March Audio P451 Purifi 1ET400A Mono Blocks

[March Audio]

Hi

Our P451 Purifi MonoBlocks are now ready, will be on the website this weekend.

They follow the form of all our amplifiers, compact enclosure milled from aluminium block with tough anodised finish.

Features:

• OPA1632 based fully differential input buffer with very low noise LT3045/94 voltage regulators. These are particularly suited for regulating the SMPS output as they have high PSRR at high frequencies where most of the SMPS noise resides. These also feed the analogue sections on the 1ET400A module.
• Separate regulated supply for the 1ET400A digital section (for info its actually missing on the prototype board shown below).
• Solid copper ETI Research speaker binding posts.
• Balanced XLR inputs (XLR/TRS combi jacks) also fully compatible with single ended RCA with adaptor cable.
• Audio input RF filter
• Touch switch power control
• Mogami balanced signal cable
• Speaker cable tightly twisted
• Mains input booted, cabling twisted, double insulated and routed away from speaker/signal wiring/boards as far as practicable.
• Power Supply is significantly over specified for a single channel amp.
• All the lovely Purifi technical performance and sound

Piccies

Just for info the bottom plate actually fits the other way round (psu to front) in the top shell.

 

[restorer-john]

Beautiful.

An object lesson in neatness, cable dress, fit and finish.

 

[amirm]

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

 

[Harry]

Looks great!
But, no need for RCA connection?
There must be some audiophiles who want to connect their preamps which only have RCA out.

 

[restorer-john]

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

Ciunas's new amplifiers certainly look better designed than the D/As...

 

[Krusty09]

Hey.

Those binding posts in the pictures look crazy big to me but in the same breath the whole amp looks very professional. Well done maestro.

 

[Lac013]

How much for a pair?

 

[March Audio]

Looks great!
But, no need for RCA connection?
There must be some audiophiles who want to connect their preamps which only have RCA out.

Hi @Harry

Its a good question. There is actually a very good technical reason for it. The amplifier is fully balanced input. Balanced inputs are fully compatible with single ended RCA, however for best performance you have to follow correct implementation of the conversion from one to the other.

The correct way to do this is not to have RCA sockets on the amp itself. You should only terminate the balanced screen at the far (source) end like this;

Unfortunately RCA single ended connections have a fundamental flaw. The low signal conductor (screen) is often connected to the chassis of components and mains earth. This means that noise currents flow in the shield between components and modulate the signal. Its a pretty dumb idea really. Its the fundamental cause of the buzz when you have a "ground loop", but even if its not overtly noticeable as in that extreme circumstance, its still a source of unwanted noise.

In balanced connections the shield is a 3rd separate wire from the signal conductors. So if wired as above those noise currents dont flow in the signal conductors, even if the source is single ended RCA, and you maintain most of the benefit of balanced connections. If you put the RCA socket on the amp the noise currents still flow in the cable shield.

So this is why I dont put RCA sockets on the amps. A simple RCA to XLR cable solves the problem. Yes we sell those too

 

[March Audio]

Hey.

Those binding posts in the pictures look crazy big to me but in the same breath the whole amp looks very professional. Well done maestro.

Thanks

Yes, fairly big but they allow for good access for large CSA cable and large spades. Plus bananas of course.

 

[Rja4000]

Speakon option?

 

[March Audio]

How much for a pair?

$2600 US

 

[March Audio]

Speakon option?

Sorry no, reason being it just makes things difficult for your average consumer. It may well be a good, possibly better connector, but not much real world advantage over say locking bananas.

 

[Thomas savage]

Lovely!

They will look and sound at home in any true hifi system .

$2500 US

Incredible, cutting edge amp moduels put together with such style and pride offered at this price.

What a time to be a audio enthusiast.

 

[ofrappier]

Hi,

What's balanced Input sensitivity ?
Max input?

Switchable as Benchmark amplifier ? (Benchmark manual):

Regards,

Olivier F.

 

[Victoria]

Hah, absolutely love the way you twist the ribbon cables and then run them over the top of the power supply heat sink; this is totally something I'd do as well! If this is how neatly every single one of your products are assembled, I'm impressed!

Have you guys ever considered another colour option for your enclosures though? Never really been a big fan of black.

And finally: are there any plans on ever having a DAC with a volume control? I really do prefer working with volume controls external to my PC, especially with that much oomph on tap from the power amplifiers.

Edit: oh my word I just noticed the standoffs and the additional PCB you mounted onto the back of heat sink too! Absolutely beautiful!

 

[March Audio]

Hi,

What's balanced Input sensitivity ?
Max input?

Switchable as Benchmark amplifier ? (Benchmark manual):

View attachment 40707


Regards,

Olivier F.

Hi

Gain is fixed 26.5dB so 2 V rms will get it to max output.

 

[March Audio]

Hah, absolutely love the way you twist the ribbon cables and then run them over the top of the power supply heat sink; this is totally something I'd do as well! If this is how neatly every single one of your products are assembled, I'm impressed!

Have you guys ever considered another colour option for your enclosures though? Never really been a big fan of black.

And finally: are there any plans on ever having a DAC with a volume control? I really do prefer working with volume controls external to my PC, especially with that much oomph on tap from the power amplifiers.

Edit: oh my word I just noticed the standoffs and the additional PCB you mounted onto the back of heat sink too! Absolutely beautiful!

We did originally plan to have silver finish but it just was not popular when tried with the DACs. The cost of the extra inventory for such small demand just doesnt make business sense Im afraid.

An updated DAC is a long term plan but not a priority. Next are the speakers.

 

[pma]

Very nice job, March Audio. And I agree with your decision not to use the RCA input connector and to offer RCA ==> XLR 3 wire solution instead, which subtracts noise across the ANA GND wire. Optimally if there is a resistor matching with output impedance of the preceding sound source, DIYer might put it directly into RCA connector.

 

[solderdude]

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

Is this built by JohnK ?

 

[restorer-john]

Is this built by JohnK ?

Clearly not @solderdude , what were you thinking? The soldering is in a whole other league of excellence.