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Audiophonics HPA-S400ET Review (Stereo Amplifier)

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theREALdotnet

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amarsicola

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A trigger input is a 3.5mm TS connector that allows the amp to be turned on by applying a 5-12V DC potential. The trigger is usually driven by a source or preamp. On the amp side, the trigger input usually terminates in an opto-coupler, providing galvanic isolation.
my misunderstanding, no the trigger is not there in the small-case version. Should be in the larger case (the one tested by Amir)
 

Rantenti

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The HPA-S400NC one is using a Hypex NC400 module, so it's different tech. Name's similar because it's still a stereo nominal 400W-per-channel power amp.


If you wanted a "super" Purifi design, rather than a competent one, you'd have to look at something like the Vera Audio where some real work has been done to measure and optimise and tune. Not just swapping bits and not even publishing results...
Sorry for my ignorance.

How are the S400NC using NCore or the S400ET using Purifi different? Is one or the other objectively better in some way? Eg, lower distortion, better dynamics, less heat etc.
 

KMO

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Sorry for my ignorance.

How are the S400NC using NCore or the S400ET using Purifi different? Is one or the other objectively better in some way? Eg, lower distortion, better dynamics, less heat etc.

If you want to dig into info, here are the datasheets:

NC400 datasheet
1ET400A datasheet

The Purifi Eigentakt module certainly objectively beats the NCore on distortion, by a fair margin. But the NCore's already so good there, it's questionable the improvement is human perceptible, not least because speaker and room distortion is way higher.

The Eigentakt wins significantly on idle losses - 1.7W compared to 4.5W, and is slightly better on overall efficiency, so will produce less heat.

Power handling is similar for both, so dynamics should be broadly the same, although the NC400 supports higher current so would be more appropriate for really-low impedance speakers. For 4 ohm or above, they're both suitable. (The new Purifi 1ET7040SA addresses the low-impedance domain, at the cost of some distortion and efficiency).

Both were to a large extent designed by the same person - Bruno Putzeys - and the Purifi is the next generation of his efforts.

To be honest, I think most of us who have chosen Eigentakt over NCore are guilty of just wanting the latest and greatest. I would not want to put money on me being able to tell the difference audibly.

Edit: Oh, and here's Amir's tests+review of a non-Audiophonics NC400-based amp, to compare to this one. But all NC400-based amps should perform broadly the same.
 
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Rantenti

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Thanks for the reply.

The Purifi is newer AND cheaper than the NCore version for the 2 x 400W amp, while both being excellent, it's quite a no brainer choice to get the Purifi. I might get two monoblocks for my speakers.

For the NCore stereo amps however, the HPA S500NC (999 EUR) is much cheaper than the S400NC (1690 EUR), I wonder why the higher powered amp is cheaper?
 

mike70

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The s400nc is dual mono ... I mean, two monoblocks in a stereo chassis

Dual mono vs stereo difference? Well, surely as always ... with standard room sizes / speakers efficiency ... very little or no audible difference in an ABX test
 

Rantenti

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I am quite confused about the gain & bypass mode choices. Audiophonics states that the bypass mode is relevant in cases where the Purifi amplifier is used with a strong preamplifier supporting a load of 2 to 4kOhm with a voltage ~ 10V RMS.

I have a Holo Audio Serene preamp on order with specs as follows

Input: RCA: Max 12Vpp (4.2Vrms) 6800 ohms; XLR Max 24 Vpp (8.48Vrms) 13600 ohms

Output: RCA: 8.5 Vrms 20 ohms; XLR 1: 17 Vrms 3ohms; XLR 2: 17 Vrms 40 ohms

I wonder what gain settings in the amp should I set to get the best performance (clipping/ dynamic range/ crosstalk, best SNR/ SINAD etc) when using the Holo Serene preamp? My room is about 25m² and I use 86dB sensitivity speakers listening at a distance of 8 feet.

Any advice will be appreciated, thanks!
 
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KMO

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From those specs you should be absolutely fine driving the Purifi amp via the XLR with the input stage bypassed, and that should produce the best results. The pre-amp's lower-than-average output impedance means it will cope with the Purifi's lower-than-average input impedance.
 

Matias

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Thanks for the reply.

The Purifi is newer AND cheaper than the NCore version for the 2 x 400W amp, while both being excellent, it's quite a no brainer choice to get the Purifi. I might get two monoblocks for my speakers.

For the NCore stereo amps however, the HPA S500NC (999 EUR) is much cheaper than the S400NC (1690 EUR), I wonder why the higher powered amp is cheaper?
Add the Nilai500 stereo kit as an excellent choice for 1225 euros.

 

Rantenti

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From those specs you should be absolutely fine driving the Purifi amp via the XLR with the input stage bypassed, and that should produce the best results. The pre-amp's lower-than-average output impedance means it will cope with the Purifi's lower-than-average input impedance.

Thanks. I must ask a dumb question. What is the bypass mode actually bypassing?
I have the Sparkos version of the amplifier. Will the amp still be using the Sparkos SS3602 OPA & SS7815 + SS7915 Voltage Regulators in the same way in the bypass mode as in other configurations?
 

KMO

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Thanks. I must ask a dumb question. What is the bypass mode actually bypassing?
I have the Sparkos version of the amplifier. Will the amp still be using the Sparkos SS3602 OPA & SS7815 + SS7915 Voltage Regulators in the same way in the bypass mode as in other configurations?
It's bypassing the buffering op-amp initial gain stage. The core Purifi power module is not very high-gain, and also has a quite low input impedance, so is not well-suited to connect directly to most typical 1-2V pre-amp line outputs - particularly ones from AVRs.

So another amplifier stage is stuck in front to add ~13dB of gain, and provide a higher impedance input.

And that would be the Sparkos SS3602 amp. That would be out of circuit in the bypass mode.

(Some other Purifi amps, like Apollon's, don't totally bypass the initial amplifier, but can switch it to unity-gain mode, so it's still buffering and providing high impedance. But most fully bypass like the EVAL-1 kit did).

If your upstream amplifier can already provide high enough level, and drive low impedances, leaving out the extra stage altogether should benefit overall performance. One less thing in the chain.

But that does mean buying an amp with boutique high-cost op-amps is totally pointless - not even merely debatable, as it would be if it was in-circuit. At least, until a change of installation means you need to use it.

Edit: The voltage regulators I think should be supplying op-amps in both the buffer stage and the main Purifi module, so they would still be used for the main module in bypass mode.
 
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Rantenti

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It's bypassing the buffering op-amp initial gain stage. The core Purifi power module is not very high-gain, and also quite low impedance, so is not well-suited to connect directly to most typical 1-2V pre-amp line outputs - particularly ones from AVRs.

So another amplifier stage is stuck in front to add ~13dB of gain, and provide a higher impedance input.

And that would be the Sparkos SS3602 + SS7815 in your amp. They would be out of circuit in the bypass mode.

(Some other Purifi amps, like Apollon's, don't totally bypass the initial amplifier, but can switch it to unity-gain mode, so it's still buffering and providing high impedance. But most fully bypass like the EVAL-1 kit did).

If your upstream amplifier can already provide high enough level, and drive low impedances, leaving out the extra stage altogether should benefit overall performance. One less thing in the chain.

But that does mean buying an amp with boutique high-cost op-amps is totally pointless - not even merely debatable, as it would be if it was in-circuit. At least, until a change of installation means you need to use it.

Thanks for your explanation. I really appreciate it. I went for the Sparkos edition as my end game amplifier as the product page said the Sparkos voltage regulators were superior in noise/ transient performance over TO-220 format regulators, which I guess are used in the S400ET "normal" version. As an endgame amp, I was hoping I buy something that is state-of-the-art while still relatively affordable.

I'm glad that at least the Sparkos voltage regulators are used in the bypass mode and I hope they are good.

On the other hand, I wonder in what case will I need to use gain configuration 1/ 2, i.e. using the Sparkos SS3602/ Texas LM4562 op amps?

I was thinking like using my Gustard X26 pro DAC and its digital volume control (attenuator) direct to amplifier? Or something like the Denafrips preamps which does not actually increase gain and output at 4Vrms? Then I will need the op amps/ voltage regulators in the amplifier to add gain

Are these examples correct? Are there any other examples which I would be using the op amps in the amplifier? Thanks again.
 
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KMO

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I'm not going to go through the specs of all possible equipment, but you need something that can output 9.6Vrms, and can cope with an input impedance of 2.2kOhm (RCA) or 4.4kOhm (XLR).

If something quotes an output impedance instead, you want it to be at least 10 times lower than the above numbers, so 220/440ohm, preferably even lower, like your Holo Serene.

A bit less than 9.6Vrms would be okay, but that's what you would need to get the maximum 400W out into 4 ohm speakers.
 

Rantenti

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I'm not going to go through the specs of all possible equipment, but you need something that can output 9.6Vrms, and can cope with an input impedance of 2.2kOhm (RCA) or 4.4kOhm (XLR).

If something quotes an output impedance instead, you want it to be at least 10 times lower than the above numbers, so 220/440ohm, preferably even lower, like your Holo Serene.

A bit less than 9.6Vrms would be okay, but that's what you would need to get the maximum 400W out into 4 ohm speakers.
Thanks. The Holo Serene has two pairs of XLR outputs, one of which has an output of 17 Vrms and impedance of only 3ohms while the other pair is 40 ohms. The 3 ohms output impedance of the Serene preamp is really convenient to make it a good match with pretty much any amplifier.
 
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TheBatsEar

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Add the Nilai500 stereo kit as an excellent choice for 1225 euros.
This is before tax. Also you need some cables and an enclosure.
 

Matias

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This is before tax. Also you need some cables and an enclosure.
I think the kit already has the complete package, including chassis, connectors and inner cables, like their NC400 kit had. But let's see when it starts actually selling.
 

amarsicola

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Does the Nilai have an input board? What is the gain?
 

anphex

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I just ordered two Audiophonics MPA-M400ET, the monoblock edition from this beast of an amp. I had a long standing itch to try out Purifi and now I pulled the trigger. The main selling features for me were the stellar build quality and the adjustable gain of the Purifi modules. So excited!
We'll see if I sell my NC400 DIY monoblocks or the Topping PA5 since I only need 4 channels with no more channel to come.

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