Cary 805, deHavilland or Atma-Sphere? Anyone cares

Sorry you are having disappointment, but FWIW, 9 watts is not enough power on that speaker! Tannoy recommends a minimum of 50 watts and given the efficiency that sounds right.

The problem you may also be up against is that 50 watts is not going to show off the speaker if you have an SET. This is because at power levels like that bandwidth is going to be sacrificed in an SET; it is the limitation of the technology that you can have power or bandwidth but not both.

This is a problem in particular if you want the speaker to play bass (and have plenty of headroom)! If I were you I would look for a push-pull amp, something triode if you can. Our customers have had good luck with the M-60 on that speaker. Getting a 60 watt tube amp to play deep bass is not challenging. You also get more extended highs.

Good Luck in any event.

No disrespect to Ralph, but I think there are significant drawbacks to OTL designs, including Atmasphere. I've owned the latest M60 with all the factory upgrades except for the volume control option. First, speaker choices are limited to those that are 8 ohms or higher, which have been pointed out. Using an Speltz autoformer for speaker/amp impedance matching is defeating the purpose of OTL. Might as well get a transformer coupled tube amp and be done, which will give you much wider range of speaker options. I've found the tube noise in M60 to be unacceptable, especially if you have high efficiency speakers. I've had several output tube failures within first 6 months of ownership. Granted this is just my amp, but I've heard from other Atmasphere owners who have had this problem. When the output tube fails, it is quite alarming because you get a loud pop. It did not damage my speaker though.

The plus side to the sound of the Atmasphere M60 is crystalline high frequency (probably the best I've heard) and ultrasmooth midrange. The soundstage is huge, but the image specificity is more diffuse than other tube and solid stage amps. Bass can be loose, if you don't have the proper impedance matching. I think Atmasphere are more true to life than any SET amp I've heard. SET amps have their magic emotionally involving sound, but I don't think they are like live music unless you limit your music to simple vocals, simple jazz ensemble, chamber music and the like. It's hard, if not impossible, to get life like macrodynamics using a SET amp unless you have 100 dB+ horn speakers, which are IMO colored transducers, although horn fans are likely to disagree.

IMHO, good high power PP tube amps sound more like the real thing and work well with almost any speaker out there, including ribbon and electrostatic speakers.

Dracule1.

Ralph may chime in here, but autoformers do not make an OTL into an equivalent of a conventional tube amp with transformers. I didn't find much noticeable difference with or without autoformers.

Using an Speltz autoformer for speaker/amp impedance matching is defeating the purpose of OTL.

From the FAQ at Zeroimpedance.com:

12) What is the difference between the ZEROs autoformer and a typical tube amplifier's transformer?

The ZEROs have a few advantages over "typical" tube amp transformers:

A) The music comes out on the same winding wire that it goes in on so the music does not have to pass from a primary winding to a secondary winding.

B) There is no DC current to contend with. When a transformer is made to accommodate a DC field, its audio transparence is compromised.

C) The impedance ratio is very small (16 ohms to 4 ohms, compared to a few thousand ohms to 4 ohms). This simply means that it is much easier to achieve things like, frequency response extremes, than with a "typical" tube amp transformer. The ZEROs sport a frequence response of 2 Hz to 2 MHz.

Regards,
-- Al

Dracule1,
I cannot comment on the M-60. I have the S-30 so my remarks are related to it.

You stated:

"First, speaker choices are limited to those that are 8 ohms or higher, which have been pointed out. Using an Speltz autoformer for speaker/amp impedance matching is defeating the purpose of OTL."

With all due respect, I don't find that using the Spelz Zeros with my S-30 and Joseph Audio Pulsars defeats anything at all. On the contrary. The sound actually improved when I put the Zeros in.

You stated:
"... the image specificity is more diffuse than other tube and solid stage amps. Bass can be loose, if you don't have the proper impedance matching."

With my S-30 the images are spot on and the bass is tight. With the right tweaks the sound is so realistic, it is uncanny. I could not be happier.

I have not had any tube noise or tube failures.