Why Pay More For Purifi 9040 vs Hypex NCX2k?

[Everett T]

Other than the fact that DSP is limited by the amount of processor power and amount and speed of the memory available plus the fact that the signal has to be converted to digital then back to analog all end up diminishing the original signal to some point. I know this from testing 5 different DSP units against a bunch of analog eqs and crossovers, the sound with all controls set to flat and implementing just the crossover on the DSP was enough for me to obviously notice a loss in "fringe" sounds and very slight details were lost with DSP.

Ive always said this, most systems are not high enough resolution in the first place to hear the loss presented by DSP use. Once you have a system that can audibly reproduce and convey sound accurately, you will realize the loss in complex sound waves due to DSP limitations.

Until there is a next level conversion in DSP which also has the power and memory to do it, I won't consider DSP for anything but a surround system, which I don't own.

Im not sure I understand what you mean by computing power and memory? Every AVP, AVR, and other units have a different structures. What do you consider as sufficient?

 

[Billy Budapest]

Would the difference in distortion specs be audible? I don't know.

Harmonic distortion, period, is largely inaudible until you start to get around the 3% range. And the distortion that will be recognizable will most likely be in the midrange where singing and speaking tones live. Also, other than lab instrument-generated sine waves, there aren’t really absolute tones in our music-listening lives where we would recognize the purity of the tone being compromised by extraneous harmonic tones.

Noise is a completely different story. That is largely audible if it is high enough in level.

 

[Billy Budapest]

Interesting reading here:

Audibility thresholds for SINAD/THD measurements

 

[GS430man]

Excellent amp, great young USA company. Congratulations @Buckeye Amps

The Micro Audio SMPS used in this amp is not just powerful. It has active power factor correction so it is efficient with power when it's working. In both idle and standby it uses trivial levels of power.

A killer power supply, perfect for a killer amp.

 

[Crook]

there is no complete evidence on how these amp sound. only measurements on signal to noise, watt, crosstalk and so forth

and the only way to prove there is an objective difference in the sound you hear is by correct level matched blind testing. Without this it is simply impossible to know if the differences heard are psychoacoustic, unmatched levels , sighted bias etc. I'm not saying there are never audible differences between amplifiers, but to prove it, you cannot just listen to them and come to a subjective conclusion. Even if we take an objectively SOTA Purifi class D and single ended valve amp, yes, you would 'expect' an audible difference, but again the only way to 'prove' the difference you hear is by using the proper testing methodology.

 

[jck2001]

That "and so forth" hides a big one: frequency response.

Again, you are glazing over the mountains of data and understanding on how sound works/how our ears pick up sound.

Not to take a side here, but one thing i'd love to see thrown into the measurement mix is the phase response of the amp across the audible spectrum at various loads, say, 2, 4, 8, 16 ohms. For a closed loop system, fr doesn't tell the whole story about performance. This is standard practice in control systems to report about phase to some extent, i've always wondered why its absent from audio amps specs. Do these things tend to be output phase invariant under dynamic load? At any rate, phase shifts could possibly account for audible differences some people claim to perceive between amps as our hearing can be quite sensitive to phase shifts, particularly since phase and timing provides cues for instrument placement in the sound stage.

 

[antcollinet]

as our hearing can be quite sensitive to phase shifts

There is some debate about this, evidenced by the fact we don't have to lock our heads in a vice to listen to music. (At 5kHz the wavelength is less than 7cm. Shifting your ear by only 2cm results in a 90+ degree phase shift)

Sound stage positioning is controlled by relative level left to right, as well as relative time between left and right. The time difference might be a ms or more. In this time, 5 full cycles of 5Khz (or one of 1Khz) will have passed your ear. This is not phase shift - it is delay.

Further - it is relative difference left to right that matters. If there is a phase variation through the amp, it will be the same for both left and right channels. Sound stage not impacted.

This is not to say phase is completely inaudible - just that it is far from as significant as many people state. This might be why no-one measures phase in electronics. It doesn't vary much in the audible band - and even if it did, it doesn't matter that much. You get far more phase distortion in your speakers - especially those with a passive crossover.

See also:

Does Phase Distortion/Shift Matter in Audio? (no*)

A viewer of my videos and member he suggested that I do a video commenting on a video that Paul McGown did on audibility of phase shifts. Here is Paul's video which was really about a different question (why we need wideband amplifiers) but turned it into phase being an audible problem: Here...

www.audiosciencereview.com

 

[Head_Unit]

for me it obvious amps consisting of very different components and topology also will sound different from each other

Maybe. We swapped a friend's old receiver for a newer one and the bass sounded quite different, versus our expectations which were...actually we had zero expectations. But another time we compared a Denon AVR-X3600H versus a $25-on-sale Parts Express wall wart powered amp. At moderate levels, hard to tell a consistent difference (at higher levels the cheaper amp clipped). *Maybe* there was a difference in the bass. Mostly it taught us audio memory is very fallible.

The way to truly test an amp (or cable etc) would be that it is all hidden, and unbeknownst you you someone swaps it out, and verifies the levels are exactly the same. Each day you see if there is a difference in the sound. My bet is the weather and your mood and how much you slept will affect the sound more than differences between any amplifiers below clipping. However I've never tried it because of course it is very difficult to do that...I can't imagine my wife swapping out amplifiers while I'm at work ha ha.


To complicate things more, I believe if you THINK it sounds better then in your brain it WILL sound better, I bet we could see it with the right MRI or whatever, even if there was ZERO difference in the actual acoustical signal. Kind of an offshoot of the placebo effect.

As for "you do know designers and makers of audio equipment fine tune their prototype products by ear?" well having been one I'll say they are (a) fallible human beings as well, and might be genuine OR deluded AND/OR do that because they have something to sell you. "We hand-tuned the capacitors blah blah"-hey it CAN make a difference, but DID it?

 

[RexrothPigeon]

don`t know why people say these things. power amps sound different from each other..its quite easy for people with good ears and an open mind to verify. even listening back on youtube tests its fairly obvious. purify vs nilai for example.

my dude, listening to recordings of amps on youtube is literally (in the literal use of the word) just pretending that you're doing a listening test of those amps

 

[antcollinet]

for me it obvious amps consisting of very different components and topology also will sound different from each other

Why - it doesn't matter what the topology or components are. Once you have achieved flat frequency response - and distortion/noise lower then the human ear can detect, then an amp must - by definition - sound the same as another amp (no matter what the design) that also achieves inaudible noise and distortion - with flat frequency response.

There is nothing else to cause a sound difference.

 

[oleg87]

my dude, listening to recordings of amps on youtube is literally (in the literal use of the word) just pretending that you're doing a listening test of those amps

I mean, you could do worse if you want to see if there’s a big difference (ie the kind of day/night difference audiophiles often attribute to amps) and you don’t have better tools. But as I pointed out in an earlier post, the volumes are not even remotely matched so its completely worthless.

 

[antcollinet]

I mean, you could do worse if you want to see if there’s a big difference (ie the kind of day/night difference audiophiles often attribute to amps) and you don’t have better tools. But as I pointed out in an earlier post, the volumes are not even remotely matched so its completely worthless.

Not to mention, the distortions introduced by the speakers and microphones - not to mention the frequency response issues cased by the room will totally swamp any differences between amps - by orders of magnitude.

 

[Jiraya369]

Why - it doesn't matter what the topology or components are. Once you have achieved flat frequency response - and distortion/noise lower then the human ear can detect, then an amp must - by definition - sound the same as another amp (no matter what the design) that also achieves inaudible noise and distortion - with flat frequency response.

There is nothing else to cause a sound difference.

the topology and components matter for psychoacoustics, in other words sighted biases

 

[antcollinet]

the topology and components matter for psychoacoustics, in other words sighted biases

Of course. That is the point. The perceived sound differences are not caused by the quality of the sound reproduction. They are constructed in the brain of the listener based on things that are nothing to do with the sound waves reaching that listeners ears.