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March Audio P451 Purifi Mono Blocks

AudioSceptic

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#41
Sorry I didn't reply about the dimensions:
330mm x 180mm x 75mm

Cases are made in China, its the only economic option. Have to say the quality and service from the company has been excellent.
That's OK. I've since seen them at your website. No bigger than they need to be, which is good.

Shame you can't get the cases made in Aus for sensible money but that seems to be how things are now.
 

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#42
Someone mentioned measurements. One problem is that my measurement system isnt an Audio Precision APX555. As such my signal generator does not have low enough noise and distortion to test to the same degree of accuracy as Amir. The 27dB gain of the amplifiers brings the noise and distortion levels up.

So FWIW I have below is a comparison of the Purifi reference board, my implementation and the measurement system in loopback at the same signal level. This is the same 5 watts into 4 ohms as Amir measures.

loopback (input gain turned up by 27dB)
motu loopback.png


Purifi reference board
Purifi At 5w.png


March Audio Implementation
MA At 5w.png


The measurement system is clearly the limiting factor, otherwise the only difference is higher low frequency noise with the Purifi.
 
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March Audio

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#44
Why not choose a 20dB gain on the input board as this would mate a standard 4V balanced level pretty well, rather than aiming for a 2V sensitivity?
Simply because the amp will also be used with single ended systems or dacs directly.

You will find most "domestic Hifi" power amps these days are in the region of 25 to 29dB gain. I may release a version next year with selectable gain. I will see what the feedback/requests are.

This has finally given me motivation to build the ultra low distortion signal generator and notch filter I have been meaning to for the last year.
 
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#45
One problem is that my measurement system isnt an Audio Precision APX555.
No need to apologize for your gear. It's perfectly good enough to characterize your product at low levels. Audio Precision are just one manufacturer of test equipment and there have been plenty, and are plenty of other perfectly good test instruments out there with numbers that challenge theirs (Panasonic/R&S etc) They aren't the only game in town, despite what some people would like you to believe. What is more important is comprehensive testing, not off-the-shelf tests with limited data points.

If you want to be different, characterise your products at various loads, frequencies and levels. More data is better than less. Make it a real job for someone to find fault with your rated specifications and be conservative and realistic.

This has finally given me motivation to build the ultra low distortion signal generator and notch filter I have been meaning to for the last year.
Or you could just just sell a ton of amplifiers and buy an AP to buy credibility with a certain subset of the audiophile community who will only be satisfied if there's that little logo on the graphs you publish. Sad, but true.
 
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March Audio

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#46
No need to apologize for your gear. It's perfectly good enough to characterize your product at low levels. Audio Precision are just one manufacturer of test equipment and there have been plenty, and are plenty of other perfectly good test instruments out there with numbers that challenge theirs (Panasonic/R&S etc) They aren't the only game in town, despite what some people would like you to believe. What is more important is comprehensive testing, not off-the-shelf tests with limited data points.

If you want to be different, characterise your products at various loads, frequencies and levels. More data is better than less. Make it a real job for someone to find fault with your rated specifications and be conservative and realistic.



Or you could just just sell a ton of amplifiers and buy an AP to buy credibility with a certain subset of the audiophile community who will only be satisfied if there's that little logo on the graphs you publish. Sad, but true.
My background is test and measurement so yes of course there are alternatives however the problem is we have got to the point with audio components where only the top end Apx555 is good enough to test them.
 
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pos

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#47
I may release a version next year with selectable gain. I will see what the feedback/requests are.
That would be great. That was one of the nice features of the evaluation buffer board.
On the nc400 you have to change or remove an smd resistor to change the gain, but at least it can be done.

I really believe 20dB would be a better target: after all balanced connection is recommended, so that should be the optimized scenario.
Why force the user to loose 6dB of S/N is that scenario? I would rather use a single ended 2V DAC in that case (and that is what I am currently using on my nc400s by the way...)
 

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#49
That would be great. That was one of the nice features of the evaluation buffer board.
On the nc400 you have to change or remove an smd resistor to change the gain, but at least it can be done.

I really believe 20dB would be a better target: after all balanced connection is recommended, so that should be the optimized scenario.
Why force the user to loose 6dB of S/N is that scenario? I would rather use a single ended 2V DAC in that case (and that is what I am currently using on my nc400s by the way...)
I hear you but realistically the only people that may benefit from that extra few dB are those with very high sensitivity speakers. Are we just therefore chasing numbers? I can put my ear on the tweeter and I'm not sure if I can hear any noise.
 
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#50
I would want to have selectable gain in my amp as well.
Not all pre-amp is perfectly linear in all volume level, a selectable gain in power amp is a major feature.
It will allow me to use a better gain structure (higher output on the frontend)

And one more setting to experiment with, we audiophile love that :D
 

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#52
.

If you want to be different, characterise your products at various loads, frequencies and levels. More data is better than less. Make it a real job for someone to find fault with your rated specifications and be conservative and realistic.
Another issue with this is that whilst that might sell to a small sub section of the market, the vast majority of audiophiles
1. Have no understanding of that data
2. Don't believe numbers matter or have any relevance to sound.

It's not how they buy.
 

AudioSceptic

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#53
Another issue with this is that whilst that might sell to a small sub section of the market, the vast majority of audiophiles
1. Have no understanding of that data
2. Don't believe numbers matter or have any relevance to sound.

It's not how they buy.
Surely your market is those who do have some understanding of objective performance? The audiophiles you describe won't even consider stuff like this in the first place.
 

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#54
Surely your market is those who do have some understanding of objective performance? The audiophiles you describe won't even consider stuff like this in the first place.
Actually I have found that's really not the case. The nature of being a small manufacturer means I do talk a lot with customers over email about their requirements and only a tiny percentage have any in depth technical knowledge.
 
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#56
I fear we are creating a new type of audio insecurity, a AP related ultimate numbers disorder.
Funny you should mention this. Just today, I'm finishing the press release for my new company which specializes in comprehensively engineered audio hardware: Objectively Confirmed Design Audio. At OCD Audio, we really sweat the details!

Sorry, Alan.
 

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#57
That is low efficiency tweeters for you :D
Try the same thing with a 110dB+ compression driver/horn (hum, waveguide) combo :D
:)

Which is what 99.9% of people have ;)

Shush! Dont mention the war horns ;)

 
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