Krell Introduces new iBias Class A Amplifier Line Preview

[jinjuku]

But not to my knowledge in the 1990's, when Krell started doing it. Their first implementation used three bias levels, complete with front panel LEDs to show you the bias level.

I will have to ask Denny or Tim. I know this has been around in the Pro-audio side of things for quite a while now. Look at Lab's Tracking Class D technologies.

 

[fuzz092888]

I remember them saying they were over 600lbs, but they must have been talking about the pair, but I will believe 377, still really heavy, lol... when you stand in front of them they are quite impressive...

It's a lot more amplifier than I'd want to lug around and of that I have no doubt. I love that giant glowing analog meter. In my fantasy world I'd probably hide the two PS units and only display the main unit though.

 

[TLS Guy]

Krell's strategy is not standard Class AB bias; they have been using predictive variable bias for many years. So have several other manufacturers, including Levinson.

All class A/B amps have variable bias. What I want to know is what is different about the way bias is controlled.

In any case it does not sound as elegant as current dumping feed forward topography.

In this case the outputs are biased well into class B so the amp runs cool and does not need fans. A very good small class A amp sends an error correction signal and it is this amp that determines the spec and distortion. Crossover distortion is completely eliminated. It is true class A performance with none of the high current heat issues.

In the 405 series the output dumpers are biased to class C!. That really goes to show how effective this approach is.

 

[Irvrobinson]

All class A/B amps have variable bias. What I want to know is what is different about the way bias is controlled.

In any case it does not sound as elegant as current dumping feed forward topography.

In this case the outputs are biased well into class B so the amp runs cool and does not need fans. A very good small class A amp sends an error correction signal and it is this amp that determines the spec and distortion. Crossover distortion is completely eliminated. It is true class A performance with none of the high current heat issues.

In the 405 series the output dumpers are biased to class C!. That really goes to show how effective this approach is.

It is different in that the bias current is raised and lowered according to the input voltage, with circuitry with a fast slew rate. There isn't a fixed bias level, there's a range. I'm not sure if the "sliding bias" technique is elegant per se, and it certainly isn't as novel as the current dumping design. One could argue that both of these techniques are overkill these days, as it is possible to build amplifiers of very high quality without either one.

I think all of us technical types are well aware of how Walker's amplifier design works (and we're all aware of your hero worship of Walker). Current dumping is an ingenious design, and I've never heard anyone deny its value, but it is not the only design strategy capable of very low distortion, and amplifiers using current dumping are not available at high power levels (or reasonable prices per watt, for that matter).

 

[jinjuku]

Is there any modern, correctly designed amp, that has any transistor cross over distortion?

 

[Swerd]

When I see pure nonsense in the ad puffery, and a high price tag, I sense a wallet biopsy not in the customer's interest.

This is no mere wallet biopsy. It seems more like a radical wallet-ectomy.

How about this baby, I seen these in NY, 100 watts pure class a like 200+ lbs.. fuzz can google it for the actual weight, since he is in the correcting mood, lol... these are only 20K$ each..

What does that class A room heater cost compared to central heating system? And which is more efficient?

 

[RichB]

Is there any modern, correctly designed amp, that has any transistor cross over distortion?

Isn't harmonic distortion something to be worried about?

There are clearly amps that measure different amounts of odd/even harmonic distortion across many designs.
Audibility is an ongoing debate, but is its existence debatable ?

- Rich

 

[RichB]

This is no mere wallet biopsy. It seems more like a radical wallet-ectomy.



What does that class A room heater cost compared to central heating system? And which is more efficient?

My house was built during the Carter years when electric heat was pushed.
I replaced that, but if I had these amps, it might still be in place because I could not move them

- Rich

 

[jinjuku]

Isn't harmonic distortion something to be worried about?

There are clearly amps that measure different amounts of odd/even harmonic distortion across many designs.
Audibility is an ongoing debate, but is its existence debatable ?

- Rich

What does this have to do with my question: What modern, competently designed amp, exhibits transistor crossover distortion?

You can measure this on a scope.

 

[AcuDefTechGuy]

I have to agree with you here, my dream system would be powered and processed by Mc labs

There you go.

 

[itschris]

What about Jeff Rowland? No love? I've always loved Mc, but the monoblocks have the two units with the big giant logo think which just looks cheap to me.

 

[jinjuku]

There you go.

Ok,

That big McIntosh logo is just arrogant. I know people love the McIntosh aesthetic but it's always reminded me of a dressed up 8 Track Player button layout from one of my parents cars.

 

[RichB]

What does this have to do with my question: What modern, competently designed amp, exhibits transistor crossover distortion?

You can measure this on a scope.

It doesn't, but doesn't class-a have the benefit of reduced harmonic distortion?

In this review of the Parasound A31, the amp was measured at 2 volts where it was operating in class-a mode and 5 volts where it was (presumably) switching.

Parasound Halo A 31 Three-Channel Power Amplifier - Secrets of Home Theater and High Fidelity


- Rich

 

[RichB]

Apparently someone objected to my this post about harmonic distortion on this thread and decided to give me negative reputation.
Personally, I think it is germane to this conversation, I could be wrong, but if you feel that way, please explain within the thread or by PM.

I do not feel this is the appropriate response, if you do, have the courtesy to PM me.
Also, I would appreciate it if you would remove negative reputation.

I am not alone in my dislike for the anonymous negative feedback feature.
Perhaps it is meant to drive people away, but it appears to be a blunt instrument.

Sorry about the derail.

- Rich

 

[AcuDefTechGuy]

What about Jeff Rowland? No love? I've always loved Mc, but the monoblocks have the two units with the big giant logo think which just looks cheap to me.

Nope. No love from me.

It's very nice looking, but just doesn't "stand out" like McIntosh.

McIntosh just begs for attention.

 

[AcuDefTechGuy]

Ok,
That big McIntosh logo is just arrogant.

Gaudy. Ostentatious. Proud of it. Damn straight.

 

[AcuDefTechGuy]

Apparently someone objected to my this post about harmonic distortion on this thread and decided to give me negative reputation.

Yeah, that is mean.

 

[ImcLoud]

This is no mere wallet biopsy. It seems more like a radical wallet-ectomy.



What does that class A room heater cost compared to central heating system? And which is more efficient?

SInce electric is 100% efficient the amp would be a more efficient heaterthen say a 95% mod con boiler, lol.. The problem is the energy you have to buy to cool the room in the summer when listening to music, will offset any winter savings...

 

[slipperybidness]

Since we are discussing dream systems....

Mine would be powered by custom-designed and custom-built amps. Of course, I would be the designer/builder. Also of course, I am nowhere near that point yet.

I have to settle for published designs for now.

As far as speakers.....probably some of the high end Focals or the KEF blades or Salon 2. Or just hire TLS or DM to do it for me.

 

[itschris]

Nope. No love from me.

It's very nice looking, but just doesn't "stand out" like McIntosh.

McIntosh just begs for attention.

Ummm...



Doesn't stand out? For crying out loud! Who are you? I don't know you anymore!