Studio Reference Amplifier

Ok. Thanks.

I am about to start some amplifier building, Lockdown has presented some free time. Only problem is there are so many Apex amps and all are great. Still if you were to choose between couple of them- Which would you.


Hello sir I hope you are fine.i like apex ax 14 .and sr200 .it's best amplifier. Sr200 is very good I am using 5 pair .and rode elite p97 preamp or tone control. I am not use hifi speaker.but 12 woofer 8 inch mid and hf 80 watt . sound is soo beautiful.my transform is 8 ampair .and it's 45-0-45 Sir miles thanks this beautiful amplifier.
 
  • Like
Reactions: 1 user
Thank you for your response! I think I managed to change something but on my other module which is not on a heatsink.Checked all the voltages mentioned above,checked absolutely all transistors and all are good! In fact,i managed to destroy a 2SA1837 in the process! Placed a 10R/10W resistors instead of fuse and connected a multimeter across it.Now,when I turn the pot,the voltage changes,not like before.But it's not stable,I think because there's no heatsink.Anyway,now I can see that transistors are warming up,when I turn the pot,that's a good thing.I'll move on the other module with the heatsink and see if I can revive it too! I will come back with conclusions and pictures.I still need to fix the hum issue!

Apex said in one his threads that (I cant remember which amp)amp input shouldnt stay open, maybe it applies to that amp too. I came to same conlusion with A40, if signal is fed everything is fine, no hum/brum, or when preamp is connected to amp.
 
Last edited:
Hello Guys, yesterday I do few muaserment on SR55
Rail voltage 42-0-42 volts
Bias 15mv on Emitter resistance(30mv as
pair
DC offset 5mv
Volt on bd139
E-C 2.25v
Volt on Output
Transistor B-E 520mv
and
AC volt on speaker
Terminal at 1K hz
with 8ohm load 26V first test,
20v second test with 60 mv bias
on Output pair.
 
Hi everyone, what is the difference of this preamp compared to other preamps (PP8, P30...). Greetings
 

Attachments

  • apex_f10.jpg
    apex_f10.jpg
    94.9 KB · Views: 401