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Questions About CAT JC-2

Those of you who know this amp can perhaps answer some of these questions:

1) What is the input impendance (not listed on CAT's website). Is it compatable with long IC cable runs?

2) I hear that tube biasing is for each channel at a time, rather than for individual tubes. Is that correct (bias all 8 tubes together). Does that mean you have to stick to sets of 8 matched tubes? If one blows, do you typically end up replacing all 8, or can you just replace the one?

3) Does it work with other tubes besides 6550's like KT-88's and KT-90's. What tubes do people have the most success with?

4) I'm looking at an earlier JC-2, not the signature version. I realize there have been steps along this amp's evolution. This one atleast has the 10 resistors rather than the 6, so is less susceptable to blowing out. In general, how quiet is this generation JC-2?

5) I'd be using this with Avalon Indras. I've heard that the CAT is a good match with Avalons. Any thoughts on that?

Thanks, Peter
peter_s
schipo
1,268 posts
 
I believe you might just find info about the Cat amp on the Arthur Salvatore site.If the info your looking for is not there give him an email.
peter_s OP
1,335 posts
 
I did get a bit of info from CAT.

The input impedance is 110 Kohms

As for replacing a blown tube, Lee said that one should replace the whole set if they are getting close to worn out, but if they are still in pretty good shape and the "blown" tube seems to have blown early in its life, it would be OK to replace just the one.

A set of tubes should last 2000 hours.
jafox
1,456 posts
 
What is a CAT JC-2? Do you mean JL-2? We are talking about Convergent Audio Technologies, right? And what CAT website are you talking about?

10 resistors rather than 6? What do you mean? The earlier JL-2 and JL-3 amps can be updated to the newer resistor sets which supposedly allow the amps to better handle a catastrophic tube failure.

And yes, biasing is done for all the tubes per channel rather than one tube at a time. This does require a matched tube set for each channel. The amps do provide to view the bias current value for each tube to determine that each is "ok".

Chances are that if the tube set has lasted over 1000 hours and suddenly you have a tube failure, replacing all is likely a good idea. When a tube died in the JL-3 or a resistor failed due to a tube dieing, I continued to run the one amp with 15 tubes....it was mighty fine. Once another tube died, that was an indication that it was time to change to a new tube set. This is most advisable before tubes start failing and causing trouble.

The issue of a long IC has more to do with the line stage's ability than that of the amp. I used a 30' RCA Purist Dominus IC from an Aesthetix Callisto Sig line stage to the JL-3's for a few years with awesome results.

Keep in mind that these are not just your average tube power amps. They have exemplary dynamic contrasts, resolution and clarity. They control "difficult" speakers like so many others can not match. And they can be taken up a notch in performance with tub rolling the 3 small signal tubes per channel.

My advice to all CAT owners is to never leave the room alone for more than a minute. One last thing: these are serious room floor heaters as they are audio amplifiers. If you are in a room that is already difficult to keep cool, the CAT amps will have you in beach clothes quickly.
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