Should I buy a Class A Amp.

There's a downside of having a father who was an electronics engineer, building amps from age 12, and still designing and building them while training for four years as an electronics engineer....

Any amp, any class (a/ab/d) can be good or bad.

Electronic components are inherently non-linear over differing temperature/voltage/current/speaker load conditions, and thus all an engineer can do is compensate for these non-linearities by using all sorts of different techniques.

Class A's tend to be more linear because they reduce the number of non-linear variables in the equation. Friends of mine run 300Wpc Class A amps and frankly, they're probably the answer if you don't mind the heat and the power bill.

Personally, when it comes to amplification, I don't subscribe to "let your ears choose" unless you promise to never say "my amp is better than yours".

The technical purity of any amplifier can be measured. Perhaps start there, and then let your ears or wallet choose.

Plinius.

I have owned a KSA200 since 1990. Incredible amp. If your system is bass challenged look no further. No one builds amps like this anymore.   In 26 years my amp only cost me $350 in repairs. I have paid more to repair an fpb mono with bad caps. Don't listen to the bs about a re-cap. If the unit was kept well vented you will be fine. If it was in a confined rack and could not breathe then that is a different story. 

If it is clean condition, and fins are black, that is a great price, for an amazing amp. 

Carefully check the condition of the amp you are buying. The fins turn more blue with heat and age.  Make sure the color is consistent. Bring a thermometer and measure temp across all 6 cooling fins. This will tell if you have bias issues. If you do it is not the end of the world.  The only issue with these amps and i have seen this on the 80, and the 160, is the small bias transistors used nylon screws to anchor to the internal heat sinks. Once the nylon fails due to heat, the transistor looses it's cool and you can get thermal runaway. Simple repair with a small  stainless nut and bolt. Easy, cheap, assuming all else is good. 

After listening for 5 minutes you will wonder why you did not do this sooner

Don't be afraid to pm me if you have any ?'s.

Enjoy

I agree. That Krell looks like the ticket. Get one second hand, get an electronics guy to give it the once over - aka http://theartofsound.net/forum/showthread.php?27792-Krell-KSA-200-for-sale-Complete-nut-and-bolt-rebuild

you'd have a sweet amp

I have a couple of sliding bias class A amps, a Threshold 400a and a Bedini BA-803.  They were used to power a pair of Acoustat 2+2.  The Threshold 400a sounded good but was a little light on the bass.  The Bedini BA-803 sounded a little better and the Acoustats had stronger bass response using it.  The Bedini has 200w/ch vs 100 w/ch from the Threshold.

I do have a pure class A amp that is currently out for repairs, a Bedini 100/100 1 meg.  It sounded the most natural and had amazing bass output with the Acoustats and other speakers.  It is also a fast amplifier and uses positive feedback.  It is 100w/ch but sounds more powerful than the other two.  It did run hot though.

For the summer time for general use I run a Jeff Rowland model 5 class A/AB amp.  It runs cool and can handle the Acoustats well.  It has a detailed yet laid back sound.  Bass is there but not as deep. 

Tube amps can also sound very nice with electrostatic speakers as I have a pair of Ray Lumley M100 tube mono blocks using KT-120 tubes.  Again a full, natural sound with strong bass but not as deep or controlled.  Soundstaging is the best with the tube amps, wide and deep with instruments in their proper locations (imaging).  The tube amps are push/pull class A/AB.

So which is best?  Like has been said, it all depends on what you are looking for.  Overall for me it is a toss up between my Bedini 100/100 1 meg class A amp and my Ray Lumley M100 tube mono blocks.