What are the most powerful Pure Class A Amplifiers ever made?

[caesar]

^^ The MBLs are not that hard to drive! You do need some power, but 200 watts seems to be plenty. It's be a different story if the speaker were outside though...

Hi Atmasphere,

I think "being able to drive" and "drive the speaker to get at its essence" are different things.




Unfortunately, tube amps cannot drive the MBL woofers. I have tried it even with the mighty VTL, and sadly even those monsters sound worse than a 1 year old playing with his toy drum. Now when I throw a large solid state amp on the woofers while connecting the mighty VTL on top, it gets the midrange and highs nicely, but doesn't have the dynamics nor the right richness on the midbass that quality SS does. There is something about moving that MBL melon from 105 to 600 Hz.

And dismally, large powered solid state amps don't always do better. I have tried several, some rated 900 to 1,000 watts a channel into the 4 ohm load and supposedly have a lot of current. Those high powered ones have do a great job with drums and dynamics that make you jump out of your chair, but many of those SS amps make the midbass sound so threadbare that Frank Sinatra sounds like a eunuch.

I love tubes on the right speakers, but there is nothing like quality SS power.

 

[Atmasphere]

The biggest problem we ran into was that peak at 2-3KHz. The speaker is a Voltage Paradigm device (its expecting half the power into that peak); to get our amps (Power paradigm technology) to play it required a Zobel network at that frequency to knock the impedance down. Otherwise the amps sounded a bit harsh because of the extra output in that spectrum. Getting them to play bass in the speaker was easy.

 

[microstrip]

(...) Unfortunately, tube amps cannot drive the MBL woofers. (...)

Caesar,

IMHO there is nothing in the graphs you show that suggests tubes are incompatible with MBLs - the Soundlab's impedance is much worst. And a well know tube amplifier manufacturer developed amplifiers using the MBL101 - the famous Convergent Audio Technology. At the time I owned a pair of MBL101b I asked about advice at Audiogon and several CAT users were enthusiastically using them on MBL101 E's. I fully agree with you about VTL mismatch - at less my MB750s did not do a good job on the 101's.

 

[microstrip]

The biggest problem we ran into was that peak at 2-3KHz. The speaker is a Voltage Paradigm device (its expecting half the power into that peak); to get our amps (Power paradigm technology) to play it required a Zobel network at that frequency to knock the impedance down. Otherwise the amps sounded a bit harsh because of the extra output in that spectrum. Getting them to play bass in the speaker was easy.

I should have known about it in due time. Effectively the MA2 sounded too forward in the old MBL101b's, highlighting their tendency to metallic glare.

 

[caesar]

Caesar,

IMHO there is nothing in the graphs you show that suggests tubes are incompatible with MBLs - the Soundlab's impedance is much worst. And a well know tube amplifier manufacturer developed amplifiers using the MBL101 - the famous Convergent Audio Technology. At the time I owned a pair of MBL101b I asked about advice at Audiogon and several CAT users were enthusiastically using them on MBL101 E's. I fully agree with you about VTL mismatch - at less my MB750s did not do a good job on the 101's.

Microstrip,

I think a lot of this is experiential. I am not saying that CAT driving MBL "is bad". I am just saying it's different and not "the best" for those who want the MBL to sound the way it was conceived by its creators. The essence of the MBL is that "jump factor" in the bass that makes live music sound like live music, realistic drive and richness in the midbass, electrostatic clarity in the midrage, and realistically sweet highs that most speakers can only dream of. Even with powerful tubes, the midrange and highs are there, but the jump factor and midbass grunt are missing. To me, that sounds a lot a Soundlab. A friend and I were listening to the Sheffield drums disc, and it was a revelation when given enough power,kind of like that famous Wilson marching band demo at RMAF. I know guys who have spent 15 years of their life hauling big, heavy amps to try on the MBLs in order to find that right combination, and they say most amps - tubes and SS - cannot do it right, with issues I described before. My experience, sadly, suggests the same.

 

[Atmasphere]

FWIW, the Soundlab had a problem in the crossover that has been corrected. They have a ton of grunt now and are a lot easier to drive, with either tubes or transistors.

 

[Sunnyboy1956]

Hi Atmasphere,

I think "being able to drive" and "drive the speaker to get at its essence" are different things.


View attachment 14282View attachment 14283

Unfortunately, tube amps cannot drive the MBL woofers. I have tried it even with the mighty VTL, and sadly even those monsters sound worse than a 1 year old playing with his toy drum. Now when I throw a large solid state amp on the woofers while connecting the mighty VTL on top, it gets the midrange and highs nicely, but doesn't have the dynamics nor the right richness on the midbass that quality SS does. There is something about moving that MBL melon from 105 to 600 Hz.

And dismally, large powered solid state amps don't always do better. I have tried several, some rated 900 to 1,000 watts a channel into the 4 ohm load and supposedly have a lot of current. Those high powered ones have do a great job with drums and dynamics that make you jump out of your chair, but many of those SS amps make the midbass sound so threadbare that Frank Sinatra sounds like a eunuch.

I love tubes on the right speakers, but there is nothing like quality SS power.

How do you know what a eunuch sounds like ?

 

[Colin Wonfor]

The biggest SECA A Class not Push Pull I have seen was the 300W TOCA, at 180KGS 1.8M high and eating 1.8KW each mono.
They are real monsters and could only run on 220- 240 AC they had 1.5F on each power rail, and a soft start that took about 10sec, on there first public outing at The Penta in London they took all the lights out on the ground floor until the soft start could be adjusted.
80 FETS parralel output devices and 80 Darlington Transistor as the constant current load.
The front panel on the pair was 25mm granite, the heat sinks were made special by Redpoint Heatinks at 300mm wide 1.75M long and 200mm deep.
And even with the huge mass some fool tried to steel them at the show, poor sod I bet the hernia is still painful.

 

[cjfrbw]

The biggest SECA A Class not Push Pull I have seen was the 300W TOCA, at 180KGS 1.8M high and eating 1.8KW each mono.
They are real monsters and could only run on 220- 240 AC they had 1.5F on each power rail, and a soft start that took about 10sec, on there first public outing at The Penta in London they took all the lights out on the ground floor until the soft start could be adjusted.
80 FETS parralel output devices and 80 Darlington Transistor as the constant current load.
The front panel on the pair was 25mm granite, the heat sinks were made special by Redpoint Heatinks at 300mm wide 1.75M long and 200mm deep.
And even with the huge mass some fool tried to steel them at the show, poor sod I bet the hernia is still painful.
View attachment 14474

It looks like a gun locker.

 

[Colin Wonfor]

And in matching pairs. With more bangs a minute than most guns.

 

[wizard]

There was many versions of TOCA SECA - 20, 50, 100, 200 and 300 watts.

Here's pictures of the 20 watt version.

View attachment 14476

View attachment 14477

View attachment 14478

View attachment 14479

 

[caesar]

Wizard,

Thank you for contributing. As a man of great taste and knowledge, how little or well respected are the Symphonic Line Kraft amplifiers in Europe and Asia?

 

[MrAcoustat]

I had a pair of Krell KMA 160s and they ran very warm. They were a little too "sweet" for my taste and did not have the balls to drive my MBLs. Somewhere on WBF I posted a list of all the heavy metal amps I've tried that survived the MBL challenge and were to my taste... it's a very short list. Krell KMA 400s and AVM MA8s.

I should add that the MBL challenge dates back to the late 80s when I heard the Black Banana Club's famous sound system. The music actually entered your body and was not even close to deafening.

Very warm & very sweet 100% true and that's what i liked about them.

 

[Colin Wonfor]

Alan Brown's A Class Amp made with IGBT and based on a design in Electronic World mag
See more on

http://www.audiochews.com/discussio...rom-electronics-world-by-colin-wonfor#Item_49

 

[mep]

It looks like a gun locker.

With Hillary Clinton standing guard.

 

[mep]

View attachment 14831

Alan Brown's A Class Amp made with IGBT and based on a design in Electronic World mag
See more on

http://www.audiochews.com/discussio...rom-electronics-world-by-colin-wonfor#Item_49

Those look like a butt-ugly garage job.

 

[Colin Wonfor]

They are he had never made anything before, and they worked first time, cool I thought.

 

[Pani]

I am surprised, one amplifier company seldom gets any mention on forums even though they make some of the very best amplifiers in the world, "Symphonic Line". Their Kraft 400 monos deliver true 400 watts in class A.

 

[mep]

I am surprised, one amplifier company seldom gets any mention on forums even though they make some of the very best amplifiers in the world, "Symphonic Line". Their Kraft 400 monos deliver true 400 watts in class A.

Their stereo amp kicks some serious ass too. It has a bottom end punch that would make a Krell blush. Not my Krell, but some of them.

 

[Colin Wonfor]

The Kraft 400 looks interesting I found the review. http://www.stereophile.com/content/symphonic-line-kraft-400-monoblock-power-amplifier