Curing the HIGH END BUZZ of an OCTAVIA

[Doug_H]

The voltage and Q4 b & e should be pretty close, since it is an emitter follower (buffer). You probably want those sitting at around 1/2 your battery voltage for it to sound right.

Doug

[petemoore]

A small cap or smaller caps, from signal path to ground or maybe across the diodes?
 IIRC mine has a .0022uf near the output to ground....0047uf maybe.

[analog kid]

I checked again around Q4 and I definitely don't see any mistakes but it's strange that with the MPSA13 I'm getting Batt voltage on Collector...2.0v Base and around 3volts on the Emitter!!! sounds TO ME like Base and Emitter vltgs are reversed>?
I 'd like a better explanation of the Cap to ground you're talking about pete. I don't see any at that end of the crkt.The only smallish cap to ground I see is a .001 at Q2 emitter to ground.
Also : I DID find this.....
http://web.archive.org/web/20001121152500/www.green-fuz.freeserve.co.uk/rmoctavia.html
The part about the correction on Q4, Sounds interesting! but althoughI can't load the page to see if my layout is correct...from the explanation at least I don't think I've got that problem. (?)

[analog kid]

OH! What about changing the resistor values in that 2X2M2 divider to bring UP the B/E voltages to take care of the problem??

[analog kid]

sorry I'm impatient.
I did try for the heck of it to change the +V/Q4 Base 2.2M resistor to a 1Meg and IT DID bring the base voltage up to apprx HALF the battery voltage. Though the problem is still there.
Q4 C  8.8v
    B  3.6v
    E  4.7 v  ( shouldn't this be LOWER than both the collector and Base?)
Q1
    C 8.6
    B    3.5
    E   4.8  
strange, Q1 and Q4 are the only ones with the vltgs set up like this. are they supposed to be .? If not can this be corrected w/ resistors too