Krell KSA-150

The KSA 150 is noted for it's class A operation, Its 150+ watt per channel power output into 8 Ohms, its ability to drive reactive loads, and its ability to double power as load is halved, all the way down to loads on the order of 1 Ohm. I've had this one for several years. It has just arrived back from the Krell factory where it was brought up to factory specifications. It was recapped at the factory in 2016, and any other parts that were out of spec were replaced earlier this year.

The KSA 150 will ship in Krell packaging, encapsulated in the Krell styrofoam protective sheath. The amp weighs about 96 pounds, and with the packaging, the box weighs 105 pounds. The dimensions of the box are 15"x23"x24". The amp is located 38506.

Included are the amp, a spiral bound downloaded copy of the owner's manual, the power cord that I received with the amp, and the XLR input shorting jumpers which will be clearly packed with the manual. The shorting jumpers are used when you make your amp-preamp connection with RCA instead of XLR interconnects. The shorting jumpers are installed across pins 1 and 3, which are clearly labeled on both of the XLR outputs. If you run with unbalanced interconnects to the preamp, then you must install the jumpers before installing the RCA cables. I've included two close up pictures so that you can see how the jumpers get installed in the case that you run with RCA (unbalanced) interconnects to your preamp.

This is a big Class A amp. Krell amps from this era are the amps that made Krell's reputation as the leader in solid state gear. The KSA 150 is rated at 150 watts per channel into 8 Ohms, but reviews and tests indicated that it had the remarkable ability to double power as load was halved, as can happen with difficult loud speakers. For example, electrostatic panels can dip down to as low as 1 Ohm at 20 kHz. See the blurb below which was Krell boiler plate / press release type material back when the KSA-150 was a current model.

I love the KSA 150. It is very dynamic, very transparent, and very capable of presenting true spatial content, pitch, timbre, dynamics, and air. I installed it in my system when it came back from Krell and it was quiet, and dynamic. It sounded great. This is one of two I had been using the last several years in a vertically biamped system.
I am selling because I've acquired a pair of Conrad Johnson LP275M monoblocks for that system.

If you have questions, please ask. I would like to find a good home for this wonderful US made stereo amplifier.

Regarding "Offers," I do not mind receiving offers, but please do not send me a detailed analysis of why you think the amp is worth 70% of what I'm asking. I've been enjoying home audio as a hobby since the 60's, and I've bought and sold a lot of gear, mostly on eBay the last 17 years. This is a great deal on a factory rebuilt KSA-150.

Krell have demonstrated an outstanding commitment to supporting their legacy products, and their support is both professional, and at modest cost. They're proud of what they've built, and they are committed to keeping their legacy products running.

Below is the blurb that describes the KSA-150 back when it was the new kid on the block.

The latest generation of high-resolution source components and speakers places new demands on the power amplifier. The Krell KSA 150 and KSA-250 meet these challenges with fresh design sophistication and long-term value. Both products can drive any speaker with an effortless quality that makes their power seem endless. Extreme clarity is maintained at all power levels. They both utilize Krell refined high-bias Class A and direct-coupled circuitry from input to output.

Their power supplies and output stages are massive. High voltage rails with extensive regulation are provided for the input circuitry. All materials and electronic components are of the finest quality and operate within their optimum performance ranges. Virtually all hand wiring has been eliminated, resulting in a dramatic improvement in sonic clarity.

The KSA-150 and KSA-250 both utilize Class A circuitry throughout the audio and power supply regulation stages. Class A gain stages deliver excellent sonic performance under diverse conditions because all active components are turned on at all times. This allows each component to operate in its most linear and precise regions. The amplifiers are able to respond to the full range of input signals with equal accuracy.

The KSA-150 and the KSA-250 are conservatively rated at 150 and 250 watts per channel into 8 ohms, respectively. The 150 will actually generate 220 watts into 8 ohms, and the 250 will generate 320 watts into 8 ohms. The 8-ohm power ratings do not account for the amplifiers superb sonic performance nor describe their maximum power. The Krell definition of power and the ability to drive low impedances is that the output must double into successively low impedances. The immense power supplies in both products allow them to double their power into one ohm.

There are many advances in thermal construction and control circuitry in the KSA -150 and KSA -250. All heat bearing structural components and external heat sinks have been designed in-house to improve thermal tracking and cooling.

This construction provides very low thermal resistance between the output transistors and the heat sinks, resulting in superior thermal tracking. It also results in a considerable reduction in overall size. Greater amplifier life expectancy is an added design benefit.

Automatic self-adjusting bias and DC offset control circuitry have been developed for the KSA-150 and the KSA-250. These circuits compel the amplifiers to conform to their intended operational parameters under all AC mains conditions.