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Entry point for Load Independent amplifiers

JeremyFife

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Hi all,
There have been a number of recent reviews and discussions of budget, entry level, amplifiers (Fossi, WiiM, various DIY options etc).
The discussions very quickly stagnate in whether these are Frequency independent (over 20Hz - 20kHz, or wider), Load Independent or otherwise have problems driving real or difficult / complex loads.

There is an implication, sometimes explicitly stated, that these amplifiers measure nicely enough but are not really suitable in the 'real' world. More nicely put: they are technically short of SOTA performance.
I appreciate that there are no simple numbers that describe SOTA, especially when trying to take the effect of driving different speakers into account ... but ...

What is the entry point (expressed as cheapest!) for a SOTA amplifier?

It may be helpful to set some parameters: reasonable power handling (100W continuous at 8Ohm), stable over the audible frequency range (20Hz to 20 kHz ... does it need to go further) and stable with loads at 4 Ohms but which dip lower (but not exceptionally low - say a 2 Ohm limit). Try not to get to hung up on intangibles like reliability, but that's interesting too.

If I throw in the Topping LA90 as a starter ... is that it, does it qualify, can we do better (cheaper)?

Interested.
 
OP
JeremyFife

JeremyFife

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Thanks both.

So: almost the first comment on the PA7 Plus review (comment #9) was
"That rise of THD+N at 10 and 15Khz may be hard to hear (for older ones like me) but the 5Khz where we are sensitive is very close to be audible.
Otherwise decent power" https://audiosciencereview.com/foru...-pa7-plus-amplifier-review.43932/post-1561476

Similarly: Buckeye NC252MP review comment #5 complains about "problems in bass range" https://audiosciencereview.com/foru...mp-stereo-amplifier-review.48196/post-1727898

This is what I meant. The implication is that these (excellent) amplifiers are not SOTA and have some real world issues.

Does it matter, and how far up do we have to go to get away from issues like this?
 

ppataki

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amplifiers are not SOTA and have some real world issues.
I am really not sure if these are real world issues. The THD+N at 5kHz is about 0.01% - the question is: how audible that really is?

1708528829038.png


I will let other more knowledgeable members chime in
 

dominikz

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I am really not sure if these are real world issues. The THD+N at 5kHz is about 0.01% - the question is: how audible that really is?

View attachment 351299

I will let other more knowledgeable members chime in
Note that 5kHz is the fundamental frequency, while harmonic distortion components are at 10kHz, 15kHz etc. According to the above diagram those are at least -75dB below the 5kHz fundamental. Given the low level and high frequency I'd argue that will be inaudible.

Also, I wonder how often real audio content requires >100W during playback at frequencies above 5kHz :)
 
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JeremyFife

JeremyFife

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Personally, I agree with this - that these artefacts are most likely inaudible and are NOT real world issues with music playback.
I'm wondering why they keep getting called out in review comments and that led to me wondering what sort of Amp would be 'better'.
 
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JeremyFife

JeremyFife

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I am really not sure if these are real world issues. The THD+N at 5kHz is about 0.01% - the question is: how audible that really is?

View attachment 351299

I will let other more knowledgeable members chime in
Can I just correct the quote you used from me. I said that "the implication is ... that the amp are not SOTA" that's not my assertion, or my opinion, but my reading of review comments.
No issues btw, I agree with your point.
 

rdenney

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Thanks both.

So: almost the first comment on the PA7 Plus review (comment #9) was
"That rise of THD+N at 10 and 15Khz may be hard to hear (for older ones like me) but the 5Khz where we are sensitive is very close to be audible.
Otherwise decent power" https://audiosciencereview.com/foru...-pa7-plus-amplifier-review.43932/post-1561476

Similarly: Buckeye NC252MP review comment #5 complains about "problems in bass range" https://audiosciencereview.com/foru...mp-stereo-amplifier-review.48196/post-1727898

This is what I meant. The implication is that these (excellent) amplifiers are not SOTA and have some real world issues.

Does it matter, and how far up do we have to go to get away from issues like this?
As you later stated, you are quoting a comment in a review thread that did not receive agreement from just about anybody. Anybody might say anything about any amp.

What is the state of the art? I don't really even know what that means. But I think it does require sufficient power to achieve reference level, which I define as the volume at which I can play my tuba along with an orchestral recording and not have to hold back. For me that means >110db SPL in each channel on the peaks. To achieve that listening level with speakers of 86 dB efficiency, which are typical of speakers one might buy for the home, one needs over 200 watts of clean power at whatever impedance those speakers presented when the sensitivity was measured. Low-power amps don't have to solve the same problems as high-power amps and that's a huge trade-off for me that undermines any designation of SOTA.

No single amplifier achieves the very best values in any given dimension--they all trade one feature for another. The Toppings measure very well but they don't attain my power requirements. The Purifi-based amps have lower distortion at higher frequencies than the Hypex-based amps, not that I think mortals can hear the difference even if they claim they can. But they are more expensive. A Hypex NC502MP stereo amp from Buckeye will cost about $695, and that seems to me about the cheapest path to a demonstrably transparent amp of greater than 200WPC into real speakers.

Buckeye sells a Purifi 1ET7040SA mono amp for $895, which means a stereo pair will be just shy of $1800. It's the more powerful Purifi module and it attains my standard for power output. I doubt there's anything on the market with usefully better specifications and that power output.

Specs: https://purifi-audio.com/document/share/34/d3a47408-a165-4d9b-8a85-692ffde3b41a

The PA5 looks great except that is produces only 70 wpc at 4 ohms, which I define a nice for a desktop amp, but not SOTA. The PA7+ is much more powerful, but still not nearly as powerful as the NC502MP and it also loses the same bit of linearity in the high frequencies.

The LA90 is excellent, of course, but like the PA series provides too little power to be SOTA in my view. Into a 4-ohm load, it's only 70 watts and it won't drive a 2-ohm load at all.

Rick "turn it up!" Denney
 

dominikz

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I'm wondering why they keep getting called out in review comments and that led to me wondering what sort of Amp would be 'better'.
I guess it is OK to demand technical perfection even if it is of no audible consequence in many use cases. But we should be careful not to equate technical perfection to audible transparency, because audible transparency is almost certainly achievable much more easily.

For sure a big part of the issue is that thresholds of audibility are not strictly defined in many cases, and there are no easily-understandable standards as to what is considered good or bad. It is also notoriously difficult to reduce a multi-dimensional problem to a simple one-dimensional categorization. :confused:

So unfortunately we're stuck in a position where audio enthusiasts need to have a pretty good grasp of audio engineering and psychoacoustics to be reasonably sure their system is 'transparent' (or close enough to stop caring about it :)).

Note also that there are other use cases where technical performance above audibility might have practical benefits - e.g. when using a DAC as a lab-grade signal generator for measurements.
 

ViperDom

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There is talk about power/watts without specifying per channel (WPC) or total. Also not mentioning RMS or Max.
The OP sets his bar @ 100W continuous at 8Ohm.
Someone responds with the PA5-II which is measured at 53 WPC Max

Just want to make sure we're all on the same page.
 

MaxwellsEq

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It's an interesting question. Outside of ASR, in the popular Hifi magazines, products from d'Agostino probably are considered SOTA. But they are... er... not entry level.

There are many threads about "how many Watts" and people are often surprised at how loud 5W can be. But for peaks, I feel more than 100W is probably a base requirement for SOTA.

I also think noise should be minimised. Distortion should be as well, although this is probably less critical.

I don't feel comfortable with load-dependant amplifiers being classed as SOTA. As an engineer, I feel that the amplifier shouldn't change the sound with difficult or complex loads. So, I would not include some of the chip-based amplifiers where output filtering is outside the feedback loop.
 

NTK

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The Sabaj A30a seems to have the necessary ingredients, but sadly I couldn't find any reliable measurements.

The SMSL (sister company of Sabaj) VMV A2, which based on the same Axign technology, is reviewed here. Its execution IMHO could have been better.
 
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dominikz

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There is talk about power/watts without specifying per channel (WPC) or total. Also not mentioning RMS or Max.
The OP sets his bar @ 100W continuous at 8Ohm.
Someone responds with the PA5-II which is measured at 53 WPC Max

Just want to make sure we're all on the same page.
Indeed.

As I see it, it makes no sense to try and define an absolute target value on power because how much power one needs will depend on individual circumstances.
E.g. a 200W @ 8Ohm amp would be an absolute overkill for me because I never even come close to maxing-out my 40W @ 8Ohm amp.
 

Iluzun

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Real world. In a great room. Denafrips Athena preamp. Smsl PL200 cd player. VPI Traveler II w/Dynavector 20x2L, Audio Technica
60th Anniversary table w/Nagaoka MP300, Eat Glo Peteite phono. 2 sets of monitors, ProAc 1SC & Musician Knight 1s. Both sets
powered by a pair of Topping PA-7 + amps. Pair of Rel TI9 subs on the Knight 1s. Both set ups go loud and clean, subjectively of course.
Toppings little amps allow for a versatility in setup and performance that I can’t get w/my A or A/B amps. I’m a believer. The music
collection has never sounded better. Quality components. Careful setup. Modest cost per performance. System context including power cords
and cabling. Yes, u can uck it up or blah it down by linking/feeding the components with the wrong mix. Use your ears, the smile on your face,
and the tap of your toes. Experiment. For me, the little Toppings have been a great value. I also own a pair of the SMSL AO300 amps I think highly of
to run a bedroom and a garage system. A bit different voicing. Still plenty of power, EArc, Bluetooth, USB-C, remotes, for under $250. Whats not
to like? Those easily drive some large sealed box speakers from the mid 80’s, ADS and Pioneer speakers w/large woofers. They sound great
and go plenty loud. Distortion? Nah, not really. In either case, I’m luving the little amps. SOTA? Nah, but the system is fun to use and sounds damn good…
 
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