshall tone stack / mid dip probably does sound nice.
Right now I'm fooling around with a couple add on T- notch filters to try out with a mid heavy pedal...

Just for sake of information, here is a nice way to work up a T- notch filter in Duncan's Tone stack calculator:

Set The resistor that goes up to ground to 20M (esentially takes it out of the circuit)
Make the bridging resistors 330K or so. One of them is the pot so you should slide it all the way to the right.
Make the bridging cap 1n  and the cap to ground 10n

Just tweak around from there and you can get a simple mid notch filter. Using the pot as a variable resistor can add fun stuff as well.

John