The "S" series stands for Sustained Plateau Bias technology which was first introduced in the Krell Audio Standard. This is a variation on the "sliding bias" idea, except that bias is changed in discrete steps rather than continuously. A so-called "anticipator circuit" at the amplifier's input responds very quickly to an increase in signal level, so that, by the time the signal reaches that output stage, the output will be biased to class-A.
The KSA S-series amplifiers did not have have the same deep bass as the former KSA / MDA series. Some felt that this was due to the anticipator circuit and the way it was employed in the s-series amplifiers. I found the S-series amplifiers to sound sterile and less dynamic than the former KSA. I am not a huge Krell fan, but I could live with a KSA 50 or a KSA 250 amplifier. If you have the space and are not too concerned with the heat issue, I would go for a KSA 250, invest in a recap (if and when needed)and you will have one of Krell's classics. People still ooh and awe over the performance and sound of a Krell KSA 250, but rarely do you hear them speak of the KSA 200"S" in the same regard. Just my 2 cents.
The KSA S-series amplifiers did not have have the same deep bass as the former KSA / MDA series. Some felt that this was due to the anticipator circuit and the way it was employed in the s-series amplifiers. I found the S-series amplifiers to sound sterile and less dynamic than the former KSA. I am not a huge Krell fan, but I could live with a KSA 50 or a KSA 250 amplifier. If you have the space and are not too concerned with the heat issue, I would go for a KSA 250, invest in a recap (if and when needed)and you will have one of Krell's classics. People still ooh and awe over the performance and sound of a Krell KSA 250, but rarely do you hear them speak of the KSA 200"S" in the same regard. Just my 2 cents.
