Hi,
Its been a long while as I haven't done anything about this project for a long time.
But recently I was able to pick it up again and made some progress.
But the Unit itself makes an annoying acoustic crackling noise. The Mornsun was quiet. Hadn't expect this...
Listening shortly after soldering these caps in: Just awful. The amp sounding even more like treble full open and and bass down. It literally made my ears hurt... Gave it almost a week to burn in. Became better, but still very aggressive and thin sounding. Although I also clearly hear the virtues of these caps, it is just not the right cap for this position. Very dynamically and clear. But gave an absolute flat 2D stage. No hint of depth.
Went back to the FM's, and that's much better. The KZ's give by far the best soundstage, but too big and too far away. Uninvolving. I like a more live sound.
I had 470uF FM's a long period at the position of the volume control. This gave a better high/low balance, buts slows down too much.
When I connect the DAC directly via the USB to the laptop, it was just restless and aggressive. Absolutely not pleasant to listen to. But the DAC connected via USB to the optimized Pi4, it sounds good. No aggressiveness and quiet. So when something is not right upfront, the KZ's will let you know...
About the Mornsun PSU
Pulling of the earth connection from the power plug gave an improvement. Noticed women's voices sounding suddenly warm.
Its an easy mod for everybody having an A20. Just pull the amp a few centimeters out and pull off the connector. Done.
The Meanwell PSU doesn't even have a earth connecter, in case you're wondering if you can do that just like that.
Sounding too thin
I solved this. Just added 100uF to the power supply of the pre-stage. Now it sounds right to me. Full Bass, Voices are sounding fuller. Now it sounds like a "real amplifier" to me. Low, mids and highs are in balance now. Some of you disagreed that it sounds too thin, others do find the MA12070 too thin, certainly compared to the TPA's.
But here it is not the MA12070 that sounds too thin. The problem is the pre-stage.
I will end this journey with this amp as you just can't keep soldering in and out caps all the time. The pcb doesn't like that. I don't want to end up with a dead amp.... I hope this experience will be of help to you.
Its been a long while as I haven't done anything about this project for a long time.
But recently I was able to pick it up again and made some progress.
I have bought this Meanwell PSU. Impression is that it all sounds a bit cleaner and rounder. But a bit less punch? @26V it becomes better indeed.
But the Unit itself makes an annoying acoustic crackling noise. The Mornsun was quiet. Hadn't expect this...
Yes, they are too short. I bought these from AliExpress. Longer indeed, so I don't need to put in the amplifier in de enclosure every time. Makes modding live easier.
As the quality of the caps at the volume control chip are of extreme importance for the perceived sound quality. I tried the recommended AN caps there. Although I had my doubt that the ESR of these caps would be too high.
Listening shortly after soldering these caps in: Just awful. The amp sounding even more like treble full open and and bass down. It literally made my ears hurt... Gave it almost a week to burn in. Became better, but still very aggressive and thin sounding. Although I also clearly hear the virtues of these caps, it is just not the right cap for this position. Very dynamically and clear. But gave an absolute flat 2D stage. No hint of depth.
Went back to the FM's, and that's much better. The KZ's give by far the best soundstage, but too big and too far away. Uninvolving. I like a more live sound.
I still like the KZ's and do not experience harshness. But the KZ's forgive absolutely nothing.
I had 470uF FM's a long period at the position of the volume control. This gave a better high/low balance, buts slows down too much.
When I connect the DAC directly via the USB to the laptop, it was just restless and aggressive. Absolutely not pleasant to listen to. But the DAC connected via USB to the optimized Pi4, it sounds good. No aggressiveness and quiet. So when something is not right upfront, the KZ's will let you know...
About the Mornsun PSU
Pulling of the earth connection from the power plug gave an improvement. Noticed women's voices sounding suddenly warm.
Its an easy mod for everybody having an A20. Just pull the amp a few centimeters out and pull off the connector. Done.
The Meanwell PSU doesn't even have a earth connecter, in case you're wondering if you can do that just like that.
Sounding too thin
I solved this. Just added 100uF to the power supply of the pre-stage. Now it sounds right to me. Full Bass, Voices are sounding fuller. Now it sounds like a "real amplifier" to me. Low, mids and highs are in balance now. Some of you disagreed that it sounds too thin, others do find the MA12070 too thin, certainly compared to the TPA's.
But here it is not the MA12070 that sounds too thin. The problem is the pre-stage.
I will end this journey with this amp as you just can't keep soldering in and out caps all the time. The pcb doesn't like that. I don't want to end up with a dead amp.... I hope this experience will be of help to you.
Thanks @Overeem and everyone for your efforts on upgrading this amp. @Overeeem - could you list out the changes you made (in order of biggest impact) that made positive improvements. Any pictures for us noobs would be very helpful (like "Just added 100uF to the power supply of the pre-stage" - what brand and exactly where/how to add it, for example). Thanks again.
See picture in post #184. There you can see what caps are changed. Had 10 uF Silmic there, changed it recently, first to FR 100uF, now 100uF KZ. These last ones are burning in now. But immediately it sounded more open and a more relaxed sound,
Had to remove the blue film cap there though, as there is no room for so many caps and the KZ's are really big.... The film cap gave more punch, more dynamics. Also a matter of taste.
Soldered them against the outside of the ceramic caps there on the 15V lines, behind the caps I made a piece blank on the ground and soldered both the caps there, for the ground connection.
Hhhmm, difficult after a so long period.
- But definitely the decoupling caps have to be changed, as the originals give an artificial plastic sound and details get lost. KZ can be picky if something is not right in the chain. The AN caps could be even better, but they cost more than 10 times the price of the KZ's... Don't know, seems out of balance. I save them for other projects. Heard transparency that didn't make me linger for more...
- The caps beside the volume control even have an bigger impact. The volume control is the weakest part of this design anyway. I find the FM's best there. But depends also on personal taste. Had a film cap over these for a while, really smooth sound with beautiful highs, but lost some clarity. It's always a trade off...
- The Ferrite core on the power cable has also an big impact on the perceived perception of rest and space, A must also. Simple and not expensive.
- Changing the PSU to Meanwell? Don't think it is really worth the money. Improves the sound for a part, but costs you half the price of the whole amp. Improvement is not in balance with the added costs... But pull of the earth connection of the Mornsun. This costs nothing and gives an improvement, at least in my case. No dirt injection from the earth mains anymore.
- Oh, opamps. I changed these to OP1656. I like them. Didn't try others. These can be very transparent.
Since the original Mornsun PSU has a PE connection it should be connected to PE like it was done by Sabaj. Period. It is awkward to judge things solely on ears certainly when it is about safety or mains filtering where ears are not the instruments to measure with. The amplifier should also be connected to a PE wall socket with a 3 pin IEC cable. It is not solely about injection from PE, it is also about the SMPS not injecting mains.
Pre-stage around MA12070 is important indeed. It should have 2 x NJM1194 really to drive the MA12070 balanced but in reality it has only 1.
Pre-stage around MA12070 is important indeed. It should have 2 x NJM1194 really to drive the MA12070 balanced but in reality it has only 1.
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Thanks @jean-paul . Are you saying 2 x NJM1194 per MA12070 in which case this amp should really have 4 of them? I suspect trying to modify the pre-stage would be very difficult/almost impossible for 2x NJM's? Are the opamps socketed or does this involve de-solder/soldering? Cheers.
It is only connected to 2 of these blue caps with a small ferrite. So purpose is not safety. Idea is probably to filter out noise, but is is also a way in...
Then it should have the NJM1195A, this one not only has better specs, but is also balanced. You don't need 2 1194's. Looked at that year ago. Not completely pin compatible though. So no drop in replacement.
These are soldered. The amp is completely SMD, so are the opamps. Suggest to use a hot air station.
Better to skip the whole thing and use a good potentiometer. But there is not much room in the device...
Hey guys - I would like to ask a "question" based on owning/hearing this Sabaj A20a amp, but it will take the discussion in a tangential direction. So, let me know if I should create a new thread or would it best be asked within the context of this thread?
Let's say Sabaj decided to re-release this dual-Merus MA12070 A20a amplifier, and the release price is around $250 +/-. I am in the process of planning for my first DIY speaker build and am looking at a speaker in the 4-Ohm (slight dip below) range with only moderate efficiency around 84dB, and going into a medium room about 15' x 22'. DAC is an SMSL DO100 balanced-out. So, what would you do: If you had the above speakers and $250 to spend, would you still buy the new A20a, or would you buy ( a DIY complete kit build can be included) a different amp (and which one)?
Cheers - David
Let's say Sabaj decided to re-release this dual-Merus MA12070 A20a amplifier, and the release price is around $250 +/-. I am in the process of planning for my first DIY speaker build and am looking at a speaker in the 4-Ohm (slight dip below) range with only moderate efficiency around 84dB, and going into a medium room about 15' x 22'. DAC is an SMSL DO100 balanced-out. So, what would you do: If you had the above speakers and $250 to spend, would you still buy the new A20a, or would you buy ( a DIY complete kit build can be included) a different amp (and which one)?
Cheers - David
Almost all the MA12070 equipped devices lack a good pre-stage. I haven't seen a single one with a real balanced pre-stage. So it seems there is work to do. The ones that have opamps driving both inputs perform best in general (as compared to ones that have a cap to GND on one input).
NJW1194 or 1195 are both not bad but a simple 4 channel potentiometer and active pre-stage either unbal-bal or bal-bal wins from either of them. I have one prepared for transformer driven inputs and an active volume control/pre-stage but I choose a too small casing and the project is stalled.
Point is that one nearly always meets the same constraints as the ICs are meant for low cost devices. If costs are no object a 4 channel relay controlled volume control with buffer opamps would be nice but the amplifier itself would be cheapest part
NJW1194 or 1195 are both not bad but a simple 4 channel potentiometer and active pre-stage either unbal-bal or bal-bal wins from either of them. I have one prepared for transformer driven inputs and an active volume control/pre-stage but I choose a too small casing and the project is stalled.
Point is that one nearly always meets the same constraints as the ICs are meant for low cost devices. If costs are no object a 4 channel relay controlled volume control with buffer opamps would be nice but the amplifier itself would be cheapest part
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That is really low. I guess you would be better of with a more powerful amp.
I have bought the MA5532MS based circuit. Mamocel reported good results.
Would be a better choice for active loudspeaker solution than the A20. Putting the amp, the PSU and the filter in one case.
But....
True, also for this MA5532MS. A NE5532 as opamp (although not bad), unbalanced, 2 times small ceramics as decoupling caps 7805's as voltage regulators.
But really cheap, and much more power.
Will be next project. See what we can do there. At least it will be much much easier to mod than the A20.
First thing will be to bridge the first decoupling caps (take them out and put piece of wire in instead). As output of DAC has decoupling caps, they are not needed.
But not in this thread.
That is why I find investing expensive components in a cheap amp that we not really can come over the "faults", not really logical.
Aim was to find out if the MA12070 is any good. Well, I am convinced by the qualities of the chip. Heard things I have never heard before. It can be very transparent and revealing. And yes, it does output (more than) enough bass and doesn't sound thin at all.
The A20 will replace my old NAD amp for a while, as the NAD really needs new caps.... I still like the sound of the NAD very much.
I am listening to the MA5532MS module now. I'm convinced. Go for such solution, not the Sabaj. It has more power and sounds better 'out of the box'. Easier to mod when you want that. Cheaper. You just have to put in a case (most expensive part...). Going for 2 x Mono, you still be cheaper and even better.
