Krell FPB 600 or 400cx?

I own Revel Ultima Salon 2s and am looking to upgrade my amp for better performance in the low end. Right now I'm just not getting any real punch or slam in the bass dept, and I know the Salons are capable of much more. I have the opportunity to go with a fpb 600 or the 400cx for around the same price. Any thoughts? Is the extra 200 watts of power on the 600 worth losing any sonic benefits of cx? Or is the cx so superior sonically that there's no comparison?


Why do you think the 400cx is that much better than the FPB 600? Anyway I am sure that the 400 watts is enough to drive the Revels with oomph and bass, especially if you have the preconcieved notion that the Cx is a superior amp. What are you using now?
I owned a 400cx for about 5 years and It is a great amp. I am assuming the 600 you are comparing it to is an older model before the C . if so i would go with the newer model.
Martin Colloms tested both of them; the 400cx got 75 on his scale, the FPB 600 got 45. See the HIFICRITIC site for more.
The 600c is better. As a matter of fact the 600 beat my 350c monos and I got rid of the monos and purchased a 600. I now have a 700cx.
Do not buy a FPB 600, my FPB 600 is now a flower planter! I took off the top of the amp, removed the insides and put a plastic tub filled with dirt. it now hold beautiful flowers next to my fireplace. It now works better than it ever has. That was the most expensive amp I have ever owned that I barely used. It went back to Krell so many times I lost count. Junk! I had to build a wood crate beacuase the cardboard boxes would ware out and Krell would charge you for new box about every three round trips. If your Revels are a tough load in regards to impedance then FPB 600 is not your amp. It is two bridged FPB 300 in one chassis. Bridge amps only see half the impedance and are not stable much below 4ohms because they only half of the imdpedance. This amp could not run my old Apogee Duetta Signatures for very long before cooking it self off. Before I bought it Krell swore up and down it would drive my speakers with out any problems. I had no idea that it was a bridge amp until a friend who is great audio tech looked inside and told me. I asked the engineers at Krell and they finally admitted that the FPB 600 was two bridged FPB 300.
That's about the silliest thing I've heard Sound. I bought the big Krell when I was a speaker designer and it drove everything I threw at it. And it sounded great doing it and still does.
What was silly is the fact that Krell would build such a big amp with lofty claims that was as powerful as they said it was in terms of watts but could not drive speakers with tough loads any thing below 4 ohms and had a steep impedance curve like most planar speakers. What made the wounds of expensive repairs worse is when they said that they would upgrade it to the 600c for way too much money, and when you asked what were the changes they told me the only thing that is used from the old amp is the chassis and the power transformer thus admitting that there may have been some design flaw(s). What hurts is I bought the FPB 600 through the audio store where I used to work and paid for lots of repairs having to keep a straight face when customers asked about Krell's customer service. Even in warranty it was $600.00 for shipping and the only shipping company they would use was Ocean Air. I once thought I would save $150.00 and ship the amp Fed Ex freight they would not accept the amp although it had the proper RA. So if are ever in the Albuquerqe area just email me, you can come over and enjoy cool beer listen to some great vinyl all while looking at some great flowers in my FPB 600 planter. To Krells credit they have recently made some good changes and I think they are fixing customer service.
I've sent my amp to Krell twice using Southern Freight once for an upgrade to 700cx and another for a checkup a year ago. The shipping was about 125.00 from GA. If there was a design flaw in the 600 I never experienced it but maybe the upgrade fixed it. I have owned the FPB 600, 600C and 700cx.
Hey Sound, send us a picture of that planter. Yeah, I thought so.
I have owned Krell equipment for many years. I currently have two Krell Evo 600e's and 2 S-275's and the Evo 707 processor. The amps and the processor are superb. I have never had a problem with Krell amps. I have had a few quirky functional issues with the Evo 707, but Krell has been incredibly responsive and it now functions perfectly. The Evo 707 sounds so good it was worth the minor inconvenience while they ironed out a few minor issues with HDMI handshakes. I love the build quality and the performance of my Krell equipment. The 600 model is the generation before the 600c. It does not have cast capability. I owned the 450MCX (extended frequency range)a few years ago and loved them. I have A-B'd Krell's mono to stereo amps and easily noticed an improvement in 3-dimensional sound staging and instrument seperation (air) with the mono blocks. I felt the MCX (450 MCX)generation high frequency reproduction was brighter (in a good way) and more pristine than the earlier generations (which tend to be a bit on the dark side). The 450 MCX also did a better job on transients. If you can find a pair of reasonably priced 450 MCX (monoblocks) in excellent condition, you should buy them. They will perform better than the two pieces you are considering. They are great sounding amps. If you do not match up with equally high end pre-amp, you are wasting your money.
and 2 S-275's


I started a previous thread looking for info on the S-150 and the S-275. I now have my sights set on the S-275. I cannot find any reviews...what is your take on this amp? I would run it in stereo (I assume since you have two you're running them in mono...?).

Anyway, this is the only relatively powerful Krell within my budget and I would love to hear about it from someone with experience...

Thank you.

I am using two Krell Evo 600E monblocks for R/L channels with music and home theater. The Evo 600e is a stunning amp. I use two Krell S275 amps for home theater only. One S275 amp is used to bi-amp my center channel speaker (my processor has 2 center channel outs) and the second S275 for the two surround channels. The S275 replaced my Krell 3X250 amp. I use cast for the 600E's, balanced connections for the S275's. The S275 is a much better amp than the 3X250 Krell. Since I don't use them for music, I don't have a feeling for their ability to create a 3 dimensional sound stage, dynamics, tight bass, transients, speed as I do with the Evo600e's. I have had no problems with the S275's, I like them very much. They are dead quiet and they provide more power than I need. They probably perform much better than the small Krell 150 monoblocks, which recieved very positive reviews. They are compact in all dimensions except for depth and weigh 50lbs each. The S275 is very nice, but it is not in the same class as the evo amps. If you plan to use the amps for music only and you don't want to pay the cash for a new Krell EVO e series amp, I advise looking for two Krell 450 mcx or 650 mcx monoblocks. I owned the 450 mcx's and loved them. They are great, extended frequency range amps (fast, detailed, 3 dimensional sound stage, great instrument seperation, nice highs, great tight detailed bass). They will not fit into a rack as well as the S275. You should be able to pick them up for a great price if you can find them. But keep in mind, you need a very good preamp and/or processor with the high end amps to get them to sound their best. I think the pre-amp/processor is every bit as important as the amp, if not more important. Hope this helps. Good luck.

Are the new evo series much betterbthen the fpb 450 mcx? I am using 2 450 mcx, a 350 mcx along with a kav 500 for the rears and sides.

The 450 mcx still sounds pretty but I wonder if the 400e is much better. I have always preferred monoblocks to stereo amps.
I agree, Krell monblocks definately sound better than their stereo amps. I have A-B'd the Krell 750mcx (stereo amp) with the Evo 400 (stereo - not the e series). They are very very close. They both sounded great. I had great difficulty picking one over the other. The Krell MCX amps are superb, especially the monoblocks and the big 750mcx. I think the MCX amps sound much better than the prior generation Krells. I love my Krell Evo 600e's, but I also loved the 450mcx. They are great, great amps.
I had an in-house demo of the Ayre MX-R monoblocks driving a pair of Revel Salon 2 and I was surprised that I preferred the 450MCX. The Ayre was more refined in the mids and highs but the 450 MCX had much better bass and had a fuller sound.

Do the EVO amps have better mids and highs than the MCX?
Two 450mcx's may be better than the 700cx, I haven't compared them. But I had a 600c and sold it to get the 350mc's and sent them back to get another 600c because I liked it better. The 600 was just smoother and more powerful in my system.
I lived with the 450 MCX for several years. When I exchnaged it for the Evo 600 (now the Evo 600E) I did not notice a significant difference (I didn;t A-B them at home). Midrange,bass treble all sound great with both amps. Both have excellent 3 dimensional sound stage, instrument seperation (air). My dealer felt the treble was a bit more prestine with the Evo amp, but I am not sure that I agree. The sound is too close to compare without direct A-B. My A-B comparison at the store was a Krell Evo 400 stereo amp A-B'd to a Krell 750MCX stereo amp. The sounded very similar. i guess it is impressive that the smaller evo 400 could match the 750MCX. T really had to strain to detect a difference. I would not trade in the MCX for the evo amps unless you get a great deal. Both are superb. The thing that made a huge difference in audio performance in my hifi was changing my Krell KCT pre-amp and Lexicon MC12B processor for the Krell Evo 707 processor. This made an obvious enormous improvement in all aspects of audio both for music (2 channel stereo using the pre-amp bi-pass in the Evo 707) and for home theater. I noticed it immediately, no AB comparison was necessary. I have been involvrd in this hobby for over 30 years. Upgrading to the Krell Evo 707 is by far the single greatest upgrade I have ever done. The 707 uses a pre-amp section very similar to the preamp used in their top of the line Evolution 2 (retails for $55,000)in all channels. The sound is absolutely stunning. The Evo 707 is amazing, it completely blows away the Krell KCT and the Lexicon MC12B.

Thanks for the great info. I wish Krell would come out with a slightly cheaper version of the 707 with CAST outputs.
If you have a good Krell dealer, between trade-in and discounts, you should be able to buy the 707 for much less than $30,000. $30,000 is a lot of money. On the other hand, compared to the evo 2, which retails for $55,000 for two channels, the 707 could be viewed as a 'bargain' since it has almost the exact same preamp in all channels, along with the processing, EQ, video, etc. The improvement over the KCT (which I used in CAST mode and is a very good pre-amp) is enormous. I was shocked. Better instrument separation (more 'air'), better 3-d sound staging, faster, better dynamics, better transients, much better tighter (more accurate sounding) bass, more detailed but with an analog tube like bloom. The Evo 707 produced a more beautiful, life like sound. This also applies to replacing the Lexicon for HT use (I used the Lexicon for HT, the Krell KCT was used for stereo music).
Krell does have a less expensive pre amp/processor, but I have not heard it. I doubt it sounds as good as the 707.
What are you using for a pre amp/processor?

Thank you for your excellent information. Can you elaborate on CAST technology...(like, what is it!?)...also, on how to mate a preamp/processor with a CAST unit (i.e.: compatibility...what to look for).

I was planning to use my PS Audio Perfect Wave DAC as a preamp. Do you see any issues? Also, did you say that the S-275 as CAST technology?

Thanks again, and happy new year (Happy New Year to All of you sick twisted audiophiles - and I mean that in a very sincere way...tongue firmly planted in cheek!!)



I have a Lexicon MC12B and a Pass Lab X-1. I am considering replacing the x-1 very shortly and MC-12B as well.

Most single box ssp don't sound good on 2 channels perhaps, the 707 might be the exception.

I will try to audition the 707 if I can find a local dealer.
Ahh...I answered my own quest about what CAST is by visiting the Krell website. Very interesting...but can you really hear any discernable differences? Does anyone other than Krell utilize the CAST protocol? If not, one would necessarily need to mate a Krell preamp with a Krell amp to take advantage of the protocol...

Cool stuff...but beyond my budget threshhold


CAST technology was developed by Krell and used exclusively by Krell. Krell has an excellent explanation of cast on their website : www,

My understanding of CAST: all electronic audio equipment operates in current mode. The electronic current is converted to voltage, transferred by cable to the next piece of equipment where it is transferred back into current, modified as necessary, converted back to voltage, transferred by cable to the speakers. Everytime the signal converts from current to voltage and back to current some distortion/noise can occur. Krell CAST equipment uses an extremely high frequency bandwidth (>2 MHz) and transfers the signal in current not voltage. This eliminates distortion that can occur durring the conversion from current to voltage (and voltage to current). Also, Krell claims that since the signal is transferred along their special CAST cable as current rather than voltage, there is no signal degradation effect produced by the cable. They claim, with CAST, the signal remains unaltered from source to speaker. I believe the Krell amps ending with C (400C, 600C, etc) were the first generation Krell amps to use cast. They have CAST in their high end amps, processors, pre-amps, CD/SACD players. I believe the Krell KCT was the first pre=amp with CAST.
CAST is very interesting, innovative technology. It is a great idea. Does it work? I have never A-B'd to compare. Reviews state that it does make a significant improvement. My guess is that it probably does make an improvement. No one else has CAST, Krell owns it.

The S275 does not have CAST.

I don't know anything about the PS Audio DAC/pre-amp. Do you like it? It probably will be fine with the Krell S275.
The Krell 150 mono blocks probably sound very similar if not identical to the S275. But the S275 will give you more power. The choice probably depends on the speakers you will be driving.

Once you get into the 450MCX, Krell KCT level of equipment, things like cable (Krell CAST cable, etc) become important considerations, also, more expense.

The pre-amp section for stereo music in the Krell Evo 707 is fantastic; far superior to the stand alone Krell KCT pre-amp I owned previosly. If you are able to audition one for music, make sure to go into the menu and sslect pre-amp for the CD player and/or record player. This bi-passes the digital processor. The Krell Evo 707 is an amzing piece of equipment. The sound is extraordinary for home theater and stereo music. I traded my Krell KCT and Lexicon MC12B when I bought the Evo 707. I cannot say enough about the Evo 707, you have to check it out.
Good luck.
Re: the FPB600 load/reliability issues...the Stereophile measurements were simply not indicative of a poorly designed or load intolerant amp....just sayin.....
I don't understand what you are trying to say. Please elaborate.
He was just sayin.... Mat.
Matjet - there was a poster earlier in the thread that felt the 600 was a poorly designed, bridged amp that had a tough time with difficult loads. When I look at the Stereophile measurements from their testing, I don't see it - that's all.
Get a KRS series amplifier - KRS 100 or 200. They'll drive those with speakers with ease and sound better than any of the other Krell amps mentioned here.
I had the FPB600 stereo amp and I drove the Magnepan 20.1 speakers with ease. Then is bought the Sound Lab Millemium one electrostatic speakers and it drove them with ease! Never any issues. Sounded spectacular. I have since then bought the Krell 650m mono blocks and wow, what can I say. If there ever was a dependable amp the FPB series is the ticket. The only thing to beware of is DO NOT plug these amps into ANY power conditioners and don't enclose them in a cabinet. Give them plenty of air and proper wall outlet amp rating. If you do this then you will get a long life from Krells.
I have owned several Krell amps and pre-amps. I love Krell performance, sound, looks and buld quality. Never had a problem. They really know how to build amps and preamps.Love their products!
I used Krell pre/power from 80s and love the excitement playing Retro/Rock n Roll/All Rounder Music ,they are aggressive sounding and squeeze your speakers making sure they sing like never before and always impress with it's dynamics.
New Krell are suppose to have improve but I am not really wooed by the built quality these days, as they are not in destructible as once thought to be.
I hope that Krell continue with the Innovation and Bring the Hi-End to No End.
I used 600c and changed to 700cx. It was a few years ago, but the cx series i find smoother and a bit darker. If using slighly bright equiptment around 600c it will prove to have a slight sting and perhaps some grain in compairson with cx.
I would go for the cx, no doubt. Even now, using Rowland Continuum, i could gladly use the 700cx or 400cx. Very nice power amps. I think you'll find the cx very nice. The only thing that i did not notice any changes in between c and cx was bass. But in the mid and treble there was obvious changes for the better. Other Krell i owned were KPS 25sc, KPS 28c and KCT.
The KPS 28c was not so much to my liking.
I would really try the cx with Classe CP-65 as i think this was a very nice pre amp.
i owed Krell FPB600 for 7years, not a single problem, enjoyed very much drive PSB Platinum T8, you could felt 20Hz, fast and very musical, i am hoping to get a mono block 600 or 650.
and upgrade to wilson Maxx2.
anyone have this combo Krell and Maxx2?
listening mostly rock/Jazz. Vinyl
The bad rap Krell got in t about being bright, sterile etc. pertained to the pre 'c' and especially 'cx' models. My 400cx is smooth & warm and still has that famous Krell slam and bass control. If you want slam and incredible lower bass extension you'll love the 400cx. When I replaced my Classe 301 with my Krell 400cx I got another half octave of low bass that was just being hinted at before.

I've also learned that the 400cx is a real chameleon. Put in a warm tube preamp up front, and that's the overall character you'll hear (plus the punch unless the pre doesn't pass it). Put in a dead neutral, highly resolving pre, and that's what the system will give you. It's a great foundation for a system.

If you are more on the neutral side, the Krell pre's with the CAST connector is a great companion choice. As Wes Phillips said when he reviewed the CAST system, it really does work to create a quieter, more open conduit. His only cautionary note was that it might be so neutral that it can sound sterile, so depends on you upstream source as to how well that works. I use a Marantz SA-7S1 CDP, which is very rich and full bodied, so that's all the warmth I need.
I am upgrading to the krell FPB450mcx amps again. I previously drove my MBL 111B and 101E with my Krell FPB350m and a FPB300 for the rear surrounds. Having all Krell electronics except for my Marantz SACD/CD driving these very difficult speakers I never had any trouble. I have all dedicated 20amp circuits for every AMP. As you all know the 350m with the 4KV transformer easily puts out 500 watts into 8 ohms as is, upgrading to the 450 status is not about squeezing more power out as many have claimed just better boards and a wider range.

Honestly, I know my system could be improved which I am doing now. But I have to tell you the KRELL FPBs at full throttle into the MBL's is stunning and jaw dropping amazing. My friends always have opinions about the cost of the system and the dominating look of it in the living room (ugly) but when I put some Pink Floyd, Led Zeplin and such in there the sound stage is massive, I mean if you have never heard MBL's before you won’t get it but I mean HUGE with virtually unlimited dynamics. So far in my audiophile little life (46-12=34 years) I have never heard a more delicate, realistic and downright dramatic system. The MBL's have extraordinary power need there are times when the Krell’s simply run out of steam and I can hear them starting to compress, I also run Velodyne subs for the bottom end. I own a pair of B&W 801N which I always wanted and they rock too, but not on the same scale as the MBL's, once you hear the Krell/MBL combo it's hard to respect much else.

Now to my point, It's very hard to get the MBL's set up in a room properly much less all the cabling and such, mostly my cables are Kimber Silver except from the Preamp to the amps that is Copper/Silver and all balanced but the new system will be CAST. Anyway the sound of this system kind of makes you want to try more and more improvements. The best sound without a doubt was with the Krells all being fed from dedicated PS Audio analog regenerators; I have not tried the digital yet.

Running all PS Audio further reduced my efficiency even more and increased my power bill even more, it also lowered significantly the headroom I can get with the amps plugged strait into the wall, I do reach the 1400 watt threshold on the PS Audio 1200s just before they shut down, driving the B&Ws for example I would never reach this level. The problem with DARK/Bright sounding Krells I found out through lots of trial and error occur above 118 volts, at 117/118 the Krell’s sound amazing, dead quiet, sweet top end, the best sound I have ever heard from any amp. I wrote krell about this I thought they were completely regulated but the difference in sound is obvious, at 117 they are butter and wine, over that they are peppers and vinigar. So for the best sound with MBL's I had to watch the dynamics and I can see when the amp increases its class A level, there are levels above the 1400 watts each, but that like I said is where the PS Audio's give up. I now understand why some claim they are harsh sounding in the treble, keep in mind I run almost all silver wire except the pre-amp cables and I use the factory Krell copper speaker cables.

I am now trying to upgrade to CAST and the newest PS Audio stuff. The difference by the way between the MONO and Stereo amps is also night and day like everyone said and I have both. I could never go back to a stereo set-up on my two channel.

Everyone says don't use power conditioning with the Krell’s, I would say be very careful what you use. Most power conditioning is lame with cheap components and crimped connections. Most are ok designs but poorly executed regardless of the cost. My PS Audio's are also highly modified for their extreme mission and single purpose. Having control of the voltage and a perfect sine wave is important.

I can say I have stressed my air conditioning and the Krell’s to their limits for long periods of time repeatedly over the years without a single issue. I can understand someone being frustrated and they are after all a small company to deal with, but to call them junk and unreliable I think something else is going on there with that guys system? I have had Bryston's, Luxman's (very good), AR's and Pass amps with my MBL's the two best were the Pass amps and Luxman's but they could not handle the MBL's like the Krell Mono's and nothing so far approaches the wonderful sound I get with the Krell/PS Audio combo, it's so emotionally involving it's hard to describe, especially since I probably already sound a little righteous about it.

I just had to say something here I think the Krell’s are very durable and capable for what it’s worth. I have had them roasting hot and pushed them to compression and still the never got harsh on me, never damaged anything and never shut down.
I have read from others that using the PS Audios with a 230-240 volt input helps a lot? I will be upgrading those too when I get the rest sorted out. Thanks for all the great posts!
Cast will cure any interconnect problems/issues resolution and up the quality a notch (sounds like your quality is there -- nothing to snuff about for sure -- better than just about everything out there).
Your statement about the Krells running out of steam "kinda freaks me out" -- I ran a question on this forum about room size and volume not volts-- I sure would like your input on that question.
Kool --

According to this Stereophile test results, the Krell FPB600 almost doubled in power going from an 8 Ohm to 4 Ohm load, and then again going down to a 2 Ohm load.

There was no indication looking at the test results to support the claim that this was a bridged amplifier. To the contrary, it said that it could drive any load of any impedance.
And the only reason it didn't quite double into 4 Ohms was because the line voltage began to sag.
I completely agree and know of this also, where you are going to see it in the FPB600-700 is driving say Soundlabs or Apogee speakers that are living below 2 ohms most of the time. There is no lack of power with this amp and don't read too much into that difference. It's only in the most extreme loads you would experience anything at all. Mr Dan designed all these amps to be pure voltage source amps, bridged or not, if they are bridged it must be in parallel anyways, I understand it's basically two FPB300's. If they were bridged in series the power would be 1200+ into 8 ohms and that would be restricting the amperage. In order to be a constant voltage source regardless of the load, the current must be unrestricted, this is why the wattage doubles with every halving of load. I'm not trying in anyway to knock any FPB amp, just understand their differences and I do not currently own a FPB600 only the 300 stereo amp and my mono's.

I just ordered a pair of FPB750MCX Mono's should be here in a week or two, can't wait to listen to my first X amps in my own system.

On another note. My son and I were doing the annual cleaning of our equipment and all the connectors. We remove all the panels and clean the inards and boards inside along with all the connectors. So we finished the KRC3 and my bedroom S300i and decided to try something which kind of relates to this thread. We put the S300i in theater bypass mode and ran it directly from the KRC3 with all the silver cabling I normally use. WOW what a difference, I never liked the veiled lethargic sound of the S300i but running in theater mode is a whole different ball game! It must completely bypass the horrible preamp section and route the balanced input directly to the amp? It sounds great not like a BIG FPB's but hey it's a $2500 amp and it sounds tight, SWEET and powerful. Gone is the top-end and mid-range shouting and raspy treble. It sounded much more like the KRC3 itself now, very musical, natural. All of the sudden it has a sound-stage and a good size one at that, depth, it made the 801N's bass sound tight and punchy. It's not the same Majesty and effortlessness you get from the FPB650MC's but hey I could listen and love this all day, and we did.

Looking for a true audiophile bargain, get a good preamp and run the S300i as an amp only, direct in theater mode, you will be glad you did. Granted it too is plugged into a PS Audio P-1200 @117 volts @ 90 hz but damn it really sounds great, it's just the preamp section that sounds so nasty.

Now do I buy a Krell EVO 202 or help my son pay his tickets off?

Sorry I meant 2 Ohms.
Over the last two weekends I have spent some time listening to some McIntosh amps and pre-amps. I've been curious to learn more about the comparison between the Mac's, Pass amps and Krell. I'm definitely more familiar with and more used to the Krell sound. That being said I get it now why some like the Mac's so much, the mid-range is great and very articulate. The Mac mid-range to me sounded very alive and natural, impressively real and musical. The top end was extended pretty well but not as sweet as I was expecting and a bit brighter than my on Krell's, I have not listened to them as much yet but the Pass amps seem to be the treble masters, very sweet and yet nothing is missing. For the BASS, I noticed right way that the Bass was not as articulate as I'm used to, what I liked in the mid-range did not extend into the bass. I could distinguish the separate bass notes but it was like there was a blanket between me and the woofers. Both the Pass and Krell were easily more articulate, crisp and powerful in the bass and the krell seemed like it could add a few lower notes.

I'm happy with my little Krell world except for them kicking Dan out. But the Mac amps do look nice and run cool and probably do not consume near the power of the Pass or Krell amps? All the amps I heard so far are great, so don't get me wrong here. Personal taste, I like the Pass amps a lot they really have a very sophisticated sound but as far as living together, they are about the same as the Krells. The Krells seem very honest to me and extremely controlling of the speakers themselves, like the Pass amps they arn't bad at anything but a little different from the Pass amps. I'm still happy with the Krells but I do admire the Mac mid-range and the mid-range and treble of the Pass amps. Imaging, depth and height the Pass amps are more clear to me that the Mac's, Both the Pass and Krell can have a huge soundstage that is more pinpoint accurate then the MAC's but I'm afraid I'm exaggerating too much the difference. Drum sets, Piano's and singers were mainly what I was listening to on all three so far for imaging, the Mac had slightly bigger images and kind of blurred the drum set together a bit, with the Pass and Krell amps I could point to each individual drum or cymbal. On the Pass and Krell amps I could not only hear the singer like I could on the Mac but I could hear which way they were projecting their voices and if the were walking around. My wife is a harsher critic, she did not like the Mac amps as much because of the bass mainly.

Just some completely subjective thoughts here, I wish I could hear the Pass amps some more they are very nice.

Hi Rob
How is your new krell 750 mono?
How much did you paid?

Right now I have my Aesthetix Callisto sgn, and io with krell 600
It sounded very good, if anyone have krell amps should try with tube pre,
I am hoping to upgrade to mono block 600mcx or higher.