Hi Jean-Paul, what do you think of the numbers difference ?
MA12070P with I2S digital input (an integrated DAC enables digital I2S audio stream input).
- Audio performance (PMP2): >101dB SNR (A-w, rel. to 1% THD+N power level)
-140µV output integrated noise (A-w)
- 0.007% THD+N at high output levels
vs
MA12070
- Audio performance (PMP2): >110dB SNR (A-w, rel. to 1% THD+N power level)
- 45µV output integrated noise (A-w)
- 0.004% THD+N at high output levels
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I have the A20a now for 2 weeks and although it certainly does things right (big soundstage, decent supply), I also agree with others that it lacks bass and is sounding to bright and thin.
I like my modified Pro 502 still more (amplifier of just €68,-). More balanced sound bass/mids/higs and much more punch (dynamic).
So I took it apart to examine the possibilities to optimize the sound, as I hear the potential, but it not all coming out now I guess. Other opamps as the OPA 1856 were suggested to improve the sound.
One thing already mentioned is to turn the power supply to max (about 25,2 V). But I looked up the power caps and these are rated at 25V. What is already too close for the standard 24V for my taste. I guess these have to be replaced. I don't want problems because these caps fail.
As I liked the balanced input I was thinking of using 2 of these for my LX-mini speakers.
But then I want to use them as pure end amp, so thinking to skip the entire volume control (no need). So more direct to the MA12070.
A question about the power caps for class D came to my mind although:
Do we need caps good in the audio range or do we need caps there that are good at the switching frequency (675 kHz) here? (besides having low ESR)
Any opinion about this would be welcome.
I like my modified Pro 502 still more (amplifier of just €68,-). More balanced sound bass/mids/higs and much more punch (dynamic).
So I took it apart to examine the possibilities to optimize the sound, as I hear the potential, but it not all coming out now I guess. Other opamps as the OPA 1856 were suggested to improve the sound.
One thing already mentioned is to turn the power supply to max (about 25,2 V). But I looked up the power caps and these are rated at 25V. What is already too close for the standard 24V for my taste. I guess these have to be replaced. I don't want problems because these caps fail.
As I liked the balanced input I was thinking of using 2 of these for my LX-mini speakers.
But then I want to use them as pure end amp, so thinking to skip the entire volume control (no need). So more direct to the MA12070.
A question about the power caps for class D came to my mind although:
Do we need caps good in the audio range or do we need caps there that are good at the switching frequency (675 kHz) here? (besides having low ESR)
Any opinion about this would be welcome.
I added two of those clip-on ferrites on the wires that connect the amp board to the speaker terminals - not a night and day difference but to my ears this added some more clarity to the amp (it has become easier to differentiate between the different output filters offered by the matching A20 dac). Next I plan on replacing the 22uF input caps - but mail from the UK is kind of slow these days (or rather customs' processing).
.Why would this be a risk? There are many end amps out there without volume control. The MA12070 has 2V input sensitivity.
Undesired noises. Are you meaning the noise from the SMPS?
Yes, I like the FM's also. Used them in the Pro 502. But these are not in SMD, as the caps in the A20a are. SMD caps haven't that low ESR.
Noticed that even when there are SMD versions of caps, that still these have worse ESR than the radial types. Any idea why that is?
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YEP , noticed that two weeks ago.
Speaks for itself regarding the amp and its manufacturer...
Yes, the sound when you put it to full volume. Starts at -10. Maybe not only from the SMPS.
Yes there are many open amplifiers without volume control blowing up speakers when something goes wrong. The volume control is a kind of fuse. It also limits noise so 2 strong points to have it.
I made a mistake with Pana FC/FM, that should be FK or one of the similar types in SMD.
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Don't know, but don't mind : "The amplifiers can pass the Radiated Emission test with speaker cables lengths up to 80 cm with just a small ferrite filter. For cables longer than 80 cm it is recommended to use a LC-filter."
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Seems not that simple. This plus the lytics choices & rated voltage, plus other things regarding the PCB design, and mostly the thin sound & shy bass, made me pass my way (for the time being).Ah it says 60 cm but OK. Maybe be an issue, maybe not.
If you would mind if there are SMD beads you could consider replacing them for SMD coils. Thinking in solutions
Even if i am not afraid of severe mods & tweaks.
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A house in 2021 is literally full of RF. It could be that is is all not so bad with the amplifier radiating a little. It would be best to really measure EMC. Of course I would prefer it did radiate not but I am sure wireless internet is also enabled.
It is an amplifier of 230 Euro, maybe we expect a tad too much. I thought it to be way better than expected for the price.
The PCB seems adaptable to SMD coils. I don't have the device anymore but it seems Sabaj choose a combination of the filtering methods. The film caps seem to be there.
It is an amplifier of 230 Euro, maybe we expect a tad too much. I thought it to be way better than expected for the price.
The PCB seems adaptable to SMD coils. I don't have the device anymore but it seems Sabaj choose a combination of the filtering methods. The film caps seem to be there.
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I can completely understand, I am also asking myself if it's worth the effort (as this thread is called
).Also noticed that the balanced input to the MA12070 (the caps besides the opa1678) are connected 1 side directly to the volume control chip, the other side is just inverted by half of the 1678. This is a budget solution saving an opamp. But this way you would expect slight differences between the positive and negative input.
Perhaps something that someone like Amir should take into account with his reviews.
Yes, you are completely right. It's a budget amplifier. For the money you get a lot of amplifier, but it can only be sold for such value by keeping things as simple and cheap as possible.
Still it has a decent power supply, nice cabinet. Can't build something like this for this money...
The RF radiation is said to be very low by Infineon. It seems lower than usual with other class D chips by design and is even advertised as "filterless". The chip would require LC filtering only for very stringent EMI requirements. I haven't noticed anything strange while I had the amplifier.
Anyway, the SMD beads as used on the cheap MA12070 modules can be soldered on the PCB tracks of the Sabaj (cut tracks with a Dremel). It one suspects without measuring it can be reassuring. Surprising that cheap modules do have the beads
Anyway, the SMD beads as used on the cheap MA12070 modules can be soldered on the PCB tracks of the Sabaj (cut tracks with a Dremel). It one suspects without measuring it can be reassuring. Surprising that cheap modules do have the beads
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