Thiel Owners

@jafant The Ayre has plenty of balls for my room (18 x 19 x 8-12) and listening tastes. The "VGT" volume control has 46 1.5 dB steps and I usually listen at a 20-24 when I have the house to myself, maybe 26-28 if I want some rowdy rock. The highest I've pushed with the Thiels is 30-32. No apparent distortion but this level becomes uncomfortably loud. With the Vandys, I had to add about 4 steps to attain similar SPLs (as an aside, I could get my old AX-7 to clip with the Vandys but, again, that was at SPLs too loud for me).

Ayre does not give the AX-5 a 2 Ohm rating. Here's what JA said in his measurements:

That the AX-5 was not as comfortable driving 2 ohms as it was higher impedances can be seen in fig.6. This plots the THD+N percentage against frequency at a level, 8.9V, equivalent to 10W into 8 ohms, where I could be sure I was looking at actual distortion rather than noise. Into 8 ohms (blue and red traces) and 4 ohms (cyan and magenta), the THD+N is very low and hardly changes with frequency, which again is a tribute to the zero-loop-feedback topology. But into 2 ohms (green), not only is the THD higher, but the level was a little unstable at the lower frequencies.

Apparently, power is slightly higher with the Twenty version but I have no idea how that might change JA's THD+N measurements. Again, I would be reluctant to drive CS5s (impedance drops to 2 Ohms in the bass) with an AX-5 but I hear no deficiency with the CS2.4SE.

Thanks! much- beetlemania
maybe I can find an AX-5 near my locale for an audition?
Happy Listening!

An amp with zero loop feedback must be extraordinarily well designed to work for music. Feedback disturbs phase response. Ayre is addressing design from first principles and I would expect all their products to be very clean, especially in the transient-temporal domain. If it sounds clean it is clean.  But, the joys of power should not be underestimated.

I hot-rodded my 1990 Classé DR-9, considered a high voltage / high current amp. In stereo it produces100 wpc > 8 ohms, 200 > 4 and 400 > 2 ohms. Nice muscle and finesse. Strapped to mono it gives 400 wpc > 8 ohms, 800 > 4 and 1100 > 2, which means the power supply runs out of current before voltage. I use them in my studio where they are surprisingly cleaner strapped than in stereo at moderate levels into a moderate sized hard-to-measure space described earlier. Anyhow, I would have thought that the 400 > 2 ohms in stereo would have been plenty, freeing the other amp for other duties. But the improvement was dramatic enough to assign both amps to mono duties.

The current behavior of your Ayre is of interest. But, more power produces an effortless transient attack that really makes music work emotionally.

According to the article cited by beetlemania -
JA measured 220w clipping into (2) Ohms w/ one channel driven.
tomthiel -

Thoughts?
Happy Listening!

The current behavior of your Ayre is of interest. But, more power produces an effortless transient attack that really makes music work emotionally.

To the best of my knowledge, Ayre, Theta and, maybe Dartzeel are the only manufacturers of SS zero-feedback amps. The Ayre VX-5 stereo amp has a bit more power than my AX-5 integrated (rated at 300 W into 4 Ohm). Stereophile measured the MX-R (non Twenty version) at 595 W into 4 Ohms and 720 W into 2 Ohms - but that product is WAY beyond my budget. The Theta Citadel ($12K) is rated at 400 W into 8 Ohm and 800 into 2 Ohms. The Dartzeels are generally more expensive than Ayre or Theta and also less powerful other than the $150K behemoth reviewed by Fremer (1025 W into 2 Ohms!). I wonder how *that* would sound driving a modded pair of CS3.7s! 

I think there are a handful of tubed zero feedback designs but these are probably less powerful than the above. And with that I apologize for taking the "Thiel owners thread" off topic!