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
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.
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.
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 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.
Thanks Jafox,

Yep, that was a typo. Meant to type JL-2.

My understanding is that the original JL-2 began with 6 resistors, then up to 10, and like you say, there is now a newer resistor set which supposedly allow the amps to better handle a catastrophic tube failure.

In order to protect against having to buy a whole new set of tubes if just one blows, I'm thinking about buying a couple extras, and rotating them through as the tube set ages. This would mean that I'd always have a couple around that are similarly aged as the rest, if a replacement is needed.

Are you half kidding about not leaving the room? With the new resistor sets, is it sufficiently safe not to worry about torching?
Well, even with the updated resistor set, that I assume will react quickly and breakdown due to a tube failure, I am still cautious to leave these amps "alone". Maybe had I not had a melt-down before the resistor update a few years ago, I might be more "courageous". Just my own feeling.
Thank you for reminding me why I love my solid state amp.
Thankfully these sorts of issues certainly don't apply to most tube amps.
Very true Brian, but most tube amps don't even begin to come close to the CAT in dynamic contrasts. Once you hear this, it's hard to go for something else.
Just want to say I agree wholeheartedly w Jafox, that it excels in dynamic contrasts n more. While it is only conservatively rated at 100w into 8ohms, these are pure Class A watts, so will drive almost any speakers on the planet.

Yes, I also have the plain vanilla JL-2 using Svetlana KT88s which I prefer slightly over the stock 6550s. Don't think there is any issue with long ICs - am using 2.5m Nordost Valhalla IC between my Gryphon pre n this.

Roll the input tubes if you can, and they will bring new joy n surprises. Was using a combo of Telefunkens n Mullards, and recently due to a preference for more body n warmth, went ALL Mullards - nice ;)

Lastly, I am driving my Kharma CE 1.2 - ceramic tweeter n mid-range drivers - which is quite similar to the Indras - with the JL-2s. The results with your speakers should be similarly spectacular