Great review. I have this beautifully designed amp and it's good match with my ZMF Verite C. There's little hiss on OTL mode and as far as I know, updated version of Solaris has pre-gain feature.

Wow... seriously this amp was better than standard wa33? this is interesting but the reviewer should have to explained more in detail what makes this amp better than wa33.

Compare with WA33. Solaris has a more dramatic dynamic also a touch faster in bass and treble speed as far as I remember ( I sold my WA33 last December, received Solaris this February). I didn't explain more details because I was not able to have a 1 on 1 comparison at this moment, unlike HA300 which is right next to Solaris.
The elite version WA33 is a whole other story.

@Burakk , thank you for mention that pre-gain update, mine has it installed. I don't get any hiss from all my headphones.

@DrummerLeo the differences is that dramatics between standard wa33 and wa33 elite, no wonder the hefty price increase on the elite.

@DrummerLeo I guess, it was added on 2020 models. It’s not really remarkable but there is.

@DrummerLeo what are the ACME 300b and Ken-Rad VT-231 the tubes you now use for your HA-300? I have the Psvane ACME 300b and the Sylvania 6sn7W metal base, and both combination gives me huge soundstage with fast transient, excellent timber, and best impact on bass that I've heard when paired w/ the ACMEs, to go along w/ the sweet mids and airy treble

@jambaj0e I have borrowed Sylvania 6sn7w metal base for a week. I think it is better than Ken rad vt231 in mid and treble. KenRed has slightly deeper sub-bass, and punchier mid-bass. I had some trouble finding NOS Sylvania, so I stick with KenRed instead.
I do agree ACMEs have a great improvement in soundstage, speed and transparency without sacrificing the sweetness in mid and treble(unlike erlog 300b, which have great dynamic and speed but the treble sounds a little harsh). But ultimately ha300 is a 300b amp, it is extremely refined, airy and smooth. Solaris on the other hand is not as smooth as HA300, but it has greater dynamic change, punchier bass, fuller body in lower frequency.
I equally love both amps, both of them are masters of their own.

When I had the Solaris here, if I turned the volume up loud with the Susvaras, the amp began do clip. Have you experienced the same thing?

then you may not be using the correct mode matching for the Susvara. We are currently supplying the Solaris with Russian tubes of the 6F5P type because these are more powerful.

Thank you for the great write up. You mention that Solaris sounds a lot smoother than RKV3, but as I understood they should have the same sound signature, or has the sound changed with new generations of amps?

@DarginMahkum, Good catch on that. I was thinking about deleting that part during editing because I think it might confuse someone. I had experience with RKV3 many years ago on a completely different setup-- different cables, different DACs, different sources... At that time, RKV3 was a pass, because it is a bit too rough and edgy in the treble. But with Solaris things are very different, I'm not sure about what caused these changes, the DAC itself or the whole setup. Also, I think Mr. Helmut had made some changes on Solaris; I believe RKV3 has 8W output power, Solaris has 12W; the 2020 edition Solaris also has an upgraded pre-gain module, I believe both changes would make some effect to the sound.

Great review and I am saddened I did not read this sooner. I know this is a headphone community and all but the Solaris has the capacity to drive speakers and so I wondered what if any yu had used and what results you had?