Slowely Upping My Game

The Holo Audio Bliss is an end-game level HP amp at a somewhat reasonable price. I also have Susvaras, one of the most difficult to drive HP's out there and the Bliss KTE will easily drive them on the low-gain setting. That means that it never leaves pure class-A status unless you turn the volume up past 0 db, which, if I don't have to with my HP's then almost no one will. Of course, that also means it gets quite warm, but after trying several dedicated HP amps, both tube and SS, the Bliss' sound is beyond reproach. Holo Audio has fantastic build quality, too.

@shooter41 Thanks for the input. The Bliss retails for $3,000.00. Given that I'm running tape outs to inputs and then adjusting the volume, I'm a little frustrated about what's available for around $1,500.00. And the headphones that I'm using could be driven with an iPhone. I mean, NASA just sent a crew to circle around the moon, so certainly someone could design a headphone amplifier for such a basic task. I guess I'm venting.

@goofyfoot I totally understand and I was similarly frustrated once-upon-a-time. I think most of us that enjoy the electronic reproduction of music started out thinking that they could get satisfying sound on a modest budget, and sometimes you can, but most of us also have that nagging feeling that, for just a little bit more, you could do better. This is the opening of the rabbit hole. I have bought and sold numerous HP's, amps, and DACs, always taking at least some loss. What I should have done, and I know a lot of folks here would agree, is decide how much of a priority it is to have satisfying sound. If it is indeed a priority then stretch as much as your budget will allow right from the jump. It's far cheaper in the long run. 

As for an even more budget friendly HP amp, I would recommend the Schiit Mjolnir. I had the previous version that had a tube input stage and it was an excellent amp, I'm sure the new one (which, like the Holo, is pure class-A) is even better. $1200. 

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.