Krell KSA-50S
Best high-current amplifier for audiophiles driving demanding, power-hungry loudspeakers.
Experience the legendary Krell KSA-50S, a pure Class A stereo power amplifier celebrated for its robust build and refined sonic performance. This amplifier delivers exceptional authority and finesse, effortlessly driving demanding loudspeakers with its high-current design. Originally rated at 50 watts per channel, this professionally restored unit now verifies around 90 watts RMS per channel before clipping. It masterfully combines musicality and dynamic slam for an engaging listening experience, embodying Krell's dedication to durable, high-fidelity audio engineering.
$1999.00
Owner Satisfaction
4.7
/ 5
Category Rank
421
/ 1719
#421 in Power Amplifiers
Price vs Category Average
-76%
Below average
Type
Solid state power amplifier
/ Solid state power amplifier
Who it's for
- Audiophiles seeking rich, detailed, and warm sonic performance
- Listeners with demanding, low-impedance speaker systems
- Collectors valuing long-term durability and investment potential
Who should skip it
- Users with limited ventilation or small listening rooms
- Owners with restricted rack space or physical lifting limitations
- Budget-conscious buyers wary of high electricity and maintenance costs
Performance breakdown
Sonic Refinement
Pure Class A topology delivers an exceptionally smooth and natural sound profile.
Current Delivery
High-current design maintains composure even when driving difficult, low-impedance speaker loads.
Dynamic Authority
Post-restoration power reserves provide impressive punch and effortless musical transients.
Build Integrity
Heavy-duty chassis construction reflects Krell's legendary commitment to long-term reliability.
Signal Clarity
Low harmonic distortion ensures a clean, transparent window into your favorite recordings.
Restoration Quality
Modern component upgrades breathe new life into this classic high-fidelity circuit.
Key Specs
Type
Solid state power amplifier
Amplifier Class
Class A
Power Output
50 WPC into 8Ω (stereo)
Verified Power Output (Post-Restoration)
~90 WPC into 8 Ohms
Total Harmonic Distortion
0.018%
Signal to Noise Ratio
100dB
Dimensions
19"W x 8.5"H x 14.75"D
Weight
52 lbs.
Features
- Pure Class A operation for superior sound
- High current delivery capability
- Exceptional build quality and reliability
- Professionally restored with new components
- Delivers high authority and finesse
- Stereophile recommended performance
- Drives demanding loudspeakers with ease
What customers say
Owners celebrate the Krell KSA50S for its legendary build quality and enduring reliability. The core appeal is its pure Class A operation, which delivers a musical sound signature marked by warmth and authoritative bass control. This amplifier effortlessly drives difficult speakers, showcasing immense current capability beyond its rated power. Listeners consistently praise the deep, focused, and three dimensional soundstage, creating an engaging experience. While the unit runs hot and is very heavy, its exceptional sonic performance rivals much newer, costlier designs. It remains a celebrated classic for serious audio enthusiasts.
Know before you buy
Class A operation keeps the amplifier's output transistors fully powered at all times, which eliminates switching distortion. This results in a highly linear, smooth, and detailed sound profile that is often described as more musical and refined than standard Class AB designs.
While the KSA-50S was originally rated at 50 watts per channel, this specific unit has been professionally restored with modern, high-quality components. Bench testing confirms it now delivers approximately 90 watts RMS per channel into 8 ohms before clipping, providing extra headroom for demanding speakers.
Yes. The Krell KSA-50S is built with a high-current design specifically intended to handle speakers with difficult impedance loads. Its robust power supply ensures it maintains control and authority even when speakers demand significant current during complex musical passages.
This is a substantial piece of equipment weighing 52 pounds, so ensure your rack or shelf can support the weight and dimensions. Because it operates in Class A, it will run warm to the touch and requires adequate ventilation space around the unit to dissipate heat effectively.
The amplifier features standard RCA inputs and traditional binding post outputs, making it compatible with most high-fidelity preamplifiers and speaker cables. Ensure your speaker cables are terminated with spades or banana plugs that fit standard binding posts for a secure connection.
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$1999