Thoughts on Krell FPB series? 600 in particular.

Or the 300 as well.
Will be using it to power a pair of Thiel 3.6s and Maggie 2.7QR some of the time. Currently have a Classe CA-200. I'm looking for more slam and I'm thinking the extra power will result in a less constricted soundstage (more open). Is my thinking right?

How about the CX series? 300CX or 400CX

Associated equipment: Wadia 850, ARC LS-2B, Cardas and PAD cables.
I would go with 400CX over the 600. 700CX would be even better, but $$$.

There is a big improvement when going from 300 to 400CX.
There's more to it than just extra power. How does the system sound when going from your 850 directly to the amp?
The Fpb 600 is an awsome amp, the cx has more sparkle on the top and the cx has an uncanny realisim to the mid-range, and more clear than the original fpb amps, neither less, both models are very fine amps that will give you what you seek for the thiels that need the power to drive them to their top performance that they can possibly do.cheers.
I had theClasse CA400 and once I got a krell fpb 600 ...well I sold the classe as its bass does not even come close and the headroom is amazing.
I have the fully recapped one for sale here as I own 2 and only need one.
The early models should be getting to the recap age as there original caps are not as good as the newer ones.
The cx is a subtle difference for thousands of dollars.
Good luck
I am a big fan of my FPB 300cx amp. Unkless you have a very demanding speaker load, I cannot imagine this amp not giving you all the slam and high end sparkle you need or want. Plus, it is bulletproof. Mine is almost 11 years old and never had even a hiccup.

I also have the 300cx and love it. Seems reliable as a rock. The 300 will work with a standard household 15 amp plug. I believe if you go 400 or 700cx the manual suggests using a 20 amp recepticle. You can look at the manual online at the Krell website to verify.
Have fun, John
Hi Jcatral14, If you are wondering what I own, It is a modded Krell FpB 700cx, modded meaning Krell themselfs put todays current caps, all caps, versus the caps that was available in 2005, I will have it back next month from Krell, It is totally renewed inside and out, everything!, A brand new 700 cx, I spent a boat load of money to make this happen!, one of the very few in this country new at this level of modds and renewed, if eany, krell told me, And yes, I have owned other Krell amps, the amp I get back, according to Krell will be alot better than the 700cx amps out there, we will see if that is true, cheers.
One has to be careful when justifying the cost to performance difference.
I mean that going from a ksa 250 to a fpb600 is not only a big step in amp output but also a different sound.
But going from a fpb 600/c to a evolution 600 is not a apples n oranges of a difference but the cost factor soon kicks in.
I had a Krell FPB300 many years ago and thought it was a sweet sounding amp with a warm, if not slightly dark tonality. It sounded a tad grainy when compared to my Rowland 8TiHC.

While researching new Krell amps recently, I often hear that the cx and mcx series of amps are some of the best of that generation. More extended in the highs, but still the same dynamics and bass slam.

@Audiolabyrinth, you will likely get Evo internals in your 700cx (that's what a Krell dealer recently told me). I recently had the 900e monos and they were dead silent, totally neutral, extended at both ends and with the typical dynamics and control Krell amps are known for. The sound is a little leaner than what I remember of my FPB300, and just a shade leaner than my Rowland, but still a great sounding amp that could drive any speaker.
Fox -600 if your playing it load you need a 30 amp. I told my electrician I want a thirty. I pop it the first day and had him come back and put in a was one of those 30 year olds that knows everything.
Krell is a great match for Thiels. I had a recently re-capped FPB 300 matched with Thiel 2.4's and was very pleased with how the Krell took over those 2.4's. Pronounced bass, good separation, just absolute control of the speaker. The 300 wasn't quite enough for the extremely demanding cs5's, but I really think you would be in good shape with the FPB 300 and the 3/6's, as they have a tough load, but not approching the cs5's.
I sold the Krell & replaced it with a CAT 600.2, a beast with 1200 wpc into 4 ohms; it brought out the bass, but doesn't have the defined middle and highs of the Krell.
Just my experience!

IN connection with your Krell re-capping, was this done by Krell? What effect -- pro or con- on the amp's sound did the recap have?


Nice! Michaeljbrown-

indeed, the Thiel CS 2.4 is a special loudspeaker, that demands both high power & high current to really sing.
Anyone else using a Krell power amp on Thiel loudspeakers?
Keep me posted and Happy Listening!
The Krell will have a greatly extended life if recapped. I wouldn't get one that has not been recently recapped. Its a beast to ship off to Krell, and will cost you about $1200.00 at least, maybe more now. Counting shipping, that's close to 2 grand.
When the caps quit, the Krell quits. My experience with Krell is nothing but good, and when I go back to sold state I'm going back to Krell.
I am using the Krell FPB-250 Mono's and they sound fantastic on my Rockport Altairs.
Jwm and others here,

I have the Krell FPB-250 Mono's as well and just recently purchased Art's Audible Illusions Modulus 3B tube preamp. I know there have been discussions on the 'gon about having to put jumpers in the Krells when using tubes to avoid harming them.

But the feedback has been unclear, Krell says you should do it while others say not to worry.

Any thoughts/guidance?


You should put the jumpers in when using single ended or unbalanced connectors. It doesn't matter using tubes or not. Jumpers are not used with balanced which makes sense.
Thanks JWM. And you didn't experience any degradation in SQ, per the above comments?
No not at all. Your other alternative would be to use a Balanced to RCA adapter, but then you have an adapter.
I had a FPB 600 for years and compare to latest SS, it's a bit grainy and dark but still a terrific amp. The only reason I sold it is to try something different. It sounds great with everything include 100 db Avantgardes. You can hear and feel stability of the sound.

When I play the track The Four Seasons, never achieve the level of dynamic swings since the Krell shivering my whole body. I'm in the camp never too much power and dynamics is what make music fun for me.

FWIW, I found network cables such as MIT worked best with all my Krell amps. I only use tube preamps with them and XLR offers the best SQ.
Knghifi, could you elaborate more on how you define "grainy"? Curious whether I can hear on my FPB-250m what you heard on your 600's.
I hear no grain on the FPB in my system and Knghifi that is why your sound was dark because of the MIT. I always hear this with MIT and the other company.
I hear no grain on the FPB in my system and Knghifi that is why your sound was dark because of the MIT. I always hear this with MIT and the other company.
Probably your system is MUCH SUPERIOR to my pre Agon OLD system :-) I'm sure quality of associated components contributed to the graininess.

I demoed many cables and found either lacking bass or too bright. At the time top of line MIT worked best. I sold MITs after the Krell.
It was good for its time, but now we got the $12k Dan D'Agostino Master Power Classic Stereo amp. It should outperform the old Krells, at least most of them. We'll see what happens.
"but now we got the $12k Dan D'Agostino Master Power Classic Stereo amp"

I just heard that driving some Avalon's - it's a different sound to the old Krells at least the FPB cast series. It is smoother on the top and more open sounding and resolving with slightly more body but it doesn't have the bass slam. There is more bass texture in its place. I think nothing I've heard has the bass slam and grunt of those old Krells.
Jwm (Jeff?), I was looking at your system thread and don't see the FPB 250m's. Did you acquire them recently? Also, did I read it right you live in Michigan (Oakland County)?
I just heard that driving some Avalon's - it's a different sound to the old Krells at least the FPB cast series. It is smoother on the top and more open sounding and resolving with slightly more body but it doesn't have the bass slam. There is more bass texture in its place. I think nothing I've heard has the bass slam and grunt of those old Krells.

Lucky you! I haven't heard it yet, how does it look? I see, well thanks for your short review.

There's also the BSC amps from Dan's son Bret if you like the old Krell sound. I'd like to hear those too.
Gareneau, yes Oakland County. They are about 4 months old. I have not updated my system, I know I'm bad.
No worries, Jeff, just curious what you have now in your system.

As it happens, my in-laws live in the West Bloomfield area - was just there visiting a week or so ago.

I'm five minutes away, by the Orchard Lake Country Club, your welcome next time you come in. Let me know in advance.
Mmmm, this is news! New amps from legendary Dan d Agostino, they look a lot like the old ksa etc.. amps of old, these new amps should make a huge splash in the audio world!, the description of sound is like my modified 700 cx done by krell a year ago,believe it or not fellow enthusiasts, a 30 amp breaker on one of the beast amps makes a huge difference in sound, like the amp must have been starving for power before! , everything imaginable is a lot better, that was an excellent tweak other than the massive modds.
Sounds great - thank you for the kind invitation.


Have you read Alan Sircom's interview of Dan here?

A 780-800 lbs amplifier named Helius? As a commenter writes - insane...really really
Hi Gareneau, no I have not, thankyou, I'm going to read it.
Gareneau, wow!, really!, 20,000 watts at one ohm, Dan is audio legend, he is making his last impressions on audio by setting the bar with sound and power before he is one day no longer with us! Bravo
I can't wait to see what a power cord for one of those things cost. you mean this series?
Dave 72, no, this super amp! Incredible!MEET YOUR MAKER - DAN D'AGOSTINO INTERVIEWExclusive talk with the top amplifier designer


by Alan Sircom | Jun 01, 2015

What’s next?

Once the Progression line is done, I’ll turn my attention back to the Helius amplifier I’m building. Helius is truly a monster amplifier. It’s made of three chassis – it’s got a ‘plus’ amplifier and a ‘minus’ amplifier because it’s a purely balanced design. People say they’ve made a balanced design, but I don’t think anyone’s made a truly balanced design like this. It’s got two completely mirror imaged amplifiers that are virtually identical, only one is inverted from the other.

And then, I took the insides of the amplifier – all the bit stuff, the transformers and electrolytics and power devices and heat sinks – and put them all in one case. But no input board: the input board is inside the base, fully isolated chamber with its own power supplies, and sits below the amplifier on some suspension equipment made by Mike Lapis of HRS fame. So there’s no vibration, then it’s totally sealed with µ-metal and copper shielding around it so no influence from the amplifier.

The amplifier is built out of a solid block material, and the toroid is 10” in diameter and it’s seven inches tall. So the toroid itself probably weighs about 130lb, and that is actually milled into a block, the outside block of the amplifier; the toroid fits into a hole and is then covered.

The electrolytics capacitors, of which there are a total of 12 in the two sides, comes out to 1.2F. Each transformer is 6kW, 12kW in total. It’s got a giant copper heatsink; 10” tall, 28” long, and 1.5” thick. That’s bolted to a piece of specially designed aluminium designed for heat reduction in aircraft known as 5051, and each fin of that heatsink is milled out whilethen  the base is bolted to the outside of the copper. And that’s three inches deep and of course 10” tall and 28” long – it’s a single piece. And that’s the heatsink for the output stage.

The capacitors, and power supplies are all in this great big block. If you imagine the block is 11” deep, 10” tall, 28” long – that’s where the block starts – and then it’s hollowed out to fit the transformer and the six electrolytics. Then in the back – where it’s ‘empty’ – is where the protection circuits and the hook ups and all that go, then that part is slid onto that heatsink, there’s bolts that go through the inside web of the heatsink to hold that block on, so it’s one rectangle.

If you add up all the parts, the amplifier is going to weigh 780-800lbs. Per channel. Each plus amplifier and minus amplifier has its own cord; it’s designed to run on 220V or 240V… it doesn’t run on 110V. And you need two of them for each channel.

It’s got an extraordinarily gorgeous meter on the front. It’s about 10-12” in width, and six inches high that sits on the front. It’s really strange – it’s almost Bauhaus in design, but looks like a Momentum from another dimension. This is not that big for the kind of power it will produce, though, because it will produce up to 20,000W into one ohm!

Once I get the Progression amplifiers done, this is next in line. I would love to have it ready for CES, but maybe I’ll just show the case. I have the metalwork ready. But it will definitely happen by March next year. Or maybe CES 2017!
Ok yeah, that's gonna be friggin' amazing to say the least!
Mikey8811: I forgot to say something regarding the new D'Agostino $12k amp vs. old Krells; better than nothing! I'd rather get the D'Agostino instead of non D'Agostino Krell. No D'Agostino, no Krell. :D
Hi I own a fpb-600 and it is amazing.If your into rock you will love this amp.The base will punch you in your face. They are old.but very trustworthy. krell has the best service too.You have any issues they will help.Stay away of the jap stuff .Even they buy from Krell.That guy thats talking about Helius amplifiers is crazy He is talking about 250.000 a pair.Who has money to Burn ?They are made in the usa.
Are these amps made in china?
Krell made four (now discontinued) products there, the S-300i, S-550i, S-350a, and S-350av.  Everything is made in Connecticut now.
Do we know why Krell junk-sourced to china for these specific models?

It is good to learn that Krell learned from mistakes and brought it back "home".

Those products were very affordable.  The S-300i/S-350a were 2500, the S-350av was 4500, and the big S-550i was 5000.  These were amazing performance/dollar products at the time.  The new Vanguard integrated and Cipher CD/SACD player are both much better, but at 4.5k/12k respectively the price is higher now too. 

Many company's make some models outside of the US to keep the prices lower.  Unrelated (sort of):  I worked at a B&W dealer for 16 years, and when the 683 loudspeaker was released from their new, non-British factory I was surprised/disappointed, but then I listened to them.  Not only were they 1500/pr but they sound much better than the outgoing, British, 604S3 ($1600/pr) that they replaced.  So equating where an audio product is made with it's performance (or reliability) might not necessarily reflect reality.

That said, rest assured, ALL Krell is made in Connecticut now.  The new Vanguard integrated, and the iBias family of amplifiers are the best sounding amps they've ever made.  Give them a listen.  :-)

The fpb-600 is a great amp but with the age now it needs a recapping
I wonder what it cost to recapp a pair of FPB 350m’s? A pair local to me but the age worries me. How do you know for sure when to do it? Does the performance change over time?