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alphaGT
10-03-2017, 22:57
Grab your reading glasses and a beverage, this might take a bit.


My New Krell

As suggested on my last post, "I'm Getting A Krell!", here is the follow up after a few months of ownership. And let's just go ahead and say, I have never been happier with my stereo! It has made all the difference in the world. Night and day, no need for blind listening tests, it is a vast difference of an order of magnitude. So very different.

I learned many years ago that when you hear a stereo, it's the amp that gives it's character. 30 years ago I had my first real high end stereo. (At least it was to me) that was an Adcom 555 and Adcom preamp, with Vandersteen 2C speakers. And it was awesome! One day, I had a new pair of tiny speakers I had purchased for the garage. I sat them on top of my 2C's, and hooked them to the amp. That day I had several friends over who knew my stereo well. After an hour of listening, I asked, what speakers are playing? And no one had realized it was the tiny 4 inch woofer monitors. The tone, the character, the color if you will, was the same. It lacked the bass of the 2C's but at median volume no one noticed.

And so it was with this stereo. My monstrous Legacy Focus 20/20's have been in this room, 16x20 feet, for 3 years now. I had an amp before I bought them, a Forte' Model 3. A 200 wpc A/B switching amp. A nice amp! It really used to pump my old speakers. Nice smooth amp, doesn't have the bass slam of the Adcom, and the top end is much more fluid, but with the Legacy's it was just not cutting it. Now the Legacy's claim to have an SPL in the 90's, and only need 50 watts to drive them according to the owner's manual. But somehow, it was lacking, it sounded great! Everyone that heard it thought it was great! But, it lacked that magical quality of drawing one into the music. That power that makes you want to play one album after the other, each selection reminds you of the following one, and before you know it you've listened to it past your bed time. A property that old Adcom setup had. Even though many today would call that system unrefined, it had the magic! And friends from far and wide would come over to spend the evenings into the wee hours as I spun vinyl for them.

So I borrowed a Crown amp from the band, a nice new D class amp that supposedly makes 475 watts at 4 ohms, which the Legacy's claim to be. And I bi-amped the speakers, I made up a very nice pair of 10 gauge wires, and used the Crown on the bass half of the cabinets. And it helped! It gave music a much needed kick in the pants. In fact, I could balance the bass and treble by adjusting the gain knobs on this XLS 2500. Problem solved! Well, not really. While it had more bass than before, which was somewhat satisfying, it still lacked the magic I was looking for. Still no gotcha, I was beginning to think it was me? Perhaps I had become jaded, perhaps I was too old to feel that passion for music? I have been through quite a lot over the past 15 years. Maybe I just didn't have that magic in me anymore?

Enter the Krell FPB-300, a full Class A amp, all Class A all the time! And the minute I hooked it up, I knew within 5 seconds I had something! It was wonderful! I could hear it all! Smooth, luxurious, full bodied, satisfying sound! But I was still in for a surprise. After about an hour, after it was up to full temperature it only sounded more fluid, more sexy, more "there". In fact I had a problem, there was too much bass slam! It was overpowering, while the highs and mids were there, I had no problem hearing any instrument or vocal in the mix, it seemed boomy. But, some minor adjustments and I think I've got that problem tamed. These Legacy speakers have 3 toggle switches on the rear that allow you to cut or let through bass, midrange and high frequencies. I forget now, maybe a 3db cut? So, I simply switched the bass toggle down, and I've been enjoying it ever since. That and some speaker placement adjustments. I did pull them farther out into the room, and adjusted toe in, until it smoothed out.

Over the past 3 years, I've bought a new turntable, and a new cartridge, and a new CD player! Actually, all used, not a single piece of my stereo is new. Well the cartridge was never used, but I bought it from someone who had never used it. It was like I was hearing all of this new equipment for the first time!

My Cary 306.200 CD player is nice, looks like it was carved from a block of aluminum. Solid aluminum drawer, selectable filters, and inputs so I can run other digital sources through its internal DAC. I haven't tried that yet, but I might test it out by feeding the output of my Minidisc Recorder through it. And it sounds amazing! I had an old Sony 608ESD that I used for the best part of 30 years! And it was a top notch player, great dynamics. But unfortunately it succumbed to the ravages of time, and the laser was failing. I looked into fixing it, but it was cost prohibitive. So swapping it out for the Cary, I heard some improvement. Nothing too outstanding, but, more balanced, a bit more air at the top maybe? Until now. Wow what a difference a day makes! Played through the new Krell, it was nothing short of awesome! The music was huge! It threw a giant image. I could see down into the music like a microscope! But it wasn't analytical, or bright, it was warm, and smooth. But if I looked for the detail it was there. In spades! In fact, I found that I was playing at much lower volumes than before. I didn't have to crank it up as high to reach satisfaction, at conversation level, it has slam! It has punch! And vocals, and guitars, and drum whacks, all as true as an arrow. That magic I spoke of that I used to get from playing vinyl, I was getting it from CD's too! I was digging deep into my limited CD collection to find a new gem, finding something new on every recording, something I had not noticed before, or something that seemed different somehow. I could make out every note the bass player was playing, even through the most congested passages. The elusive kick drum was so evident! Guitar picks were easily discerned, each pluck, or finger slide, string buzz, laid bare in front of me!

This says as much about the speakers as it does the amp. But without the amp, the speakers just couldn't do it. Who needs a subwoofer? Certainly not I, bass synth could be heard way down, vibrating the floorboards. 5 string bass's low B string was slamming! Certainly preserved the boogie woogie in songs that grooved, I found myself unconsciously toe tapping to everything! And occasionally throwing that imaginary drum stick up to take a lick!

Then I got to cleaning a few records, and playing then immediately thereafter. And I thought for a while that this new Cary CD player had won the top spot? But, after about two albums I was reminded of that magic that comes from clean vinyl. Perhaps the CD player did have greater dynamics. And it allows me to pick each note apart, the black as soot backgrounds. By all accounts, if one were to listen to each for only one minute, they most certainly would pick the CD over the vinyl. But after hearing a half dozen albums, I realized that the magic had been found! I could not stop playing records. I was digging back for old favorites one after the other, Blue Oyster Cult's Cultasaurous Erectus, Hendrix's Electric Ladyland, Pat Travers' Crash and Burn, Stevie Ray Vaughn Double Trouble, Pink Floyd's Meddle, Heart's Dreamboat Anne. The acoustic guitars on that Dreamboat, and female vocals, a highly underrated album. And the list kept growing!

I've got to say, and I've said this in my last post, I always hesitate, and worry, and wonder if this new piece of gear is worth the price? Every time, even used this is a lot of money! Will it be worth it? And every time, a resounding yes! The money is soon forgotten, but the increase in sound quality, the increase in musical enjoyment lasts and lasts! I have gotten more use out of my stereo over these past two months than I have over the past year! It has hardly been powered down. When I'm not playing records or spinning CD's, I'm listening to my Magnum Dynalab FT101 tuner! Again, I am now hearing it like it was the first time, how FM could be such a quality source? Most impressive, and great for times when you don't feel up to jumping up and down to flip records. The sound is very full, and warm, bass going way down, treble so smooth. Lots of air, un-congested and spacious.

But my overall impression of the amp? Warm, full, with great slam and heft. But smooth, crystal clear highs without being edgy, fluid midrange, both male and female vocals are so true and real. It is the preverbal iron fist in the velvet glove. It reveals minute details all the way through, any and all parts of the recording are evident, even multi-tracked vocals reveal each track of it. Synth and keyboard are huge! Piano has that reverberant quality, left hand keys sound very real. Soundstage is wide, not in the room, but beyond the wall. But I believe that has more to do with my speaker placement than the amp. The soundstage could be much tighter, and possibly between the speakers if I could place them closer together. But it doesn't detract from the music, whatever it's doing it works. I could kick my own butt for not buying that Krell I've wanted since 1986!

When I first heard a pair of Krell monoblocks driving a pair of Martin Logan Sequals. The salon had a Klyne preamp set up with two CD players I wanted to audition connected so I could switch back and forth. I sat there playing my own CDs for hours! The salesman finally had to interrupt me, I was having a bit too much fun! So, I've waited 31 years to fulfill my Krell desires, and I think of all the wasted years, I could have had that setup so many years ago, if I had only taken that second mortgage on the house. I guess all things in their own time. Now that I'm divorced there is no one to shame me for spending all my money on stereo! And all of this is with my Parasound Halo 3 preamp, I paid $300 used for it. What improvements will I hear once I've upgraded that to a Audio Research LS27? Or similar. It still has the bent fin from shipping, but at this point if it never gets fixed I'll be OK. I may never sell it anyway.













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hifinutt
11-03-2017, 05:41
thanks for the write up Russell , sounds like a beautiful amp indeed.

alphaGT
11-03-2017, 05:46
Yea I've been laid up for a few days and I got bored, so thought I would write a bit! Sorry : but thanks Phil, I never expected to enjoy it this much!


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Macca
11-03-2017, 09:42
Great write up Russell, we don't have the same Krell but I recognise a lot of what your saying, especially about the bass slam. You can never have enough bass slam ;) I didn't know what to expect, I'd read of Krell being hard, cold, 'nails down a blackboard' etc. The reality is nothing like that.

alphaGT
12-03-2017, 13:13
I've heard that too, and I just don't see it. If I had to characterize the overall sound in one word. I would say warm. What are they comparing it to if they hear hard and cold? They must have heard it in compromised conditions? If you try hard enough, you can make anything sound bad.


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walpurgis
12-03-2017, 13:23
Russell's description of the sound is much the same as my thoughts about my Monarchy Audio power amp, which I suppose could be regarded as a scaled down Krell. Good Class A definitely suits my ears. Clean, smooth, clear and punchy!

Macca
12-03-2017, 14:54
I've heard that too, and I just don't see it. If I had to characterize the overall sound in one word. I would say warm. What are they comparing it to if they hear hard and cold? They must have heard it in compromised conditions? If you try hard enough, you can make anything sound bad.


Has to be bad matching, crappy pre-amp or something.

I wouldn't say mine was 'warm' sounding, it sounds a lot like a beefier Radford STA15 to me. It is very easy on the ear, the opposite of nails on a blackboard, but not warm. I suppose the pre-amp used will affect the outcome hugely.

alphaGT
13-03-2017, 05:02
A new, or I should say another, preamp is next on my list. While I love my Parasound Halo 3, it is not a "high end" , preamp. I want a good tubed pre that has all the features I enjoy in the Halo 3. I'm sure an Audio Research LS27 will not sound, "warm", I'm also considering a used BAT VK-32 I think it is? It also has all the features I desire. Remote control, tape loop, balanced output, room for 5 inputs. These are not hard to find here in the states, I've got many of them on my watch list. There are many tubed preamps around but many fail on one or the other of my wants. I read that many mate Audio Research with Krell, hopefully it will brighten things up.


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danilo
01-05-2017, 03:31
Perhaps?
Before going off on a tangent hunting Pre's.
Build/assemble yourself a Dead simple Passive pre Basically a 10 k pot stepped attenuator at least, but no less than a 15$ Alps Blu Box pot.
Connect wires/interconnects to it attach any source with a decent output ie CDP or DAC.
Then listen.
Should be the cleanest purest sounds that that Krell is capable of.
There will be no impedence issues in the way either.
IF it doesn't please.. then You have system issues:
with the "Forbidden Planet" Krell
OR possibly your sources OR speakers are not anywhere near as good as you were led to believe.
Fairly common occurrence.. actually.
Us Audio Weenies Are herd creatures ;)

Pharos
01-05-2017, 10:11
I agree, but would make it a 100k pot, log of course just to ensure better non loading of previous O/P.

danilo
01-05-2017, 15:28
Use whatever pleases :-) but a 10 k is the usual sweet spot and 25k if 'still' using coax wire for interconnects

alphaGT
02-05-2017, 05:20
I may have a few pots around, nothing like an Alps, mind you. But may be worthy of an experiment. I used my old CD player, my Sony ES had a volume controlled output, and I plugged it directly into the amp, my old amp. Just to see what effect my preamp was having. And I have plugged my CD player directly into the amp, it was loud! But, not too loud. Having no control over the volume was not convenient, but it was interesting to see what no pre sounded like. I was quite surprised at the time how little the preamp was messing things up.

I've been listening to my new amp for several months now, and my urge to replace the preamp had wained. More careful speaker placement, and just getting used to the way it sounds, as it sounds very different from my old amp, it's growing on me. I find that I play it far more than I did my old amp, which is the real test of good stereo. Regardless of price, wattage ratings, or popular badges, how much you listen is the true test of sound quality. I was nearly convinced it was just me, being older and less interested, but now I know that it was my old system, a poor match between my speakers and amp. Which I always suspected as second most likely. The more I play it the better it sounds, I'm growing quite fond of it, if I wasn't before, and I feel hardly any need for change right now. Oh, I'll buy a new preamp, I'm an Audiophile! I can't help it! But I'm in no hurry at this point.


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danilo
13-05-2017, 02:28
Good on you for trying.. Many wouldn't.
Small issue tho; on MY Sony ES .. it's volume control out made for significantly degraded sounds. Nothing subtle about it either.
Dunno IF it was my specific Sony or not.. But when I fitted a 50$ (new) Toshiba dvd unit.
(Hey! it was flavour of the month and I too have been known to follow the herd ).
The DVD player was Sooo much better sounding... the Sony went in the closet permanently.
May still have it.. haven't looked for it in over 10 years. But the housemate tends to throw out junk I've forgotten about.. surreptitiously of course ;)
Rambles aside, the Sony ES may not be the Primo unit I (and you?) assumed/purchased it to be. Simply wasn't a very pleasing sounding thing at all
Certainly it's volume controlled 'out' was Shabby.
Try another source, as further experiment ?
New gear, whatever it may be, is tricky to evaluate.
IMO.. the ONLY real and relevant reaction is within the first 5 ~ 10 mins where our brains are still holding the previous situation as reference
But..Human brains adapt Very Quickly to sensory change and all too soon the New becomes assimilated as the current normal.

alphaGT
13-05-2017, 11:05
Good on you for trying.. Many wouldn't.
Small issue tho; on MY Sony ES .. it's volume control out made for significantly degraded sounds. Nothing subtle about it either.
Dunno IF it was my specific Sony or not.. But when I fitted a 50$ (new) Toshiba dvd unit.
(Hey! it was flavour of the month and I too have been known to follow the herd ).
The DVD player was Sooo much better sounding... the Sony went in the closet permanently.
May still have it.. haven't looked for it in over 10 years. But the housemate tends to throw out junk I've forgotten about.. surreptitiously of course ;)
Rambles aside, the Sony ES may not be the Primo unit I (and you?) assumed/purchased it to be. Simply wasn't a very pleasing sounding thing at all
Certainly it's volume controlled 'out' was Shabby.
Try another source, as further experiment ?
New gear, whatever it may be, is tricky to evaluate.
IMO.. the ONLY real and relevant reaction is within the first 5 ~ 10 mins where our brains are still holding the previous situation as reference
But..Human brains adapt Very Quickly to sensory change and all too soon the New becomes assimilated as the current normal.

That was many years ago I attempted the experiment plugging the Sony ES directly into the amp. I used the attenuated outputs first, and finding that it didn't destroy anything. Switched to the direct outputs. It was Loud! And no turning it down either! But, not too loud, sounded quite good actually, I used to all afternoon in this way, going through a selection of CD's. but that was 20+ years ago, and back then I had heard little to top my Sony 608ESD. For the price anyway.

I have not attempted that experiment with my new system. The Krell is a monster, and it could damage things if it were too loud! But, unity shouldn't be so loud as to hurt anything. I may have to start with something that starts in slowly, not Pink Floyd when all the clocks start chiming! My present CD player is a Cary 306, built like a tank, works flawlessly, and sounds damn amazing. Stupid expensive when it was new, but I got a great price on a used one 4 years old. I've had it less than a year, and it still surprises me.

I've been moving some things around, my two nephews happened around last weekend so I recruited them to move the Krell up onto its new shelf! I sure can't lift that thing. So now I am able to get to the cabling better, and possibly try my experiment soon. I've been so busy lately I haven't much time to even listen to it. My band is playing a gig this weekend, a proper lady has taken a shine to me, and I've still got guitar parts on my desk waiting to be worked on. If this is retirement I don't know how I ever found time to work a job? But things will slow down soon and I can't get back to it.

I've been saving up my money for a top of the line preamp, thinking hard about an Audio Research. But, as I get close to my goal, a new purchase for a phono cartridge keeps bothering me. I saw a Cadenza Black for sale, only 50 hours on it, about a thousand dollars off new. And darn if I didn't see a pair of Martin Logan Sequals within driving distance for only $600! I've always wanted a pair. Audiophilia is a terrible illness to suffer, like a chronic gambler or sex fiend, I just can't help myself! Stop me before I upgrade again!


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danilo
13-05-2017, 18:06
:eyebrows: Friend said similar years ago: How do people with Jobs get Anything accomplished?
I replaced my decade long used/loved George Wright Triode type Pre with a cheap 10K stepped attenuator, a 1$ wee wooden box from the Dollar store and interconnects.
Massive SQ improvement.
Had I not heard /done it, I would have laughed at the suggestion of improvements
Dunno about running an input sans a Pot of some kind.. Lotsa power on a short leash in that amp.

walpurgis
13-05-2017, 19:05
:eyebrows: Friend said similar years ago: How do people with Jobs get Anything accomplished?

I know the feeling. Things that you didn't expect, seem to expand in their need for your time once you retire. Weird! :scratch:

Colinijohnson
14-05-2017, 07:55
What did you pay for the Krell?Everything has a price...


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YNWaN
14-05-2017, 09:53
You've put your Krell on a shelf! Blimey, I hope that is a blooming sturdy shelf?

alphaGT
14-05-2017, 11:23
What did you pay for the Krell?Everything has a price...


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I paid $2500USD, not a steal perhaps, but a fair price for an amp in this condition. Like new, except for the bent fin thanks to Fed Ex.


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alphaGT
14-05-2017, 11:26
You've put your Krell on a shelf! Blimey, I hope that is a blooming sturdy shelf?

https://uploads.tapatalk-cdn.com/20170514/03d2bd631d5e01b92cd1b55bab69fc14.jpg

A small table actually, its surprisingly sturdy.



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Macca
14-05-2017, 13:05
We need a Krell owner's club :)

alphaGT
15-05-2017, 03:51
We need a Krell owner's club :)

Two members so far!


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JohnJo
15-05-2017, 07:42
We need a Krell owner's club :)

You could have a bake off over Skype or FaceTime :lol:

Macca
15-05-2017, 11:30
Reminds me of a pal I used to have called skanky Al. Years ago now when BMWs were still quite rare cars on the roads he bought a knackered one for £100. It had almost no paint left on it and was literally held together with gaffer tape. Nevertheless he would always wave cheerfully to the other BMW drivers he encountered on his travels.

alphaGT
18-05-2017, 19:19
Reminds me of a pal I used to have called skanky Al. Years ago now when BMWs were still quite rare cars on the roads he bought a knackered one for £100. It had almost no paint left on it and was literally held together with gaffer tape. Nevertheless he would always wave cheerfully to the other BMW drivers he encountered on his travels.

That's funny, reminds me of a friend who bought a scrap Harley Sportster, covered in grease and barely run, smoking exhaust, but as soon as he bought it he tore the sleeves out of his jackets and always acted as if the bikers were after him! Fancied himself a real gangster with his $500 Harley.


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Rush2112
18-05-2017, 19:38
I may have missed the mention but what about a Krell KRC 3 it works for me !

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alphaGT
19-05-2017, 16:41
I may have missed the mention but what about a Krell KRC 3 it works for me !

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Definitely worthy of consideration. I've seen a few Krell preamps on Audiogon at some reasonable prices. One that was on my watch list was the Krell Phantom, a really nice looking preamp, modern looking and highly rated. And less than $2,500 USD. I can't recall exactly. The depreciation of audio gear is amazing. Before the internet used gear was hard to find, but now I wouldn't dream of buying new. Most used gear is one third to one forth it's new price. Personally I can't imagine what a $7k preamp sounds like? But due to depreciation I may soon find out.



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Macca
19-05-2017, 16:51
What speaker cable are you using, Russell?

Rush2112
19-05-2017, 18:51
Definitely worthy of consideration. I've seen a few Krell preamps on Audiogon at some reasonable prices. One that was on my watch list was the Krell Phantom, a really nice looking preamp, modern looking and highly rated. And less than $2,500 USD. I can't recall exactly. The depreciation of audio gear is amazing. Before the internet used gear was hard to find, but now I wouldn't dream of buying new. Most used gear is one third to one forth it's new price. Personally I can't imagine what a $7k preamp sounds like? But due to depreciation I may soon find out.



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Perhaps I should mention I have FPB 200 the 300 is certainly better especially with difficult loads Martin Logan, Wilson etc a friend had FPB 300 with Martin Logan SL3 and B&W 802's and Wilson Alexandria's although I think he swapped the 300 to 600 monoblocks for the Alexandria's. The sound for me with Sonus Faber Alecta Amators is all you hope for, detailed warmer side of neutral loads of control and slam but above all, musical and emotional, and I have very broad tastes in music !!

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Rush2112
19-05-2017, 18:55
Perhaps I should mention I have FPB 200 the 300 is certainly better especially with difficult loads Martin Logan, Wilson etc a friend had FPB 300 with Martin Logan SL3 and B&W 802's and Wilson Alexandria's although I think he swapped the 300 to 600 monoblocks for the Alexandria's. The sound for me with Sonus Faber Alecta Amators is all you hope for, detailed warmer side of neutral loads of control and slam but above all, musical and emotional, and I have very broad tastes in music !!

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PS my cables are Transparent Musicwave Plus Bi-Wire and all my interconnects are DPA Black Slink and I run phono and cd in full balanced mode as is pretty to power.

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alphaGT
20-05-2017, 00:46
PS my cables are Transparent Musicwave Plus Bi-Wire and all my interconnects are DPA Black Slink and I run phono and cd in full balanced mode as is pretty to power.

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Sounds like a top notch system! I'm sure the FPB 200 is near the 300 under most loads. If not for the size of my speakers, I would have been happy with a 200 watt amp. But that was my goal from the start, to find an amp that could do justice to these monster Legacy Focus 20/20's.

I'm running balanced cables from preamp to amp, but my phono and CD are still single ended to the pre. And all my cables are Harmonic Technologies, Precision, and Truth Link. And a pair of Legacy speaker cables that came with the speakers. So I've still got some upgrading to do to catch up to where you are! I'm shopping around for some nice balanced cables, and have been re-terminating my speaker cables to get the most out of what I've got. But I don't want to get too far ahead of myself until I choose a preamp. And the Harmonic Tech cables I've got are no slouches, I was highly pleased when I first introduced them into my system before I got this amp. Always good to meet another member of the Krell Owners Club!


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sq225917
20-05-2017, 08:26
The fbp series aren't class a to their rated limit all the time, they have a series of stepped bias positions that they select from according to input signal and thermal conditions. They're better thought of as just enough class a to play the signal when its needed. Still, theyre more class a than previous krell offerings that were mostly high ab.

That's a mighty fine amp.

alphaGT
22-05-2017, 10:29
The fbp series aren't class a to their rated limit all the time, they have a series of stepped bias positions that they select from according to input signal and thermal conditions. They're better thought of as just enough class a to play the signal when its needed. Still, theyre more class a than previous krell offerings that were mostly high ab.

That's a mighty fine amp.

I know she runs hot! I literally heated my room with it in the colder months! So it's definitely biased pretty high to be giving off 5,000BTU. It's hot even if music is not playing. Sure seems like a class A for the most part. It is an older model, and I do know that later models are designed to be more economical. But all that aside, it is above everything else I've owned. Whatever it's doing, it's doing it right!


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Macca
22-05-2017, 11:13
True class A will run hotter when idling, playing music through them actually cools them down.

Arkless Electronics
22-05-2017, 12:55
True class A will run hotter when idling, playing music through them actually cools them down.

Running hot at idle is no guarantee that an amp is "pure" class A whatsoever. Most "class A amps" are not class A to full output as it requires such ridiculous effort and spending of money in order to keep it cool enough! Many will remember the Musical Fidelity A370 which was thought of as class A by many... although it was rated at 185WPC (and gave about 210WPC in practice), those LP record sized heatsinks, one per channel, were only enough for 18WPC to be in class A!

Generally I'd be suspicious of claims of over 20WPC or so of class A power, especially if there is no cooling fan. A cooling fan works miracles in getting rid of heat and a heatsink capable of say 20 W class A without a fan could be good for 50-60W with a fan! The problem here of course is that some people are averse to the idea of a fan due to the noise from it, but, I've found it possible to use a slow running fan in virtual silence... Due both to this, the music drowning out any fan noise and the prevalence of cooling fans in PC's and related equipment these days anyway, I don't see a fan as a big issue personally.

There are many more advantages to class A than merely getting rid of crossover distortion BTW! Pretty much everything measurable gets much better when class A is used!! The only down sides are it will be big, it will be heavy, it will be very expensive and it will use loads of electricity... If there is any interest I may come back to these things in more detail.... Technical stuff usually kills a thread though!

danilo
22-05-2017, 17:19
Not All A amps are created equal.. You should know that ... ;)
Some designers are Giants, while others shouldn't be allowed near Solder.
Middle ground is populated by plodders.. which imo may be even worse.

Need Big Power in an A ? Buy a Pass Labs unit.. Big bux though. Free lunches are Rare.
IF one can live with 25 w or less a Firstwatt does the job.
Better than Most Any other amp product.
At least any that I've heard or owned.

Some Firstwatts run surprisingly Cool, while others run warmer. Differing topologies is the why.
Mine for example has not yet exceeded 40C and that's at an almost 2 a bias. Yeah it does have serious heatsinks tho
Unlikely, after ~50 years of sporadic seeking, that I will be replacing it.

Lotsa myths in Audio land. Trust None of them.. until proven otherwise

danilo
22-05-2017, 17:25
Not All A amps are created equal.. You should know that ... ;)
Some designers are Giants, while others shouldn't be allowed near Solder.

Need Big Power in an A ? Buy a Pass Labs unit.. Big bux though. Free lunches are Rare.
IF one can live with 25 w or less a Firstwatt does the job.
Better than Most Any other amp product.
At least any that I've heard or owned.

Some Firstwatts run surprisingly Cool, while others run warmer. Differing topologies is the why.
Mine for example has not yet exceeded 40C and that's at an almost 2 a bias.
Unlikely, after ~50 years of sporadic seeking, that I will be replacing it.

Lotsa myths in Audio land. Trust None of them.. until proven otherwise

Arkless Electronics
22-05-2017, 17:38
Not All A amps are created equal.. You should know that ... ;)
Some designers are Giants, while others shouldn't be allowed near Solder.

Need Big Power in an A ? Buy a Pass Labs unit.. Big bux though. Free lunches are Rare.
IF one can live with 25 w or less a Firstwatt does the job.
Better than Most Any other amp product.
At least any that I've heard or owned.

Some Firstwatts run surprisingly Cool, while others run warmer. Differing topologies is the why.
Mine for example has not yet exceeded 40C and that's at an almost 2 a bias.
Unlikely, after ~50 years of sporadic seeking, that I will be replacing it.

Lotsa myths in Audio land. Trust None of them.. until proven otherwise

So I see....

Macca
22-05-2017, 17:54
True class A will run hotter when idling, playing music through them actually cools them down.

So is this right then or what?

BTW I never said running hot was proof of class A - I mean it could just be faulty or crap.

Arkless Electronics
22-05-2017, 18:04
So is this right then or what?

BTW I never said running hot was proof of class A - I mean it could just be faulty or crap.

It is correct yes. Power dissipation shifts from the output devices to the load as the output goes up. At full output the class A amp may run about a third cooler than at idle. For a conventional class B (A/B really...another story) amp it runs at it's hottest at around 1/3 of max output. For the hard of thinking, that does not mean when the vol controls at 3.3!! (or 3.66 either if you have an ex Spinal Tap amp!:lol:)

Barry
22-05-2017, 23:32
There are many more advantages to class A than merely getting rid of crossover distortion BTW! Pretty much everything measurable gets much better when class A is used!! The only down sides are it will be big, it will be heavy, it will be very expensive and it will use loads of electricity... If there is any interest I may come back to these things in more detail.... Technical stuff usually kills a thread though!

Yep, my 25W Class A monoblocks, dissipate 400W when idling, weigh 30Kg each, are about a cubic foot in volume and run so hot I can't use them in the summer.

alphaGT
23-05-2017, 06:27
So I did a bit of reading on the subject. Krell claims that the FPB amps can deliver Class A power to its full rating. Due to a process called Sustained Plateau Bias II it raises and lowers the bias as demand dictates. Of course this is what Krell has to say in the owner's manual.

In practice, it does an amazing job of performing this function. A Google search on sustained plateau bias 2 brings up much interesting reading. And I found one article where the writer performed some tests on my exact amp, which makes it all the more interesting for me anyway.

http://audioinvestigations.blogspot.com/2015/05/thinking-about-sustained-plateau-bias.html

Some mumbo jumbo about what he measured as he pushed the amp. It seems it has about 4 levels of bias it jumps back and forth between as required. Keeping it in Class A at all times. Well all times except if it runs hot. If the amp gets too hot, it will lower the bias level and let it run into A/B to keep the temp within safe parameters. Or if it runs out of current. So, that brings up many variables. Speaker load, current demands, room temp, and the volume you are trying to achieve, and others. But, if your speakers present an easy load, and your room is cool, and you aren't trying to break the windows, it should remain in Class A pretty much all the time.

If you really want to get into some heady reading, I read most of this:

https://books.google.com/books?id=7djSyLcX4coC&pg=PA425&lpg=PA425&dq=sustained+plateau+bias+II&source=bl&ots=D04E7-OHhe&sig=PwX2T5A4bleoDGoIl_W3ItObtP8&hl=en&sa=X&ved=0ahUKEwiI69POnYXUAhUk6YMKHRGPAUUQ6AEILTAD#v=on epage&q=sustained%20plateau%20bias%20II&f=false

That really takes me back to my college days. Great stuff if you're having trouble sleeping. And there was a whole page on Google on the subject, if anyone was interested enough to read it all. But these modern designs allow us to have large class A amps that would have been cost and weight prohibitive in the past. Not that a $10k amp that weighs 130lbs is practical.


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struth
23-05-2017, 06:41
My MF A1000 was supposedly class A all the way. It certainly got damn hot and had a lot of cooling fins.

mikeyb
23-05-2017, 06:49
My wife says I'm Class A and I'm definitely hot all the time 😊

But I might be biased 😂

struth
23-05-2017, 06:52
My wife says I'm Class A and I'm definitely hot all the time ��

But I might be biased ��

:rfl:

Arkless Electronics
23-05-2017, 13:41
My MF A1000 was supposedly class A all the way. It certainly got damn hot and had a lot of cooling fins.

I doubt it.... I would expect much bigger heatsinks than that for 50W class A.

struth
23-05-2017, 13:50
I doubt it.... I would expect much bigger heatsinks than that for 50W class A.

That was what they said re it... 16 output transistors.. specs were

Power output : 2x 50W (Class A, 8 Ohm)
MC input : 600µV
MM input : 8mV
Line inputs : 350mV
S/N ratio : > 60dB (MC)
> 75dB (MM)
> 85dB (lines)
RIAA accuracy : ±0,7dB
THD : < 0,5% (20Hz...20Khz)
Channel separation : > 85dB
PC : 215W continuous
Dimensions : 48,3 x 12,2 x 33,5cm (A1000)
19,4 x 12,2 x 33,5cm (PSU)
Weight : 11kg (A1000)
7kg (PSU)

Arkless Electronics
23-05-2017, 13:50
Yep, my 25W Class A monoblocks, dissipate 400W when idling, weigh 30Kg each, are about a cubic foot in volume and run so hot I can't use them in the summer.

I would expect that these give class A into 4R, 50W, if they dissipate that much! Nice!

If an amp is specified as say 20W into 8R, class A, then it will only give 10W class A into 4R.... it may well double its power to 40W yes, but only the first 10W will now be in class A. I suspect Barry's amp is biased at probably double the class A current actually needed to give 25W. This is excellent but not cheap!! This means that when the amp is close to voltage clipping into 8R (at 25W) it is still nowhere near to coming out of class A;)

Arkless Electronics
23-05-2017, 13:52
That was what they said re it... 16 output transistors.. specs were

Power output : 2x 50W (Class A, 8 Ohm)
MC input : 600µV
MM input : 8mV
Line inputs : 350mV
S/N ratio : > 60dB (MC)
> 75dB (MM)
> 85dB (lines)
RIAA accuracy : ±0,7dB
THD : < 0,5% (20Hz...20Khz)
Channel separation : > 85dB
PC : 215W continuous
Dimensions : 48,3 x 12,2 x 33,5cm (A1000)
19,4 x 12,2 x 33,5cm (PSU)
Weight : 11kg (A1000)
7kg (PSU)

And you believe them? I used to work for them remember:eyebrows:

struth
23-05-2017, 13:53
Sounded bloody marvellous and I really should have kept it

http://www.thevintageknob.org/museum/pics_v2.php?c=1&x=630&t=0&s=1&n=1

http://www.thevintageknob.org/museum/pics_v2.php?c=1&x=630&t=0&s=1&n=2

http://hifisale.narod.ru/_si/0/10714081.jpg

alphaGT
29-05-2017, 11:53
Sounded bloody marvellous and I really should have kept it

http://www.thevintageknob.org/museum/pics_v2.php?c=1&x=630&t=0&s=1&n=1

http://www.thevintageknob.org/museum/pics_v2.php?c=1&x=630&t=0&s=1&n=2

http://hifisale.narod.ru/_si/0/10714081.jpg

Beautiful! Many complain that too much is spent on aesthetics, but I think a great piece of gear should look like a great piece of gear! Pride of ownership and all that.


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