Slowely Upping My Game

Looking around at various OTL headphone amplifiers, leaves me with the impression that a Feliks or Woo Audio would make sense for headphones at 300 ohm’s but would be overpowering for a pair of 32 ohm headphones. 

Just to be clear, most OTL tube amps become LESS efficient into 32 ohms, because of their high output impedance. A lot of power gets burned up before the headphones. These amps are generally a lot happier feeding into 300 ohms. An OTL tube amp with 300-ohm Sennheisers (e.g. HD600) was a classic pairing in the early days of head-fi. However, since inefficient planars started taking over the high end, I guess OTL tube amps have dipped in popularity. They’re not good for much power into 50 - 60 ohms unless they’re using big power tubes. Small signal tubes won’t cut it there (e.g. Susvara).

Now this doesn’t exactly matter when you use extremely efficient dynamic coils such as you have. You’ll have enough power regardless. But a typical OTL tube amp will definitely cause an audible bass boost into most 32-ohm dynamic headphones, because of their common rise in the impedance curve at bass frequencies (you can see this in measurements). You have no damping factor with a high output impedance, so the frequency response starts to reflect the impedance curve. It’s a distortion BUT some people really like this effect. Just depends on the headphone & listener. 

Planar-dynamics and electrostatics took over the high-end from dynamics (moving coils) for a reason - their drivers are larger AND lighter, and this often results in better sound. The ONLY dynamics mentioned today in "ultimate best headphone" discussions is Sony MDR-R10 and (maaaaybe) ATH-L5000. Dynamics are kind of like tweeters repackaged as small-scale full range drivers. If I find a reason in listening to dynamics these days, it would be to pair with an OTL tube amp for an overdrive of "sweet" distortion and fat lush sounds!

Also, OTLs with bigger power tubes may have lower output impedance that what we were used to (back in the day), and those may be more accurate and powerful for 32 ohm headphones. 

@shooter41 I looked into the Mjolner when I bought the Lyr 3 and had my doubts based on some internet reviews. WOO makes three different amplifiers that cost around that same price range. The Quicksilver also retails for $1,200.00. I get the impression that there aren’t many folks who connect their power amp to their headphone amplifier. Numerous times I’ve mentioned this on various threads and never has anyone ever posted, ‘yes, that’s what I do’.

@mulveling Thanks for the response. I’m not as tech savvy as you but something I failed to mention, is that I had a headphone input added to my ASR Emitter II when I had it built. I contacted Herr Friederich, the designer when I connected my 32 ohm Aurorus Borealis headphones. The response I got;

‘The amp is too powerful for your headphones. The Emitter has a 10 ohm high power resistor in series to the headphone output. So it can put out up to 50 V ac into 40 ohms. What is about 50 watts in your headphones, what is way too much! So for safety it is best to install a voltage devider’.

I came to the conclusion after further communications with Mr Schaefer that connecting a headphone amp to the power amp via tape outs was the best option.

Anyway, any thoughts? These design details just leave me rather clueless.

@goofyfoot , you mentioned the headphone amp being more of a "volume control" and the $1500 figure. If that's what  you are looking for, maybe take a look at the Linear Tube Audio MZ2. I currently have the same Woo amp as @ghdprentice , but started my tube headphone amp journey with the MZ2. 

The D1 is highest on my to try list. You mentioned not enjoying planars, but if  you get the chance to listen to the ZMF Tessidera, it  might change your mind. 

@snookhaus It appears that the MZ2 is no longer in production. What about the WOO Audio WA6-SE or the WA2? As for the D1, I have high hopes. Back Order is a little annoying.

@snookhaus The ZMF Tessidera's look nice but as far as I know, we don't have a ZMF dealer near Cincinnati.