March Audio P451 Purifi 1ET400A Mono Blocks

[restorer-john]

Speakers are higher priority ATM.

Where do you think they are going to land price range wise? Under AU2K or 2-3K?

 

[Voxy]

Probably a couple of months. Speakers are higher priority ATM.

u building speakers too?

 

[March Audio]

Where do you think they are going to land price range wise? Under AU2K or 2-3K?

TBC but more than that

 

[March Audio]

u building speakers too?

Yep. Should make their first appearance at the Sydney hifi show in April.

http://www.hifi2020.com

 

[Billy Budapest]

Probably a couple of months. Speakers are higher priority ATM.

Using Purifi speaker drivers?

 

[March Audio]

Using Purifi speaker drivers?

Yes

 

[Billy Budapest]

Yes

Cool. I’ve been waiting for an implementation. They look weird but looks aren’t everything!

 

[Sparky]

I wonder if I would benefit from a pair of these?
I use a Cyrus Stereo 200 power amp into an RME ADI2 DAC using Spendor A7 speakers.

These Purifi amps are really intriguing and seeing how they measured is something else altogether!

Any thoughts @March Audio

 

[March Audio]

I wonder if I would benefit from a pair of these?
I use a Cyrus Stereo 200 power amp into an RME ADI2 DAC using Spendor A7 speakers.

These Purifi amps are really intriguing and seeing how they measured is something else altogether!

Any thoughts @March Audio

Hi @Sparky

I have not heard the Cyrus so it's difficult to tell, however it won't compete technically with the Purifi P451. I can't find a good set of measurements, but Cyrus spec states 0.1 % thd + n ( 60dB sinad) which is very poor, but probably just where they have taken the rated power measurement.

The P451 is also more powerful and will have better current capability but your Spendors are not particularly difficult loads. Dipping to around 6 ohms. The phase angle excursion at about 70Hz isn't so pretty, but it has a reasonable 87dB sensitivity.

Hope that helps

 

[Billy Budapest]

That's for show. When you buy one, this is what you get!

Is that a “Gainclone” amp?

 

[Sparky]

Hi @Sparky

I have not heard the Cyrus so it's difficult to tell, however it won't compete technically with the Purifi P451. I can't find a good set of measurements, but Cyrus spec states 0.1 % thd + n ( 60dB sinad) which is very poor. P451 is way ahead at 104dB (0.0006%).

The P451 is also more powerful and will have better current capability but your Spendors are not particularly difficult loads. Dipping to around 6 ohms. The phase angle excursion at about 70Hz isn't so pretty, but it has a reasonable 87dB sensitivity.
View attachment 49956

Hope that helps

@March Audio

It really does help! Thank you so much!

I wish there was a way to download your knowledge into my brain as it's impressive.

Looks like the Cyrus is going on eBay...

Are you considering any significant upgrades or changes to the design before I look into buying?
I wouldn't want to spend this sort of money only to find you've overhauled it in a month's time!

I ask that question with the best of intentions and mean no disrespect.

 

[March Audio]

Hi @Sparky

I have not heard the Cyrus so it's difficult to tell, however it won't compete technically with the Purifi P451. I can't find a good set of measurements, but Cyrus spec states 0.1 % thd + n ( 60dB sinad) which is very poor, but probably just where they have taken the rated power measurement.

The P451 is also more powerful and will have better current capability but your Spendors are not particularly difficult loads. Dipping to around 6 ohms. The phase angle excursion at about 70Hz isn't so pretty, but it has a reasonable 87dB sensitivity.
View attachment 49956

Hope that helps

@Sparky Found some measurements.

CYRUS Power output at 1% THD+N: 262.4W @ 4 ohms
P451 Purifi output at 1% thd + n : 425 watts at 4 ohms


Frequency response

Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy-speaker load


THD + n v power

(Line up at 50W to determine lines)
Top line = 4-ohm SMPTE IM distortion
Second line = 8-ohm SMPTE IM distortion
Third line = 4-ohm THD+N
Bottom line = 8-ohm THD+N

For reference P451 Purifi at 5 watts is 0.0006% THD + (104dB sinad) and the Cyrus is 0.005% (86dB)


V frequency

(8-ohm loading)
Red line = 1W
Magenta line = 5W
Blue line = 10W
Cyan line = 30W

Spectrum

Stereo mode
1kHz signal at 10W into an 8-ohm load


So not terrible, but certainly not as good as the P451. The major thing that caught my eye was just how much distortion increased with frequency. Really not good in that respect.

Other thing I noticed is the Cyrus seems quite noisy. 114uV V about 25uV for the Purifi. Probably only an issue for high sensitivity speakers.

 

[March Audio]

@March Audio

It really does help! Thank you so much!

I wish there was a way to download your knowledge into my brain as it's impressive.

Looks like the Cyrus is going on eBay...

Are you considering any significant upgrades or changes to the design before I look into buying?
I wouldn't want to spend this sort of money only to find you've overhauled it in a month's time!

I ask that question with the best of intentions and mean no disrespect.

No changes that will affect sound quality, minor case mods.

 

[March Audio]

@Sparky

One more technical issue I have noticed is that the frequency response of the Cyrus is significantly affected by load.

Red line = open circuit
Magenta line = 8-ohm load
Blue line = 4-ohm load
Cyan line = NHT dummy-speaker load

At 8 ohms its flat past 20kHz, but look at the 4 ohm blue line. It's 2dB down at 20kHz. That's a huge variation! Most definitely audible. The cyan simulated speaker load is also pretty wobbly.

This means a variable sound dependant on the speaker. Do not use speakers with a low impedance at high frequencies with this amp. Luckily your Spendors impedance rises at HF.

I know I have a vested interest here but the more I look at the Cyrus performance the less impressed I am.

 

[restorer-john]

I know I have a vested interest here but the more I look at the Cyrus performance the less impressed I am.

I think it's pretty safe to say the AP plots for the Cyrus and the Purifi are not in the same league. No vested interest whatsoever here, but I'd go for the Purifi if I was in the market for high performance Class D.

 

[Sparky]

@March Audio

Good morning.

So, getting ready for work and I see you've added more information regarding the Cyrus.
I really appreciate this as only strengthens my resolve to upgrade. Don't get me wrong, the Cyrus is a good little amplifier and it sounds quite good too considering.
It's a hybrid class D and is designed and built in-house at Cyrus which is not something I'm a fan of as the numbers can be "forced" to look great when in actual fact, they're not as rosey as you would imagine.

I think you've got me sold on the clear technological advances of your unit compared to the Cyrus.
The measurements say it all.

It's safe to say that you may well have a new customer in the very near future.

@restorer-john - Agree with you here. He is stating facts and I would rather hear truthful information than anything else.

 

[ironhorse128]

@March Audio

What is the idle power consumption of one of the P451? I am curious as I am planning on buying two and I heard that the idle power consumption might be up to 16 watt.

 

[March Audio]

Hi @ironhorse128

I will double check and remeasure (probably tomorrow) but 16 watts isn't far off, might be a bit lower nearer 12 watts.

To be clear this is switched on but no music playing. That's actually very efficient.

In standby its around 0.2 watts.

My general recomendation is not to leave any electronics like this on permanantly. You just life the capacitors more quickly for no gain in sound quality, plus of course waste electricity.

Btw we have just implemented 12v trigger functionality on the control board if that helps.

 

[Sparky]

Hi @ironhorse128

I will double check and remeasure (probably tomorrow) but 16 watts isn't far off, might be a bit lower nearer 12 watts.

To be clear this is switched on but no music playing. That's actually very efficient.

In standby its around 0.2 watts.

My general recomendation is not to leave any electronics like this on permanantly. You just life the capacitors more quickly for no gain in sound quality, plus of course waste electricity.

Btw we have just implemented 12v trigger functionality on the control board if that helps.

Damn..... I wish I would've known that before I bought my P451's!

Oh well, who cares about 12W idle when you have these babies in your system!

 

[Sparky]

@March Audio

What is the idle power consumption of one of the P451? I am curious as I am planning on buying two and I heard that the idle power consumption might be up to 16 watt.

Do not hesitate to buy if you're in the market.
You will not go wrong I assure you!

One very very happy customer here!