
Grados & OTL/OTC Tube Amps
I bought a Valhalla 3 this summer as my first OTL tube amp purchase and have been loving it. I landed on the Valhalla vs the many other options out there specifically because of the Impedance Multiplier as my headphones (RS2x & Arya Organic) are both low impedance. Figured it would be necessary.
The ubiquitous wisdom online suggests low impedance cans do not play well with OTLs due the high output impedance of the amp vs. the low input impedance of the headphones. More specifically, I’ve read that the headphone impedance should be roughly 8x the amp’s output. Thankfully, the impedance multiplier makes this a non-issue.
However, in the months since and using it daily, I’ve found that my preferred settings when paired with my Grados (38ohm input impedance) is High Gain w/o Feedback (60ohm output impedance) with the multiplier off. To me, it sounds better than the low or high gain settings w/ feedback and multiplier on.
So my question is: Why does this work? Why am I not hearing a ton of unpleasant distortion, flabby low end, etc. with this pairing? The Arya Organics absolutely need the multiplier and sound better with it, so is there something about Grados (impedance spikes in certain frequency ranges maybe?) that makes the apparent mismatch a non-issue? Am I misunderstanding this?
tl;dr: 38ohm Grados sound great on tube amp with high 60ohm output impedance, why? how?