Plexi-Sound in a box

[jpb_guitars]

Just thought about a box that produces a heavy overdriven Plexi-sound with a fuzz in front of it.
Any ideas how to built one?

Jan

[Ed G.]

The Thunderchief from runoffgroove.com is a fet emulation of a plexi.

[Gary]

Ed's "Brown Sound in A Box" is really good!

[Paul Marossy]

I second the BSIAB.

[Ed G.]

I'm rediscovering my own creation, so to speak. AFter fooling around with so many different circuits (there's so many out there), I breadboarded a modified BSIAB (using a direct coupled source follower) and noticed how punchy and amp-like the sound was.

The original BSIAB was put together a few years ago, then given to a friend as a trade for him installing a stereo in my truck. I always intended to build my own, but got sidetracked with other circuits.

So...after fooling around a bit with the circuit, and comparing it to what I've been using (an opamp driving a blackfire gain stage) I've come to the conclusion that the BSIAB is more dynamic and amp-like. Just what I've been looking for.

I'm also pleasantly pleased at the low noise in the circuit. The dual minibooster circuit is a very bright circuit to my ears, so the 300pf and 1000pf filters in there effectively eliminate almost all the noise and help keep oscillations under control. It's sort of like a built-in emphasis/de-emphasis noise reduction circuit.

I'm going to try some more tweaks and may release a BSIAB II in the near future. My goals are a more usable tone control range and better bass response.

[Bucksears]

Can't wait Ed. A BSIAB II would be sweet!!

I built a BSIAB about two or three years ago, but have never 'boxed it up' until now. It's getting the 'royal treatment' along with my other boxes. I'm thinking about upping the .047 cap to around .1 for better bass, per your recommendation, and playing around with MPF102's and J201's to hear which ones work for me.
- Buck
www.bucksears.com

[Ed G.]

I'm kind of torn about the .047 cap. On one hand, it gives the circuit a nice Marshally 'snarl' and bite, and if I try to go bigger, it makes the midrange sound a bit fuzzy and indistinct. That .047 makes the circuit cut through a mix. On the other hand, it does affect the bass response, naturally.
I'm going to try some ideas from R.G.'s site, as well as different FETs.
Using a direct-coupled source follower does reduce the compression and sustain, but it makes it more punchy. I find you can 'play' the pedal and it makes you play expressively.

[Paul Marossy]

I like my BSIAB. Looking forward to seeing Ver. 2  

[Kleber AG]

 I like the BSIAB too.

But I always find it too compressed (IMHO), and I remember a long time ago I tried MPF102 at the whole circuit and really liked the tone, but it has less gain of course...

It would be great idea for BSIAB2!!!
Regards
Kleber AG

[Ed G.]

The BSIAB WAS too compressed.
Coupling the source follower directly to the last stage changes this. Amp like response to the max, but now I'm wanting a bit more sustain.
What I'm thinking of doing is this: Ed Rembold (I'm pretty sure it was him, and if you read this, Ed, please jump in) mentioned something about running a resistor from the 9V supply to the (was it the gate?) of the source follower to bias it at 4.5V to give the source follower more headroom. I was thinking about using a trim pot instead of the resistor, maybe I could 'dial in' the amount of compression I wanted that way.
I also want to try out different fets in there, like 2N5457. I'm going to take my time with this, try out different ideas and such.
It's crazy, I've been thinking about this pedal all day. I really forgot how good it sounded. Not just the sound, but the FEEL was there. Quietest pedal I've ever heard, also.

[Ed Rembold]

Ed G,
You have a PM.

Thanks, Ed R.

P.S. If your SF is direct coupled to the previous stage, which happens to already be biased a 1/2 Vb, there will be nothing to be gained by running another R from the gate of the SF to Vb.

[Bucksears]

>>The BSIAB WAS too compressed.
Coupling the source follower directly to the last stage changes this.

How is this done, exactly? I'd love to try this with mine.

I have a few notes scribbled on a Post-It note (might be related to this)that I have with the BSIAB schem I printed out. "1M res. between B+ (or BT) and source = more headroom"
I'm not sure what I meant by B+ (I guess 9v?).

- Buck
www.bucksears.com

[Ed G.]

direct coupling the SF is exactly that, you connect the SF's gate to the drain of the preceding stage.

Ed,
I guess I was not clear, I was going to do the 4.5v thing to the original schem.

Basically, I want to get somewhere 'in between' the punchy amp like dynamics of the direct coupled SF, and the sustainy compressed sound of the original schem.

[WGTP]

I have been using a Black Fire stage into a Srpp stage, with no source follower.  Sort of a X between the 2.  Like to see a scheme of the op amp BF you were using.  I like compression.  

[RDV]

I like compression.  

Me too...if it only starts squeezing once I'm already louder than everyone else! :twisted:

Regards

RDV

[Ed Rembold]

Ed G.

Then you know what I'd try-

direct couple the SF, but tie the gate of the SF to ground through a 1M pot, as you vary the 1M pot, you may find a certain range may be useful, to provide you with "compression control". After you "find the range" you can sub in a fixed high value R and a smaller value pot (in series), and have your desired "full range of compression".

Ed R.

[Jered]

Great idea Ed, I need to try that, abd I agree the BSIAB is a great sounding circuit.
 How are pedal sales Ed?
 Jered

[jpb_guitars]

Hello,
I've built the bsiab from generalguitargadgets.
It sounds not bad, but I haven't biased the tranny's yet.
But i don't know how.
What voltages should i have on the pins?
I'm using BF 245 A. (Not able to get J201 easily)
Thanks for your help.
Jan

[nooneknows]

I once built a bsiab with BF245A and it didn't sound very good. If you haven't any other fet, try putting the highest gain 245s you have as the lower tranny.
The circuit works a lot better with J201 (I bought them from Smallbear), here in Europe I think you can find them at RS-Components

[jpb_guitars]

Hi nooneknows,
I will do that. Just thought to get the best out of the BF245A's.
I can get the J201 from banzai-effects hear in Germany.