Krell S-150M Mono Blocks

Anyone have any first-hand experience with these? I saw something in TAS about them being solid state amplifier of the year...??

Thanks in advance.

Have had Krell in the past but have not heard these units. I'm writing to say that Music Direct will let you try these for 30 days and if I were in the market....
Thanks Cio52.

Steve Stone (TAS) loved them, but they are the "baby" krells and I wonder about power handling/capabilities
In a recent review in HIFICRITIC Martin Colloms found that the Krell S300i integrated had a very robust power output and considerably outdistanced some of their older large amps. These SHOULD be even better but in audio very little is certain.
One of the things I believe Krell always does is under-rate the watts and if you look at the high current capabilities (doubling of watts from 8 to 4 ohms) I don't think clipping or speaker matching will be a problem. I did look at the Music Direct website and these units are on back order. Not surprising with a great TAS approval.
I've switched my sights on the Krell S-150 Mono amp to the Krell S-275 Stereo amp here If anyone has any experience with this amp, I would appreciate some input.

I'm using a Class D amp currently (PS Audio GCC-250) and I plan on returning to A/B operation. Since my budget is $5,500 and I want as much power as I can afford, this Krell has peaked my interest. According to Steve Stone (TAS) the S-150 has extremely good highs and mid-range, as well as the renowned Krell bass control. The S-275 is based on identical circuitry…

Since I’m driving Krell speakers (Resolution IIs), I assume that Krell amps will be a good match. I’m certainly open to other SS amp choices, but I am interested in hearing about this particular amp. I would also invite opinions, or comparisons, about similarly priced SS amps (based on firsthand experience of course).

Merry Christmas to everyone.

Big holiday cheers…!

Hello Ben...
I have had a few Krell's over the years and keep going back to the FPBc/cx's. Although the more recent units are still all great amps with some of the better build quality, there just seems to be something missing. Given the used prices on the older FPBcx's it sure makes solid sense to me. You do lose some convenience with their massive size/weight but I find a warmth, smoothness, cohesion and naturalness that seeems to be lacking in the newer lines. I do use a KAV 3250 as well for Ht but FPB 600c for reference and love it still.
Thanks Richard, I appreciate your input. I remember hearing great things about the FPB series...boy, they are massive!

The first thing I am going to do, is to take my Class-D amp to the dealer and compare it with the Krell (my dealer will have an S-275 in after the holidays). I have read that even the newer Class-D amps (which my GCC-250 is is circa 2005, with an ICE-based design) give up some latitude in the upper frequencies and are said to be less open and airy (i.e.: three-dimensional)…even grainier than their solid state counterparts. If I do not hear more than a very subtle difference, I will gladly save my $5,500. If I hear the kind of difference that I did when comparing the new McIntosh MC-203 (SS) to the Krell Evo 402e, then I will definitely consider the purchase. In that comparison, the difference between the Krell and the Mac (not really a fair comparison considering the Krell costs more than three times what the Mac does) was literally night and day…the Krell providing so much more detail, clarity and openness in the upper frequencies, and noticeably better controlled bass. This very discernable difference was exciting to me.

I have no idea how my PS GCC-250 will fair in comparison with the smaller Krell (and even the Mac MC-203), but I am anxious to find out. In the mean time, I really appreciate input from my brethren A-Goners!!

Merry Christmas Richard…

HI Richard,
I also have a Krell 3250 which I use to power the front channels in my 5.1 system. Since this system has dual self-powered subs, I really don't use the 3250's low end. But, I do like the amp a lot. My HT system uses B&W 805S and its varients. These are good speakers and seem to get along with the 3250 very well. I think the 3250 was a hell of a deal.

Hi 2chnlben

I'm on almost exactly the same route as you. Having had a brief encounter with an S-275 at a dealer I intend to have a home demo. My speakers are Harbeth Super HL5s; driven by the S-275 at the dealers they sounded better than my home system where they are driven by Alner-Hamblin SA-400 monoblocks (class D tripath 1.25Kw each). Specifically I found the top significantly better in terms of air and transparency, while the bass was similar in quality and speed. I also intend to audition the Bel Canto 500ref monoblocks to see how much better current class D amps sound.
I'd be very keen to hear the results of your audition.


Indeed, we are on a very similar quest!

After being prompted by my dealer, who recently picked up the McIntosh line, I went in to hear the new Mac MC-302. As a reference, we were comparing the 302 to a Krell Evo 401e (certainly not a fair comparison, but an excellent reference). The Mac is so darn cool looking (and built like a tank) that I was hoping I would like it. The difference between the 302 and the Evo 402e however, was literally night and day. The upper frequencies were presented so much better via the Krell (as was the bass) that I immediately decided against the Mac. Unfortunately, the Evo series is out of my budget range.

Now, I don’t image the S-275 is going to compete with the bigger (and more expensive) Evo amps, but if it sounds anywhere near as good as the 402e, then I am going to seriously consider buying it. Next week I am going to take my amp (PS Audio GCC-250 – class-D) into my dealer and do a little “shoot-out” with the S-275, the Evo 402e, my amp and the Mac. I’ll post my findings, so stay tuned.

I too will appreciate learning about your findings. Please do post your comments or feel free to email me via the members section.


I have two KRELL S275's; I use one for my HT center channel (bi-amped) and one for right and left rear channels. I use two Krell EVO600e's for right and left front channels. The S275's replaced a Krell 3X250 AMP. The S275 sounds much, much better than the 3X250; cleaner, clearer, faster, more detailed, more dynamic and life-like sound. Since I do not use the 275's for music, I cannot comment on 3 dimensional sound staging. I like the S275's very much. Although they are not in the same class as the EVO amps, their sound is similar. I think they are terrific amps, much better than previous equivalent Krell class amps (3X250). If the EVO amps are out of your price range, the Krell S275's deserve your consideration. I don't think you will find anything better in its price range. Krell is very, very good at building great amps and pre-amps (Krell is among the best, if not the best electronics company in the high end audio business-check out Martin Collom's review in HiFi Critic on Evo 402 and 402e).
What pre-amp and speakers will you be using?
I have a FPB 300cx and don't even think of changing. There is absolutely nothing about the amp that bothers me (other than its massive size and general ugliness), much I love about it and like a good friendship, after more than 8 years we still get along famously although others (pre's, spkrs, cables, DAC's) have come and gone.

Hello 2chnlben,

From what i was able to read on them, they have a very small power supply vs their power rating. If you have 8 ohm , high eff speakers, maybe , if not i would stay away ..

2chnlben if you have a 5K budget , why not look at the FPB series, an FPB300/600 can be had for less than 5K.

The Krell CX series amps are absolutlely superb, especially the monoblocks. I think the Evo e series amps are sliightly better. I had 450mcx's and loved them. I now have Evo 600e's (and S275's).
Doubt if anyone is going to read this after a year but here's my story on the S-275:

I had 2 amps - an LFD Integrated Zero and bridged Alner-Hambin SA400 mono blocks - each amp had its strong points. I've just completed an amplifier 'quest' to find a power amp with the best qualities of both the LFD and the Alner-Hamblin. It was successful but took several months. While my findings are obviously specific to my room, system with Harbeth Super HL5s, ears and tastes, other forum members may find my listening notes comparing amps of value. In each case I substituted the 'new' amp for the existing amp, listened for several days making notes, replaced the old amp and checked my notes. The SA400s were the prime amp for comparison. Size and ventilation constraints (amp to be placed in a cupboard with doors) ruled out class A and valve types, as well as behemoths. I chose the following short-list by reading reviews and talking to dealers. I was fortunate (in UK) to have 3 very helpful dealers who loaned me amps - I bought the last one below.

Listening Notes

Musical Fidelity M6PRX
Compared to SA400, M6PRX has excellent treble detail and tone. Conveys nuance and flow of music far better. Similar, good retrieval of low-level detail. More weighty low end with better dynamic range. 'Darker' background. Relatively poor definition of start of notes - attack seems inhibited - no 'pop' on anything but louder bass notes. Decay of notes is richer. Better coherence of sound but can tend to homogeneity in complex passages (muddy). Cannot hear the 'space' between notes as can with SA400. M6PRX has less precise stereo lateral placement, poorer depth and less recording ambience evident. Overall a lusher, lazier sound: very good class B - similar to Lentek etc - but could become boring. Not as transparent as LFD.

Leema Hydra 2
Compared to M6PRX, Hydra is very similar in terms of tone, nuance, flow of music, and coherence of sound from low to high frequencies. Treble is more transparent than M6PRX but can occasionally be fierce (violin, soprano voice). In this respect I prefer both the SA400, which does not retrieve as much detail, and the M6PRX which is never fierce. In complex passages the Hydra 2 lacks some clarity i.e. the space around each soloist or section of an orchestra, however it is much better than M6PRX but not as good as SA400. Certainly not a muddy or lazy sound. Good retrieval of detail. Drive is definitely better than M6PRX but still not as good as SA400. Ambience also not as good as SA400, but background is not as dark as M6PRX. As with M6PRX less precise stereo lateral placement and poorer depth than SA400. Overall exciting but coarse treble.

Primare i32
Large change in sound as 'run in'. Following comments are for performance after 150 hours but sound may improve further with time. Compared to SA400s, the i32 has excellent treble transparency and tone but with a little (residual?) coarseness on violin and soprano voice - overall best in this area apart from LFD(?). Voice and piano are more natural than SA400s. Richer lower treble (more body) but with occasional 'hoot' on one or 2 notes. From the bass up to the low treble there is some 'cloudiness' (much reduced from initial state) which limits soundstage cues (width, depth) and ambience retrieval. Compared to the SA400s this is particularly noticeable. Bass of the i32 is agile and reasonably well defined but not as good as the SA400s - there is a lack of 'pop' on anything but low drums. There is markedly less 'drive' than SA400s produce, although coherence and flow of music is very good with more subtle detail evident than through the SA400s. Bass is not as weighty as others (apart from LFD?). I wonder if having 2 pre-amps / volume controls in series (Bel Canto DAC and i32) may reduce transparency, and also if the (relatively) low power (headroom / current capability) of the i32 may reduce speaker control and bass definition. Perhaps both aspects might be improved if monoblock power amps based on a bridged version of the i32 power stage were available? Overall the i32 amp is the best of those I have auditioned so far (particularly in the treble) but relative to the SA400s it falls short in 3 areas that I value highly (drive, bass definition and ambience retrieval).

Bel Canto Ref500
Very large change in sound as Ref500s 'run in'. Comments for sound after Ref500s run for 150 hours; still improving perhaps, but only slowly. The combination of transparency and tonal accuracy from the Ref500s is very beguiling. Minor splashiness in treble is small compared with how sounded initially. Treble quality is now the best yet (apart from LFD?) with natural sounds on high voice, violin, etc. Well defined bass from low thro' to mid but not as weighty as MF M6PRX or SA400s. Very good micro- and macro-dynamics. Able to appreciate for the first time many nuances of performance interpretation. Micro-dynamics probably best of all amps heard. Macro-dynamics (overall dynamic range) also best due to lower noise floor(?) but may also be because can turn up volume more without onset of distortion (tonal accuracy remains fine). Drive not as good as SA400s but better than others. Similarly ambience retrieval and soundstage depth not as good as SA400s (or LFD) but close (and has improved considerably as hours built up). While Ref500s do sound agile, the attack of notes is not as defined as thro' the SA400s. Maybe in some music this is because the decay of notes is so well reproduced on Ref500s that this can mask the attack of a following note? Staccato notes sound fast and well defined. Overall very satisfying musical sound and, on balance, an advance over the SA400s. Definitely amps I could live with, however I have a slight worry that the Ref500s could be slightly too comfortable. While they are not 'lush and lazy' like the MF M6PRX they are perhaps lacking in sufficient 'presence' for my taste i.e. drive and ambience. Returning to the SA400s this was very noticeable.

Krell S-275
Harmonically rich and transparent across sound spectrum. Subtle and smooth compared with all but LFD while not being lazy like MF M6PRX. Excellent spoken and sung voice, and violin reproduction. Best amp I've auditioned as regards clarity in complex loud music passages (choir with orchestra, symphonic climaxes, words of vocals within busy, loud rock, etc). Micro- and macro-dynamics excellent; comparable with Ref500s but heavier and more substantial. Drive very evident but of a different quality to that of SA400s; on S-275 it is often nuance and emphasis within a musical line, while on SA400s it is more direct impact (leading edge of note). This is very noticeable in bass where SA400s appear to sound cleaner with better pitch and flow, however all these aspects are present with S-275 but are better integrated with rest of sound spectrum. Bass is heaviest of amps auditioned. Compared with the SA400s, the S-275 bass sometimes appears woolly on the lowest notes, but maybe this is just more volume!  As with Ref500s excellent sound of decay of notes may mask some attack of subsequent notes. Soundstage size similar to Ref500s, but individual performers or sections within it better defined. Ambience retrieval not better than SA400s but more airiness around solo singers and instrumentalists. Overall the S-275 provided the most musical performances with a very involving sound. I had to play some CDs thro' to the end when I had only intended to check 1 track. Restrained, delicate and often subdued but conveying emotion, vitality as appropriate - not at all what I had expected from a Krell amp. Maybe there is a synergy between this amp and the relatively restrained Harbeth SHL5s. Returning to Ref500s from S-275 showed S-275 richer harmonically, with more natural extreme treble, more detail and better separation of performers, but less clean bass transients.

Thanks David. I did indeed read your post "after a year," and I appreciate it. I too like my S-275 better than many amps I've heard and had in my system at similar prices. I do prefer the bigger (and better...much more pricey too...) Krell Evo 402e. I hear similarities in the S-275 that are high points of the big bad 402e. Al in all a good little amp that does a lot of things right for the investment.