Audiophonics HPA-S400ET Review (Stereo Amplifier)

[amarsicola]

Hi, I need some help.

I use a Topping A90 as a preamp connected via XLR to the Audiophonics HPAS400ET.

I use the “M” gain setting on the Topping (+6dB).

Since my DAC is a Topping D90 connected via XLR (4V out) to the A90, so the output voltage to the Audiophonics amp should be 8V.

Why don't you just connect the D90 to the Audiophonics and sell the preamp? You are adding unnecessary stuff in the middle. If you use A90 for headphones, you could connect it to D90 via RCA and use XLR for the Audiophonics, or use a simple XLR selector as an alternative

 

[amarsicola]

My speakers are B&W 702S2 with 87dB sensivity and work at 6 Ohm most of the time with 3 Ohm peaks.

Sorry to say, i would focus more on loudspeakers here, B&W have a quite "idiosyncratic measured behavior" as stereophile says...
Check Amir's reviews of Kef R11 or Revel 208 (similar price range of your B&Ws towers) to have an example of a correct frequency response. Don't hate me now ;-) I was a victim as well of sexy British manufacturers (PMC) with poor objective performance

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[JohnnyNG]

I’m also curious about your question, I had a similar feeling when i tried a Pre90 to the HPA-S400ET on buffer-bypass mode. I also thought that the “matching” impedances between them were fine, so in theory it should have worked fine. However i returned the HPA to medium gain buffer and kept it the ever since because it felt more right to my ears (or expectations)

Very much agree with this. I have a pair of MPA-M400ET monos and my plan was to use them in bypass since, as you note, driving them should be no sweat for a Pre90. Compared to medium (or high) gain, however, bypass just sounded kind of muted and "colorless". Took me a while to give in and change them back to buffered since I didn't think what I was hearing made sense.

 

[maruko]

Do you use any adaptive loudness? The gain offsets your loudness curve and may reduce bass if your reference level is different.

No

 

[maruko]

Why don't you just connect the D90 to the Audiophonics and sell the preamp?

It’s ok to use the digital volume control? Any loss?

 

[maruko]

Sorry to say, i would focus more on loudspeakers here, B&W have a quite "idiosyncratic measured behavior" as stereophile says...
Don't hate me now ;-)

I don’t hate you because my B&W are yet on eBay and my next purchase is Revel M16

 

[maruko]

Very much agree with this. I have a pair of MPA-M400ET monos and my plan was to use them in bypass since, as you note, driving them should be no sweat for a Pre90. Compared to medium (or high) gain, however, bypass just sounded kind of muted and "colorless". Took me a while to give in and change them back to buffered since I didn't think what I was hearing made sense.

Same identical thing for me

 

[Salt]

It’s ok to use the digital volume control? Any loss?

Yes, and no.

 

[Salt]

Very much agree with this. I have a pair of MPA-M400ET monos and my plan was to use them in bypass since, as you note, driving them should be no sweat for a Pre90. Compared to medium (or high) gain, however, bypass just sounded kind of muted and "colorless". Took me a while to give in and change them back to buffered since I didn't think what I was hearing made sense.

If You compared level adjusted and ABX-ed ...

 

[VintageFlanker]

It’s ok to use the digital volume control? Any loss?

You lose ≈1dB SNR per dB of volume attenuation.

 

[amarsicola]

It’s ok to use the digital volume control? Any loss?

I remember hundreds of discussions about this, one of them is https://www.audiosciencereview.com/...olume-control-vs-analog-volume-control.20512/
Try to put everything at max volume while playing nothing. Would you hear any noise? It is true that you might loose something in terms of sound/noise ratio, but with topping dac and purifi amp the noise is irrelevant in absolute value, and still the environment will give you most of background noise.
AND, most importantly, would you hear any difference compared to your current setup?

 

[nemesis.ie]

Regarding buffered/not buffered "issues":

Are you measuring for comparison or is this just "by ear"? Can it be adjusted via EQ?

I run unbuffered to remove tweeter hiss and have room EQ in place and certainly don't find anything muted/missing. Bass from the speakers (80 Hz XO to subs) is punch and powerful. Both with my previous Emotiva speakers (C2+, C3+, B1+, A1+) and current Fyne Audio F500s, F500Cs and F502Cis.

They sound the same as the level matched Topping PA7+ (driving 2 Emotiva A1+s) after EQ too.

No noticeable bass difference versus the previous Emotiva UPA-1 nor HC-1 amps in this respect either. The Audiophonics units take up much less space and run cooler (more efficiently) of course which is the big + along with SN/R/lack of tweeter hiss due to the low gain setting.

IMO EQ is important.

 

[cicastol]

Hi, I need some help.

I use a Topping A90 as a preamp connected via XLR to the Audiophonics HPAS400ET.

I use the “M” gain setting on the Topping (+6dB).

I'm using this configuration (bypass, A90 medium gain) and IMHO is the best.

 

[Salt]

A source with low output impedance and 8-10 V max output voltage should be able to drive the amplifier module flawless without buffer.

 

[wyup]

You need a powerful preamplifier to drive the high load of 4.4 kΩ, with an output impedance as low as possible to drive it with enough current and capable of 9V. For this I would choose a preamp with dedicated substantial transformers.

Topping Pre90 and D90 preamps might be a toy for this load. They have low output impedance and high voltage output level at high gain, but how can it pull oscillating current at low voltages, that's to say normal volumes?
I never liked Topping Pre90 or D90 because they both hide in specs that they have a low input impedance of 2 kΩ in XLR. What do you do if you have a ladder dac like a Denafrips Ares of 1.2 kΩ output impedance? It can't drive the Pre90, so the problems start there.

Everybody seems to use these Topping preamps with the Purifi. If you want to bypass the input buffer opamps, which are no substitute for a proper preamplifier by the way, choose a powerful one. Not just low output impedance or high brute voltage, but 'cojones' from the transformer to pull from the load at low voltages. The input buffer from the Audiophonics using opamps and big value resistors is the easy way to bring up the impedance, but this is rather a compromise (noise from the resistors and the opamps changing the sound).

This is my two cents.

 

[JohnnyNG]

You need a powerful preamplifier to drive the high load of 4.4 kΩ, with an output impedance as low as possible to drive it with enough current and capable of 9V. For this I would choose a preamp with dedicated substantial transformers.

Topping Pre90 and D90 preamps might be a toy for this load. They have low output impedance and high voltage output level at high gain, but how can it pull oscillating current at low voltages, that's to say normal volumes?
I never liked Topping Pre90 or D90 because they both hide in specs that they have a high input impedance of 2 kΩ in XLR. What do you do if you have a ladder dac like a Denafrips Ares of 1.2 kΩ output impedance? It can't drive the Pre90, so the problems start there.

Everybody seems to use these Topping preamps with the Purifi. If you want to bypass the input buffer opamps, which are no substitute for a proper preamplifier by the way, choose a powerful one. Not just low output impedance or high brute voltage, but 'cojones' from the transformer to pull from the load at low voltages. The input buffer from the Audiophonics using opamps and big value resistors is the easy way to bring up the impedance, but this is rather a compromise (noise from the resistors and the opamps changing the sound).

This is my two cents.

Interesting. Based on Amir's review, Pre90 SINAD stays high up over 8V but is there something in the FR etc. that may have been missed into a punishing load? Stereophile tested the Pre90 as well but it seems mostly into 100k ohms.

 

[amarsicola]

I don’t hate you because my B&W are yet on eBay and my next purchase is Revel M16

Check measurements of the new AsciLab speakers, to be released soon...

 

[amarsicola]

The input buffer from the Audiophonics using opamps and big value resistors is the easy way to bring up the impedance, but this is rather a compromise (noise from the resistors and the opamps changing the sound).

Amir tested the Audiophonics both with bypass and with the buffer, result is that sinad is quite the same (maybe you loose 1db). The opamps that audiophonics uses are more than good, if i'm not wrong they are the ones suggested by Putzeys himself. I think there is no evidence anything goes wrong if you connect directly the topping dac to the audiophonics.

 

[wyup]

So then why all these people complain that bass is lacking with bypass and Pre90/D90?
There is more than meets the eye.

 

[amarsicola]

So then why all these people complain that bass is lacking with bypass and Pre90/D90?
There is more than meets the eye.

Or is it just an illusion? A microphone can give us the answer