Krell FPB 600 or 400cx?

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!

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?

Rob

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.

Rob