PS Audio M700 Monoblock Amplifier Review

[GaryMnz]

Then get a 200 dollar amp that fullfills the need. If this amp is sold at 200 dollars, it will be highly recommended.

Eh? I'm not referring specifically to this amp, just the statements made. They need to be addressed, in the interest of science which this forum is all about.

 

[GaryMnz]

If you own a pair of 100dB sensitive speakers, you want the noise floor at low wattage to be very low, or else it becomes audible. The noise floor in your room at low frequencies is high enough, but at higher frequencies it can be very quiet.

If you own a pair of 80dB sensitive speakers, let’s say you get 2dB of room gain, but -8dB for sitting decently away (~12ft), this gives you 74dB. For movies you want to reach at least 100dB, so you need +26dB, or 400W into 8ohm (800W if talking 4ohm).
Most speakers can’t handle more than ~100Wb (hell, some cheaper drivers can’t even handle >20W), but I’ve seen ratings for 500W peak.

Yes but that is theory. Measuring the actual power you are using is reality. It can be very interesting.

 

[GaryMnz]

I can tell you my experience about it. The ambient noise level is about -92dBFs in my living room.

Despite this noise level there is clear difference between 16bit and 24bit resolution. 16bit sounds raw and lumpy at highs without DAC dithering on. Dithering hides resolution problem.

An another strange thing, when I tested my old Chord Qutest against new Matrix X-Sabre Pro, the differences were clear, audible, despite their 114 / 121 SINAD significantly under ambient noise level.

I don't know the reason, but it is what I hear.

My new order an Okto Research Stereo DAC, I would like to compare it with the Matrix when it arrives. SINAD is similar but THD (without noise) is very different, I'm curious about the difference, if it will be audible.

You too miss my point. I wasn't talking about resolution of digital devices but the possible dynamic range under normal living conditions.

 

[GaryMnz]

Unfortunately, they don't understand.

The same guys that think a clean 100W/ch will give them all the power they need, also think they can reproduce the full dynamic range of what CD is capable of in a normal listening environment. News flash: they can't even come close.

If people are going to bang on about needing a bare minimum of 96dB, they should also realize that their amplifiers will need to have a minimum of ~1500W/ch into a sensitive speaker (>91dB@1M/1W) to reproduce that range, even allowing for the quietest parts to disappear into the noise floor of their own (quiet) listening environment.

Basically, the amount of posturing bullsh#t in relation to this is astounding.

Good reply. And they'll go deaf on the peaks

 

[GaryMnz]

How about just presenting the actual noise floor in uV with a bandwidth and weighting? You know, with a proper millivoltmeter? An electret into a preamp and into an A/D is not a valid 'noise floor'. That HF noise on the FFT is a combination of a whole lot of influences.

Nope. We just need a spl meter number. As long as it us a calibrated number in some way

 

[GaryMnz]

Unless you have a way of taking high-resolution (in the temporal domain) measurements this isn't going to necessarily tell you the whole story, right?

In any normal residential-type listening room, looking at VU meters or measuring this way will tell you that you're rarely using more than a couple of watts, and almost never much more than 10 watts.

Assuming we're listing to music and not pink noise, I find it's all about a system's ability to play those brief transient musical peaks with no distortion. For example, for some number of milliseconds (microseconds?) the attack of a well-recorded snare drum is orders of magnitude louder than just about anything else likely to be happening in your music. That's the sort of trick that requires efficient speakers and/or absolute gobs of power (and, I guess, an impressive slew rate?) to pull off in a convincing way.

That won't even show up on the average voltage meter, unless you have one that resolves to very very small slices of time.

Good answers, my post though was a challenge posed to our host.

 

[GaryMnz]

Don't run with that argument please. It is faulty and devoid of science. Peer reviewed papers have been written on this which you can see at the end of my article here: https://www.audiosciencereview.com/forum/index.php?threads/dynamic-range-how-quiet-is-quiet.14/

Bottom line, you can have 120 dB dynamic range in a room with respect to what we hear. The noise floor of a room measured with a SPL meter is absolutely wrong.

Just go in a listening room and close the door. Is it quiet? If so, then you have very low perceptual noise floor. Diregard the SPL meter because it is measuring low frequency noise that is well below you threshold of hearing in those frequencies.

As for peaks, that is a personal decision as to how loud you want the transients to be. I have a 1000 watt amplifier and I can tell you that I have turned it up near max volume at times. Granted, the material isn't at 0 dBFS always but in a large space, the last 500 watts makes a tiny difference because it is just doubling just like going from 1 to 2 watts.

Rubbish on the used power. I challenge you to set up a measurement of your system as used at what you would call loud normal levels and to report here.

I have done this with both a peak detector and oscilloscope in multiple situations, audio shows, retail environments, and domestic situations. The results confirmed my belied that we chase high power because the marketing guys have sold the idea to us.

In the 1970s a typical domestic amp was 25 watts. Typical speakers weren't at all efficient. How did that work?

 

[restorer-john]

That won't even show up on the average voltage meter, unless you have one that resolves to very very small slices of time.

An average reading meter does just that. Peak reading (often with peak hold) will show peaks.

A couple of big swinging moving coil 'power' meters are just an indicator, not an accurate measure. But they do serve to show how much voltage you need to accurately reproduce transients. It's very easy to use 40V RMS (200W@8R) on dynamic content on a small pair of bookshelf speakers.

AS for 'very very small slices of time', attach an oscilloscope/DSO to the speaker terminals and look at (record) the actual peaks. Not only will it shock you (not literally), you'll also see how often a typical amplifier clips on regular (loud) content.

 

[amirm]

In the 1970s a typical domestic amp was 25 watts. Typical speakers weren't at all efficient. How did that work?

They were very different. Much larger boxes. Today, there is pressure to not have big boxes in people's living rooms so sensitivity has dropped as a result.

 

[amirm]

Rubbish on the used power. I challenge you to set up a measurement of your system as used at what you would call loud normal levels and to report here.

Watch your language. If you want to challenge us with the numbers you have, post them. Not doing so is rubbish.

 

[restorer-john]

In the 1970s a typical domestic amp was 25 watts. Typical speakers weren't at all efficient. How did that work?

In the 1970s, we had LP, open reel, cassette and FM radio. Remind me, what dynamic range did we have again? 30-60dB if we were lucky.

And 1970s speakers were efficient actually. They just couldn't handle much power.

Along came digital in October 1982 with 96dB to play with. And did they ever play with it.

 

[GaryMnz]

Don't run with that argument please. It is faulty and devoid of science. Peer reviewed papers have been written on this which you can see at the end of my article here: https://www.audiosciencereview.com/forum/index.php?threads/dynamic-range-how-quiet-is-quiet.14/

Bottom line, you can have 120 dB dynamic range in a room with respect to what we hear. The noise floor of a room measured with a SPL meter is absolutely wrong.

Just go in a listening room and close the door. Is it quiet? If so, then you have very low perceptual noise floor. Diregard the SPL meter because it is measuring low frequency noise that is well below you threshold of hearing in those frequencies.

As for peaks, that is a personal decision as to how loud you want the transients to be. I have a 1000 watt amplifier and I can tell you that I have turned it up near max volume at times. Granted, the material isn't at 0 dBFS always but in a large space, the last 500 watts makes a tiny difference because it is just doubling just like going from 1 to 2 watts.

Suprisingly you are confused as well. The article you referred to is an argument for needed digital resolution not possible dynamic range in a domestic environment. And of course as someone else mentioned there is the actual recorded dynamic range which is always going to be much less than the 96dB figure you said you liked to see in sinad from an amplifier.

 

[GaryMnz]

Watch your language. If you want to challenge us with the numbers you have, post them. Not doing so is rubbish.

You are being evasive. I am challenging you to back up your claims with numbers. You have the tools, your site is set up to deliver the data.

 

[Billy Budapest]

And, very important, thanks to the PS buffer added to the IcePower 700ASC module -> dominant H3

Or without harmonics at -90 dB as the IcePower module or dominant H2 (how much?), never dominant H3.

Almost two years have passed and I still have not received a response from the technical department in this regard, when I mentioned it the first time in a thread about the new D-Class at Audiocircle forums.

Has PS Audio ever explained exactly what their “gain cell” is supposed to do? I know it is a potted module that you cannot disassemble or see inside, and they have been using it for about 20 years. They’ve never really explained what it is, though.

 

[restorer-john]

Rubbish on the used power. I challenge you to set up a measurement of your system as used at what you would call loud normal levels and to report here.

It's less about the continuous average level and more about the ability to deliver enough voltage to not clip any transient on any programme content. For that, you need a lot of voltage. A lot more than you realize.

 

[GaryMnz]

They were very different. Much larger boxes. Today, there is pressure to not have big boxes in people's living rooms so sensitivity has dropped as a result.

Most 70s speakers I recall were modestly sized. Often stand mounted. Today's tend to be much larger.

 

[PeteL]

NC1200's crush this, so why bother? Willing to bet they choose ICEpower due to margins.

Maybe because no amp manufacturer that I know uses them? Do you?

 

[MZKM]

Most 70s speakers I recall were modestly sized. Often stand mounted. Today's tend to be much larger.

Talking volume here, not just height.

 

[GaryMnz]

It's less about the continuous average level and more about the ability to deliver enough voltage to not clip any transient on any programme content. For that, you need a lot of voltage. A lot more than you realize.

Yes that is why I said measure the peaks and then convert the voltage to rms and then calculate the nominal 8 ohm power to determine what rating an amplifier would need to have to deliver that measured peak.

 

[Matias]

New thread for this discussion?