X,
Ha ha, the TH soldering went very smooth thank you, easier than SMT.
Now feeling a bit angry with myself on not starting earlier. Thanks for the encouragement. 
Thank you Vunce!
Look forward to powering up the ALPHA soon.
The PSU I shall be using is a Dual-rail power supply with 4 x 22,000uf caps per channel, 400VA toroid with 2x18V rails. From recent posts understand that 2x20V or 2x22V would be better. I'll start with what I have now - no more procrastinating!
Thank you Hugh!
Look forward to powering up the ALPHA soon.
The PSU I shall be using is a Dual-rail power supply with 4 x 22,000uf caps per channel, 400VA toroid with 2x18V rails. From recent posts understand that 2x20V or 2x22V would be better. I'll start with what I have now - no more procrastinating!
Thank you Hugh!
Yes, that's correct.
To identify your hum problem, disconnect the sources and short circuit the rca-in to rca-ground.
I've made some male rca connectors with shorted signal and shield that I can plugin.
If hum is gone then it's probably a ground-loop between source and amp, try adding a 10 ohm resistor in series between rca socket shield and pcb shield in.
To identify your hum problem, disconnect the sources and short circuit the rca-in to rca-ground.
I've made some male rca connectors with shorted signal and shield that I can plugin.
If hum is gone then it's probably a ground-loop between source and amp, try adding a 10 ohm resistor in series between rca socket shield and pcb shield in.
Hum problem and ground loop is gone, only problem is I didn't make 10r lift as it supposed to be done
asking just because I want to do it right, even though amp is quiet now.
Hugh, I have 10r lift in now. Speaker return changed to star ground but C103 in its original place unmodified. And amp is almost dead silent, only little hum when ear on cone, theres miniDSP in my system and that alone makes same kinda small hum what I have now, so can't be sure is it even amp related anymore. Anyway, it's so small hum that you have to get to speaker and know what you are trying to hear it's pretty good now.
If it's still important to change C103, I will do it of course
Oh, and did I mention that Dc offset is 12mv on both channels. Pretty good if you ask me
it's pretty good now.If it's still important to change C103, I will do it of course
Oh, and did I mention that Dc offset is 12mv on both channels. Pretty good if you ask me
Hmm, found this while going through this topic.
And about that 10r resistor, I have 7w there since couldn't find smaller 10r from my stash.
And about that 10r resistor, I have 7w there since couldn't find smaller 10r from my stash.
Thank you Danny, you have been very helpful.
Did quick'n'dirty dartzeel build inside my backup case, have to test and if it works, I'll take Alpha to garage once more. C103 mod and final build for the case, gotta buy some big alusheets tomorrow since there is lots of space to cover up. Finally found some inspiration.
Did quick'n'dirty dartzeel build inside my backup case, have to test and if it works, I'll take Alpha to garage once more. C103 mod and final build for the case, gotta buy some big alusheets tomorrow since there is lots of space to cover up. Finally found some inspiration.
In the above diagram, the speaker returns went directly to the Star GND outside the board so no high currents pass through the 10R ground lift. Although this is different than what I run now that I don’t have smps and cap Mx. There is no 10R on GND connection to the two separate GND wires back to the F6 CRC.
I wanted to mention that the Alpha BB built as two independent monoblocks each with own PSU and trafo and powercord has no noise or hum. I have been listening to it almost a month on a daily basis and I can say it is an easy amp to live with. Very reliable and fuss free. I turn on the fans, then apply power and the amp starts up and plays with great sound quality. Always stays cool below 38C and fins are at 28C. The sound is of course, superb. I may not need to build another amp for a long time.
However, I know Hugh never stops designing or doodling on LTSpice...
However, I know Hugh never stops designing or doodling on LTSpice...
I you are ordering transformers, go one value up in VAC, by the time you account for rail sag, etc it will be closer to the desired value the ordering the exact one. For B.B. I would go with 28vac. That gives 39.5v no load. After drawing 3 amps it will settle to around 36v which is where you want it. I made the mistake of ordering 25vac and that’s 35v no load but now it’s at about 29.5v with load due to maybe saturation from 125vac primaries.
After yesterday’s very informative “ground scheme” theme, I got right back into my ALPHA today to tweak. I did have a few setbacks, but ultimately my ALPHA is the quietest it’s been so far.
I have a standard earth ground and removed the earth ground loop breaker diode setup.
I removed the C103 47uf caps and replaced with 1000uF and connected the gnd side to the PSU ground.
Disconnected the speaker return from the Alpha boards and connected it to the PSU ground.
Installed a 10R resistor in series with each Alpha pcb 0V tab.
Along with the previous tweaks (except earth ground loop breaker), this configuration is very, very quiet!
Question: what’s the minimum wattage rating for 10R resistors?
I have a standard earth ground and removed the earth ground loop breaker diode setup.
I removed the C103 47uf caps and replaced with 1000uF and connected the gnd side to the PSU ground.
Disconnected the speaker return from the Alpha boards and connected it to the PSU ground.
Installed a 10R resistor in series with each Alpha pcb 0V tab.
Along with the previous tweaks (except earth ground loop breaker), this configuration is very, very quiet!
Question: what’s the minimum wattage rating for 10R resistors?