I've been using my AP10H with Focal Elear headphones over the past week. Now these are quite strange cans. They have big gap between 4k to 6k. I sorted that with PEQ in Roon. There are also forum criticisms saying they are too bassy. I tried them with a JDS Atom, the amp that measures close to perfectly according to Audio Science Review but couldn't get on with them. They are very lively, a strong dynamic sound compared with my Sennheiser HD650s but with the atom they sounded unfocussed and a bit harsh and definitely not too much bass. I found myself going back to the Sennheisers before a headache set in.
Next try was with a Schiit Valhalla 2. This was better and surprising. The Schiit is an OTL valve amp said to be best suited to 300 ohm Sennheisers or 600 ohm Beyers etc. The sound was fuller than the Atom, better bass but lacked clarity in the mids and highs, so not a permanent solution.
So I grabbed my AP10H from the bedroom system. It's little used as I found the atom to be better with Sennheisers. The NVA was too powerful with the HD650s. I could hardly turn the volume pot before it was too loud. Expecting this to be worse with the 80 ohm Elears I didn't have high expectations. How wrong I was though. The sound is full, refined and thoroughly enjoyable. The bass is superb.
Also, there was a bit more range available on the volume pot before it got too loud. The Elears sensitivity is 104 dB, the HD650 is 103 dB so this was surprising. I think the highs may be a bit reserved though. They're present and sound refined, more like listening to good speakers than headphones.
So, I was wondering whether the AP10H has a high output impedance and whether this might be playing a part in the results I'm getting.
The final step will be to put a linear power supply on the Raspberry Pi I'm using as a Roon endpoint. Both the switchers I have cause a slight buzz through the AP10H. It's not audible when music is playing but I'd like to get rid of it.
