Cat JL2 with blown board. Advice needed

Dev,

The SL doesn't run hot (not in my application or Jay's). It currently is offered in matte aluminum and black (chrome aranya is discontinued). The pre
is offered in aranya only. They make a tubed and SS pre.
As expected the tubed pre does some things better than the SS and vice versa. The pre uses 6922's in the signal path and EZ80/6V4 in the PS (yes, tube selection in the PS has a big influence on the sound). The stock 6922's are Sovtek.
Surprisingly they don't sound bad in this pre. They have been dreadful in every other component I have heard them (including the CAT pre's and amps). They are quiet, cheap and reliable and that is why so many manufacturers use them. Somehow Rolf from SL has found a way to make them sound decent in his pre. I am not going to rehash a discussion with Bombay on the merits of tube rolling in the CAT pre and amp. I'll just say that if you are using the stock tubes in them, you aren't even close to realizing their potential. Most that have rolled in them agree with that statement. John Fox uses JL3's and runs the tubes I sent him to audition (after trying countless combos of very expensive NOS). The only things our systems had in common were CAT amps (and some cabling) yet the same tubes produced the best sound in both our systems.
I know you refuse to buy ultra expensive tubes but sometimes they are the best (there is a reason people spend that much for them). Again, I don't post much on these forums anymore because I don't have time to waste arguing. No matter how many times some reviewer says that XYZ tube amp "plumbs the depths of what is possible in bass reproduction" or similar nonsense, their BS will not rewrite the laws of physics. I suspect that your friends with Apogees, Dali's _____ fill in the blank difficult to drive speaker, will be as surprised as I was when they directly compare their tube amps to SL in their systems.
Everything is relative. They may currently think their tube amp is doing the bass just fine until direct comparison. The VTL's have double the damping factor (sorry numbers sometimes tell valuable stories) of the CAT
and especially in tetrode do the bass better than CAT. Again it is CURRENT that controls bass not WATTS. There is a reason that most tube amp manufacturers will not tell you what their amps damping factor is. I called and spoke with Luke Manley's wife when I was considering the Wotan's.
She refused to tell the damping factor which I later found online. If you do a Google search on damping factor you will find a wealth of information that explains it in understandable scientific terms. It the the bass that costs all the money to get right. Some people are fine without it and love their SET powered ultra sensitive speaker systems. But if the objective is full range done right, damping factor and physics can not be anecdotally explained away. The problem with having heard bass reproduced correctly is the realization that nothing else (the rest of the spectrum) is right without it. FWIW IMHO

Bart

Bart,
No one is trying to argue with you! Your inputs are well taken.
What I'm trying to convey here to Defender1844 (& anybody else reading this thread) is that they are NOT limited to only s.s. power amps for their application. Basically what you are saying is that the s.s. Kraft 250 is it & nothing else would work for Defender1844! I'm saying that Defender1844 has tube & s.s. power amp choices.
Hey, I'm a S-L user for longer than most people on this forum so I should be the one recommending nothing but S-L amps. That would be very limiting - very capable tube power choices exist as well.

Agree that tube rolling is very subjective - some like it a lot, other like it some & some do not like it at all. I just happen to fall in the 1st 2 categories.
With the CAT pre I happen to fall in the 2nd category - I liked it but with some qualifications.
With my Jolida 502A & Cary Sixpac tube amps, I out-right loved tube-rolling.
I've found tube rolling to be very gear dependent.
You feedback on tube rolling is well-taken.

>> Again it is CURRENT that controls bass not WATTS
You are right in a round-about way. Tt's impedance that control bass. Hig(er) current is a sign of a very robust power supply, which in turn can happen usually when the output impedance is very low.

Bart,
we are mostly saying the same thing the only difference is that you are limiting him to s.s. power amps & I am saying that he has both tube & s.s. power amp choices.
Anyway, I do not want to argue with you - I agree it's pointless.
The info is there in this thread - let Defender1844 read it & do whtever he want with it. Peace!

I emailed Ken Stevens, made him aware of this thread and asked if he’d like to offer any advice. As he’s not a registered member, I volunteered to post his response and recommendations.
++++++++++++++++++++++++

Hi, Defender 1844. I think we talked about this over a year ago. I really advise people not to use ANY tube amplifier in A/V systems or for background music. As I mentioned last year, I use a cheap Denon receiver for my A/V and physically switch speaker wires to the CAT amps when getting serious about audio. That's also why our SL1 A/V bypass engages when the preamplifier is turned OFF - it's literally a passive pass-through at that point.

I recall that you were quite insistent about using the CAT JL2 in your A/V system. I believe I recommended biasing the tubes a bit low to begin with (and then never adjusting bias thereafter of course) Did you follow this recommendation? I'm not being critical of you, just wanted to know if you did this.(This is not a proven recommendation - just an idea I had that might help. We really don't get many people using the amps in A/V systems.) Obviously if you did as I suggested then I won't suggest that other people try it.

An upgrade is certainly not needed to get this amplifier up and running again. We would be glad the send your dealer replacement fuse resistors. For the past three months, we've been using new ones which are more predictable and less likely to flame up, however we won't really know if they solve any problems until one of them blows! As yet, they have not. BTW, the purpose of the fuse resistor is to prevent damage to the ultra-expensive output transformer should a tube short internally.

Finally, regarding the comment someone made about damping factor as an indicator of bass quality: I find that DF is no more a predictor of bass quality than THD is a predictor of transparency. The JL2 has bass which is handily superior to ALL other tube amplifiers and almost all SS amplifiers despite a modest damping factor. On the other hand, anyone who has listened to a Crown IC 150 (DF of 20,000) will tell you that high DF could well be accompanied by really mediocre bass. I'm not saying that high DF is a bad thing, in fact "all other things being equal" it’s probably a good thing. But all other things are never equal, and there are many things far more important than DF (or any other spec).

The JL3 monoblocks do have a higher DF than the JL2 and they do have better bass. In fact the JL3 probably has the best bass of any amplifier in the world, including even the Kraft 400 (the much better sounding big brother of the Kraft 250). Clearly, much more than the higher DF is responsible for the superior bass of the JL3.

BTW it is the Kraft 400 which I have recommended to some people who are insistent on SS power, NOT the Kraft 250. In fact recently I heard from George that the 250 sounds much more like the cheaper RG series than it sounds like the Kraft 400. He said it was decidedly lightweight and over-controlled, lacking the richness of the 400. (The 400 could also be described as somewhat lightweight, but much less so than the RG series or, according to George, the 250)

Ken Stevens
President
Convergent Audio Technology, Inc.

++++++++++++++++++++++++

Tfrumweiller,
good response from Ken himself. I tend to agree w/ him about DF being an indicator of bass response given that there is much interaction of the amp w/ the speaker to make just DF be the sole parameter.

Very interesting comments on the Symphonic Line Kraft 250 power amp! I DO NOT take any offence to them - just want to let all know for ample clarification.
At present I am using Ken's SL1 Signature preamp with my Kraft 300 (not 250) & I can confidently say that the combination does not lack bass. In fact I am very happy w/ the combination & The only change I'd make is to shell out some money to buy one of Ken's newer preamps like the Renaissance or the Legend. I believe the newer preamps throw an even wider, deeper & more life-like soundstage. If I only had some money......

I do not know which preamp George is using in his setup? I don't know why he is hearing a light-weight bass?

From Ken Stevens:
++++++++++++++++++++

I said the Kraft 250 was described by George as being lightweight and overcontrolled. This is completely different from saying it "lacks bass".

Ken Stevens
President
Convergent Audio Technology, Inc.

++++++++++++++++++++