Buying experience
I ordered the Audiophonics HPA-S400ET Sparkos Edition a couple of weeks ago. It was out of stock at the time of order, but I was promised a 15 day lead time.
My buying experience with Audiophonics was very good: detailed and instant replies to my questions, and updates on the shipment (1 day UPS shipping from France to Denmark). I was able to purchase B2B with my VAT no.
Setup
B&W 802 Diamond speakers, [insert amp here], Trinnov ST2 Pro correction hardware, Imperium monitor controlller, Lynx HiLo DAC.
Current Classé CA-2300 Delta
My current amp was a Classé CA-2300 Delta, Class A/B. Purchased for approx. 52.000 DKK (EUR €7.000 / USD $7,000) in 2013. The left side blew something recently and I had to get it serviced for a whopping €/$1,345.
The Classé sounds great, lots of power, very clean. It uses quite a bit of electricity in idle mode and has a quiet fan that rarely gets to spin up. I don't put my amps into standby as I use them every day in the studio at random times.
Loaner NAD C298
I got a brand new NAD C298 on loan, but it didn't sound right to me.
Most likely it's simply me being used to different (Class A/B) amp for many years. The low end felt lower and less solid with the C298, the midrange (perhaps as an indrect result) more pronounced compared to the Classé.
Another explanation for my dislike could be a technical mismatch, namely that the still active Trinnov ST2 Pro profile was based on the Classé and it not matching the C298. Or it could be psychoacoustical: the C298 might be more precise; but cleaner also means less perceived sub frequencies due to lower harmonic distortion than what I was used to.
The C298 pulled up a very low level hiss even when turning down the gain to the minimum setting or when using the fixed setting - I wasn't able to find a way to remove the hiss.
The annoying auto-sense can be shut off, fortunately, but I didn't bother for the two weeks I had it on loan.
New HPA-S400 ET Sparkos Edition
With the HPA I was able to set the jumpers to bypass the gain. To match the bypass setting, I changed the jumpers in my Lynx HiLo DAC on the isolated monitor output from -11 dBu to -24 dBu to ramp up the voltage. This allowed me to reduce the hiss to an inaudible level and have plenty of power.
Nice case and neatly done inside. Everything looked stellar. All torques screws had equal pressure, which satisfied my OCD.
Unlike the C298 the HPA-S400 ET sounded right in the low end, which contradicted my inital assumption that the Trinnov profile could be the culprit. Since the HPA-S400ET measures even better than the C298 then psychoacoustics aren't to blame either. So either it's good old placebo or confirmation bias, or the C298 I have on loan is a bit off from the factory.
I decided to hire the same external consultant I used in 2015 to help me make a new Trinnov measurement for the HPA. Same room, same speakers, same monitor controller, same studio console, same measurement mic, same guy(s). The Trinnov 3D measurement mic was placed using a gyro laser level. This allowed us to get the same placement ± a few mm in the sweet spot.
The differences in the measurements between the Classé and the HPA were small or inconclusive, but then again an acoustical measurement is a different beast since there are many variables. The largest difference was around 10 kHz where there was a ±1.25 dB between the two amps in the same setup, withe HPA having more energy there. Obviously I can't tell which is "correct" - only that there's a difference.
We did several additional measurements between 0 and 40 cms on the Z-axis and they all confirmed a variation in this frequency area, so it's not acoustical, i.e. not due to a difference in mic placement between the two amps. It will make the HPA sound a bit more sparkly compared to the Classé or vice versa, if you will.
I'm saving on electricty with the HPA, about €/$399 a year (Danish energy prices are crazy), so I'm probably buying another HPA (non-Sparkos) to replace another old Class A/B amp. That's a big bonus you can tell yourself (or your wife) when switching out ye olde Class A/B for a brand new Class D.
One criticism is that the HPA doesn't come with any kind of manual or even a piece of instruction paper, but that's what Google is for. Also, the heat sinks on the sides of the unit can resonate at high frequencies. I'm not sure if that's a real life issue at 3 meters listening distance, but I'm thinking about dampening them somehow. Last thing: the power on LED is quite bright and can't easily be dimmed.