Yes it's a logical comparison but you need to understand the particular specification and the implications of the numbers.Purifi 1ET400A is the evolution of those two modules, the DIY and the OEM. It is logical to make the comparison to know what they have improved.
And I was not the first to compare with NC400.
Because they are two very important values, which are usually hidden by manufacturers, especially the Hi-Fi or High-End.
In the audio forums there is an old controversy about the power cords and whether they affect or not. As usual on the Internet, everyone knows everything. It turns out that a PSRR > 90 dB guarantees that, if you have a terrible electrical supply like in my house, the amplifier will be immune to a large part of these problems.
If you also use a good and, unfortunately, expensive SMPS I can forget about the DC that swarms my grid.
That is why I am very interested in this module, because it promises a lot a priori.
It remains to be seen if these great specifications imply excellent sound. I already have it in my second system but I would like it to be much better and that it went beyond the deficiencies detected and that I do not think it can improve any more because of the design of the amplifier itself. 3D sound and, above all, sound planes when listening in the far field.
Now the music fills the room thanks to the great dispersion of my small coaxes but I lack the above. When you first listen to the sound plans, you do not forget it in your life! And I want it with SS and not with tubes.
- The End -
You can hear three distinct depths. There is the main orchestra and soloist at the first level. Then there is a small group of strings at the next level- maybe 20-30 feet back. The echo chamber instruments were placed at the third level WAY in the back of the church (which has a lot of reverberant energy). The effect is really interesting, and the engineers captured it very well. You hear the main orchestra and when they are silent or only the violin soloist is playing, you sometimes here this island of strings much further back at the second level. And when Vivaldi whats the full echo, you hear the third layer very far away. Subjectively it sound like they are almost one hundred feet back. They may well have been...
orangejello and the presence/sound plans
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So what I'm wondering is how this will sound compared to the nc400. When is performance so good that it doesn't matter anymore?
Ouch. That one will be a mandatory listen for all my friends when they visit me. Will let you know if they sue me for emotional damage.
Laurie Anderson - My Compensation
Pixel - Brown Shirt
Monolake - Ghosts
Pixel - Lion
Penta - Here We Come
In a good room with good speakers these should sound pretty interesting..
Good question.When is performance so good that it doesn't matter anymore?
+1 for the VU meters, I almost bought a Oppo HA1 for the meter. Then I saw one in person and wished I had.
Bruno. I currently have an SMPS1200 and two Ncore 400 modules on order to go into a Ghent case. When the Purifi modules become available, is there any way you could include instruction and a wiring harness to connect it to that SMPS1200 if I just want to swap out your modules for my NC400s.Hi all,
Just checking in!
First off, mega thanks Amir for doing this review. And more generally for running this forum. It is enormously heartening to see someone working to collect actual data for a substantive technical discussion and comparison between products. It's even more heartening to see that indeed, substantive discussion ensues.
Amir mentioned I'd be saying something about the high-frequency IMD results. Let's start by explaining why I prefer to measure distortion strictly inside the audio band. There is an ongoing controversy about whether signals above 20kHz might or might not be audible, but what is not controversial is that signals below 20kHz are much, much more audible than signals above 20kHz. So if you are in a situation where you have to choose between optimizing performance below 20kHz or above 20kHz, you go for optimizing the bit that we are most likely to hear. Even high-res enthusiasts seem to have tacitly accepted this a long time ago. Remember DSD? A DSD AD/DA converter that, when measured over 20kHz, would easily clock a SINAD of 120dB would "degrade" to 50dB as soon as you upped the measurement bandwidth to 40kHz. But what you heard was of course 120dB, the rest was for the bats. Note the delicious irony. DSD was hawked on the grounds that you needed >20kHz bandwidth for high fidelity, while its skyrocketing supersonic noise floor was excused on the grounds that it was inaudible. As it is, DSD is perfectly listenable. I can find no more eloquent argument that the ear is not very sensitive above 20kHz than DSD...
Anyhow, this is why I like to test amplifiers with test signals that in themselves would be audible (i.e. fit below 20kHz) and also read the distortion and noise only in the band below 20kHz. Of course, I know perfectly well that if you then do a THD versus frequency sweep, any readings above 10kHz are meaningless because even the second harmonic will be outside the audio band. But as our sensitivity to those harmonics drops off rather quickly around 20kHz (as does the ability of most speakers to reproduce them), it's fair to conclude that they do not say much about sound. On the other hand, we can't just go ignoring any underlying non-linearity. We still need to test for misbehaviour at high frequencies. If you choose to limit measurement bandwidth to 20kHz you have to include something like the 19kHz + 20kHz test. I didn't invent that procedure btw, I got that from Bruce Hofer at AP who recommends it. In fact his version is even neater, he uses 19.5kHz and 18.5kHz, making sure that even order products sit at even multiples of 500Hz (from 1kHz upward) while odd products sit at odd multiples of 500Hz, from 17.5kHz down, potentially fitting 37 distinct IMD products inside the band. This refinement doesn't make much difference with the 1ET400 amp of course since there aren't that many IMD products poking up over the noise floor.
Given the choice between a sinewave test at 20kHz which only produces inaudible products and a two-tone test that produces all kinds of in-band distortion I go for the latter. By implication, we should be designing a control loop that maximises loop gain all the way up to 20kHz, but not beyond. Any control system obeys a law called the Bode Inequality. This is the closest we control theorists have to mass-energy conservation. In the case of a class D amplifier it implies that if you maximise loop gain over a largeish fraction of the switching frequency you'll have to take it down really fast afterwards. So that's why the wideband THD vs frequency plot goes up somewhat suddenly at the end. It's a compromise I'm knowingly making. Consider the alternative: I could instead pander to the bat-eared crowd and choose to minimise harmonic distortion components up to 40kHz, say. That would mean accepting a lot less loop gain below 20kHz and hence higher distortion in the audible frequency range. It's not a good tradeoff.
Anyhow, this should explain why the high-frequency IMD spectrum is so much cleaner than a wideband THD test would lead you to expect. But as I see it, the former is the one that is most likely to have a meaningful correlation to sound.
(While I'm at it I ought to point out that the idle noise is noise shaped. This is visible on the broadband noise plots where you can clearly see the rise after 20kHz. The extra outband noise is caused by the comparator and driver chips and ends up being noise shaped by the control loop. I only wanted to mention that because the wideband THD vs F plots are mostly swamped by this HF noise which bore some explaining.)
In vindication of that POV we've now seen more than one enthousiastic "subjective" reviews of the 1ET400A go up expressing delight that we have both great measurements and great sound (as if that were a contradiction). I'd like to state here that in our company, as listeners we are fanatic about sound and as engineers we are fanatic about measured results. The trick is to pick a set of measurements that have a modicum of relevance to psychoacoustics (in the case of amplifiers, accepting that hearing goes south beyond 20kHz and that music is more than sinewaves). Once we get the lab result that we expected, we go and listen carefully to make sure we're not missing anything. That's rarely the case so the next stage (playing great music and breaking open beers) tends to follow quickly afterwards.
Oops that's another page long post. I was wondering if I could ask for a favour. I have a proclivity to spending lots of time on very detailed answers but there's other work on my plate too. So what I'd like to do is sign off for something like a week and then sift through any items that come in during that period. So let's have all your questions and round about next weekend the two of us here will go through them.
About correlation between sinewaves and music, we see more and more the 32 tones test (32 sines equally spaced on log scale from 20Hz to 20 kHz).... in the case of amplifiers, accepting that hearing goes south beyond 20kHz and that music is more than sinewaves...