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Audiophonics HPA-S400ET Class D Purifi amp

mocenigo

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RME recommend adding these xlr attenuator which are selectable from 10-30db. JTS MA-123. Just add them to the output xlr on your dac. I use them with my Audiophonics Hypex and can keep the volume at around -20 to -10 for music. Other brands are available.

The JTS are excellent, and more expensive "audiophile" ones are probably unnecessary, as the resistors in the JTS seem to be very closely matched and non inductive. Of course feel free to make your own using Duelund CAST resistors - as far as boutique stuff goes they are not outrageously expensive. But I have used JTS ones and I cannot really say I have ever detected any degradation in audible sound quality.
 

outfaced

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I got my AUDIOPHONICS LPA-S400ET already for a bit more than a week ... side by side with dual mono A/B P1 poweramp from ATC (2x the cost of the AUDIOPHONICS amp).
Really interesting thing this comparison.
Frankly speaking will be happy with both of them and cant say which is better, even there are very different and this is not a matter of critical listening at all, but the differences strike you with the first tones.
To make it more visual the purify is like a sharp vivid hi-res image from a top of the line camera and the P1 is like a painting form a famous painter where with strokes of the brush are trigering the imagination and you enjoy the beauty even is not the real thing. :)
Was a little bis surprised from the difference considering ATC is a brand with roots in the studio equipment with purse for realism in the sound reproduction. To be more specific the ATC has more fine details especially on the top end where it sounds far more airy and interesting BUT all of this is fake and although i enjoy this details every time i play over the ATC, after switching to the purfy comes the more natural sound. Perhaps not so beautiful in the meaner of the painting-beautiful but caches you with natural presentation, full body sound and more punch. It very depends from the mood and from the music playing which one really shine ... The P1 has more the potential to "sit back and relax listening" and softens the music on a very specific way - bass is still fast and punchy, everything is there, but i can listen for hours. The purify is more exiting, but can get also a little bit too obtrusive sometimes.

Now ... because i like tuning and experimenting i am interested if somebody tried other input buffer board or another opamps. I know they don't measure better but its interesting if they sound different and how.
Thomas & stereo said there are noticeable difference with the Neurochrome Input Buffer ... and there are also many opamps possibilities also.
 

luxpiotr

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Someone can tell me about sonic quality of Audiphonics vs EVAL1 vs NAD?
What is quality of input buffer in Audiophonics LPA-S400ET? Is it worse than EVAL1 or NORD or VTV or NEUROHROME?
Is it possible to buy Audiophonics and then change input buffer for example VTV?
 

litemotiv

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Someone can tell me about sonic quality of Audiphonics vs EVAL1 vs NAD?
What is quality of input buffer in Audiophonics LPA-S400ET? Is it worse than EVAL1 or NORD or VTV or NEUROHROME?
Is it possible to buy Audiophonics and then change input buffer for example VTV?

In principle all variants should sound transparent, but you have the option to change the Audiophonics OP amp if you want.

Audiophonics uses TI-LM4562 by default, which on paper has slightly lesser specs than the OPA1612 and OPA1656 which are used in the other custom implementations (EVAL, VTV, Neurochrome, BoXem etc). It will almost certainly be the case that you will not be able to hear a difference, but if you want to put your mind at ease you can get one of those OP amps instead.

I think NAD uses their own buffer implementation but i'm not sure.
 

Kennyknetter

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Someone can tell me about sonic quality of Audiphonics vs EVAL1 vs NAD?
What is quality of input buffer in Audiophonics LPA-S400ET? Is it worse than EVAL1 or NORD or VTV or NEUROHROME?
Is it possible to buy Audiophonics and then change input buffer for example VTV?
Amir has tested various input buffers, only to find no differences. Just go with any of them.
 

tmtomh

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Amir has tested various input buffers, only to find no differences. Just go with any of them.

I agree. I bought this Audiophonics HPA amp back in May 2020, bog-standard with no special options, and I have no complaints: no audible distortion, no detectable frequency nonlinearities, dead quiet without any audible hiss or hum with ear up against speaker, runs cool, plenty of power. My view is that the best input buffer is the cheapest/default one, because why pay more for no difference in performance?

Subjectively the amp sounds slightly "cleaner" and seems to have slightly more controlled bass than my prior amp (Adcom GFA-5400), but of course those subjective differences might disappear if I did a proper blind test. At the very least it certainly performs no worse than that heavy, hot, Class AB piece of "big iron" (no offense to Adcom - it's still a great amp IMHO). What I know would hold up objectively is that the Audiophonics is much quieter than the Adcom without a signal playing, as the Adcom produced low-level but clearly audible self-noise. And what's also objectively true is that the Purifi modules have very good speaker protection, whereas the Adcom has... none. And to the best of my knowledge, the amp does not have the notorious "pin 1" XLR grounding problem.

I would actually recommend the Audiophonics amp even more today than I did after I first got it, because the current version has been slightly tweaked from the original: the current version has some different internal component orientation and cable routing, eliminating an issue where the R channel would have audible hum if nothing was connected to the input. Of course this is a non-issue in practice since it's literally impossible to actually use a power amp for listening unless you have something connected to the input - but still, it's good to see that Audiophonics addressed this engineering/design issue. I also think the new ones have a 12V trigger, whereas mine didn't come with one. And while I know this is not a priority for a lot of members here, I also appreciate that the Audiophonics amp includes both balanced and unbalanced inputs.

The only downside I can think of with this amp is that if you want to change the gain setting (low gain from input buffer; high gain; or bypass) you have to open it up and move one circuit board jumper on each input buffer channel. Some other amps have externally mounted gain-change switches (although on the other hand some have only two settings and some have no ability to change the gain).
 
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amarsicola

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Dear @Audiophonics , you say that in bypass mode the Purifi amplifier can be "used with a strong preamplifier supporting a load of 2 to 4kOhm with a voltage ~ 10V RMS"
Now i am wondering if a 5volts good dac such as a Topping D70s (that you also sell) could support such 2 to 4kOhm load (In my case i wouldn't bother not having the Purifi working at its maximum capability).
And, using the bypass configuration, is the input board still providing filtering from radiofrequency interferences?
 

mocenigo

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Amir has tested various input buffers, only to find no differences. Just go with any of them.

He did not test a build with the Neurochrome buffer, which has a significantly higher S/N ratio and lower THD, IMD than the other buffers (the Neurochrome is a composite amplifier and all other ones are simpler single opamp circuits). Since noise and distortion are amplified by the Purifi module and added to the latter’s, there could be (and some easy back of the envelope estimates using the publicly available data strongly hint at) better SINAD with a Neurochrome/Purifi build, with the standard buffer gain of 13Db and probably more so with a 7Db buffer gain setting.

This would be interesting to test, but I am quite confident that there are differences, mathematics usually does not lie.

I think that (subjectively and not controlled) the Neurochrome/Purifi combination sounded better than the Eval kit and also with another single opamp (discrete, Sonic Imagery) board.
 

tmtomh

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Wait, so does the Audiophonics default buffer have better or worse specs than the OPA buffer in the EVAL,VTV, etc.? One person above says worse (albeit likely not audible) while another person says better.

Can anyone clarify? Thanks!
 

mocenigo

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Wait, so does the Audiophonics default buffer have better or worse specs than the OPA buffer in the EVAL,VTV, etc.? One person above says worse (albeit likely not audible) while another person says better.

Can anyone clarify? Thanks!

The LM4562 has slightly worse noise and distortion measurements than the OPA1612, but the difference is so small that it probably does not change the total SINAD of the complete amplifier for buffers that have a simple single ended circuit (like the EVAL buffer, the VTV, Nord, Apollon, Audiophonics buffers and many others).

If you use the LM4562 in a buffer whose circuit is a composite amplifier (which uses two cascaded opamps, with nested feedback loops), then the performance of the whole buffer gets significantly better and in this case some argue that is also better to use than a OPA1612, because the phase has smaller shifts (and therefore the feedback loop is more effective).

So if the Neurochrome buffer works better it is because of the circuit: just compare the measurements on Neurochrome's site with those in the data sheets of the LM4562 and OPA1612, which apply because they refer to a simple single ended circuit.

(Note: I am also oversimplifying a few aspects. Not all buffers of the same type are born equal. PCB design has a role. The type of power supply also plays a role. And if a circuit has intrinsically better CMRR this may trump a bit the differences in CMRR between opamps. Some discrete opamps like the Weiss have an extremely good CMRR (88 Db from 20Hz to 20Khz) whereas the Neurochrome buffer starts to drop above 1Khz. This said, I have no idea what is the impact of this on the sound, but the Weiss discrete opamp beats any integrated one on the market, performance wise, and it is probably the only discrete opamp that does that, so there are many, many variables to consider.)
 
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S-unny

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KMO

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They were talking about a trigger output from the DAC to automatically turn on the power amplifier when the DAC is turned on.
 

DSS

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After comparing published specifications, I see the only difference between AUDIOPHONICS LPA-S400ET and the new
AUDIOPHONICS MPA-M400ET is XLR input impedance: 100 versus 96.
I also see a fuse in S400 versus a switch in M400...

Planning to buy next week...Any help deciding one to choose, a single stereo S400 or a couple of M400 , please ?
Thank you.

https://www.audiophonics.fr/en/powe...eo-amplifier-purifi-2x400w-4-ohm-p-14557.html

https://www.audiophonics.fr/en/powe...mono-class-d-purifi-1x400w-4-ohm-p-14951.html
 
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