‘Time Has Come Today’, a late ‘60s hit by the Chambers Brothers, began to play in the back of my head when I read Herb Reichert’s Stereophile review of Heretic Loudspeakers’ AD-614 back in March. In it, Herb observed:
My friend David Chesky and I believe that humans are way more sensitive to distortion and timing than frequency response, and that the majority of today’s box speakers create their own “signature” time smear that we can hear but don’t notice—except when it’s not there. Like when listening with headphones. According to Gaboury, the main speaker-design question is always “Should speaker designers focus on the frequency domain or the time domain?” He thinks the time domain should be prioritized. And I agree.
https://www.stereophile.com/content/gramophone-dreams-71-heretic-ad614-loudspeaker
Interesting, I thought briefly, but as often happens in the old-brain-tumble-cycle that is my life, I forgot about it. The May arrival of Old Forge’s demo pair of AD-614 brought it back to top of mind, but in a circuitous way.
As I listened to all sorts of music via the 614s, I began to notice that there was a ‘groundedness’, a corporeality, a ‘you-are-there-ness’ that was, in my experience, exceedingly rare. It made everything I played more accessible, more directly communicative, more enjoyable. What causes this? Is it the coax driver? The serial crossover? I’d say both and probably more.
I was reminded of a shift I heard in the Audio Note (UK) room at CES one morning. Someone was supposed to bring the TT Three Reference turntable, but had been delayed a day, so we started with its predecessor the Voyd Reference. Peter Qvortrup was playing death metal first thing in the morning (Help!) It was well-reproduced, but I couldn’t get into it. Then we moved the arm and cartridge to the just arrived TT3 Ref and re-played the last track. Suddenly it made more sense to me, held a greater appeal—and I dug it!
What the heck happened? What changed? I decided that an improvement in speed stability made it sound more grounded. The more resolute timing had removed/reduced an obstacle to my enjoyment; my brain was doing less work to hear it fully—properly. Interesting, and again promptly forgotten.
As I started trying different amplifiers, I discovered this grounded/U-R-There quality was better supported by some than others. Where the 614 sounded lovely with the Lab12 Suono, (single-ended KT150 power amp), they enjoyed a considerable improvement via the Audio Note (UK) Conqueror (stereo 300B power amp).
What changed? The input/driver tubes changed from 9 pin minis to 6SN7s. Power tubes shifted from triode-wired beam tetrode to directly heated triodes. Rectification shifted from SS to tubed—5U4 to be specific. (I don’t what the differences are between their OPTs, but throw it in as a variable of unknown sort/degree.) Finally, and perhaps looming still larger: the Conqueror uses no negative feedback.
This ramping up of listening satisfaction/excitement peaked with the arrival of the Thoress EHT Mk II Integrated amp. I found myself playing at length genres I generally give short shrift and enjoying them thoroughly. I struggled to avoid the listening area until after I completed the business minutiae, otherwise it just wouldn’t get done. What’s going on here?
The unusual approach taken by Reinhardt Thoress in this amplifier at least partially answers the question. The power is solid state. No negative feedback is employed. Voltage amplification is handled by a 6J5 (equal to half of a 6SN7) for each channel. Current is supplied via MOSFETs. Thoress calls it the simplest possible approach.
Apparently, at least so far, single-ended operation without negative feedback seem to be key. Sticking with a larger, very linear triode for voltage gain seems to play an important role. Solid state rectification and even solid state current sourcing seems to be penalty-free when done right, (which surprised the heck out of me.)
The dots I’ve managed to connect in my limited survey are: Keep it simple, don’t mess with the signal, go triode, skip negative feedback. Avoid anything that messes with timing!
Or, skip the head-scratching and come hear this magical combination at Old Forge Audio! If you’re not in the area, (and by area I mean CT, MA, RI and downstate NY), you can hear this pairing, (along with Wattson Audio’s Madison streamer/DAC and Luna Cables), at CAPITAL AUDIO FEST Nov. 8-10 in Room 801.