I emailed Ken Stevens, made him aware of this thread and asked if hed like to offer any advice. As hes not a registered member, I volunteered to post his response and recommendations.
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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" its 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.
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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" its 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.
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