BSIAB2 sound degrades badly if used before other effects pedals-why?

[Tantalum7]

After breadboarding a BSIAB2 using the gaussmarkov schematic, it sounded great by itself, but when I plugged it into a digital delay I had made (off plans from BYOC), the overall volume increased tremendously when the DD was switched on, but the sound was far more muddy.  When the DD was switched off (a true bypass ckt), the volume dropped to lower than it had been when nothing followed the BSIAB2 and the sound was still a bit muffled.

I tried putting my Fulldrive 2 before the DD, and there was absolutely no change in sound quality with the DD switched on or off.  Putting the DD before the BSIAB2 doesn't cause a volume increase, I prefer the DD after the distortion in my effects chains.

Is there something inherent in the BSIAB2 circuit that could cause this, and more importantly can it be fixed?  Is there a buffering or impedance issue at work here?

[ACS]

I'm a complete rank amature with this, but it sounds like a buffering issue to me.  Do you have a Boss pedal kicking around somewhere?  Put it between the two (bypassed of course) and see if that makes any difference...

[MohiZ]

Have you tried it with other pedals than the digital delay?

[sengo]

Do you happen to have anti-hiss/anti-radio interference capacitors between the input and ground of any of your pedals? I had a similar problem a while ago and with the helo of the forum found out I was using capacitors that were too large, each pedal in my chain had one, and I had them positioned before the bypass switch, so as I added pedals to my chains the capacitance became larger and larger, and rolled off more and more of my guitar's frequencies. This may not be the issue at all, but I figured it's worth bringing up.

Nick

[Tantalum7]

Thanks for the info, everyone.  I'll do a few more tests and see what happens.  I have a few Boss pedals around to test, and I can look at the schematic of the DD to see if there are any unusual caps on the inputs. 

[petemoore]

I'll do a few more tests and see what happens.  I have a few Boss pedals around to test, and I can look at the schematic of the DD to see if there are any unusual caps on the inputs. 
  He was talking about accumulative [many] losses from adding passive components to effects, but outside of the bypass switch, so that when the pedal is off those components still draw signal down..I think.
  I would guess the DD, unless it strays from a schematic in this way, has all the tone alteration components 'within' the non-bypass routing, in bypass mode there is nothing except a direct connection between input and output [through switch contacts of course].
  Looking for a Boss pedal will tell you...what it sounds like with buffer between the II and DD, otherwise impedance match or mismatch can be gleaned from the schematics, this also might be good to know to find out 'if either' or 'which one' deserves buffer attention...I would guess the BSIAB II is fairly low impedance output, not sure about the DD input impedance...may help when deciding where to place the buffer.

[Tantalum7]

It seems that the DD is the suspect pedal.  Running the II into other pedals shows no deleterious changes in the sound.  When I put a Boss pedal between the II and the DD the dramatic increase in volume no longer occurs when I switch on the DD, but the tone muddying still occurs--now just at a lower volume.  It's still a bit odd to me that the Fulldrive doesn't seem to have it's tone affected by the DD.  I'll still have to see what might be in the DD circuit that could change the tone of the II so dramatically.  Once again, thanks for the suggestions.

Scott

[Ben N]

The one striking difference between the BSIAB and the Fulltone is the output impedance, it seems to me--the BSIAB has that whole tone stack and volume control all following the last FET and increasing the output Z, whereas the Fulltone has that nice simple BJT output buffer. If the DD input is not buffered, it could well be sensitive to those differences. I'd bet a TS-style buffer at the end of the BSIAB would make it behave just like the Fulltone with the DD.

[Tantalum7]

The one striking difference between the BSIAB and the Fulltone is the output impedance, it seems to me--the BSIAB has that whole tone stack and volume control all following the last FET and increasing the output Z, whereas the Fulltone has that nice simple BJT output buffer. If the DD input is not buffered, it could well be sensitive to those differences. I'd bet a TS-style buffer at the end of the BSIAB would make it behave just like the Fulltone with the DD.

Well, it's on the breadboard right now.  I can pretty easily see what might happen with with a TS-style buffer.  Thanks for the suggestion.

Scott

[Tantalum7]

Well, I built a TS style output buffer using the 808 resistor values and the volume increase going into the DD when switched on was cured, but the tone was still like mud compared to the bypassed signal.  I checked the DD schematic, and I can't see anything that looks like an input buffer, but I still have no clue as to why the DD sucks all the life out the the BSIAB2 for me. 

[Ben N]

OK, I'm stumped.

[liquids]

A lot of the info here is good...and interesting....check your wiring, grounding, etc.  You may have something internal on the BSIAB that is connected but weakly passing a signal...

I realize that is unlikely given that you have good volume, but it's worth checking...where are you running your volume knob?

I can say, I've run my pedals into a rack delay...with very low input impedance---it NEEDS a good and clear buffer before it. 

Even the a 'buffered' dirt pedals I've had (though on a DPDT switch, most active pedals should be 'buffering' to a degree when they are on) running into the rack Digital Delays I've used we're not as 'clear' as running a boss buffer in.  They expecting a signal coming off a board, not a guitar, so you need a bufferered guitar signal if not more.... 

That's not to say a boss buffer is the best, but it's a good, familiar frame of reference...but overall this is very confusing to figure out and not typical of my experience with BSIAB's.   Never thought about the BMP tone stack issues mentioned above without any buffer stage post tone stack...