Hmm Cal....
you got me thinking the other day - looking at post #807
I actually haven't used those speakers again and know that the default to many who use this amp are full range speakers but wonder if you and I were seeing a similar behaviour. The amp sounds great with conventional speakers that use a crossover / zobel network.
..dB
you got me thinking the other day - looking at post #807
I actually haven't used those speakers again and know that the default to many who use this amp are full range speakers but wonder if you and I were seeing a similar behaviour. The amp sounds great with conventional speakers that use a crossover / zobel network.
..dB
Commuting to work, but will check tomorrow. No borbelys. Which are the cascode transistors?
Thanks.
Thanks for the thought db. It's not speaker specific though, happens on both crappy and nice speakers for one channel, works on both for the other.
The reason I found out on the nice speakers was because I turned on the amp with my preamp off there, but my phone on (but without music playing) when testing.
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everything looking good ....... you can try to decrease 5mV to zero, with R7 trimpot ; be sure that you're measuring on proper pin ( one is buffer side , second is xformer side)
reconnect jumper and try again
if you still have motorboating , disconnect jumper and try feeding an amp post buffer - connecting some decent source (DC free please!) to amp's GND and jumper header pin at xformer side
if you tell me which channel is in case ( what's written on pcb) I can pinpoint you which pin is which , with small pic
reconnect jumper and try again
if you still have motorboating , disconnect jumper and try feeding an amp post buffer - connecting some decent source (DC free please!) to amp's GND and jumper header pin at xformer side
if you tell me which channel is in case ( what's written on pcb) I can pinpoint you which pin is which , with small pic
so , as I understood you ( you probably didn't oriented probes properly ) , there is -3V45 at SIT gate (opto pin 4 ) and -4V4 at mosfet gate (opto pin 3 ) , both ref to GND , which means you have hefty 0V95 as voltage window for opto bjt
care to take some pics of let channel pcb , so we can take a peek at ?
find enclosed little pic of relevant pins of jumper header ;
as shown on pic , upper pin is buffer's side , while lower pin is xformer's ( and rest of amplifier , downstream) side
try test with signal to lower pin ( do not forget gnd) , thus leaving buffer from story
though , logic dictates that you made some systematic mistake , same thing happening on previous left pcb and now on second ......
care to take some pics of let channel pcb , so we can take a peek at ?
find enclosed little pic of relevant pins of jumper header ;
as shown on pic , upper pin is buffer's side , while lower pin is xformer's ( and rest of amplifier , downstream) side
try test with signal to lower pin ( do not forget gnd) , thus leaving buffer from story
though , logic dictates that you made some systematic mistake , same thing happening on previous left pcb and now on second ......
Attachments
Yes, sorry, I didn't pay attention to +/- on voltage readings.
Source connected to pin 8 of transformer & ground (w jumper removed) = music. No motorboating if source is disconnected.
Pictures coming.
Also, I never got to this point with the "old" left channel board. The capacitor got melted before I got to test for sound...
