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March Audio P451 Purifi 1ET400A Mono Blocks

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AudioSceptic

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Hi Mike

No its not a problem, won't cause any harm.

BTW the newer versions of the control board default to off.
I'm confused. I suggested smart plugs a while ago and then asked you if that would be OK, to which you gave a different answer. I must be missing something.
Are they situated such that you can't easily switch them off, or disconnect them from the mains? If so, have you considered using a smart plug like the Meross <https://amzn.to/3bn5lLb>? I have the version with built-in energy monitor so I can not only switch things on/off on a schedule (or on demand from phone app or using Alexa), but also see how many watts are being used.

[Edit] March Audio, would there be a problem with just switching off the mains, as opposed to a "controlled" power off/on?
Hi

Only problem is it wouldn't work :). The amps at mains power application default to standby.
 
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The current version of control board defaults to power off (standby) at application of mains power. This was a change made due to customer feedback and to coincide with adding the 12 volt trigger functionality.

Mike's version is an older one which would default to on.

Hope that helps :)
 
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AudioSceptic

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The current version of control board defaults to power off (standby) at application of mains power. This was a change made due to customer feedback and to coincide with adding the 12 volt trigger functionality.

Mike's version is an older one which would default to on.

Hope that helps :)
Yes, it does, but I thought we were talking about Mike's (Sparky's?) version anyway. Whatever, it all makes sense now, thanks. :)
 

Mashuri

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These look awesome, especially with your OCD attention to detail. I just ordered a pair to power my KEF Reference 1’s. I’ll likely get a NAD C658 (yes, I read Amir’s review) as my source and see how everything works together post-calibration.
 

Sparky

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These look awesome, especially with your OCD attention to detail. I just ordered a pair to power my KEF Reference 1’s. I’ll likely get a NAD C658 (yes, I read Amir’s review) as my source and see how everything works together post-calibration.

They look the part mate. Love the machined metal and slightly curved edges. They're a quality bit of kit. :cool:
 

Mashuri

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I’ve had these for a month now and they are awesome! Next, I plan on ordering a DAC8 Pro but have no idea what output voltage I should specify. Any suggestions?
 

Matt_Photo

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They look the part mate. Love the machined metal and slightly curved edges. They're a quality bit of kit. :cool:
Hi Sparky, am I right in thinking you purchased the amp in the end to replace the Cyrus Stereo 200? What are your thoughts about the differences? I have a Cyrus 8.2 DAC integrated and am consider changing it all up and moving to one of Alan's amps and then changing for a dedicated Pre to go with my Chord Qutest. I might have considered the RME ADI 2 if it had one more digital in, especially knowing it can be used straight into the amp to control volume.
Anyway love to know your thoughts if you did make the jump from Cyrus. Cheers
 

Sparky

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Hi Sparky, am I right in thinking you purchased the amp in the end to replace the Cyrus Stereo 200? What are your thoughts about the differences? I have a Cyrus 8.2 DAC integrated and am consider changing it all up and moving to one of Alan's amps and then changing for a dedicated Pre to go with my Chord Qutest. I might have considered the RME ADI 2 if it had one more digital in, especially knowing it can be used straight into the amp to control volume.
Anyway love to know your thoughts if you did make the jump from Cyrus. Cheers

Hi Matt_Photo.

Yeah, I tried the Cyrus and found it to be quite good at first but it's flaws soon became apparent.
The noise floor was the main issue with me being able to hear tweeter hiss from over a metre away!
I wanted to take advantage of the "audio sense" technology whereby the unit would switch itself on when it detects an audio signal and off when a signal was no longer present.
This was extremely flawed in use and I found it to switch off during music/movies and sometimes not switch on at all when I knew audio was playing.

The P451 monoblocks are in an entirely different league though! :)
Noise floor is super low and only hear hiss at the tweeters if my ear is pressed against the tweeter.
Very powerful with oodles of current on tap.
They look the part and run warm to the touch after hours and hours of use in a semi-enclosed cabinet.
All high quality parts used with no issues at all during my use of them. (That is not strictly true as I had to send one back for a diagnostic but it turns out a loose subwoofer cable in the back of my preamp was causing some anomalies so no fault on the part of March Audio and Alan looked after me throughout the whole process).

The newer version has the option of a trigger input which I would've loved to have but it wasn't part of the design of my units I'm afraid.
I use smartplugs instead and use alexa to turn them on and off when needed.

I use an Anthem STR preamp with mine and its a great match. I did have an RME ADI2 FS for a while and that was a fantastic unit too.

I highly highly recommend Alan's power amp range.

Mike.
 

Here2Learn

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@March Audio
One of the things that bothers me about all NCore/Purifi amps to date is the lack of a pass-through output of the input for bi/tri-amping. It used to be common for power amps to have something like this.

Without one, it would mean either requiring a pre-amp with dual outputs that operate together, or a DAC with variable output on multi-channels like the Okto Research DAC8PRO.

Have you thought about passing the input through so bi/tri-amping is possible? I'm potentially interested in the P451 if it had such a feature
 

DonH56

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@March Audio
One of the things that bothers me about all NCore/Purifi amps to date is the lack of a pass-through output of the input for bi/tri-amping. It used to be common for power amps to have something like this.

Without one, it would mean either requiring a pre-amp with dual outputs that operate together, or a DAC with variable output on multi-channels like the Okto Research DAC8PRO.

Have you thought about passing the input through so bi/tri-amping is possible? I'm potentially interested in the P451 if it had such a feature

Normally bi- or tri-amping requires a line-level filter network (crossover) before the amplifiers. I do not understand why a "pass-through" is needed?

I do not recall such a feature being common on power amps in the past.

If all you want are additional preamp outputs, they make splitter cables for that, but that alone would not provide the crossover needed for bi/tri-amping.

Confused - Don
 
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March Audio

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@March Audio
One of the things that bothers me about all NCore/Purifi amps to date is the lack of a pass-through output of the input for bi/tri-amping. It used to be common for power amps to have something like this.

Without one, it would mean either requiring a pre-amp with dual outputs that operate together, or a DAC with variable output on multi-channels like the Okto Research DAC8PRO.

Have you thought about passing the input through so bi/tri-amping is possible? I'm potentially interested in the P451 if it had such a feature
Hi

I have to say I don't think I have ever seen any power amp with this feature. Sorry no the p451 will not have this feature.

Bi/tri amping whilst still using the speakers internal crossover is IMO of little benefit. However if you wanted to do this just use a signal splitter. The input impedance is high enough that paralleled amp inputs shouldn't cause an issue for any decent source.

Bi/tri amping and using external digital crossover is a different thing (very much worthwhile) where you would require a multiple output dac.
 
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March Audio

March Audio

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Hi Matt_Photo.
I wanted to take advantage of the "audio sense" technology whereby the unit would switch itself on when it detects an audio signal and off when a signal was no longer present.
This was extremely flawed in use and I found it to switch off during music/movies and sometimes not switch on at all when I knew audio was playing.



Mike.
This is our reason for not implementing that feature. In my experience it never behaves reliably.
 

Here2Learn

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I have to say I don't think I have ever seen any power amp with this feature. Sorry no the p451 will not have this feature.

ATC P2 Pro is one example.

From their manual:

"Single ended inputs via RCA phono sockets and differential (balanced) inputs via XLR sockets are provided. Each channel has two phono input sockets, the ‘Link’ phono sockets may be used to connect the amplifier inputs to a further ATC power amplifier, for instance when bi-amping, or as a subwoofer channel. If linking multiple P1/P2 amplifiers together, the single ended inputs and outputs must be used. If the balanced input and single ended output are used together, 6dB lower output level will result from the ‘linked’ amp connected via the single ended output "

I find the feature useful for subs. I have dedicated amp that came with my sub and takes such and input which my preamp doesn't offer.
 

Julf

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I find the feature useful for subs. I have dedicated amp that came with my sub and takes such and input which my preamp doesn't offer.

A simple splitter cable will accomplish the same.
 
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March Audio

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A simple splitter cable will accomplish the same.
Yes. it doesnt really make any sense to build the feature into the amplifier. it would increase cost for all when its a niche requirement that few would take advantage of. It can be accomplished with a simple cheap splitter for those that need it.
 

ABall

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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;

View attachment 40703

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.

Hi March, I am now saving for these lovely amps, I like that you have gone for a well engineered buffer rather than offering all the mega expensive discrete opamps.
Could you please tell me if this single ended to balanced is the same if we go the other way? I am having some trouble with my Gustard x16 Dac going from its balanced output to the single ended input of my current amps. Gustard have now given me 2 conflicting answers and are blaming language and I also have a shield on my home made cables which isnt accounted for in their diag.
Many thanks
Alan
EDIT: Im a little confused sorry, you say "You should only terminate the balanced screen at the far (source) end like this" but the picture shows the screen connected at both ends? Its connected to RCA shell and pin 1. Could you please elaborate?
Many thanks.
 
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mk1classic

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Hi March, I am now saving for these lovely amps, I like that you have gone for a well engineered buffer rather than offering all the mega expensive discrete opamps.
Could you please tell me if this single ended to balanced is the same if we go the other way? I am having some trouble with my Gustard x16 Dac going from its balanced output to the single ended input of my current amps. Gustard have now given me 2 conflicting answers and are blaming language and I also have a shield on my home made cables which isnt accounted for in their diag.
Many thanks
Alan
EDIT: Im a little confused sorry, you say "You should only terminate the balanced screen at the far (source) end like this" but the picture shows the screen connected at both ends? Its connected to RCA shell and pin 1. Could you please elaborate?
Many thanks.

A little off-topic but this shows how it should be done for amplifier designs with balanced connections only.
RCA to XLR vs XLR to RCA will require different connections internally.

See how Benchmark have two different cables, with floating screen and without.

BENCHMARK RCA TO XLRM ADAPTER CABLE FOR ANALOG AUDIO - PIN 3 TO RCA SHIELD
https://benchmarkmedia.com/products/benchmark-rca-to-xlrm-adapter-cable
This special adapter cable connects unbalanced analog RCA outputs to balanced analog XLR inputs.
Use this cable to connect unbalanced line-level RCA analog audio outputs to the balanced analog audio inputs on an AHB2 or an ADC1. May also be used to connect the unbalanced outputs on a DAC1 or DAC2 converter to the balanced inputs on an amplifier (if the balanced outputs on the DAC1 or DAC2 are already in use). This adapter cable will work with electronically-balanced XLR inputs or with transformer-coupled XLR inputs.

BENCHMARK XLRF TO RCA ADAPTER CABLE FOR ANALOG AUDIO - PIN 3 FLOATING
https://benchmarkmedia.com/products/benchmark-xlrfm-to-rca-adapter-cable-pin-3-floating
This special adapter cable connects transformerless balanced analog outputs to unbalanced analog inputs.
Use this cable to connect the transformerless (electronically balanced) analog output from any Benchmark product (such as a DAC1 or DAC2) to an unbalanced analog input on a power amplifier or Hi-Fi "preamplifier". This cable will work will all Benchmark balanced analog outputs. Please note that this cable will not work with the transformer-coupled analog outputs found on some non-Benchmark products because pin 3 of this cable is floating.
 

ABall

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A little off-topic but this shows how it should be done for amplifier designs with balanced connections only.
RCA to XLR vs XLR to RCA will require different connections internally.

See how Benchmark have two different cables, with floating screen and without.

BENCHMARK RCA TO XLRM ADAPTER CABLE FOR ANALOG AUDIO - PIN 3 TO RCA SHIELD
https://benchmarkmedia.com/products/benchmark-rca-to-xlrm-adapter-cable


BENCHMARK XLRF TO RCA ADAPTER CABLE FOR ANALOG AUDIO - PIN 3 FLOATING
https://benchmarkmedia.com/products/benchmark-xlrfm-to-rca-adapter-cable-pin-3-floating
Ah great, many thanks for those links!
 
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