Splatty BSIAB

[modsquad]

Okay just built my second BSIAB II based off of the "old" GGG layout.   I had the board already and its not the same layout as what's up on GGG now but found my old documentation.   Anyway built it biased Q5 to 4.5v and it works, however its very splatty with the distortion.   I haven't had a chance to take voltages yet, but was wondering if using a different diode from the 1n914 could cause it to sound that way.   I didn't have on so I put one that looked similar but was too small to be able to read the letters (I know, russian roulette but I was in a hurry).   Just wondering if anyone had insights.   Tomorrow I am going to sit down with it and check all the other voltages.

[petemoore]

   I guess 'the diode' is for RPP.
   As such if you have sufficient DC voltage on the circuit side of the PS diode...you have voltage the circuit can work with, alternately the correct or no diode can be used, however other RPProtection method must be used.
  Splatty = Misbiased or a miswire [very often].
  The circuit has Jfets, mis-pinout is likely also.

[JDoyle]

Make sure that your 'new' diode wasn't a Zener and therefore dropping V+, making a 4.5V bias far from ideal.

Pete is right, 'Splatty' means misbiased transistor somewhere and you should definitely check the pinouts, which is essentially the same thing as a misbiased transistor, if you think about it.

If you get a chance to post voltages we'll be able to help more...

Good luck!

Jay Doyle

[modsquad]

Thanks, I am thinking that I might have put a Zener diode in there, the numbers on it were unreadable.   Could a 1n4... diode be used in place.

[Zben3129]

Easy to test, just pull the diode completely. All it is for is so that if you reverse the + and - on the power supply that hopefully the direct short the diode provides between gnd and 9v will keep the current from getting into the circuit and frying things. You don't need the diode for the circuit to function as it is just for safety. Make sure you do end up replacing it once you get the problem diagnosed however. And no reverse polarity in the meantime!! 

1n400x will work
1n914
1n4881 (or whatever that common silicon diode is)
1n34a


Zach