Review: Krell KSA-150 Amplifier

Category: Amplifiers

Years ago I had the opportunity to listen to a Levinson system at Difinitive Audio in Seattle that made my jaw drop. If you closed your eyes the performers were in the room with you. Jazz was Jazz, Rock was Rock, Classical was Classical. Everything was just perfect. The way it should be.
Realizing that I just could not afford a $100,000 system, my seach started. Sound familiar? I worked my way through a number of system variants and wound up with Cal Audio Sigma and Delta source (getting a little long in the tooth now) a Krell KSP-7B preamp, a much modified Adcom 555 and my Acoustat Model 1 speakers. I had been very happy with the sound and the resolution of detail my system was able to produce. It just did not have the authority or control I had been looking for. I also knew the 4 ohm impedance Acoustats were just not an easy load to drive with a combination of electrostatic pannels and woofer module. The Adcom had to go. Since I would be buying used I did a lot of home work. With no auditioning at home before you buy, I called a LOT of friends. I really liked the sound of the Krells I had heard, knew of their ability to double power down to 1 ohm and what the heck they would match my preamp. I finally settled on replacing my Adcom 555 with a Krell KSA-150. (Plateau biasing, 150 watts/channel doubled down to 1 ohm). I purchased it for $1750. When it arrived I found what I would eventually call the amps only draw back, it's weight. At approx. 90 lbs get some help to move it. I understand completely why Krell also puts handles on the back of the amp. I placed the KSA-150 on my amp stand and I hooked the amp up with (used) MIT Proline balanced interconnects, two separate runs of (used) MIT T2 speaker cables. All the connection points seemed robust, with the detachable power cord a good feature. OK I'll catch hell for this but my amp stand is a well built old antique commode filled with sand. Don't knock it, it works and DOES make for a conversation piece. Since used means no break-in period, I turned it on and let it warm up. The soft start is a nice feature that doesn't dim the lights like my Adcon did. When I came back to the room the differencs was not subtle. Bass authority was astounding with no sense of strain. Detail resolution was significantly better. The immage now had better focus and front to back depth with overall smoother sound. I no longer have to wonder if it's an acoustic bass. One of my favorite albums (sorry I just dated myself)........ CD's is Norah Jones. The music just sounds right with silky smooth vocals and a wonderful piano. Those who have the oportunity to attend a LIVE symphony .... do so for comparison and enjoyment. If you can clearly hear the separate instruments as I can now and they are not a blurr playing the same note you are on the way. With the right material you can forget it's recorded. The addition of the Krell KSA-150 made the musical experience more real and enjoyable and I have no urge to update my amp having lived with the KSA-150 for six months. With Krell's reputation for taking care of their equipment, build quality, and sound, the KSA-150 is a keeper. I would recommend a good used KSA-150 to anyone looking for a quality amp (new or used)in $1500-$2000 price range, especially if they have a difficult load to drive.

Associated gear
Krell KSA-7B
Cal Audio Delta transport
Cal Audio Sigma D to A
MIT interconnects
Acoustat Model 1 speakers

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Good review and I second your comments as a Krell owner. All these people who trash Krell must have a weak link in the chain because my good recordings sound fantastic and my bad recordings sound unlistenable. Krell reveals it all without sugar coating the material. In fact, every recording sounds different because you can hear into the recording methods. All my former equipment couldn't come close to resolving that clearly. Continue to enjoy the amp as it sounds you are.
I have just had a similar experience with a Krell. Last week my family and I were on vacation in Singapore. I saw a used mint condition KSA-250 for sale at C.K. Audio, for $4,500 Singapore. After a lot of bartering we finally agreed on a sale price of ~$2,000 US ($3,900 Singapore)! Fortunately, because there a 5 people in my family and we were traveling relatively light, I was able to combine luggage allowance and ship the Krell home for free (I live in Paris), not bad I thought for a ~125lbs amp. Needless to say I was concerned about it getting damaged or lost. Fortunately everything went well and a very large Krell box arrived on time with my luggage and no damage. I set the Krell up as soon as I got home (It is extremely simple to adjust the input voltage on the KSA-250 from 100V-240V). First CD tried was Norah Jones (on a Pioneer Elite DV-38A DVD player with a pioneer Elite C-72 pre-amp and B&W 805N speakers). Talk about shock and surprise (I have still not stopped grinning). Bass is rock solid, stereo imagery and resolution is incredible (I previously used a Pioneer Elite M-91 power amp to drive the speakers). It really does sound like Norah Jones singing in a night club live, several people have made the same comment, including a few HiFi skeptics. In short, probably the best upgrade I have ever made. Especially when I think about the skepticism I had about amp upgrades in general, not any more though.

Next year, when I return to the USA, I will be looking for a second KSA-250 to bi-amp my B&W 801Ns that are currently in storage (simply too big for a Parisian apartment). I can't wait!

Marcus McHugh
Upgrade your Krell Ksa-7B with
Audible Illusions M3 with 7dj8
TeleFunken tubes.your ksa 150
and M3 pre-amp will sings a 3D
Hi Chiefdaug, glad to hear the Ksa-150 brings out the best in the Acoustats. The Ksa-150/250's were two of the best amps ever built by Krell IMHO and are a great buy on the used market. I have a Ksa-250. The Ksa-150/250 were from what Krell called it's programmable series and could be converted into monaural differential amplifiers. The 150 became the MDA-300 and the 250 became the MDA-500. I have mine in use with a passive preamp (volume control) and my sony xa777 sacd player, you may want to try this with your's some day. It has taken my sound up another notch.
Marcus, great job and great deal on the KSA-250. It is a superb amp and was my first Krell. However, I lived in AZ at the time and in the summer, the heat it produced was too much, so I traded it in for the FPB. Winters in Paris can be cold, but now you'll have a perfect room warmer in addition to great sound.
I bought my first Krell KSA-150 and a KBL about 8 years ago I can remember, I was so excited.My very own "Class A " Amp. Enjoyed every day I could listen to my baby. As time moved on ,I decided to change my speakers, then moved up to KRC pre-amp, Krell of course, and then to the Krell FPB-300. I keeped my KSA-150 for a short time to make sure I was doing the right thing. I reviewed the FPB 300 and was very impressed with the change. I found it much more musical, I could play some CD's that sounded horrible on the KSA-150 , the CD's seemed to sound much much better on the FPB-300, my new speakers came alive. *************But I did notice one thing that I miss, and that was that the KSA-150 had a much better soundstage than the FPB-300.( Or different) When I played "Angel" from one of Bruce Springsteen CD's. The KSA-150 had the voice forward and the cello in the background playing it to perfection. So I'm feeling somewhat of a trade off.************ I'm now going for the FPB-600 hopping to find bigger and better changes. ((((((((( To be heared))))))))*****The KSA-150 is a classic class A Amp and for the money today ,worth the audition, it's a steal deal!!!!!
Hi - Do any of you guys know the input impedence of the KSA-150? I want to drive it with a Theta Miles cdp's analogue volume control. My current amp,Aragon 4004,has a 22mv input imp. It is a perfect match.
Any comments on the improvement I might get upgrading to the 150?
Gooddomino, The Ksa-150 is a good choice for your cdp. It should drive the Krell to full power. The Ksa-250 is a little harder to drive for a passive volume. As far as the sound between the Aragon and the Krell, that will depend on your speakers, if you have very good speakers you will hear it, if not stay with the Aragon.
how are the sa100 sa80 or sa50 amps?
Same sound qualities? post here or email me if you have any input.thanks
I've had the KSA-150; nice amp and very well built. I later went to the Classe 15 which, to my ears, sounded better and ran a lot cooler.
I like the commode amp stand. What a great idea.
Just a quick note:
replaced a friend's 200w Accurous with the Krell KSA 80B and it must have been like the
adcom to Krell experience. I had a GFA555 before Mcintosh, spectral and Pass Labs. but, i say it must have been the same as it was really profound, as one would expect.
Heavy amp, big odd heat sinks. Slightly cheap binding posts, I don't like plastic cappings, but it was extended in highs and lows and clean through out. Had somewhat of a hum.