There is an update to this, but I'll start from the beginning.
I did the voicing of the headphones on several amps:
SAEQ Hyperion Ge (at 32 Ohms),
Firstwatt J2 (at 32 Ohms) and
VM-1a in Triode Mode,
representing a group with very similar "organic" sound, where J2 is a bit "bigger" sounding that the other two (which are very, very similar, almost identical sounding amps).
Then,
RAAL-requisite HSA-1b, VM-1a in Pentode Mode and Benchmark AHB2 (at 32 Ohms), serving as a "control" amp.
And recently, Solaja dropped by with 300B² prototype (used with 32 Ohms Interface), which was very interesting and Dragan from SAEQ with his new uber-amp prototype
which (used with 32 Ohms Interface) sounded really accurate, smooth yet lively...I liked both a lot.
Dragan from SAEQ also brought the SAEQ HSA-1c that was not strictly developed to sound best only on ribbon headphones, like RAAL-requisite HSA-1b, but to inject more life into planars, for more versatility, and I listened to it on XLR inputs and it was a bit too open for me, like Benchmark, which is not my favorite amp any more.
I wanted to explore more about this C version, so I tried it on RCA inputs and things settled down nicely. Plugged in a smoother sounding cable and that was it.
Then, I've had a panel of 4 listeners, my control group of local audiophiles, speaker listening guys, to see what they say about Hyperion Ge vs. HSA-1c.
The listening was at pretty high SPL.
The result was 50/50. Half preferred SAEQ HSA-1c and half preferred Hyperion Ge. My vote didn't count, but I'm in Hyperion Ge camp.
So, it was just like what you could expect.
I'll explain...
Amps can have even-order, 2nd harmonic-dominant or odd order, 3rd harmonic-dominant distortion characteristics.
It is known that people's preference in distortion characteristics of amplifiers are about 50/50 in preference to even/odd distribution of generated harmonics.
The HSA-1c is not a typical representative of odd order group, it has a good amount of 2nd, but it is close enough to be sorted in that group and Hyperion Ge is typical representative of even order 2nd harmonic-dominant distortion content with almost logarithmic envelope of all other harmonics up to 5th and practically no higher harmonics than that.
Now, if you listen to headphones softly, you will likely not hear much of a difference.
It takes speakers to really load beefy amps like these, but at power levels for headphones, especially with people that listen softly, it is more likely that you will rather hear the general tone balance of the amps, more influenced by the choice of caps and wiring type and wire layout inside...
So, to show that I'm serious, we will do the WOH Heidelberg with SAEQ HSA-1c, properly driven at RCA input with the right cable for the job.
There will also be other amps to test, of course, it's a show...