• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

PMA-NC252MP power amplifier

Matias

Major Contributor
Forum Donor
Joined
Jan 1, 2019
Messages
3,191
Likes
5,766
Location
São Paulo, Brazil
P.S.: the small spectrum peak at 8kHz that is present in all measurements does not come from the amplifier, but it is a bug from my measuring system. Haven't fixed it, yet :(.
8 kHz is the frequency of USB noise as far as I know. Try a USB filter maybe it can fix.
 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
Just to mention the “obligatory” SINAD at 5W/4ohm/1kHz - it is 98.15 dB.
Measured as sqrt(THD^2 + N^2) with @22kHz BW
 
Last edited:

Burning Sounds

Senior Member
Joined
Dec 22, 2016
Messages
438
Likes
664
Location
Co. Durham, UK
Really nice work!

Could you measure the temp of the caps that sit above the output coils? They are right above the output coils in your module orientation so collect all the rising heat from the coils. They are 105 deg C caps so not really a concern, but I do find that is the hottest place in my amp (Apollon multi-channel NC502MP amp with the modules oriented this way.) The heatsink temps rarely get above 40deg C. Apollon add an additional heatsink to the Hypex heatsink.
 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
Really nice work!

Could you measure the temp of the caps that sit above the output coils? They are right above the output coils in your module orientation so collect all the rising heat from the coils. They are 105 deg C caps so not really a concern, but I do find that is the hottest place in my amp (Apollon multi-channel NC502MP amp with the modules oriented this way.) The heatsink temps rarely get above 40deg C. Apollon add an additional heatsink to the Hypex heatsink.
Thank you. Yes I could, later. By now I have “measured” temperature of those capacitors by my fingers, it is slightly above human body temperature. The hotest parts are those coils you mentioned. The side heatsink with fins does a great thermal management job, they remain slightly above room temperature. The heat should not be a killer of this amplifier, definitely.
 

Larry B. Larabee

Senior Member
Joined
Nov 24, 2021
Messages
348
Likes
176
Bridged Mode and clipping indicators wouldn't hurt. Is the soft-start prefab?
 

restorer-john

Master Contributor
Joined
Mar 1, 2018
Messages
8,755
Likes
24,334
Location
Gold Coast, Queensland, Australia
@pma Keep an eye on the flexed PCB issue I have highlighted previously. I note yours is bent somewhat too.

 

KSTR

Major Contributor
Joined
Sep 6, 2018
Messages
2,022
Likes
4,421
Location
Berlin, Germany
@pma Keep an eye on the flexed PCB issue I have highlighted previously. I note yours is bent somewhat too.

PCB flex is guaranteed to break MLCC's in the long term -- even when those are soft-terminal type. With any ripple current present they fail in a spectacular way, simply exploding.
 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
@pma Keep an eye on the flexed PCB issue I have highlighted previously. I note yours is bent somewhat too.


Yeah, I am aware of your experience. One of the reasons this amp is just an evaluation sample and will be tested at least 6 months or 1 year.
 

Mnyb

Major Contributor
Forum Donor
Joined
Aug 14, 2019
Messages
1,292
Likes
1,678
Location
Sweden, Västerås
Good luck with this endeavour, even if you won’t do this commercially ( I don’t know if you’re retired and end enjoy’s life ).

I don’t think it’s ott to actually heatsink these models to their maximum thermal spec , modelling the use case and life expectancy in an economic model is something for big audio companies :D .
And my experience with industrial VSD’s ( variable speed drives frequency converters DC drives etc ) tells the same story about cheating on caps copper and aluminium and ventilation. Temperature management and long term reliability goes together, keep it cool ( room temperature) every degree counts.

That said the amplifier case you use may fit 2 or 3 modules ? The other side heatsink is empty for example. Could more modules fit this case and still maintain good thermal management ?
 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
That said the amplifier case you use may fit 2 or 3 modules ? The other side heatsink is empty for example. Could more modules fit this case and still maintain good thermal management ?
Hello, IMO it would be absolutely safe to run 2 modules in this same case, one per heatsink and get a 4-channel amp. I would like to repeat that this sample/prototype is rather a module evaluation to me than planning a business with power amplifiers. I believe that the experience gained and disclosed might be useful for some assemblers that plan to make implementations into bigger cases like this one.
 

Mnyb

Major Contributor
Forum Donor
Joined
Aug 14, 2019
Messages
1,292
Likes
1,678
Location
Sweden, Västerås
Hello, IMO it would be absolutely safe to run 2 modules in this same case, one per heatsink and get a 4-channel amp. I would like to repeat that this sample/prototype is rather a module evaluation to me than planning a business with power amplifiers. I believe that the experience gained and disclosed might be useful for some assemblers that plan to make implementations into bigger cases like this one.
I very much like the idea of you evaluating this , all others seams to work the other end "how small can i make it " . You gain ( pun intended ) valuable insights of value to others as you say
 

Chr1

Active Member
Joined
Jul 21, 2018
Messages
203
Likes
92
This looks fantastic.
Definitely getting slightly bored with reading about tiny class D desktop amps.
Look forward to following it's development for sure.
 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
Thanks for all comments and replies!

Good sound and a Merry Christmas and a Happy New Year to all!

PF2022.JPG
 

daniboun

Addicted to Fun and Learning
Joined
May 2, 2020
Messages
688
Likes
697
If you are interested, check this review, it is probably the best I read about the NC252MP :


You amp has a neat design, but the case is very huge ) You could get a smaller one ?

I did my NC502MP in this small box, all the Alu Heatsink from the bottom of the module is also in contact with the case via a thermal paste to ensure the best thermal dissipation.

 
Last edited:
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
If you are interested, check this review, it is probably the best I read about the NC252MP :


You amp has a neat design, but the case is very huge ) You could get a smaller one ?

I did my NC502MP in this small box, all the Alu Heatsink from the bottom of the module is also in contact with the case via a thermal paste to ensure the best thermal dissipation.

Thank you, I think if you read this thread you would understandd why the case is "big" with big heatsinks. I want to run it at lowest temperature under any possible conditions like long-term full power. I do not want the module to be limited at 1/5 maximum power in a longer run. The module itself has idle power consumption of 15.5W (you may check in the datasheet, 8.5W SMPS, and 3.5W per amp channel). If I use the heatsink with thermal resistance of 0.4°C/W, the temperature increase at idle is +6.2°C. If you use a conventional implementation with the module mounted on sheet metal, the thermal resistance can be estimated from (and is likely several °C/W).


and the temperature will be increased much much more. The second reason is that the the 19" wide case fits to my audio components. A small box does not. I have no need to use small boxes and to reduce life span and product reliability. However I know - who cares ;).

So this is my design philosophy, I do not care about miniaturization at expense of reliability.

There is a good link by Hypex

BTW I know the review that you have linked here above.

Regarding your amplifier, the analog input wires are placed just above the SMPS and this is really not a good idea. I suppose it has never been measured, right? And the input XLR's placed right next to the AC mains input ....
 
Last edited:
  • Like
Reactions: EJ3

daniboun

Addicted to Fun and Learning
Joined
May 2, 2020
Messages
688
Likes
697
Regarding your amplifier, the analog input wires are placed just above the SMPS and this is really not a good idea. I suppose it has never been measured, right? And the input XLR's placed right next to the AC mains input ....

I shorten the cable to the XLR inputs ) BTW, these cables are shielded.
I did not measure it but compared it to the Audiophonics model, and this one is absolutely dead silence, even with your ears glued to the speakers.

I did not want to hurt you, your amp is fantastic too ) Thanks for your explanation !

here my NC252MP version

 
OP
pma

pma

Major Contributor
Forum Donor
Joined
Feb 23, 2019
Messages
2,902
Likes
5,776
Location
Prague
Below is the amplitude and phase frequency response, the later especially for @maty (i know he loves to see a phase response ;)) and maybe also for @pkane . It is measured by a 2-channel method, both amplitude and phase error of the soundcard are compensated by comparing a measured channel with a reference channel. This is more difficult to make properly in REW, which asks for impulse response delay compensation and time shift, otherwise REW gives improper results in phase response. I did not want to debate this in the PA5 thread. Please note that the NC252MP has no amplitude drop and phase deviation at 20Hz, as it is DC coupled. Again, this can be measured and verified only by the 2-channel method, otherwise the soundcard LF roll-off would be seen in the measurement.

PMA-NC252MP_FR+phase.png


PMA-NC252MP_phase.png
 
Top Bottom