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!
Nice work zman!
I placed speaker return to the star ground, not audible difference but as told, I use Alpha for bass duties only for now.
Just to be clear; I will desolder C103 off from pcb, connect negative with wire to star ground and positive back to pcb?
I placed speaker return to the star ground, not audible difference but as told, I use Alpha for bass duties only for now.
Just to be clear; I will desolder C103 off from pcb, connect negative with wire to star ground and positive back to pcb?
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.
Juntuin,
If there is no further hum, leave out that 10R earth lift.
It appears on this amp it's not needed, although on my AB amps I use it every time.
I would leave it alone now.......
Hugh
If there is no further hum, leave out that 10R earth lift.
It appears on this amp it's not needed, although on my AB amps I use it every time.
I would leave it alone now.......
Hugh
If you lift entire ampboard 0V like Juntuin did, does that both lower effective PSU voltage and increase speakerimpedance with liftresistor value (seeems it is in series with speaker) ? And wouldn't that require a very big 10r resistor, I mean not a 1 watt resistor ?
No, you can't lift the entire board with speaker ground !
Unless you take the local PS decoupling (C103) and speaker return out of the ground lift and connect those directly to star or PS.
Unless you take the local PS decoupling (C103) and speaker return out of the ground lift and connect those directly to star or PS.
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 🙂
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 🙂
Danny, question was what happened when juntuin did mount that 10r resistor that way. Should the resistor have burnt ? Did he change speakerload, reduce psu voltage at ampboard ?
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.
7w, that's the reason why it didn't get burnt.
When the gnd leg of C103 cap is also connected with speaker return to the star outside the gnd lift, then the last hum will probably disappear.
X did that also in the latest version of his BB Alpha.
When the gnd leg of C103 cap is also connected with speaker return to the star outside the gnd lift, then the last hum will probably disappear.
X did that also in the latest version of his BB Alpha.
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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...
X I am about to order xformers and looking at different cap values/manufactures. From a weight standpoint mono blocks makes since. Obviously xformers and caps are doubled.
Just asking.
Just asking.
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?