P801 Power Amp

Oniiz86 wrote:
@james dyson I'm sorry but I have to ask, are you the same "james dyson" who was just banned from ASR, moderators & members bizarrely thinking you were Alan for some strange reason?

I am. I have no idea what the ASR moderators are up to. It is really bizarre. They might think I'm Alan because I gave Buckeye a hard time for posting misleading and inaccurate specs on his website and slammed him for not testing his products. I got chastised by the mods for that before the ban Some manufacturers are obviously protected on ASR. Did you see the Buckeye stereophile review thread got closed so people don't see what amazing mess he made with the amp shutting down and high distortion?

james dyson wrote:
I am. I have no idea what the ASR moderators are up to. It is really bizarre. They might think I'm Alan because I gave Buckeye a hard time for posting misleading and inaccurate specs on his website and criticised him for not testing his products. Some manufacturers are protected on ASR. Did you see the Buckeye stereophile review thread got closed so people don't see what amazing mess he made with the amp shutting down and high distortion?

Unfortunately this is par for the course at ASR. You are not the first and wont be the last to get banned there. I got banned because I criticised Amirs testing regimes. Since then he and his minion moderators have used any opportunity to bash March Audio.

As you have identified there is nothing impartial about ASR. Factions, fanboys and people who think they know. Jeez, Amir is so paranoid he thinks I have time and the inclination to troll the site. It beggars belief. I think its all a bit weird to be honest.

Anyway, just ignore ASR. There really is very little of interest audio wise going on there. Same old dac tests over and over. SINAD is everything ignorance. No credible mainstream companies send their kit in for review or have anything to do with the site. No one in the industry wants to deal with Amir.

To move on. In answer to your question, yes those power sweeps will be published soon..

Thanks Alan. Looking forward to the data. Will you do low frequency sweeps also? It's shocking how the ASR moderators behaved, then you get idiots piling on.

james dyson wrote:
Thanks Alan. Looking forward to the data. Will you do low frequency sweeps also?
It's shocking how the ASR moderators behaved, then you get some idiots piling on.

Sure will do low frequency. Already promised for @SmartOne_2000

Let's just leave the ASR subject. It's just the negative and nasty side of social media. All too common.

Let's concentrate on the P801 😀

Alan March wrote:
And why just 2 volts output? Rather arbitrary. For a 9040 with the usual ASR testing at 5 watts, it needs 4.475v applied to the load. With 14.4dB gain from the 9040, this is an output of about 850mV from the buffer. This lower level will make noise performance far bigger contributing factor to THD+N (SINAD). SNR will be much lower than at 2 volts.

In the other direction, what's the distortion at 10.5 volts into a 1.5k load?

Really these numbers are all a bit meaningless unless you have numbers from another buffer to compare, or even more relevant, if you have the data for a full amp, I.e. it driving a 9040, 6525 etc.

Doing a few calcs I would estimate this buffer would be below 109dB THD+N (SINAD) at 5watts when used with a 9040 or 6525 module. OK for the older 1et400 module, but not these new higher performing variants.

Apparently, a new buffer design is coming this April, compatible with the Purifi 7040 and 9040 amps.

Alan March wrote:
Sure will do low frequency. Already promised for @SmartOne_2000

Let's just leave the ASR subject. It's just the negative and nasty side of social media. All too common.

Let's concentrate on the P801 😀

Nice ... thought you forgot me for a bit :)!

Alan March wrote:
Unfortunately this is par for the course at ASR. You are not the first and wont be the last to get banned there. I got banned because I criticised Amirs testing regimes. Since then he and his minion moderators have used any opportunity to bash March Audio.

As you have identified there is nothing impartial about ASR. Factions, fanboys and people who think they know. Jeez, Amir is so paranoid he thinks I have time and the inclination to troll the site. It beggars belief. I think its all a bit weird to be honest.

Anyway, just ignore ASR. There really is very little of interest audio wise going on there. Same old dac tests over and over. SINAD is everything ignorance. No credible mainstream companies send their kit in for review or have anything to do with the site. No one in the industry wants to deal with Amir.

To move on. In answer to your question, yes those power sweeps will be published soon..

@Alan March I'm truly sorry to bang on about it but this is a bit disconcerting coming from Buckeye Amps who has always been very civil & polite, there is no need for this nastiness, the belief that @james dyson is one of your phony accounts which I believe he purchased a P482 amp from you from the UK, Buckeye Amps had this disparaging comment below,

Not to harp on the subject but what is truly amazing is that Alan created the same name account on his own forum to post in his own threads. It's quite sad, really. Like the recent discovery of Elon Musk using a burner account to hype himself up.

Oniiz86 wrote:
@Alan March I'm truly sorry to bang on about it but this is a bit disconcerting coming from Buckeye Amps who has always been very civil & polite, there is no need for this nastiness, the belief that @james dyson is one of your phony accounts which I believe he purchased a P482 amp from you from the UK, Buckeye Amps had this disparaging comment below,

It's total nonsense.

Dont forget that Buckeye have been highly embarrassed by the Stereophile incident so he is looking for ways to divert attention off his mistakes and poor quality control.

I don't need to do this sort of thing. Its crazy. We are a successful company with great products. I think it betrays a lot about Buckeye to attack in this way. He needs to disparage successful competitors. Its right out the Trump playbook. I eat cats and dogs too 😉. Also betrays the nature of ASR to allow it.

As I said before, this is the ugly side of social media. I ignore it. The company success, plus the quality of our products and service speaks for itself.

Oniiz86 wrote:
@Alan March I'm truly sorry to bang on about it but this is a bit disconcerting coming from Buckeye Amps who has always been very civil & polite, there is no need for this nastiness, the belief that @james dyson is one of your phony accounts which I believe he purchased a P482 amp from you from the UK, Buckeye Amps had this disparaging comment below,

Hey @Oniiz86 . I am a real person. It's a cold day here in Gloucester UK. I have bought a P482 and it is superb. I chose March Audio after questioning Buckeye and looking at their test data. It was obvious Buckeye is just throwing modules in cheap boxes. Lowest common denominator stuff. No understanding.
March Audio is a different league altogether

Alan, just curious to see how the P801 stacks up to Purifi's reference amp (older 1ET400A module but using the OPA1612 opamp in their buffer board) as far as noise, distortion etc are concerned. Not interested in the power spec comparisons since the modules are different. Measured by your favorite person at ASR 🙂 .

BTW, can you indicate the amp P801 gain used when measuring the listed specs (unless otherwise noted, ofcourse)? Was it high or low gain? XLR or RCA signal inputs? Thanks!

SmartOne_2000 wrote:
Alan, just curious to see how the P801 stacks up to Purifi's reference amp (older 1ET400A module but using the OPA1612 opamp in their buffer board) as far as noise, distortion etc are concerned. Not interested in the power spec comparisons since the modules are different. Measured by your favorite person at ASR 🙂 .

BTW, can you indicate the amp P801 gain used when measuring the listed specs (unless otherwise noted, ofcourse)? Was it high or low gain? XLR or RCA signal inputs? Thanks!

This is the 1et400 using the Purifi Eval buffer.

Unfortunately Amir uses such a low resolution FFT we can't see very far into the noise floor.

This is the P801

You can see the higher harmonics because we use an appropriate FFT resolution that allows us to look deeper into the noise floor.

Also, as I note in this post

https://forum.marchaudio.com/index.php?threads/p801-power-amp.66/
The noise floor of the amp is lower than indicated in the above plot. This is due to the inherent noise of our signal generator. It's a very good generator,, but not good enough with low enough noise to truly show the amp performance.

This is the amps true noise floor with inputs shorted. 6dB lower. True SINAD is about 116dB.

Thing I need to emphasise here is that whilst we use the opa1612, the topology is not the same as the Purifi eval board.

Gain is 23dB in our testing. If the 1et400 test was at this lower gain it would improve its SINAD by about 2.0dB.

We only have XLR inputs because RCA is fundamentally flawed. Noise currents flow in the shield. Note that XLR inputs are fully compatible with RCA sources using a correctly wired adaptor cable which mostly eliminates the issue of noise currents.

Alan March wrote:
This is the 1et400 using the Purifi Eval buffer.
229

Unfortunately Amir uses such a low resolution FFT we can't see very far into the noise floor.

This is the P801
230

You can see the higher harmonics because we use an appropriate FFT resolution that allows us to look deeper into the noise floor.

Also, as I note in this post

https://forum.marchaudio.com/index.php?threads/p801-power-amp.66/
The noise floor of the amp is lower than indicated in the above plot. This is due to the inherent noise of our signal generator. It's a very good generator,, but not good enough with low enough noise to truly show the amp performance.

This is the amps true noise floor with inputs shorted. 6dB lower. True SINAD is about 116dB.
231

Thing I need to emphasise here is that whilst we use the opa1612, the topology is not the same as the Purifi eval board.

Gain is 23dB in our testing. If the 1et400 test was at this lower gain it would improve its SINAD by about 2.0dB.

We only have XLR inputs because RCA is fundamentally flawed. Noise currents flow in the shield. Note that XLR inputs are fully compatible with RCA sources using a correctly wired adaptor cable which mostly eliminates the issue of noise currents.

Thank you, Alan for the detailed and informative answer.

On another point, and this might be propriety information, I wonder how the published amplifier specs are representative of the amps you build on a daily basis. That is, If I had access to your database o_O and for I plotted a histogram of THD+N at 5W data, for example, how 'tight' would the histogram be? Would I see a large narrow peak at some central THD+N value with a few short peaks on either side or would we have a broad histogram?

...Odd question, I know...

SmartOne_2000 wrote:
On another point, and this might be propriety information, I wonder how the published amplifier specs are representative of the amps you build on a daily basis. That is, If I had access to your database o_O and for I plotted a histogram of THD+N at 5W data, for example, how 'tight' would the histogram be? Would I see a large narrow peak at some central THD+N value with a few short peaks on either side or would we have a broad histogram?

...Odd question, I know...

I can understand the question, its very reasonable. Published specs could be "golden samples" and unrepresentative.

We test every amp, so have a good idea of the variations between units. Component tolerances obviously cause them to vary, but its only by a small amount. The bell curve is narrow. The published specs are of "typical" units.

For example, the data in the post above was of a unit that was on the upper side of the bell curve with SINAD over 116dB. The spec is 115dB.

Alan March wrote:
I can understand the question, its very reasonable. Published specs could be "golden samples" and unrepresentative.

We test every amp, so have a good idea of the variations between units. Component tolerances obviously cause them to vary, but its only by a small amount. The bell curve is narrow. The published specs are of "typical" units.

For example, the data in the post above was of a unit that was on the upper side of the bell curve with SINAD over 116dB. The spec is 115dB.

The highlighted statement is excellent. Thank you!