McIntosh is one of the most dependable brand names when it comes to high-end audio systems. For years the brand has been recognized by audiophiles throughout the world as equipment that delivers clear and consistent quality in music. McIntosh is probably best known for its amplifiers and preamps, but the company produces many other components and parts for stereo and home theatre.
What are the specs for the Krell KSA 100-mkII?
- 100 Watt class-A stereo power amplifier
- Power rating (manufacturer):
- 8 Ohms - 100 Watt, 4 Ohms - 200 Watt, 2 Ohms - 400 Watt, 1 Ohm - 800 Watt, 0.5 Ohm - 1200 Watt
What else to know about the Krell KSA 100-mkII?
"The Krell KSA-100 Class A poweramplifier was the first stereo amplifier from Krell Audio Industries. At the start of the eighties Connecticut witnessed the birth of another highend audio company within its stateborders: Krell Industies. ‘Class A power to the people’ could have been one of the inspiring thoughts for Daniel D’Agostino chief designer of Krell Industries. Of course there were already some Class A designs in the domain of the power amplifier but most and probably all of them were confined to relatively small powerratings. Even the huge monaural Class A amplifier from Levinson, the ML-2’s, could only muster 30 to 40 Watts of power at 8 Ohms. Other noteworthy low power Class A designs were John Bedini’s 25/25 Class A amp and Jean Hiraga’s ‘Hiraga Classe A’. The only high power Class A amp in those days was a stereo 125 Watt Class A design from the SUMO electric company named ‘The Gold’ designed by James Bongiorno. D’Agostino envisioned and designed an array of high powered Class A amps in which the KSA-100 (abbreviation KSA stands for Krell Stereo Amplifier) was the most powerful stereo amplifier rated at 100 Watts Class A power at 8 Ohms.
The KSA-100 is a configuration of two completely separated amps only sharing the same huge chassis. Each amp has its own powersupply (one Avel Lindberg 1250 VA toroidal, two 40,000 uF Sprague or Mallory large cans per channel), driverboard and poweroutputsection. Another so called true dual mono design was the ML-3 from Levinson but this amp was biased in AB mode. To get rid of all the Class A generated heat from the outputsection Krell opted for forced cooling with Papst fans blowing down (the MK II version blew upwards in sync with the natural convection flow of heat) trough circular arranged heatsinks with eight TO3 encased powertransistors per channel attached to it. As a matter of fact the ‘The Gold’ from the SUMO company also used fans to cool down the amp. Using active cooling instead of natural convection kept size and cost in check because huge expansive heatsinks would be needed to drop off the 650 Watts continuous power consumption. Seven years later Krell did make huge convection cooled mono-amps as their reference series (KRS-100 & KRS-200) with the same Class A output but with a significant raise in price and weight compared to the forced cooled versions.
Although Krell has always been strongly associated with Class A biasing it’s their ability to drive extremely tough loads, like the renowned amplifier killer the Apogee Scintilla (1 Ohm version) fullrange ribbonspeaker, that really illustrated the kind of DNA a Krell was made of. Only a few other amplifiers in this era, and most of them were amps with low powerratings, could drive speakers at such low impedences. Opening up the “hood ” of the amp gives you a strong visual indication of the ‘brute force’ method used to get an unflappable amp that could drive anything on the market then and today. D’Agostino’s assault on the highend poweramplifier market was very successful worldwide due to these first designs. After Levinson and Threshold, Krell established itself as a strong contender on the highend audio-market.
This range of first Krell designs redefined the meaning of bass-slam. The KSA-100 sounded much more powerful then it’s relatively modest rating of 100 Watts with acceptable levels of refinement in the middle and high regions of the frequency-spectrum. This stereo-amp is a alround workhouse that was often mated with tube preamplifiers from Audio-Research and Conrad Johnson. Not delicacy and transparancy as the best offerings from Levinson and Threshold but nevertheless highly recommend." - highendclassics.com
Brief History of McIntosh
Long mapped-to Binghamton New York – the current headquarters and manufacturing center for Krell Labs – not many people know the brand was originally launched outside of the Nation’s Capital in Silver Spring Maryland, in 1949. In 1956, the brand built their original facility in New York, according to the official brand website.
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The following images show actual Krell equipment purchased by StereoBuyers.