Krell FPB 600 or 400cx?

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!