Krell KSA-50S // Vintage / Class A Solid-State Amplifier

The Krell KSA-50S is a pure Class A stereo amplifier that exemplifies Krell’s reputation for raw power, refined sound, and bulletproof construction. Released in the 1990s, it delivers 50 watts per channel into 8 ohms, but don’t let the modest wattage rating fool you—this amp punches far above its weight class, doubling power output as impedance halves, all the way down to 400 watts into 2 ohms in monoblock configuration. This makes it a current monster, capable of driving even the most demanding speakers with ease.

Designed with audiophile precision and built to last, the KSA-50S combines musicality, control, and dynamic slam, delivering a sound that’s as effortless as it is engaging. It’s a favorite among those who value authority and finesse in equal measure.

Production

1993-97

Condition

9/10

Serial No.

31-10394

Orig. MSRP

$3300

Restoration

• Replaced output and driver transistors and opto isolator for left channel
• Verified power output about 90 watts RMS per channel to clipping

Factory Specs

Type   Solid state power amplifier

Power output   50 WPC into 8Ω (stereo)

Total harmonic distortion   0.018%

Gain   26 dB

Input sensitivity   1.34V

Signal to noise ratio   100dB

Dimensions   19"W x 8.5"H x 14.75"D

Weight   52 lbs.

Documentation

Krell KSA-50S Owner's Manual

Liner Notes

"The KSA-50S is undoubtedly a contender, but its sonic character makes it essential for you to audition it in the context of your own system. Recommended—but news we've just received from Krell could make this moot. Apparently the KSA-50S might be discontinued in September, due to lack of demand: Krell customers appear to be more prepared to spend the big bucks for the bigger amplifiers. Given the '50S's sweet sound and massive power delivery, I feel that this is a pity."
- Stereophile

Stock No.

8858515603677