I bought this amp as an upgrade to the amp section of RME ADI-2 DAC.
While this section is good for All in One unit, I did not expect to be shocked after adding the RNHP to the chain. If you are a spec believer, well that's fine, but that's not the case here. Forget about numbers and watts. These are just numbers. We are talking for proper drive, effortless sound, complete instrument separation with wider space, punch, rich and vivid midrange.
I am using TIDAL connected to Audirvana Player with a MacBook Pro. USB cable from Audioquest. XLR cables are pro line of Bespeco. Headphones cables are stock.
My headphones are:
Sennheiser HD650: I have a tube OTL headphone amp for this pair and its super addictive but I preferred it with the RNHP and it drove it to the full potential easy. Not much to say for this headphone as its midrange is reference level already and this amp added a vividness without distorting it. A very nice pair! I suppose the HD600 will behave the same but I don't have it here to test.
MrSpeakers Aeon Flow Open gen.1 : This was my least exciting headphone and with RME sounded so relaxed that sometimes I found it super laid back and the reason that I kept it, was to listen to only jazz relaxed tracks. Well this headphone was the surprise with the RNHP. It came to life and I am not hyperbolic at all here. It is so exciting and so resolving, the timbre feels right and all instruments sound as they should and too realistic. This headphone is the reason that proves that watts are numbers. 14ohm and 94db is not easy to drive and many amps found it difficult as a load but the RNHP is not. The biggest surprise here.
Audeze LCD-X : Well RME did already a pretty good job with this headphone alone, of course with EQ settings as this Headphone is so wrong in timbre and tuning, yet resolving and super addictive bass (when add few db to 100hz region of RME EQ). RNHP did improve the mids a bit and relaxed the highs just a touch. Bass had more impact but did not extended to layers so much as the RME amp.
Genre Pairing: This amp loves everything with instruments and vocals. For electronic music only and heavy bass or so, a THX or a good measuring amp with power and drive will do the job (maybe better)
I love warm headphones and the RNHP made them even better. It will not correct a bad headphone but it will give the kiss of life to the already and correctly tuned ones.
This is easily the best upgrade I have ever done after finishing the source and headphone part.
Hope that helps.