Pre-amp suggestions for Thiel 2.4/Pass Labs XA30.5

If you're staying in Class A 90% of the time you are OK. Leaving Class A is not going to cause any harm. At 4 ohms you still have 240 watts of Class A/B headroom left when you leave Class A.

Some people feel that you need amps with a lot more power than what is required by your speakers to get the best sound. Others don't. If it sounds good to you, that's the main thing.

You can also get a preamp with higher gain so that you get more volume out of your system. c-j and Aesthetix preamps have gain in the 26 db range which is considered high, I believe, if you're interested in tubes. I don't think either has a phono preamp though.

Here's a quote from Nelson Pass from a discussion about choosing a Pass amplifier for the 2.4s...

"The XA30.5 will beat out the X250.5 for the first 20 watts or so because it has a much higher bias, and this is particularly true of low impedance loads. (I used Thiel 3.6's to voice the original Aleph 0, and they were 2 ohms across the board). I suggest you take a look at the article Leaving Class A posted at Pass Laboratories which discusses this in detail."

(from: http://www.diyaudio.com/forums/pass-labs/175913-pass-labs-amp-combination-thiel-speakers-need-mr-pass-advice-everyone-5.html)

Hi all ! If it sounds good at lower volumes and gets worse at higher volume change amps . If it doesnt sound right to you at any volume (with the preamp in the system), change the preamp. The Cary slp-03 is killer for $2500 new / $1500 used , a true gem with nos tubes .

Cal3713, I don't read that as Nelson Pass specifically recommending the XA30.5 over the rest of the comparably priced Pass line for the Thiel 2.4's, only as a recommendation below 20 Watts. Seems like a highly qualified recommendation for a speaker that's manufacturer recommends a minimum of 100 Watts. I will grant you that the XA30.5 does seem to behave more like a very high biased 100 Watt "double down" Class AB amp, than a 30 Watt limited pure Class A amp. Perhaps capable of 75 Watts of Class A power into 3 Ohms before sliding into another 225 Watts of Class B power into 3 Ohms? On the other hand, I'll hazard a guess that the X250.5 is probably biased in such a manner as to be able to produce about 18 Class A Watts into 3 Ohms before sliding into about 730 Class B Watts into 3 Ohms? If you have a smaller room and/or don't listen very loud, the XA30.5 could very well work very well for you.