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Krell anticipator circuits of the 1990s

"Krell FPB-600 Stereo Power Amplifier

This big power amp features the evolution of the plateau biasing circuit introduced in the KSA series of amps. This circuit anticipates the power demands of the output by monitoring the incoming signal as the demand for power increases, the more power the amplifier supplies. After a grace period of fifteen seconds and no additional high current signal demands, the Krell FPB-600 amplifier returns to its appropriate power setting. This feature allows for Class A bias output without all the wasted electricity and heat."

Do you believe the anticipator can up the bias quickly enough?  A guy hits a huge bass drum, the anticipator circuit senses this and ups the bias in time for the hit to be amplified in Class A?

We are talking a micro second.  Once he hit it the start of the moment was over.  This was a con.  Created by Krell because they were under pressure from the emerging green lobby to cut power consumption.  Qualified Krell service engineers have not been able to explain to me how it can work.

Me?  I still have my KRS200s.  Pure Class A.  So there's my answer.

 

clearthinker
ditusa's avatar
ditusa
2,158 posts
 

+1@jasonbourne52,

Qualified Krell service engineers have not been able to explain to me how it can work.

In my opinion they could not explain how it works because they knew it was marketing baloney.

Example of marking baloney in audio see below:

This feature plateau biasing circuit allows for the Krell FPB 600 amplifier to have Class A bias output without all the wasted electricity and heat. Really?

This is all very unsatisfactory and in the result I continue to use my KRS200s.

I agree, keep the Krell KRS200s if want new ''real'' class A amps see Pass XS300 mono block amps, they will give you all the heat you need to keep your English castle warm. 😎

 

Mike

https://www.passlabs.com/product_tags/class-a/

 

mceljo
1,357 posts
 

@dlcockrum - My friends amplifier is a Krell KSA-100S.  It has sustained plateau biasing with four lights on the front to indicate the various levels.  Not quite the same implementation, but similar concept.

invalid
1,307 posts
 

There is opto-couplers in my ksa 300s amp. It will give you 300 watts of class A power for only a little while as the heat sinks aren't big enough to sustain it. If it gets to a certain temperature it will be class A/b on the top two bias levels until the temperature comes back down.

retiredfarmer's avatar
retiredfarmer
361 posts
 

I heard  a set of bryston  7b monoblocks  compared  to the krell fbp600. I am not s bryston  fan but I found them to sound much better in that system  that day. A friend used to have a set of krell kma monoblocks  I really liked them. I never liked the 600. 

bsmith
68 posts
 

ksa 80 from 1991 never been serviced.

Brings it everyday.

So much power it scares me.

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