Convergent Audio JL2 Triod Amp MK II Upgrade

JL2 stereo amps manfactured in 2004 and later have incorprated a power supply upgrade similar to the CAT Ultimate preamp upgrade for the mark II stauts according to Ken stevens. The new upgrade on the JL2 has not offically be called the MK II becaucse Ken does not like to change names very often but the new amps being produced now are superior to the pre 2004 models that were manfactured by Convergent Audio. Ken indicated that with the upgraded JL2 the sound is purer and more transparent than the earlyer produced amp. The cost of the upgrade is $1000.

I found this out when I had to send my JL2 back to the factory to replace some resistors that went bad. In the process of fixing the amp he offered me the upgrade which I accepted because it was already there. This is the first problem I have had with the JL2 in 2 1/2 years I have owned it. The fix also replaces the resitors and adds (4) more to make it far less likely to happen again something that is also incorprated on the new model of the JL2. Ken Stevens told me the JL2 does not use any fuses to protect the large transformer and instead uses (10) resistors for a purer and more vibrant sound compaired to fuses which are more commonly used on tube amps such as the Jasis Defy 7.

I will post my impression of the upgrade once I recieve it back and get some time to listen to the difference.

The problem with the resistors seems to have happened with most of the JL-2's. It's a great sounding amp, but when I had to pack up a 175 lb beheamoth, and wait over a month for it to come back,
I had to ask myself if it was worth it. I decided no, and have found happiness, and wonderful customer service with Vladimir Lamm.
Peace of mind, and a responsive manufacturer go a long way when it comes to enjoying one's system.
I agree the original (6) resistors on the JL2 have been a problem with some amps as I recently found out. The resistors fail rather than damage the very expensive input power transformer in the rear. Ken recently altered the design of the CAT JL2 to include (10) resistors which he believes will very greatly reduce the occurance of failure. Other than this one problem the amp the JL2 has preformed flawless for over 2 years.

I also have same problem with my JL2, and am not very happy with the customer service at CAT. Returning phone calls or respond to email is not their forte.
A issue at Convergent Audio is that Ken Stevens is the go to man for everything and he does not delegate so all authorization and communications must go thru him and as you mentioned he can be difficult to get a hold of. Sometimes I call back 3-4 times during the day to catch him at the workplace but when I do finally get him on the phone he will talk your head off for at least one hour. The conversations I have had over the years with him have been quite informative and interesting even if I only understood 1/3 of the technical information he was telling me. If your JL2 goes out for any reason Expect to be down at least 30 days, it takes several weeks to transport your amp back and fourth to the factory plus several weeks in the shop. Yes I wish there was better customer service with Convergent Audio regarding repair of there products but it is what it is and I don't expect that to change anytime soon.

The resistor problem with earlier JL2 amps will probably force most owners to ship the heavy beast back to the factory sometime in the first 3 years of the life of the amp for the repair and summer time is probably the best time to get the work done. The JL2 amp gets hot, is heavy, has allot of tubes (22) and hard to move so why do we go thru all of this? Because it sounds so good and at its price point or even much higher has no completion in my biased opinion. The taunt bottom end and beautiful clarity is something to behold on the Convergent JL2. Late at night after several hours of warm-up with all tubes glowing and the music flowing I ask myself is it worth all the extra work and the answer to me is Yes, Yes, Yes.
"Because it sounds so good and... has no completion in my biased opinion."

Are you saying it's not a complete amp? Did you buy it as a kit? To the best of my knowledge, CAT equipment is only available in complete form.

"The taunt bottom end..."

How did the bottom end taunt you? I've heard the JL2 and I think it's got about the best bass response of any amplifier I've ever heard, tube or solid state.


Holton Corsey
Most manufacturers make no effort to protect their output transformers, but our transformers are considerable more expensive due to both size and exotic low loss core material and so we REALLY don't want to have to replace one. As a former equipment modifier, in my tweak years, I can attest that most old amplifiers have compromised output transformers due to sudden tube death. (A Dynaco ST70 with two good transformers is a very rare thing!)

But, that being said, I must admit that our six pack of metal film resistors have been overly protective (we could use one wirewound or power film instead but this hurts the sound and a fuse is even worse). We have upgraded this now to a ten pack of resistors and hopefully this solves the problem. If not we may consider just eliminating the protection altogether.

Ken Stevens
Convergent Audio Technology, Inc.
My apology to Mr. Stevens. Although we both tried to get in touch with the other, unfortunately, I did not get his messages and neither did he mine. We have been playing phone tags for the past few weeks. So my previous comment is incorrect. Just want to rectify the record.
Regards, Nick.
Thanks Nick,

Just a short comment on CAT customer service. I own a CAT SL1 and JL2. Recently I dropped my pre "face first" while moving the equipment. All the switches were broken. I called Ken, sent him my pre, and in two or three days it was repaired on its way back home. Got the pre back, looks great, sounds great. In all it took 5-7 business days. The repair price was reasonable. I have no reason to doubt that Lamm offers great customer service (I also own a Lamm pre), and I would put CAT in that same category - at least that has been my experience.