March Audio P502 Stereo Amplifier Measurements

[DonH56]

Wonder if a cable ground came loose or was cold-soldered (perhaps on the module itself)?

 

[March Audio]

Wonder if a cable ground came loose or was cold-soldered (perhaps on the module itself)?

Certainly a distinct possibility.

 

[AudioTodd]

oh thats a long story, to do originally with a cock up by the case manufacturer. The next batch of cases will be around the other way, and in fact I may even mark channel 1 and 2 as Benchmark do. Remember it is just labelling. For a power amp it has no relevance which way you actually hook the cables up so long as the correct input goes to the correct output, no need to look The XLR goes to the posts directly underneath.

Gotta say I love your participation here. Since I’m probably Benchmark’s best customer (well over 10 components from them) I’m not in the amp market, but if I need a compact powerhouse I can have confidence in, I’m gonna seriously give your gear a chance as I totally respect and appreciate what you have added to this invaluable forum. Cheers!

 

[Putter]

While I have no direct interest in the product, although I have wondered for years now why digital amps haven't become universal as they seem to be in less expensive consumer products like compact stereos (Sony comes to mind), it's refreshing to see this kind of open exchange between manufacturer and reviewer. Yes, I see similar interaction in Stereophile, but it usually comes down to manufacturer setting up their hand picked amp/speakers or replacing their 'defective' component with no explanation.

 

[confucius_zero]

Okay but no panther no recommendation? what's the verdict?

edit: ahhh "This is not a review because the @March Audio is a long time member of the forum and I like to avoid conflict of interest. " gotcha.

 

[Samoyed]

Well....

 

[bcurtin]

@Amir would it be possible to measure THD+N vs. frequency as a function of power up to the max rated power? You had performed a similar measurement with the NC400 DIY amplifier and curious how this one behaves.

 

[restorer-john]

@Amir would it be possible to measure THD+N vs. frequency as a function of power up to the max rated power? You had performed a similar measurement with the NC400 DIY amplifier and curious how this one behaves.

We know how it behaved, it shut down prematurely.

My heavy stress test of frequency versus power caused the unit to shut down momentarily. I did not retry it as I don't want to risk damaging the unit.

It was to be expected and it has been predicted by me and others due to various reasons, not the least of which is the inability to maintain high frequency at high amplitude without the current sensing loop on the output coil telling the unit to shut down to prevent cooking the LPF capacitors. The test apparently starts at high frequencies and steps back to low, perhaps if Amir went the other way (low to high), it would get a lot further along before the protection kicks in.

Amir was too scared he'd blow it up (it's not his to destroy or damage), so it didn't get tested for that again. A pity, because we don't know how long it lasted, or where it triggered off. Consider other amplifier tests, he has published the results showing where they shut off...

I'd like to see some investigation on the channel differences during the warmup. Consider one channel is right up against the power supply txf and components, the other is spaced away a little.

The amplifier clearly has a ton of short term power in a very compact package. These Class D amplifiers are likely an excellent choice for a lot of people and March's implementation is one of the more attractive offerings out there.

 

[bcurtin]

We know how it behaved, it shut down prematurely.



It was to be expected and it has been predicted by me and others due to various reasons, not the least of which is the inability to maintain high frequency at high amplitude without the current sensing loop on the output coil telling the unit to shut down to prevent cooking the LPF capacitors. The test apparently starts at high frequencies and steps back to low, perhaps if Amir went the other way (low to high), it would get a lot further along before the protection kicks in.

Amir was too scared he'd blow it up (it's not his to destroy or damage), so it didn't get tested for that again. A pity, because we don't know how long it lasted, or where it triggered off. Consider other amplifier tests, he has published the results showing where they shut off...

I'd like to see some investigation on the channel differences during the warmup. Consider one channel is right up against the power supply txf and components, the other is spaced away a little.

The amplifier clearly has a ton of short term power in a very compact package. These Class D amplifiers are likely an excellent choice for a lot of people and March's implementation is one of the more attractive offerings out there.

Read the review but missed that comment - thanks for pointing out that Amir had tried but couldn't run this test. The NC252MP data sheet shows this behavior to half the rated power, so I was curious if at least that data was repeatable and hopefully testing to higher power if the amp is capable of it without going through the process you described.

 

[Wes]

The March seems to be the least expensive amp at 92 SINEAD or above - is that right?

 

[restorer-john]

The NC252MP data sheet shows this behavior to half the rated power

It would have no problem with the same test at half rated power.

Realistically, as March will no doubt point out, testing at high power and high frequencies is not a typical use scenario. One of the inevitable compromises you must make for high powered Class D is preventing excess dissipation in the LPF filter components (and HF THD). The easiest way is to limit the HF power to take advantage of the typical spectrum of recorded music.

Play some test tones and it all goes out the window. But realistically, who plays HF test tones at high power if they still want a pair of working tweeters? Nobody.

I'm trying to be philosophical about Class D. It's incredibly powerful, efficient, compact and lightweight and performs pretty well. It's not state of the art in the performance stakes due to fundamentals it really can't do much about. BP has pushed the performance out of the joke category and into the upper echelons of HiFi in a few short years. That's an incredible achievement. It's not for me and likely never will be, but it's just the shot for this modern world.

 

[boXem]

It would have no problem with the same test at half rated power.

Realistically, as March will no doubt point out, testing at high power and high frequencies is not a typical use scenario. One of the inevitable compromises you must make for high powered Class D is preventing excess dissipation in the LPF filter components (and HF THD). The easiest way is to limit the HF power to take advantage of the typical spectrum of recorded music.

Play some test tones and it all goes out the window. But realistically, who plays HF test tones at high power if they still want a pair of working tweeters? Nobody.

I'm trying to be philosophical about Class D. It's incredibly powerful, efficient, compact and lightweight and performs pretty well. It's not state of the art in the performance stakes due to fundamentals it really can't do much about. BP has pushed the performance out of the joke category and into the upper echelons of HiFi in a few short years. That's an incredible achievement. It's not for me and likely never will be, but it's just the shot for this modern world.

Is this new zen philosophy face to class D part of new year's good resolutions?

Just kidding, it's really appreciated, especially on the internet, when people are able to change their standpoint to a more moderate one. It's not everyday we can see this.

 

[murraycamp]

Amir - quick question. I notice on the SINAD graph there are a couple of amps on the chart that I don't see measurements/reviews for (the Nord Signature 1200 and the Purifi dual mono 990). Are those numebrs taken off the spec sheets or did I just miss the reviews? Thanks in advance.

 

[hyperknot]

I'm trying to be philosophical about Class D. It's incredibly powerful, efficient, compact and lightweight and performs pretty well. It's not state of the art in the performance stakes due to fundamentals it really can't do much about. BP has pushed the performance out of the joke category and into the upper echelons of HiFi in a few short years. That's an incredible achievement. It's not for me and likely never will be, but it's just the shot for this modern world.

@restorer-john asking as someone still super new to this scene, what would be a device which you'd prefer over an NC400 or a Purify based amp for performance? Say, in the same power region, aroung 400W.

 

[amirm]

Amir - quick question. I notice on the SINAD graph there are a couple of amps on the chart that I don't see measurements/reviews for (the Nord Signature 1200 and the Purifi dual mono 990). Are those numebrs taken off the spec sheets or did I just miss the reviews? Thanks in advance.

I should be more consistent with names. Here they are:
https://www.audiosciencereview.com/...-se-1et400a-dual-mono-stereo-amp-review.9938/
https://www.audiosciencereview.com/...e-nc1200dm-signature-stereo-amp-review.10261/

 

[March Audio]

@restorer-john asking as someone still super new to this scene, what would be a device which you'd prefer over an NC400 or a Purify based amp for performance? Say, in the same power region, aroung 400W.

Bruno designed both. I'm probably biased but the Purifi is a step forward in performance and sound IMO.

 

[blueone]

While I have no direct interest in the product, although I have wondered for years now why digital amps haven't become universal as they seem to be in less expensive consumer products like compact stereos (Sony comes to mind), it's refreshing to see this kind of open exchange between manufacturer and reviewer. Yes, I see similar interaction in Stereophile, but it usually comes down to manufacturer setting up their hand picked amp/speakers or replacing their 'defective' component with no explanation.

Don't call Class D amps "digital", even by accident. You'll get a multi-post lecture here. ;-) But don't feel bad; even an Audio Precision article called them digital, and mindlessly got me to do it. Wikipedia has a moderately understandable explanation (to those without an analog electrical engineering background) of how they work:

https://en.wikipedia.org/wiki/Class-D_amplifier

Note the terminology section.

 

[restorer-john]

@restorer-john asking as someone still super new to this scene, what would be a device which you'd prefer over an NC400 or a Purify based amp for performance? Say, in the same power region, aroung 400W.

Look, if I was starting in HiFi and wanted to leap to the top of the class with amplification, the Purifi based amplifiers are a great option. So is the Benchmark. Both are class leading, compact, lightweight and not too expensive. Compared to the prices (adjusted for inflation or not) we paid for high powered, low distortion amplifiers back in the day, those two are realistically great value.

For me and most of us, HiFi was a slow progression based on affordability and keeping up with the advances as they occurred. With the benefit of our collective hindsight, audiophiles today can skip a lot of the incremental upgrades and pointless sideways steps most of us have taken over the decades.

So, unless the appeal of vintage battleship build or retro-chic is your thing, you'd be hard pressed to find a better platform to build an audiophile system around than amplifiers such as these. I'd buy two monoblocks and be done with it.

On that note, I'm off to my storeroom to find some vintage gear to play with, who knows, after 10 years sitting in a box, it'll likely need some work. Like I need more jobs...

 

[hyperknot]

Look, if I was starting in HiFi and wanted to leap to the top of the class with amplification, the Purifi based amplifiers are a great option. So is the Benchmark. Both are class leading, compact, lightweight and not too expensive. Compared to the prices (adjusted for inflation or not) we paid for high powered, low distortion amplifiers back in the day, those two are realistically great value.

Thanks a lot, it really helps to put things in perspective. What I see about vintage gear is that even though they are lovely (all my cars were 15-25 year old Japanese cars, actually Made in Japan), if you are an absolute beginner with electronics then it's simply not a realistic choice to buy something 30-40 years old for up to say 1k EUR.

I'm afraid I'd immediatley need to find a local repair guy and hope he can bring it back to specs. 1k EUR can (almost) buy me a nice DIY Purify system which might even serve me for the next 10 years without touching it (though the SMPS might need to be replaced after a while).

 

[confucius_zero]

My lord, is this enough to effectively power Magnepans to 90db 1ft distance at least??