BSIAB II issue

[bulldogguitars]

I finished breadboarding the bsiab2 over the weekend, its working but.... When the note starts to decay it sounds like it wants to sizzle, and  not much sustain. Almost sounds like a noisegate thats gating to hard. Q5 I set the bias at approx 4.55v. Any suggestions would be greatly appreciated.  I hope this old dog can still learn some new tricks.

[MKB]

The first thing to try might be to tweak R16 a bit.  The voltage does look right, but on mine the pot is sensitive, and the gating sound can be present if R16 is not set right for the FET you have in Q5.  I adjusted mine initially with a voltmeter, but it sounded best when tweaked by ear.

Also, what voltages do you see at the drain of Q1 and Q3?  Also, what is the voltages on the gates of Q2 and Q4?  Maybe a resistor value is wrong and one of the other FET's are biased improperly?

[Ed G.]

I'd set it by ear. I never check mine with a multimeter.

[bulldogguitars]

I didnt have silver mica caps and had to use ceramics. Im assuming their a bit noisier than the silver micas. Im on my way out to band practice, Ill post the voltages, soon as I get back. Thanks alot guys    Danny

[GonzoFonts]

I tried to breadboard this thing a few times with no luck.

I think trying to breadboard this thing is a lost cause because there is just so much gain in the circuit that its not bread board friendly.

I plan on ordering the kit from GGG to see if thats any better.

Good luck.

GF

[bulldogguitars]

I wonder if having it on the breadboard, and the length of the leads is what is causing my problem. Possibly some stray signals between components. I think I will just etch a board and try that I guess. Any good sources anyone know of for Press N Peel Blue. And what do you guys think of it. Ease of use that sort of thing?

[Ed G.]

Well, I designed it on the breadboard. I then moved the components over to the pcb and it sounded pretty much the same.
Could be the fets. Some are just bad, they vary sometimes. I'd use an audio probe to see where along the signal path it gets 'splatty'. There's only a few points you'd have to test, just after each gain stage.

[GonzoFonts]

bulldogguitars,

When the note starts to decay it sounds like it wants to sizzle, and  not much sustain. Almost sounds like a noisegate thats gating to hard.

Your issue sounds like something is not biased correctly. I've breadboarded a lot of effects and usually when I get the symptoms you describe above, its because had incorrectly biased a transistor (example: connecting the collector of a transistor to ground instead of +9V).

Ed,

Well, I designed it on the breadboard.

Thanks for the info. When I built mine on a breadboard, I was able to verify that the tone circuit worked (after all, its a simple non-active filter).

Could be the fets. Some are just bad, they vary sometimes.

I was able to get the first stage (everything up to Q3, and added a 10uF cap at the end for DC blocking before sending the signal to my amp) to work but it was very noisy and it had massive amounts of gain - almost too much. When I added the second and third stages (i.e. everything between Q3 - Q5), the circuit just oscillated like crazy - completely out of control.

After a few attempts with the same results, I just assumed that there was simply too much gain in the circuit to be able to reliably breadboard it. For the record, I used 2N5457s for everything and maybe all of the  2N5457s I have are bad.

I just bought a bunch of J201s so I may try building one with all J201s.

Thanks.

GF

[bulldogguitars]

Some of the voltages Im measuring are quite high and some are low at least compared to the build notes.  Biasing FETS is new to me. Setting the bias on Q5 was simple enough, but do I just need to adjust the Drain resistors accordingly fot the other trannys.

[Ed G.]

I'd double-check the connections, sometimes on breadboards you don't get real good connections. If the circuit is built as stated, it should work.