I have been into high end audio for 20 plus years and have had about everything from Audio Research, Mark Levinston, Vintage Marantz and Mac tube gear and the Krell KSA 100 MarkII is the best class A amp for the money on the used market, period!! I have it installed in my system driving a set of rare Purist Audio Design Sattelites and Subs and the sound is warm and pure with an awsome soundsatge.
I listen to rock, jazz and classical music and this amp does well and all fronts. I not into all that audiofile review stuuf, I belive you let you "ears" do the reviewing and when it comes down to the bottom line, "you" and only "you" are the one that has be happy with the system you have put your heart and soul into.
My cuurent system consist of two KSA 100 Mark 2 amps, Audio Research LS5 Pre-Amp, Audio Research CD-2 player, Live Wire interconnects and Purist Audio Design speaker system (simular to the wilson watts and puppies).
I have heard other Krell products in the past and they have not impressed me but a friend of mine turned me on to this "gem" of an amp. If you are looking for something that will drive the most demanding speakers this is it. I will warn you that in the winter time this will act as an additonal furnace in your listening area because it runs hot. And if you are always looking at you electric bill then forget it because this unit loves power because of its pure class A operation. Well, enough of my babbling, all I can say is for under 900 bucks you will not find anything that performs as well as this amp.
My friend just upgraded to a KSA-200, so he gave me his KSA-100 Mark II to sell on eBay for him. But he offered me a good price if I'd buy it myself.
I was not expecting this amp to be such an improvement over my Aragon 4004 MkII, but I can't deny it after hours of comparing the two back to back. In fact, I was biased against hearing a difference because I wanted to hang on to my Aragon. The 4004 is well known and respected; it's very neutral but detailed and with good bass response. The Krell is huge, heavy, generates a lot of heat, and won't fit on my stereo cabinet. Those of you with some experience know that personal bias can make a big difference in what our ears perceive. Also, the Aragon is rated at 200W per channel into 8 Ohms, while the Krell is only rated at 100W at that impedance. So I was fully expecting the 4004 to at least keep up. Despite these biases against the Krell, it easily won in my back to back testing.
Well, first of all the KSA-100's power rating is apparently extremely conservative, because music was actually a tad louder at the same volume setting than with the Aragon. My speakers are Sonus Faber Concertos, noted for being difficult to drive and needing a beefy amp.
So what was the obvious improvement in the sound? Mainly threefold:
1. A clearer and more detailed upper midrange and high end. With the Krell, I nearly got goosebumps listening to tracks with fine vocals; it felt like the singer was in the room. With the Aragon, the music sounded like the recording it was.
2. A much wider and deeper soundstage. Instruments in the right channel sounded like they were coming from somewhere *beyond* the right speaker. Percussion often sounded like it was coming from behind the speakers somewhere, just where you'd expect the drum kit to be. With the Aragon, the sound was boxier and more confined, especially at higher volumes.
3. Greatly improved imaging. Closing my eyes, it was difficult to locate the speakers whereas before it was pretty clear. Instead of the soundstage being comprised of separate point sources as before, it's now continuous and the channels meld in the middle.
Another minor improvement is that the upper bass seems tighter, more controlled. This area still needs improvement and I think the only solution for this is to get full range speakers (the Concertos are small), but the KSA-100 did improve matters. I was able to hear the upper bass line more clearly in my rock music, whereas before it just muddled in with the subwoofer. Because of this, I was able to lower the crossover frequency of my sub to about 60 Hz (but up the gain a bit).
Overall, the sound is much warmer and livelier than with the 4004. After getting the 4004 I'd spent months enjoying my music collection several times a week. Guess what, it's time to do it again, the music sounds that much better. I suspect that this amp is finally letting my CD player (with tubed output stage) sing with the warmth it's known for.
Ok, so the amp is large and heavy. It's nearly two feet deep and well over a foot wide, and weighs around 100 lbs. It contains two internal fans to dissipate the enormous amount of heat it generates; the fans are completely inaudible to me unless I put my ear very close to the grille (and risk getting burnt!). As with all large Krell amps, there's a pair of handles on either side for easy transport with two people.
I love hearing the two loud clicks as the protection circuitry completes its self-check. This is a true Class A dual mono amp, with a huge transformer for each rail.
Well, I'm sold and am keeping it, putting the 4004 up for sale. Unfortunately this means that I'll need to get new furniture to put it on.
Btw, before bringing the amp home we also auditioned it for a few hours directly against my friend's KSA-200. The KSA-200 has better bass response and a more detailed top end, but isn't as warm in the midrange. This is most evident with male vocals, which through the KSA-200 sound a good deal quieter relative to the instruments. A startling difference, actually. The KSA-200 may be better suited for classical music. The KSA-100 seems to be better suited to rock and mainstream music.
For $900-$1200 used, this amp is an incredible bargain IMO. Due to its rugged construction, it's just as good used as new. The only issue to think about is aging of the capacitors. At some point they may need replacement. Everything else in the amp will last for decades to come.
My other equipment:
Ah! Njoe Tjoeb 4000 CD player
Aragon Soundstage preamp
Sonus Faber Concerto speakers
ACI Titan subwoofer
It is interesting that the previous reviews are all glowing, yet in AudioAsylum people basically beat the crap of the KSA 100. My experience - an ex-owner of Krell 300i integrated - agreed with the AudioAsylum fellows. I simply *hated* Krell after owning the 300i.
In fact, the notion of "cold, analytical" Krell sound appears so wide-spread, many suggest to mate Krell amps only with smooth-sounding tube pre-amps, esp. when using power hungry speakers. I once did an audition on an pair of Maggie 3.3R. The sound, from Wadia 9 to CJ tube preamp (P11V whatever?) to Krell KST 100 is downright AWEFUL - grainy, muddy, and still no bass. I cannot tell its sound from the (pitiful) NAD S300 integrated amp, which I owned before.
Anyway, I found an bargain in eBay for an KSA 100 Mk II, and I jumped on it purely on leap of faith. I mate it with VTL 2.5 preamp, and SOTA Time Domain 4 speakers. The sound is a major surprise, and agrees 100% with the previous reviews here.
The sound is on the warm, full body side. Airy yet have the clean bass slam and fast attack. Soundstage is very 3D, with lotsa details. Overall sound is very coherent and simply beautiful. I'd say the overall sound is more like an warm-sounding tube hybrid amp.
So there you have it: An successful story of mating an tube preamp and Krell amp.
This is my first Class A separate amplifier. My stereo history starts with a Harmon Kardon Receiver and a Pioneer VSX-451 Receiver. It wasn't until my father passed on at a very early age of 53 that I was able to own such equipment such as the Krell KSA-100.
The Krell has been in my father's / my possession for 10+ years. It has been back to the factory for custom-cooling fans, so as far as heat is concerned, be just that, concerned! Well ventilated, you should have no problems, however, the fan idea was a spousal compromise my father had to make in order to satisfy my Mom. (Krell KSA-100 out of site is out of mind. Well so my Mom thought anyway..)
This system was played flat through a Nakamichi OMS-7, NAD whatever, Sony whatever & Panasonic CD & DVD players, the Krell PAM-3 Pre-Amp and KEF 107.2 Loud speakers. If anyone were familiar with the PAM-3 you would realize that this setup offers nothing more then flat music via absent Treble & Bass controls. The PAM-3 also offers switch able circuitry to maximize the outputs from various CD reader architectures and a switch able pre-amp impediance in order to maximize pure signal throughput. Which brings me to the next point about the PAM-3. Throughput! This is all it is, so my analog signal from CD / DVD to Amp is cleaner then any $15,000+ DSP system could come close to being at this time.
Frequency response is excellent. For the system described above the Krell KSA-100 breaks into 250 watts per 4ohm KEF speaker. Noise is limited to your neighbors crying kid and the dog barking out back. The KEF Speakers are big, and produce well, and compared to the Pioneer and a McIntosh MC2505 it offered a hugely distinguishable punch to the sound.
I have seen these selling for $1000+ used, and recommend picking one up if you are looking for a very powerful, heavy, clean powerhouse at a bargain price.
Please note that my ratings for this product are based on buying one used for a good price. You will not be disappointed!