It was more likely your friends room, rather than the class of the amp used.
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Probably a combination of both. I have upwards of 20 different amps. I happen to have a G.A.S.500 newly rebuilt by Mike Bettinger of gasudio. This thing is literally brand new. It is superb. However the ones I've just gotten back from Roy Esposito are the ones that knock my socks off: the Acoustat TNT200. I have three of these and one TNT120 I will be using for an active JBL 4345 system I'm currently building. Roy has rebuilt these with mono switches and balanced input option. Bridged, they put out over 1100 watts but even in stereo mode, just one of these will shake your floor. Super fast with a damping factor of over 1000 up to 1khz. The lowest, strongest bottom end I've experienced so far. The most realistic amp I have ever heard. Roy was part of the engineering team that designed the Acoustat products and runs a small facility dedicated to their revival.
I think you may be going about this the wrong way. As far as power ratings go, there is no standard. For example 10 different amps from 10 different companies all rated at 100 watts per channel will all put out a different amounts of power. As far as being class A, I don't think thats it, either. You should have no problem getting the same kind of power from an AB amp.
There are so many factors that may be responsible for the results you are getting we can only guess at what the problem is. I'll list a few things that might be worth looking at.
-Other components; especially the preamp. Don't underestimate the importance of the preamp. I've literally had situations where upgrading the preamp was the equivalent of adding a subwoofer.
-Koestner says it may be the room. I agree. (Its more likely a combination of different factors, just to be more clear)
-Unless I'm mistaken, your speaker is a bookshelf/stand mounted design.
-It looks like you are biamping with 2 completely different amplifiers. I don't even know where to begin on this one except, stop. Just use 1 amp. If you can't get results with a DNA500, I'm not sure what to tell you; except..
-You just may like the sound of the old Krell amps. Many do. If that's the case, it may make sense for you to buy one. Just one. (If you must have 2 amps and biamp them, I highly recommend you buy 2 stereo amps, exactly the same, and do a vertical biamp. I don't feel its necessary, but at least you wont be doing anything that will mess up your sound quality.)
In my experience, its not the watts that matter for what you seek. Not necessarily the Class A topology either. The Krell is known for bass wallop and is a very high current design. High current (and high capacitance maybe?) usually make a big difference...i suspect in addition to bass volume, the Krell is tight-fisted as well...which means the bass has both impact and snap...the VTL should have volume and impact...as much snap i cannot say.
Get a Krell if that is what you seek...other Class A amps include Pass Labs, Gryphon, Vitus...all of which throw serious bass. I know and own Gryphon. Again i am not convinced its just about the Class A design. For just the bass element, you can also use big Brystons, or possibly Classe, Rowland.
BTW, i think Celestions are great...my first speaker was the SL6si...and i always wanted to hear the mighty SL6000 system...congrats. A seriously great system by all accounts. Enjoy.
Just a suggestion- get some very clean recordings of bass guitar, pipe organ,
percussion ensembles, etc. how close your chair is from the back wall makes a huge difference in the amount of perceived bass- my listening position is far from any rear surfaces, and so i have to "live" with 90% of the bass coming from the speakers alone.
i would forget about old Krell amplifiers unless you just HAVE to have one. a KSA-250, unless you already have one and won't part with it, is pretty much a relic. anyway it would have to be refurbished to get it back to where it used to be.
your audio-memory in this case may be taking you on a long ride to nowhere.
you would have to duplicate your friend's room to fairly evaluate what you would need to do. plus a dozen other things. but i would start with the cheapest route- sit down with some excellent recordings with bass output, and not just loud (i.e. Black Sabbath).
and no insult, but if you can add a subwoofer, that would definitely solve your problem once and for all.
Pass makes some very highly lauded Class A amps.I have also heard Plinius amps they had slam as well. Slam is different than the deep bass you get from a sub.
I am not sure we need to second guess you. I always seem to like class A sound myself, go with your gut. One of the better suggestions IMO is to get a refurbished Krell from that era. If not re-capped and tuned up you may be dissapointed.
Krell's are known for their bass slam as they regulate the high voltage to the output transistors. This is mostly unheard of and very expensive to do. This makes the amp have a very low source impedance hence the bass slam. I had always felt that the older Krell's sacrificed top end performance. I would not purchase a Krell of that vintage as they wind up having capacitor issues because of the heat generated by the amp. They are also very expensive to run and dissipate a tremendous amount of heat, i.e wasted energy. If you do feel the necessity to own a Class A amp, try listening to a Pass Labs Amp. High current delivery is most important when driving a dynamic speaker and that is not necessarily a function of Class A or class B amplifiers.
Thanks for all the suggestions and insight.
perhaps I should provide a bit more context of my set up and room situation.
My set up is::
PS PWD Dac =>Joles Electra LA-150MKII => Ampzilla 2000MKII => Celestion SL600; McCormick DNA 500 => Celestion 6000 subs
The Celestion sl6000 system is a monitor+di-pole sub combo, where the monitor is a SL600 and the 6000 subs; So I pretty much have to bi-amp.
My set up is in a dedicated music room ~ 22x26x8 with a fair amount of sound treatment. I have 2'x6' bass traps in 3 corners of the room and sound panels in the other four walls.
I did move the bass traps out of the corners of the room to test things out. There was more bass, but not the slam level that I'm still seeking. To be clear, it isn't deep bass I'm missing it is that slam factor as mentioned above.
I recognize the Krells are know for slam and dynamics but the Ampzilla and McCormick had been know for being high current amps too. This is why I'm some what puzzle especially because my friends amps were just 100w & 200w krell's and the Ampzilla is 300W and the McCormic is 500w into 8 ohms.
I had ran the system using my PS PWD direct into my amps just to make sure the Joules Electra was not the factor as the Joules is a tube pre. There wasn't any noticeable loss of bass when I had the joules in the path, so it stay.
Both the McCormick and Ampzilla had served me well with many hard to drive speakers including ribbons and electrostats. I'm some what stun that a cone speaker would be tame by these beastly amps.
Do Krell's really have such dominance in the slam department that even well design amps such as mine are not in the same league?!
Would love to hear from someone who has heard my amps and Krell's to tell me if I'm just going down the garden path here.
Go to hificritic.com Read the review from 1994 or so some Martin Colloms on the SL6000 setup...he uses one of the big Krells...possibly even the 250.
The Krells really are a tremendous bass muscle amp. I am sorry i cannot say that i've heard yours which no doubt are good...its just that the SL6000 does seem to be difficult to drive well and to 'full capacity'.
You might also find that room setup makes a difference. ARe you looking for more presence of bass...or more taut, gut-punch? the latter is often helped by the amp having limitless reserves.
thanks for the tip on the review.
I am looking for that taut, gut-punch as you described. That very much what I heard/felt in my friends basement with his SL6000 and the Krell combo.
His basement was bigger than my listening room and even in moderate volume, he had room locking effect with some of the heavy bass material we were sampling.
I couldn't achieve that same room locking effect with the same recording in my room thus far.
Crazy to think I may have to lug one of those monster Krell's into my 2nd floor listening room...probably will break my back doing so :)