Audiophonics HPA-S400ET Review (Stereo Amplifier)

[KaMatthi]

Well the IOTVX has no option of changing any settings.

Sorry for not being clear. The Audiophonics is way more satisfying compared to the IOTAVX. It’s not day and night though. But it makes more fun for sure. The IOTAVX does its job very well just not that satisfying like the Audiophonics.

 

[nemesis.ie]

Ah, that makes more sense.

So did you get to try bypass mode?

There shouldn't be night/day difference on any properly designed amp that can cope with the speakers connected.

 

[KaMatthi]

I did not, that will be done tonight.

 

[nemesis.ie]

Looking forward to hearing how that goes and if you notice any difference in tweeter hiss (assuming you can hear any currently).

 

[KaMatthi]

Hello, so I tested today in the morning the bypass setting. The popping while starting the amp on my tweeter still exists. Afterwards no hiss can be heard. But I came to some constraints while I took a new dirac measurement. The gain of my IOTAVX (my second one) is so high compared to the gain for bypassing is very low. Setting them up into equal volume was difficult. Now I am wondering what would be the second best choice. Coniguration 1 or 2?

 

[nemesis.ie]

Another option might be attenuators on the Iota?

 

[KaMatthi]

What exactly do you have in mind?

 

[nemesis.ie]

Work out how many dB the Iota is over the Purifi in bypass and pop the appropriate attenuator on the input of the Iota.
Probably about €5 to €10 each. Maybe try one to start with and see how it goes.

Or e.g. a nobsound "little bear" is about €40 and gives you a volume control for 2 channels. I use them with Emotiva HC-1s (!) for running subwoofers.

 

[KaMatthi]

Before I am going to evaluate that, I still need with the high gain to check with a new Dirac measurement. To be fair, last time listen to the Adiophonicsamp, I did not remeasure all new. So maybe the high gain configuration would be the 2nd best option?

 

[nemesis.ie]

I'm not familiar with how Dirac calibration works or what "pre-setup/calibration" options it has. I use a Trinnov.

 

[KaMatthi]

Well I guess, it doesnt matter what measurement system is behind. If you drive different amps with different gain, probably everyone need to remeasure...?
According to Amirs' measurment the option gain high is not way much worse than bypass or am I mistaken?

 

[nemesis.ie]

Well you need to balance everything in any system for sure.

What dB difference did you see in the measurements? Remember it's logarithmic, just a few dB is a huge difference.

 

[KaMatthi]

I need to check.

 

[maruko]

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.

The Audiophonics gain buffer is set to off, so with this setting the amp has 10V input sensivity.

Since I perceive a loss of low frequencies energy (I feel it like “weakness”) and a predominance of medium-high frequencies with this setting (compared to the configuration with input buffer ON And even more compared to other AB class amplifiers I had such as the Pass X150 and Gamut D200), I wonder if it is only my subjective impression or if indeed, it may depend on the fact that the input impedance of the amplifier with the deactivated buffer is “only” 4k Ohm, instead of the 96K Ohm with the active buffer.

Since the output impedance of the Topping A90 is only 40 Ohms, should be sufficiently low compared to the input impedance of the amplifier with the input buffer set to off (ratio of 1:100, 10 times greater the 1:10 rule of thumb).

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

 

[Head_Unit]

input impedance of the amplifier with the deactivated buffer is “only” 4k Ohm, instead of the 96K Ohm with the active buffer...Since the output impedance of the Topping A90 is only 40 Ohms, should be sufficiently low compared to the input impedance of the amplifier with the input buffer set to off (ratio of 1:100, 10 times greater the 1:10 rule of thumb).

Specifications are not always correct, and the impedance is rarely flat versus frequency --> changes can affect the pass-through frequency response. However, these ratios make imagination the most likely difference...then again again the buffering circuitry could quite conceivably affect the sound.

 

[maruko]

the buffering circuitry could quite conceivably affect the sound.

Could you better explain this? Affect the sound in what aspect? Frequency response?

 

[Joel G]

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)

 

[maruko]

Me the same. I ended up with the buffer ON and the gain set to 20dB.

My only concern was if the output voltage from the Topping A90 (8V) could be a little too high for the input sensivity of the amp at this settings (4V).

But in the end I think that 8V output voltage has to be considered at full 100% volume pot and anything around 70% should be much less than 8V. I'm right?

 

[VintageFlanker]

My only concern was if the output voltage from the Topping A90 (8V) could be a little too high for the input sensivity of the amp at this settings (4V).

No worries. You will hear your amplifier clipping long before you happen to feed it with 8Vrms.

 

[anphex]

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.

The Audiophonics gain buffer is set to off, so with this setting the amp has 10V input sensivity.

Since I perceive a loss of low frequencies energy (I feel it like “weakness”) and a predominance of medium-high frequencies with this setting (compared to the configuration with input buffer ON And even more compared to other AB class amplifiers I had such as the Pass X150 and Gamut D200), I wonder if it is only my subjective impression or if indeed, it may depend on the fact that the input impedance of the amplifier with the deactivated buffer is “only” 4k Ohm, instead of the 96K Ohm with the active buffer.

Since the output impedance of the Topping A90 is only 40 Ohms, should be sufficiently low compared to the input impedance of the amplifier with the input buffer set to off (ratio of 1:100, 10 times greater the 1:10 rule of thumb).

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

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