@sndlvr Are you looking to use it parallelled or bridged? There are some discussion here.
On another topic, i'm about to build my own ACA Mini to hold me over while i drill and tap my sinks for the SissySIT, and finally finish that build. The plan is to run the ACA Mini in my remote office setup, powered on 24/7. That place on occasion has power outages, and i seem to recall reading somewhere that cutting power to the SMPS on the primary (mains) side and then reapplying it after either a very short time, or some longer time, can result in quite a bit of noise/thump even if its not damaging to the speakers. Is it worth it to try to come up with a simple relay-based circuit which will disconnect the amp power in the case of a power outage?
Also i never found a definite answer, about pulling the jumpers out to switches and switching them while powered on, what kind of noise can i expect when switching with speakers connected, maybe even a little signal flowing?
My speakers are about 93 dB sensitive (Dali 400, not helicon, 4 ohms), and my SMPS is a 150W MeanWell 24V one, plan is to build a little separate enclosure for it, with the Murata coil in the amp enclosure.
I'll press ahead anyway and all of this is relatively easy to check, with a dummy load and a scope, and some test speakers if i'm feeling brave, but greedy boys will be greedy, also for info 🙂
On another topic, i'm about to build my own ACA Mini to hold me over while i drill and tap my sinks for the SissySIT, and finally finish that build. The plan is to run the ACA Mini in my remote office setup, powered on 24/7. That place on occasion has power outages, and i seem to recall reading somewhere that cutting power to the SMPS on the primary (mains) side and then reapplying it after either a very short time, or some longer time, can result in quite a bit of noise/thump even if its not damaging to the speakers. Is it worth it to try to come up with a simple relay-based circuit which will disconnect the amp power in the case of a power outage?
Also i never found a definite answer, about pulling the jumpers out to switches and switching them while powered on, what kind of noise can i expect when switching with speakers connected, maybe even a little signal flowing?
My speakers are about 93 dB sensitive (Dali 400, not helicon, 4 ohms), and my SMPS is a 150W MeanWell 24V one, plan is to build a little separate enclosure for it, with the Murata coil in the amp enclosure.
I'll press ahead anyway and all of this is relatively easy to check, with a dummy load and a scope, and some test speakers if i'm feeling brave, but greedy boys will be greedy, also for info 🙂
@Kris0603 I'd like to run them bridged mono using either a RCA or an XLR plug carrying a balanced signal from a balanced preamp. Could I just duplicate the wiring scheme on the backplate of the ACA 1.8? Thanks for the link but it didn't quite provide a clear answer.
Also is the power output of the mini less than the regular ACA? Don't believe I have seen that anywhere.
And why would you put a Murata coil in the amp enclosure?
Also is the power output of the mini less than the regular ACA? Don't believe I have seen that anywhere.
And why would you put a Murata coil in the amp enclosure?
The Murata coil creates a LP filter on the DC line, together with the 0.33 ohm resistor and the following 15mF cap, this reducing even further the noise ingres from the SMPS.
I have extra Murata coils (with 3D printed box for them) and lots of AmyAlice full kits still if anyone is interested in trying either, or both.
I have been thinking of the Amy for mono block ACA Reduxes.
is there a benefit with an added Murata?
is there a benefit with an added Murata?
@Stanislav LP is low pass?
How good is it? Equal to a linear power supply, as good as an IFI wallwart?
Perhaps I should explain and ask advice. I had two ACAs but gave one to my daughter. I used to like running them in bridged mono mode from a balanced preamp/dac. I'm thinking I might be able to build an aca mini (just because I have not built one yet) and set it up to be a complimentary monobolock amp to my remaining ACA. Will that work?
PS- @birdbox those parts and boards are very cool!
How good is it? Equal to a linear power supply, as good as an IFI wallwart?
Perhaps I should explain and ask advice. I had two ACAs but gave one to my daughter. I used to like running them in bridged mono mode from a balanced preamp/dac. I'm thinking I might be able to build an aca mini (just because I have not built one yet) and set it up to be a complimentary monobolock amp to my remaining ACA. Will that work?
PS- @birdbox those parts and boards are very cool!
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Yes, low pass.
An online LC calculator tell me the combination of L = 400 uH with C= 15mF cuts at 64Hz, so plenty of attention after that frequency.
It's not as simple as that because that calculator does not take into account the Rs of the filter.
But LC is a 2nd order filter unlike RC which is 1st order, meaning steeper, more attenuation as the frequency increases.
As we know SMPS noise is mostly HF noise.
An online LC calculator tell me the combination of L = 400 uH with C= 15mF cuts at 64Hz, so plenty of attention after that frequency.
It's not as simple as that because that calculator does not take into account the Rs of the filter.
But LC is a 2nd order filter unlike RC which is 1st order, meaning steeper, more attenuation as the frequency increases.
As we know SMPS noise is mostly HF noise.
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When it comes to cleaning up SMPS power, I am extremely impressed by the AmyAlice filter. My primary experience with this is Nelson Brocks F5m Redux amp(s), which have the AmyAlice circuit on each rail of the F5m Redux monoblocks. I found Nelson Brocks implementation to be slightly superior in sound to my stock F5m linear PSU F5m. That's what convinced me to buy a ton of Mark Johnson's AmyAlice boards and acquire parts in quantity to share kits with the diy community. Every SMPS build I make going forward will have AmyAlice PSU filters because of that experience.
As far as the Murata coil, it's an easy to implement option using the 3D printed coil box I posted for anyone to use. I have not had a good A to B comparision with ACA Mini using the coil as a filter vs without. My very limited experience testing this comparison was not very scientific and I could not hear an audible difference during my quick comparison. However, the caveat is I didn't spend much time comparing coil vs no coil sound, so, unlike my AmyAlice comparision, the Murata coil comparison is not really beneficial. My hope is others have spent time comparing and can comment on the impressions of using the coil.
So coil vs no coil.....I am not sure how that effects the sound on ACA Mini. It certainly didn't hurt the sound on my brief system test. I just couldn't decern any noticeable improvement on the system I was testing.
As far as the Murata coil, it's an easy to implement option using the 3D printed coil box I posted for anyone to use. I have not had a good A to B comparision with ACA Mini using the coil as a filter vs without. My very limited experience testing this comparison was not very scientific and I could not hear an audible difference during my quick comparison. However, the caveat is I didn't spend much time comparing coil vs no coil sound, so, unlike my AmyAlice comparision, the Murata coil comparison is not really beneficial. My hope is others have spent time comparing and can comment on the impressions of using the coil.
So coil vs no coil.....I am not sure how that effects the sound on ACA Mini. It certainly didn't hurt the sound on my brief system test. I just couldn't decern any noticeable improvement on the system I was testing.
RE PS, I found (search function is your friend, I posted here on tries and results/gains TO MY EARS) that the following works great with the Mini:
AS FOR THE REST, WARNING: I haven't tried a linear supply on the Mini, or the Amy Alice (I should one day just for the sake of it, shame on me being located so remotely).
I am though a big fan of Mark's PO89ZB SMPS filters (using over a dozen of them with various components!) and a while ago I tried on another unit "linear regulated + cap tweaks" vs "SMPS + PO89ZB filter + cap tweaks". Very very close,... and at the end I even prefered the SMPS version. Of course this was another unit, and there are several linear PS performing better or worst etc., but the key point is IMHO to remember that some circuits have very poor power supply noise rejection and hence NEED a regulated or extremely stable voltage supply. Regulated SMPS are very good on that. Further, Class A draws a nearly constant current and Meanwell SMPS are excellent when load variations are few, far better than their adverstised max noise and ripple (see their test reports). In short: quality SMPS and Class A do make sense (note for other reasons they also make sense for Class D but that's another topic). Class AB they can make less sense...
As we are talking here Class A and low PS rejection, Papa has been very clever using SMPS, not even mentioning it is far safer and far easier for kits. Of course Papa has done 90% of the work by having already in his kits a PS filter (often RC) that is filtering a lot of the SMPS noise.
Despite this, we found that all SMPS benefited from an additional PS filter and sometimes even uprated PS caps, eventhough "on the paper" all that shouldn't be needed. Most SMPS work at frequencies between 60kHz and 800kHz and hence generate quite a bit of nasty things at HF, but that's surely not all the story.
I tried the Mini with Mark's PO89ZB SMPS filter (huge fan of that one) and for the first time it didn't sound better, overal on a par or even very slightly worst than without. I tried the Murata coil and it sounded to me that good that it didn't left me wanting in any department, so I went tweaking elsewhere 🙂.
Note that the Murata Coil leads to a LCR filter that is, on the paper, better performing than the Amy Alice on mid to HF. At HF they cross path but at such a high degree of filtering/attenuation that basic theory doesn't make sense anymore (there are other bits at play at that attenuation level). BUT, as said, there is surely more to it with these filters... and I haven't tried the Amy Alice, so can't compare. I know though that to my ears (and Gilles and all other friends that tried the Mini at theirs, coil in and out through an easy plugging) the Murata Coil is quite an enhencement of the existing... and "my bet" is the Amy Alice is also an excellent performer.
My finding is Mini + uprated Meanwell + Murata Coil + caps tweaks sounds excellent and - now that's a bet / guess and I would be delighted to be proven completely wrong -, won't be easily beaten by any other $$$ linear PS (regulated or not) because of 2 things:
1- Diminishing returns, we are getting close to something that is very good re PS and sound
2- The sonic signature of the Mini is quite pronunced and hence likely to dominate any further fine tuning re PS (linear can enhence the bass or the soundstage, but then I wouldn't want to enhence the slight perceived bass hump of the Mini together with the deepest bass that could indeed be improved if using top full range LS, nor would I want to dillute further the soundstage created by the negative 2nd harmonic... it is all a delicate balancing act).
So once you have a properly filtered quality SMPS air gets thin for real improvement. Sound balance, that's another topic, more tweaking then.
Last but not least, the Mini is a very simple build and, if you like its addictive sound signature, with the right LS it is very difficult to beat South of 1500$ with commercial offerings. The beauty of it is it is VERY SIMPLE, NON EXPENSIVE and bullet proof. The SMPS contributes to this... as is the absence of any housing. I would leave it like that, that's IMHO part of the beauty /concept. If wanting really a lot more, there are other amps...
So for all these reasons, with the Mini I would stick to a good SMPS and either use as additional filter the Murata coil (simply excellent on the paper and in practice in this specific application), or perhaps try the Amy Alice (no reason not to), and also try the other tweaks (caps) Birdbox has put together because at that price they are a steal and in my very biased opinion quite good sounding.
All IMHO and IME, no flames please ;-)
Claude (built a few Minis at various tweak levels and spent silly time comparing them together)
- Uprated Meanwell PS (low noise, low ripple, higher rating of 120W)
- Murata SMPS filtering Coil
- Some additional PS bypass caps
AS FOR THE REST, WARNING: I haven't tried a linear supply on the Mini, or the Amy Alice (I should one day just for the sake of it, shame on me being located so remotely).
I am though a big fan of Mark's PO89ZB SMPS filters (using over a dozen of them with various components!) and a while ago I tried on another unit "linear regulated + cap tweaks" vs "SMPS + PO89ZB filter + cap tweaks". Very very close,... and at the end I even prefered the SMPS version. Of course this was another unit, and there are several linear PS performing better or worst etc., but the key point is IMHO to remember that some circuits have very poor power supply noise rejection and hence NEED a regulated or extremely stable voltage supply. Regulated SMPS are very good on that. Further, Class A draws a nearly constant current and Meanwell SMPS are excellent when load variations are few, far better than their adverstised max noise and ripple (see their test reports). In short: quality SMPS and Class A do make sense (note for other reasons they also make sense for Class D but that's another topic). Class AB they can make less sense...
As we are talking here Class A and low PS rejection, Papa has been very clever using SMPS, not even mentioning it is far safer and far easier for kits. Of course Papa has done 90% of the work by having already in his kits a PS filter (often RC) that is filtering a lot of the SMPS noise.
Despite this, we found that all SMPS benefited from an additional PS filter and sometimes even uprated PS caps, eventhough "on the paper" all that shouldn't be needed. Most SMPS work at frequencies between 60kHz and 800kHz and hence generate quite a bit of nasty things at HF, but that's surely not all the story.
I tried the Mini with Mark's PO89ZB SMPS filter (huge fan of that one) and for the first time it didn't sound better, overal on a par or even very slightly worst than without. I tried the Murata coil and it sounded to me that good that it didn't left me wanting in any department, so I went tweaking elsewhere 🙂.
Note that the Murata Coil leads to a LCR filter that is, on the paper, better performing than the Amy Alice on mid to HF. At HF they cross path but at such a high degree of filtering/attenuation that basic theory doesn't make sense anymore (there are other bits at play at that attenuation level). BUT, as said, there is surely more to it with these filters... and I haven't tried the Amy Alice, so can't compare. I know though that to my ears (and Gilles and all other friends that tried the Mini at theirs, coil in and out through an easy plugging) the Murata Coil is quite an enhencement of the existing... and "my bet" is the Amy Alice is also an excellent performer.
My finding is Mini + uprated Meanwell + Murata Coil + caps tweaks sounds excellent and - now that's a bet / guess and I would be delighted to be proven completely wrong -, won't be easily beaten by any other $$$ linear PS (regulated or not) because of 2 things:
1- Diminishing returns, we are getting close to something that is very good re PS and sound
2- The sonic signature of the Mini is quite pronunced and hence likely to dominate any further fine tuning re PS (linear can enhence the bass or the soundstage, but then I wouldn't want to enhence the slight perceived bass hump of the Mini together with the deepest bass that could indeed be improved if using top full range LS, nor would I want to dillute further the soundstage created by the negative 2nd harmonic... it is all a delicate balancing act).
So once you have a properly filtered quality SMPS air gets thin for real improvement. Sound balance, that's another topic, more tweaking then.
Last but not least, the Mini is a very simple build and, if you like its addictive sound signature, with the right LS it is very difficult to beat South of 1500$ with commercial offerings. The beauty of it is it is VERY SIMPLE, NON EXPENSIVE and bullet proof. The SMPS contributes to this... as is the absence of any housing. I would leave it like that, that's IMHO part of the beauty /concept. If wanting really a lot more, there are other amps...
So for all these reasons, with the Mini I would stick to a good SMPS and either use as additional filter the Murata coil (simply excellent on the paper and in practice in this specific application), or perhaps try the Amy Alice (no reason not to), and also try the other tweaks (caps) Birdbox has put together because at that price they are a steal and in my very biased opinion quite good sounding.
All IMHO and IME, no flames please ;-)
Claude (built a few Minis at various tweak levels and spent silly time comparing them together)
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Hi All ! Well, for sharing. The assembly of my ‘double ACA mini’ is now complete. To retain the ACA mini's concept, a completely open chassis, made of Plexiglass. Perforated to ensure good ventilation around the radiators. Two Murata coils are on the chassis, close to the DC inputs of each amp. One central switch to select between two sources. Two switches on the LS output paths, to enable a 'power mode' (bridging the +). Ok, that’s a gadget that I will probably use very rarely, but while at it…
This is the culmination of the various listening tests carried out with Claude (all of the tweaks he mentionned in previous posts are included). The best configuration to my ears. These very musical little things sound wonderful, with flesh, detail, finesse. The V bi-amp brings, among other things, aeration, openness and depth to the sound stage in a substantial way, especially with my Klipsch which tend to project forward. When I first heard the ACA mini without any mods, I was already blown away by the capabilities of such a small, low-power amp. This piece is now next level to my ears.
Enjoy music !
Gilles.
This is the culmination of the various listening tests carried out with Claude (all of the tweaks he mentionned in previous posts are included). The best configuration to my ears. These very musical little things sound wonderful, with flesh, detail, finesse. The V bi-amp brings, among other things, aeration, openness and depth to the sound stage in a substantial way, especially with my Klipsch which tend to project forward. When I first heard the ACA mini without any mods, I was already blown away by the capabilities of such a small, low-power amp. This piece is now next level to my ears.
Enjoy music !
Gilles.
Ah, by the way, for fun… My ears consider that 2 PS improve the benefits of the bi-amp. Downside : things lying around on the floor, creeping cables and I hate that ! Also, I don't like to throw away things that might still be useful. So, I decided to reuse the casing of an old, unusable tape player lying on a shelf for years, to hold the 2 PS.
Probably the biggest power button I will ever have...
Probably the biggest power button I will ever have...
What a beauty!!!!!!!!!!!!
I had seen the plans and details beforehand, but didn't expect it... to look THAT great!
While you are kind complementing my soldering skills and tweaks, I do confess I do trully admire your aesthetic sense and care when it comes to builds!!!
Perhaps YOU should assemble my Black Beauty LOL!
BTW, Gilles listened until this WE without his 2 filtering coils, so he is in a great position to share why he went the trouble to fit them ;-)
I love that build: it remains open / wo casing, looking gorgeous (still revealing the great Minis) and being non expensive. Yes, 2 Minis are still not expensive and I am eager to try these at yours in V biamp mode (passive Xover so far) to see how they fare vs bigger proposals. Suspense
Note that Gilles needs less than 2W per LS (as we found out), and doesn't need a high damping Factor, so if this double Mini sounds better (and no doubt it does), it is not power or DF related... hmmm...
Enjoy your listening, I believe you are done for a while, and let the frogs sing again so I have an excuse to turn up soon again LOL
Claude
I had seen the plans and details beforehand, but didn't expect it... to look THAT great!
While you are kind complementing my soldering skills and tweaks, I do confess I do trully admire your aesthetic sense and care when it comes to builds!!!
Perhaps YOU should assemble my Black Beauty LOL!
BTW, Gilles listened until this WE without his 2 filtering coils, so he is in a great position to share why he went the trouble to fit them ;-)
I love that build: it remains open / wo casing, looking gorgeous (still revealing the great Minis) and being non expensive. Yes, 2 Minis are still not expensive and I am eager to try these at yours in V biamp mode (passive Xover so far) to see how they fare vs bigger proposals. Suspense
Note that Gilles needs less than 2W per LS (as we found out), and doesn't need a high damping Factor, so if this double Mini sounds better (and no doubt it does), it is not power or DF related... hmmm...
Enjoy your listening, I believe you are done for a while, and let the frogs sing again so I have an excuse to turn up soon again LOL
Claude
I feel the same way. With my ACA Mini I originally used the P089ZB filter. When I replaced it with the AmyAlice the background was quieter allowing the music to have more detail.
I have not tried the coil and can’t compare it to the AmyAlice.
When I originally recommended using the Murata 1433428C coil, in post #849 of this thread, my idea was to synthesize a well behaved LRC filter, by driving the big electrolytic capacitors already on the ACA mini from a carefully chosen inductor. Nothing else should be connected between the Murata coil and the ACA mini, that would ruin the LRC filter's performance. I am delighted to observe that the beautiful build in post #3,092 got it exactly right. There is nothing between the Murata coil and the ACA mini except connecting wire. Well done, good on ya!
Of course builders are free to install additional filtering contrivances and gizmos however they like, but I strongly recommend putting all other circuitry upstream of the Murata coil.
SMPS ---> PO89ZB_first ---> AmyAlice ---> PO89ZB_second ---> MurataCoil ---> ACA Mini
is one example. There is nothing between the Murata coil and the ACA Mini, so you aren't ruining the MurataCoil LRC filter's performance. All the other doodads are upstream.
Of course builders are free to install additional filtering contrivances and gizmos however they like, but I strongly recommend putting all other circuitry upstream of the Murata coil.
SMPS ---> PO89ZB_first ---> AmyAlice ---> PO89ZB_second ---> MurataCoil ---> ACA Mini
is one example. There is nothing between the Murata coil and the ACA Mini, so you aren't ruining the MurataCoil LRC filter's performance. All the other doodads are upstream.
Yes, thanks Mark for correcting!
As Mark wisely suggested, this is THE coil and THE right position (LRC of course and not LCR- typo of mine, doesn't change the rest of the comment though as we fitted the coils of course correctly at mine and Gilles). There aren't that many non expensive coils that fit the bill... I found no other / no better one hence coming to the same conclusion and sticking to that one, although after Mark who was first posting on that tip... and I presume perhaps even tried it successfully before me with the Mini? He seems anyway to be first when it comes to filtering SMPS, so we shouldn't forget to credit him !🙂
As for me, given Mark's credentials, I am more and more interested in trying AmyAlice, for example with the Mini either "instead" or "additional" to the Murata coil.
Last but not least, I posted on that already but could be useful... I tried 1 and even 2 chained PO89ZB (so to be clear "SMPS+1 or 2 PO89ZB in series+Mini"), and even later "SMPS+PO89ZB+Murata+Mini" (in that order of course) but it didn't perform better TO MY EARS vs SMPS+Murata+Mini. As said already, SMPS+Murata+Mini performed better than SMPS+PO89ZB+Mini to my ears.
Oh, and me being me, I couldn't help trying "SMPS+ 2 Murata coils in series + Mini", but that combo also didn't bring any further benefits vs one single coil.
As Mark already said, you get a very strong filter combining the (relatively big) Murata coil and the existing RC filter on the Mini (and that's also a big C in case of the Mini), and it simply works great while remaining very simple... and comparisons are so easy, plug in, plug out.
BUT I haven't yet tried coil vs AmyAlice with the Mini, or AmyAlice+coil+Mini. Who knows, Mark does miracles when it comes to filtering... Perhaps someone did already?
Argh, too many projects, back to my own amp LOL!
Enjoy the Mini
Claude
As Mark wisely suggested, this is THE coil and THE right position (LRC of course and not LCR- typo of mine, doesn't change the rest of the comment though as we fitted the coils of course correctly at mine and Gilles). There aren't that many non expensive coils that fit the bill... I found no other / no better one hence coming to the same conclusion and sticking to that one, although after Mark who was first posting on that tip... and I presume perhaps even tried it successfully before me with the Mini? He seems anyway to be first when it comes to filtering SMPS, so we shouldn't forget to credit him !🙂
As for me, given Mark's credentials, I am more and more interested in trying AmyAlice, for example with the Mini either "instead" or "additional" to the Murata coil.
Last but not least, I posted on that already but could be useful... I tried 1 and even 2 chained PO89ZB (so to be clear "SMPS+1 or 2 PO89ZB in series+Mini"), and even later "SMPS+PO89ZB+Murata+Mini" (in that order of course) but it didn't perform better TO MY EARS vs SMPS+Murata+Mini. As said already, SMPS+Murata+Mini performed better than SMPS+PO89ZB+Mini to my ears.
Oh, and me being me, I couldn't help trying "SMPS+ 2 Murata coils in series + Mini", but that combo also didn't bring any further benefits vs one single coil.
As Mark already said, you get a very strong filter combining the (relatively big) Murata coil and the existing RC filter on the Mini (and that's also a big C in case of the Mini), and it simply works great while remaining very simple... and comparisons are so easy, plug in, plug out.
BUT I haven't yet tried coil vs AmyAlice with the Mini, or AmyAlice+coil+Mini. Who knows, Mark does miracles when it comes to filtering... Perhaps someone did already?
Argh, too many projects, back to my own amp LOL!
Enjoy the Mini
Claude
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