Well, I finished my BOZ pre last night and tested it out one channel at a time. I'm getting the perscribed 40v across R104 and everything sounds good as long as I follow the turn on procedure (source -> pre -> amp)
But if I stray from that, or turn the amp on too soon, I see about 20v DC at the output of the amp, which is a LM3875 chipamp. Of course this pushes the speaker's cone out all the way (and I'm sure has damaged it) but that's what test speakers are for
Further investigation proves that it happens when the BOZ gets turned off too. so anytime the amp is either ramping up, or down (power on/power off) it shoves a bunch of DC noise to the amp for about 5 seconds.
The only change I made to the circuit was to remove the output pot (P101) and use a 100k pot in place of R107, with the wiper going to the 1uf C104.
Questions? Comments? Suggestions?
TIA,
Michael.
But if I stray from that, or turn the amp on too soon, I see about 20v DC at the output of the amp, which is a LM3875 chipamp. Of course this pushes the speaker's cone out all the way (and I'm sure has damaged it) but that's what test speakers are for
Further investigation proves that it happens when the BOZ gets turned off too. so anytime the amp is either ramping up, or down (power on/power off) it shoves a bunch of DC noise to the amp for about 5 seconds.
The only change I made to the circuit was to remove the output pot (P101) and use a 100k pot in place of R107, with the wiper going to the 1uf C104.
Questions? Comments? Suggestions?
TIA,
Michael.