BSIAB II owners

Bucksears · June 21, 2006, 09:21:16 AM

(First off, let me just say that I had removed the last .0022uF cap from the low pass filter at the end of the circuit since I've always thought that the BSIAB II is a little too dark and didn't have the treble for the 'bite' I wanted on hand.)
After getting some GREAT tones out of my BSIAB II with the volume up a bit, the gain at around 25-30% and the tone at almost 100%, I was feeling experimental and decided to clip the OTHER .0022uF cap from the LPF. (Both 10k resistors are still in place)
THAT did the trick. Any desire for a distortion sound that I thought I was missing has greatly diminished (but we all know will never be completely gone; still want that perfect Plexi in a box).

Here are a few quick settings that I like:
Hot Rodded Marshall - Gain 100%, Tone 50-60%, Volume to taste
VH1 - Gain 60-70%, Tone 50-60%, Volume to taste
Early AC/DC - Gain 25-30%, Tone 60-75%, Volume a bit louder to push the speakers

If you have a few .0022uF caps lying around that you can go back to if you don't like the mod, I would HIGHLY recommend trying this if you feel the BSIAB II is too dark. The best similarity I can draw would be, if you consider the DS-1 to be BRIGHT and the BSIAB II to be DARK, this mod puts the BSIAB II right in middle.
- Buck

DuncanM · June 21, 2006, 01:41:31 PM

Is your tone pot a 100k "Log" or a 100k "Lin" ?

Bucksears · June 21, 2006, 01:48:16 PM

I'll check tonight; my first thought is linear, but I could be mistaken.

- Buck

alfafalfa · June 21, 2006, 02:34:29 PM

Hi, What I found to be very helpful is wiring my gainknob the other way round like a negative log pot.
It helps to get more subtle shades of distortion.

Alf

Xavier · June 22, 2006, 01:28:40 PM

I still can't get used to it. I use the tone pot all the way up but to my tastes it adds highs, but in the wrong frequency. It sounds rather harsh. And it cuts too much bass. Sounds OK but kinda unnatural. I mean the distortion character is perfect, the best I've heard in any other DIY pedal, but the overall spectrum is ....cut lows, cut highs...seems to work in a narrow frequency band. I'm using both J201's and 2N5457's, but that only seems to affect the gain structure, not the overall freq. response.

I'll try your mod, if I get it right is just clipping out that cap?

Bucksears · June 22, 2006, 01:45:22 PM

Xavier,
I agree. Stock, it adds highs, plus a few mids in a nasty way, but cuts bass. Granted, it's a very thick, tight sound if you back off the tone, but there's no bite to it when you up the volume.
Yes, first I cut just the last .0022uF cap, then the other .0022uF cap in the low pass filter; the 10k resistors stay intact. (basically you can cut the caps with a wire cutter and not have to touch your soldering iron) I like it MUCH more and it saved that pedal from being an 'alternate' to a keeper.

- Buck

Xavier · July 10, 2006, 09:22:10 AM

I have just performed your mods. Clipping out the last cap didn't make any notorious difference, but then I've also clipped out the .022 cap between the two 10K resistors to ground

The effect has been the "take out the blanket from the speaker". All the clarity has suddenly appeared, and now the tone control is way more usable. Now I'm able to set the tone control at 50% and have a balanced eq response.

Then I've tried different values for C8 (100nF). I've tried 1uF and it was too muddy, so finally I've soldered in a 330nF cap. Slightly more bass but still retains the tightness.

Way, way more usable and natural sounding now. What a nice mod.

My conclusion about the BSIAB is that in order to get that tightness and punchiness you necessarily need to cut the bass frequencies before clipping the signal. The problem is recovering them back. I think the only way to achieve that is to stick a 3 band eq at the end of the circuit.

Gain loss? I reach unity gain (with gain pot at 50% and tone at 50%) at 25% of the volume pot, so I guess it won't be much of a problem if I stick the 3 band eq. The one in the AMZ OD pro was very nice, so I'll look for that one.

I nominate the BSIAB for the absolutely best dist DIY pedal, specially with these small mods, palm mutes sound awesome.

Bucksears · July 10, 2006, 09:45:22 AM

I'm still blown away by this. It's like suddenly, I'm not chomping at the bit to get another distortion. There are about five or six different gain settings I tweak between and I can get almost COMPLETELY different sounds; it just excels all the way around the gain dial now. Here's what I'm getting:
gain @ 9 o'clock (with the volume up on the amp and pedal) - early AC/DC, early Marshall sound
10-11 o'clock - slightly hotter sound of above, good for Black Crowes blues rock
12 o'clock - Van Halen I
2-3 o'clock - GnR's 'Appetite/Destruction' tone
gain maxed - a very 'metal', yet Marshally sound

All of these are with the tone set right on that 'biting edge' that I've been wanting out of this circuit. The great thing is, you can still back off on the tone to darken it up slightly if you want. I'll definitely try that 330nF mod for a little more bass.
I agree, the BSIAB II has got to be one of the best DIY distortions out there in terms of tone and versatility. I've been building pedals a lot lately and every time I try a new one out, I have to hook up the BSIAB II for a few minutes and riff. I'd like to build at least one or two more with additional toggle footswitches and have the variety of sounds preset.
- Buck

sta63bmx · July 10, 2006, 10:00:34 AM

I will have to give this a whirl. I switched from a J201 to a BS170 in Q5 (on the GGG layout) and it really woke the pedal up. It seems much more crisp and amp-like. It was good before, just a little darker and heavier. Now it REALLY sounds incredible. I'll have to give these a whirl. I have yet to put my BSIAB in a GOOD enclosure, because I don't want to be without it. I used to use my TS clone all the time, but the BSIAB has completely replaced it.

Ed G. · July 10, 2006, 10:39:56 AM

How the hell did I BS170 bias in the BSIAB???

I understand people might find the bsiab dark...it is voiced for the brightness of a fender amp, so some extra filtering was needed to 'brown' it out some.
But hey, tweaking is what DIY is all about!

Bucksears · July 10, 2006, 11:02:16 AM

Quote from: Ed G. on July 10, 2006, 10:39:56 AM
I understand people might find the bsiab dark...it is voiced for the brightness of a fender amp, so some extra filtering was needed to 'brown' it out some.
But hey, tweaking is what DIY is all about!

Exactly. Ironically though, I have a Super Reverb reissue, which started out as quite bright (new), but is now nice and warm. It has a tight bass sound, but not as deep as 2x12's. The (minor) modification to the BSIAB 2 works out very nicely with my rig and I couldn't be happier. THANKS AGAIN!!
- Buck

Xavier · July 10, 2006, 11:03:08 AM

aaah, so now it totally makes sense.

I'm using my BSIAB into a MARSHALL mosfet amp. That is, it doesn't have half the bass that a fender amp has, and much less top end. You are right. Now I understand...... I'm trying to build the marshallized version I guess

BTW I'm also curious about the BS170 thing............

Thanks Ed !!!!

wampcat1 · July 10, 2006, 11:09:05 AM

I too want to know how the bs170 swaps out so easily. I'd love to learn that trick!

sta63bmx · July 10, 2006, 11:28:48 AM

Am I missing something? *scratching head* Let me double check. I could swear it's a BS170. It might be an MPF102, but I thought it was a BS170. If I have led you astray, I apologize greatly. I will doublecheck it tonight. I put it in and the bias was off quite a bit from the J201 in there, but I found a good spot pretty easily and fired it up. I will double check it tonight. Either way, this transistor change was like magic for me.

My recipe for tone is a good SG or Les Paul copy with PAF-style pickups into a BSIAB into a decent tube amp. Pretty simple.

Xavier · July 10, 2006, 12:38:21 PM

BTW, now that I have clipped out 2 caps, should I also jumper some of the resistors also?

Bucksears · July 10, 2006, 02:44:53 PM

As in, REMOVE some of the resistors and replace them with jumpers? I can't comment on that, but I like the sound where it is now and won't try it.
Honestly, I don't think I want more treble than I have now as it really has a nice balance around the rotation.

- Buck

MetalGuy · July 10, 2006, 04:30:02 PM

I was advising agianst those filters from a long time. The first time I powered my BSIAB2 I felt there was something wrong with it. Those filters suck!

Xavier · July 10, 2006, 05:23:06 PM

Well I'm just back from rehearsal with my band. I've found myself setting the tone control at 25%. There's a slight high end fizz even at the lowest setting, so tomorow I'll try dropping in a 500pF silver mica in C16. 2n2 was definitely too much but "nothing" seems to be a little too much also. Otherwise balance is better now.

more updates tomorrow

powerplayj · July 11, 2006, 05:44:45 PM

FWIW, the MPF102 will bias in Q5. Bucksears suggested using it in the Dr. Boogey at the Q1 position. After successfully quieting down that beast I tried it in the BSIAB2. It also made a significant difference in the noise at higher gain.

jrc4558 · July 11, 2006, 05:55:26 PM

Quote from: MetalGuy on July 10, 2006, 04:30:02 PM
I was advising agianst those filters from a long time. The first time I powered my BSIAB2 I felt there was something wrong with it. Those filters suck!

These filters dont suck. They are just too dark for your setup, as they were for mine. swapped 0.0022s for 0.001s and now its a beautiful trebly sounding, yet w/o excessive noise still.

News:

BSIAB II owners