Very odd. I have had about 10 of them running here, and have not run into or heard of this elsewhere.
I suggest trying the amp in another system, or with a different preamp and/or speakers.
"I just assembled the kit so no changes if one disregards some thermal goo on the output mosfets." 😉
Thanks. The intermittent nature of the issue complicates troubleshooting as well. I want to try a 24V linear supply to see if it makes a difference.
have you handy laptop supply?
19V (as usual) is applicable, at least to test with 3rd one
so called Anti-Gremlin procedure
19V (as usual) is applicable, at least to test with 3rd one
so called Anti-Gremlin procedure
Do both channels have the same issue? Maybe a bad solder if the problem is intermittent. Both channels would be a different issue.
Hey all. Thanks again Nelson and friends for providing these kits. I got my ACA Mini playing music a couple nights ago after some trouble getting it biased correctly. Thought I had done something wrong at first but it turns out I just needed a little more patience and finesse in biasing. Anyway, I’m loving the sound of this little amp.
I’m wondering if I can use one of Mark Johnson’s PO89ZB SMPS noise filters on this.
I know the PO89ZB is rated for a max current of 3 amps, and the meanwell supply provided with the ACA Mini kits is rated for 3.75 amps…but what is the actual current draw of the ACA Mini? I can’t find that info anywhere and am having trouble figuring out a good way to test it. If I had a male-to-female DC barrel extension cable I could cut apart, I’d be golden.
I’m wondering if I can use one of Mark Johnson’s PO89ZB SMPS noise filters on this.
I know the PO89ZB is rated for a max current of 3 amps, and the meanwell supply provided with the ACA Mini kits is rated for 3.75 amps…but what is the actual current draw of the ACA Mini? I can’t find that info anywhere and am having trouble figuring out a good way to test it. If I had a male-to-female DC barrel extension cable I could cut apart, I’d be golden.
Hi
Your bias is normally 0.45A max per channel so a total draw of 1A at 24Vdc for this stereo amp. Your 3A filter will be perfect.
Eric
Your bias is normally 0.45A max per channel so a total draw of 1A at 24Vdc for this stereo amp. Your 3A filter will be perfect.
Eric
I have been looking for that info but couldn't find it either.
My (pure) guesswork is the ACA Mini draws less than 3A and that should be Ok for the said filter that I also used so far with a lot of success with other units.
I like to stick to the specs, but let's face it, Mark is always very safe so the tracks should be probably fine even with 5A, not to mention coils (original BOM = rated for max 6A) and resistors are more than OK aswell with "a tad more than 3A"...
That is not saying of course that it works best out of its specs, but your ears can judge that then.
Have fun and let us know!
Claude
My (pure) guesswork is the ACA Mini draws less than 3A and that should be Ok for the said filter that I also used so far with a lot of success with other units.
I like to stick to the specs, but let's face it, Mark is always very safe so the tracks should be probably fine even with 5A, not to mention coils (original BOM = rated for max 6A) and resistors are more than OK aswell with "a tad more than 3A"...
That is not saying of course that it works best out of its specs, but your ears can judge that then.
Have fun and let us know!
Claude
Thanks Eric... If 1A and 24V then 24W overall... for 2x6W output with 50% efficiency... would be quite fine...
Wonder though why this SMPS has been chosen then, as some lower power units can have better ripple etc. - or perhaps the problem is when switching on with the caps loads (although quite moderate in value), in which case the current could be perhaps more, but still the filter should cope with some extra temporarly amperes...
Wonder though why this SMPS has been chosen then, as some lower power units can have better ripple etc. - or perhaps the problem is when switching on with the caps loads (although quite moderate in value), in which case the current could be perhaps more, but still the filter should cope with some extra temporarly amperes...
if you consider power used is 24V x ~0.4A = ~10W
power generated is 5W seems like ~50% efficient to me. In line with PP class A operation.
I set my bias cold at 0.22-0.24V across the output resistor. When it gets to temp the bias moves to the correct ~0.3V. My room temp is 19.5C so the results can be a little different the heatsinks go to 54C.
Discovering this amp, not even owning a std ACA, and I am by far not good enough at amp's schematics to see what current flows where LOL!
Further, I don't have such an amp "yet", and admittely haven't spent time on it... so your inputs are great, many thanks!
So Push-pull indeed, "only one bias current" flowing through both output devices per channel, 2 channel per amp and 52% efficiency. That is discarting the FE stage and other bits (bias), assuming these are negligeable or very small vs the output stage, which seems logical.
If so... then Mark's filter will be delighted under this ideal work conditions... and for those building 2 ACA Mini (enabling hoppefully various "bridged "configurations as the std ACA seems to offer them) then perhaps a single "reasonable / non expensive" SMPS (even the one already provided?) feeding 2 SMPS filters could be worth a try and save further costs sides SMPS when building 2 ACA mini.
There are some resistors slowing somewhat the inrush, but with 2 amps 60000uF PS caps have to be pumped up, I presume not every brick likes that. A soft start could be a good idea. TBH, I am even amazed the std SMPS copes with 30 000uF (1 amplifier with 2 channels): perhaps I am missing something, or perhaps it has been chosen because it can cope with that load at start up without going into hiccup mode?
Just thinking out loud in the WE while trying to fix my car, so ignore if it is another of my completely stupid posts early in the Sunday LOL!
Claude
Further, I don't have such an amp "yet", and admittely haven't spent time on it... so your inputs are great, many thanks!
So Push-pull indeed, "only one bias current" flowing through both output devices per channel, 2 channel per amp and 52% efficiency. That is discarting the FE stage and other bits (bias), assuming these are negligeable or very small vs the output stage, which seems logical.
If so... then Mark's filter will be delighted under this ideal work conditions... and for those building 2 ACA Mini (enabling hoppefully various "bridged "configurations as the std ACA seems to offer them) then perhaps a single "reasonable / non expensive" SMPS (even the one already provided?) feeding 2 SMPS filters could be worth a try and save further costs sides SMPS when building 2 ACA mini.
There are some resistors slowing somewhat the inrush, but with 2 amps 60000uF PS caps have to be pumped up, I presume not every brick likes that. A soft start could be a good idea. TBH, I am even amazed the std SMPS copes with 30 000uF (1 amplifier with 2 channels): perhaps I am missing something, or perhaps it has been chosen because it can cope with that load at start up without going into hiccup mode?
Just thinking out loud in the WE while trying to fix my car, so ignore if it is another of my completely stupid posts early in the Sunday LOL!
Claude
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Could someone perhaps explain R4 C5? I understand the extra low pass filtering aspect once everything is loaded, less so the rest / transient aspects (other than the slower charging and decharging through R4).
I wonder in fact if this network is perhaps the reason the SMPS copes with 30000uF load at start-up... Kind of perhaps somehow "timing" the loading (voltage rise at start-up) on C3?
Many thanks, trying to learn... and really intrigued by this small amp
Claude
I wonder in fact if this network is perhaps the reason the SMPS copes with 30000uF load at start-up... Kind of perhaps somehow "timing" the loading (voltage rise at start-up) on C3?
Many thanks, trying to learn... and really intrigued by this small amp
Claude