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Amplifiers - Krell KSA50 MKII
I own since a long period 3 marvelous amplifiers. One THRESHOLD SA/3.9 upgraded, one KRELL KSA 50MKII and a pair of JADIS JA80.
Today, we are reviewing the KRELL.

This one is the second generation of the KSA product line.
It comes from the first serie "KSA" from KRELL. This serie works fine like the 2 following ones, KRS and KAS. Do not take any of the other series, as you would be disappointed !

With this product ,KRELL became a famous manufacturer. The review has been done on the Florent's system (reference system #2).

This KRELL KSA is very massive, the front plate is 2mm in stainless steel and the other parts are made of aluminium with a lot of holes, but it is not as robust as its THRESHOLD 3.9e brother.
Inside, you discover a double mono design, which is great  and the use of Mallory capacitors (2x 37,000 µF) for each side and 2X800VA for the power supply.

The transistors are the well known bipolar Motorola MJ15003 and 04, but with a "Krell" label on it.

No surprise, they are working fine like in the Threshold. The Krell is rated 50w in Class A.


You discover immediatly a warm presence with beautiful sounds, but with a small fog on the spectrum. In fact, this amplifier is not really accurate. It prefers to give you pleasure with a cool and relaxing sound.
Accelerations are like the dragsters' one, but they generate some very unpleasant high mids. At the opposite (bass), there is a very rounded boum boum.

Voices are also marvellous but not real.

As a summary,  it is not a cold and accurate amp like a MARK LEVINSON for example (we refer to the old fashioned models...).

If you are in love with classic CDs, then go away, you will never heard the sound of the silence: there is a fan regulating the temperature inside the amplifiers, and it always works, continuously generating some noise.

Congratulations for having done this great amplifier Mr Dan D'Agostino, because you are really near the beautiful sound of vaccum tubes. It has been great to follow on the way because your products now are far away from this concept, but (still) show huge prices (maybe even more expensive than previously ?).
It would be a good thing to find a solution for removing the noise and for increasing the accuracy.

Pro :

  • it is transistor "prince"
  • medium is very sweet, really magic.
  • allways pleasant to listen
  • definition poor but great general sound
  • genial handcrafted product

Cons :

  • general fog
  • bass are too rounded but the slamm is awsome
  • accelerations are too fast and they generate unpleasant high mids
  • be careful, temperature can be upper 55°C, so stay in the room in case of fire...
  • fan is very noisy

New listening done one year later.
A lot of changements have been done during this year on the reference system 2 :

- Bought a "Black Noise"
- Bought a Kubala Sosna Emotion power cord
- Move to Tesla drivers tubes from 50's on the Jadis JP80MC
- Bought a new amplifier Threshold SA/4e

On the first listening, I feel fantastics accelarations and huge bass. Qualities from the past with beauty of sound are now top notch and the unpleasant highs have deseapered, bass have more slam than before and are more dry (really good!), end of notes are awsome. (the best of the world).
I must admit that my previous configuration was not at the top for these product.

Pros points are the same except :

  • definition is really better
  • stridents high-end disappared
  • general fog going away
  • a fun feeling is now present like intalled by magic

Conclusion :
Trying to listen a system must be done in perfect condition and with an "ultra" optimized system. It's what we have now !
I am very proud of this conclusion because in the future, we will do a very good job and no errors in the review.

This amplifier gets the best note,


New listening session done 3 months later after the second one
The following modifications have been done on the reference system 2 :
- New Jorma Design Super Power cord, the Kubala Sosna Emotion has been removed.
- New drivers tubes on my  JP80MC preamplifier (Telefunken from 1950) + new high grade capacitors on the tube.
danger.jpgI have to admit that I have done a mistake. Following the fact that my Krell was out of order (fire), the repair has moved it back to the manufacturer specifications for the capacitors, transistors and of course the BIAS.
Since this modification, it runs really better and it does not produce anymore this huge heat !!!!!!!!! You can put your hand on the upper chassis without any trouble even after 5 hours of use ...

Consequently, only the following cons remain:

Cons: The ony one cons is the fan really not fair with classic music (it is too noisy).


Review done by Florent (provence13 on the Forum).

Creation date : 25/11/2007 @ 17:08
Last update : 11/01/2016 @ 21:04
Category : Amplifiers
Page read 1780 times

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Reactions to this article

Reaction #2 

by provence 26/08/2010 @ 09:41

If you have one channel in order, see it and do the same in the other.
Krell are dual mono, so left and right are similar.

Reaction #1 

by petedenham 25/08/2010 @ 19:40


  hope you can help me.

  looking at the krell from the front. i have removed the two huge right channel psu caps and have forgotten which way they go back in. does the rear one have the + on the left and the front one have the + on the right.

  i look forward to hearing from you, thanks, pete.k

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