• 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). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

March Audio P701 Mono Block Power Amp

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#1
Just a quck update on the forthcoming P701 monoblock power amp.

I was going to be releasing a NC500 based mono block amp next month, however the NC1200 module has just been released and I will be utlising this module instead. The NC1200 has basically the same or better performance than the NC500. Major difference is that its drive capabilities have been greatly improved. The NC1200 8 ohm rating is 400 watts, 4 ohm is 700 watts and 2 ohms is 1200 watts. Current output is now 38 amps. The NC500 would manage 400 Watts, 700 Watts and 550 Watts and 26 amps respectively. As such this will drive the most difficult of speaker loads. Noise and distortion levels really are superb. In the typically used range, around 5 watts THD is about 0.0007% or -103 dB.

Note the buffered 128dB SNR and 20uV noise levels

Some Hypex data

n1.PNG

n3.PNG

n4.PNG

n5.PNG
 
Last edited:

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#5
Very much looking forward to receiving a pair, I didn’t think Hypex would release the 1200!
Keith
Indeed. My understanding is that along with the NC2K it was reserved for exclusive use by certain OEM companies. Obviously this has changed!
 

DonH56

Technical Expert
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
3,162
Likes
3,860
Location
Monument, CO
#10
Interesting. I noticed the 40-ohm source impedance; that is pretty low, at least IME, when I have seen more like 100 ohms to 1k ohms for preamps and AVR preamp outputs. Wonder what the noise etc. is with a 100-ohm source? Are you going to be designing your own input buffer (that and power supplies seems to be one of the bigger differentiators in performance among Hypex amps)?

The FR is spec'd at 0 to 50 kHz, but PBW only down to 20 Hz. Is that at -3 dB or just a number they picked?

Curious the hump in distortion around 30 W.

What for a power supply?

This one has me curious and more than a bit interested. Like to know how it sounds on Salon2's too (so can hardly wait for Amir's testing!) - Don
 

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#11
The module can be used in two ways, using its in built input buffer or with it bypassed so you can add your own, so it's not always clear which condition they are referring to with some of the specs. However I suspect that was to benefit the non buffered scenereo which has a low input impedance of 5.3 k, or maybe even just the output z of the sig gen.

Doesn't an output impedance of 1k seem very high for a pre amp? 100 seems more typical.

I will get the modules next week so will know more then. In an earlier revision of the datasheets it does not have the 20hz lower limit. 35kHz upper limit is due to dielectric losses according to note 2.

When you say differentiators, is that from a marketing or real performance POV? :)

I will be using the built in buffer initially, until such point that I see a genuine technical advantage from an alternative.

The psu is the smps1200A700. Specs above tested with that psu.
 
Last edited:

DonH56

Technical Expert
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
3,162
Likes
3,860
Location
Monument, CO
#14
The module can be used in two ways, using its in built input buffer or with it bypassed so you can add your own, so it's not always clear which condition they are referring to with some of the specs. However I suspect that was to benefit the non buffered scenereo which has a low input impedance of 5.3 k, or maybe even just the output z of the sig gen.

Doesn't an output impedance of 1k seem very high for a pre amp? 100 seems more typical.

I will get the modules next week so will know more then. In an earlier revision of the datasheets it does not have the 20hz lower limit. 35kHz upper limit is due to dielectric losses according to note 2.

When you say differentiators, is that from a marketing or real performance POV? :)

I will be using the built in buffer initially, until such point that I see a genuine technical advantage from an alternative.

The psu is the smps1200A700. Specs above tested with that psu.
Thanks Alan.

Tube preamps are what I had in mind for 1K-ohm Zout. The handful of SS preamps I checked were in the 100 to 470 ohm range with one more like 10 ohms (don't recall them all, just looked around bit at manuals and reviews I could find in a quick search).

Differentiators, well, both, of course... But since the datasheets and reviews only call out the end-to-end performance it's hard to see what real (technical) performance advantages are actually from the front-end buffers. Subjective reviews all claim better performance/sound with this or that "custom" input stage, natch. I seem to recall one manufacturer claiming lower noise and better noise/CMRR with their discrete balanced input but I don't recall which manufacturer. But of course marketing is what sells products most of the time... I was moreso wondering if you had tried rolling your own front end buffer and what the results were, or if you had any solid technical data showing if they really helped or not. Completely not challenging, just curious if the supposed advantages claimed by others could be (had been) verified or not.

Wonder what the gain of the buffer circuit is? Does it accept balanced and unbalanced inputs (SE and differential?)
 

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#16
Thanks Alan.

Tube preamps are what I had in mind for 1K-ohm Zout. The handful of SS preamps I checked were in the 100 to 470 ohm range with one more like 10 ohms (don't recall them all, just looked around bit at manuals and reviews I could find in a quick search).

Differentiators, well, both, of course... But since the datasheets and reviews only call out the end-to-end performance it's hard to see what real (technical) performance advantages are actually from the front-end buffers. Subjective reviews all claim better performance/sound with this or that "custom" input stage, natch. I seem to recall one manufacturer claiming lower noise and better noise/CMRR with their discrete balanced input but I don't recall which manufacturer. But of course marketing is what sells products most of the time... I was moreso wondering if you had tried rolling your own front end buffer and what the results were, or if you had any solid technical data showing if they really helped or not. Completely not challenging, just curious if the supposed advantages claimed by others could be (had been) verified or not.

Wonder what the gain of the buffer circuit is? Does it accept balanced and unbalanced inputs (SE and differential?)
Hi Don

My view is that I am more than a little dubious regarding op amp rolling. Any differences will be minimal with decent op amps and circuits. I have never seen any measurements from any of the manufacturers that offer alternative op amps for the Hypex range that demonstrate their efficacy, and any circuit/opamp that can make a genuinely noticeable difference to the sound (as opposed to audiophile delusion) is more than likely significantly colouring the sound/has performance issues.

When I get the modules in my paws next week I see what the standard buffer implementation is, perform some measurements and gain an informed view on the worth of exploring alternatives.

Datasheet shows 11.6dB unbuffered V 27.8dB buffered gain, so 16.2 dB. Any balanced input will accept SE so no issues there :)
 

DonH56

Technical Expert
Technical Expert
Patreon Donor
Joined
Mar 15, 2016
Messages
3,162
Likes
3,860
Location
Monument, CO
#17
Hi Don

My view is that I am more than a little dubious regarding op amp rolling. Any differences will be minimal with decent op amps and circuits. I have never seen any measurements from any of the manufacturers that offer alternative op amps for the Hypex range that demonstrate their efficacy, and any circuit/opamp that can make a genuinely noticeable difference to the sound (as opposed to audiophile delusion) is more than likely significantly colouring the sound/has performance issues.

When I get the modules in my paws next week I see what the standard buffer implementation is, perform some measurements and gain an informed view on the worth of exploring alternatives.

Datasheet shows 11.6dB unbuffered V 27.8dB buffered gain, so 16.2 dB. Any balanced input will accept SE so no issues there :)
Got it, thanks. I was not sure what the default buffer was (if any -- somehow I missed that; 70+ hour workweeks will do that for you, and then I had a long rehearsal last night, pooped out!) It stands to reason they would not have such great performance numbers without something decent, and equally stands they would not be so well-respected (and have such significant market share) if their default implementation was, errr, substandard. No thought to hand you more work, just purely curiosity on my part (and a misread of the spec).

Buffer's probably not needed in a pro amp.

I remember when people started substituting MOSFET video opamps into audio preamps and then wondered why the noise went through the roof... They thought a FET was FET and didn't quite understand the physics differences between a JFET and a MOSFET. One guy tried using mW GaAs FETs figuring an abundance of bandwidth would be great. I actually got to explain why a 50 GHz transistor with a 1/f noise corner of about 100 MHz was not the best choice for his preamp... A little knowledge and all that jazz (or should I say "all that noise" ;) ).

A decent 2-ohm power spec definitely makes these more interesting to me. And probably @amirm , though he's likely buried under a long list of things to test (and a bit of snow).
 

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#19
It looks like it can also jump start your car if needed.
Welding is another possible use :)

Yes I think it is all the power anyone would domestically need. I do not have any plans to implement their NC2K module. 2.5kW into 4 ohms and 48 amps.
 

March Audio

Major Contributor
Manufacturer
Patreon Donor
Joined
Mar 1, 2016
Messages
3,961
Likes
3,839
Location
Perth Western Australia
#20
Got it, thanks. I was not sure what the default buffer was (if any -- somehow I missed that; 70+ hour workweeks will do that for you, and then I had a long rehearsal last night, pooped out!) It stands to reason they would not have such great performance numbers without something decent, and equally stands they would not be so well-respected (and have such significant market share) if their default implementation was, errr, substandard. No thought to hand you more work, just purely curiosity on my part (and a misread of the spec).

Buffer's probably not needed in a pro amp.

I remember when people started substituting MOSFET video opamps into audio preamps and then wondered why the noise went through the roof... They thought a FET was FET and didn't quite understand the physics differences between a JFET and a MOSFET. One guy tried using mW GaAs FETs figuring an abundance of bandwidth would be great. I actually got to explain why a 50 GHz transistor with a 1/f noise corner of about 100 MHz was not the best choice for his preamp... A little knowledge and all that jazz (or should I say "all that noise" ;) ).

A decent 2-ohm power spec definitely makes these more interesting to me. And probably @amirm , though he's likely buried under a long list of things to test (and a bit of snow).
@DonH56 after a look at the NC1200 modules I have decided that I will be at least testing an external buffer. I do need to implement some input filtering with this module as the on board buffer is wide open, so I am going to knock up a board for this and to use either the LME49724 or the OPA1632 as a buffer.
 

Similar threads

Top Bottom