Conrad Johnson Owners.com

Anyone willing to take a chance? Someone on Audiogon did the swap and posted the quote below. So now I am curious.

Even my little Jolida Fusion JD-3502 takes everything from EL-34's to KT-150's.

Here is the quote:

"Call me a rebel CJ told me flat out NO, but I just replaced the kt120's in my CJ Premier 12's with kt150's, 60 hours in no issues, been monitoring the transformers to see if they get hot, no issues. the sonic difference is astounding in my system. I have had these amps for 18 years, and have run 3 brands of 6550's, 3 brands of kt88's, for almost 3 years kt120's. I switched to kt120's because of better bass and better dynamics, but I always felt they brought a little touch of electronic edge, I didn't know if that was coming from somewhere else in the chain. Back to the 150's, the sound is so dramatically better, I will never go back unless my amps blow up or I do. Dynamics like nothing I have ever heard, no grain or edge, best bass, best and deepest soundstage ever and most musical"

Hi Joe,

I took a look at New Sensor's tube data sheets for both their KT120 and KT150 specifically looking at the heater current draw and there really isn't much of a difference at all. Both draw no less than 1.7A while the KT120 will draw no more than 1.95A versus 2.0A for the KT150. We both know that c-j can be a little conservative at times in their advice. The KT120 is a prime example. When the KT120 initially came out, any call to them asking whether it could be used in their amps was answered with a definite no. Once the supply of SED =C= 6550C tubes became unreliable, c-j's tube of choice became the KT120.

Now, I'm not condoning you sticking those big suckers in your ARTsa or anything but, just sayin'

Regards,
Joe

Ha! Wink, wink. I totally understand. Thank you for the tube data. It makes sense that they are not too far apart and I doubt the amps would be unable to handle them.

I'm still looking at approx. $800 to buy a set of KT-150 tubes for the ARTsa (probably about that much for a set of KT-120 from CJ anyway). I think CJ wants over $1800 for a set of KT-120 tubes for the ART mono amps. I'll do it, but probably after CES to see what comes out, if anything.

If anyone makes this change, please post your results.

Hi Bill,

How's your amp doing? If I remember correctly you have the ARTsa?

Joe

Hi Joe,

Yes mine is an ARTsa, driven by an ET5. Since we last corresponded I have added a TEA2MAX. Conrad-Johnson loves me. Anyway, all is well. I listen to music every day when I am home for at least 2-3 hours, with 4-5 not unusual and even more time on the weekends. It all sounds great to me. I have to admit, though, that it sounded great to me right out of the box. In other words the improvement in sound with running time either did not happen, was too gradual for me to notice, or my tired old ears are just all shot to hell anyway. Regardless, I really love the way the whole package sounds. Thanks for asking. How are you doing?

Bill

Hi Bill,

I am doing great, thank you. I rotate my gear with other amps but everytime I go back to my CJ gear, wow! all is right again. Nothing sounds as great. I use my ART monos with the GAT or from the preamp/dac section of a Devialet 400. Slightly different flavors, but each great in its own way. I had intended on replacing my ART monos with the ARTsa but have not been able to bring myself to setup the ARTsa, but I will.

Have you been keeping track of the hours on your tubes? I sent an email to CJ tech support and they recommend replacement at 1500 hours for my ART monos and ARTsa. I have lost count of the hours on my ART monos, so I am a little nervous for the future. I am not sure how common it is for tubes to take down an amp or have something more serious happen. I guess I am a little paranoid. but I will get over it. It sounds too good to worry.

joeinid wrote:Hi Bill,

I am doing great, thank you. I rotate my gear with other amps but everytime I go back to my CJ gear, wow! all is right again. Nothing sounds as great. I use my ART monos with the GAT or from the preamp/dac section of a Devialet 400. Slightly different flavors, but each great in its own way. I had intended on replacing my ART monos with the ARTsa but have not been able to bring myself to setup the ARTsa, but I will.

Have you been keeping track of the hours on your tubes? I sent an email to CJ tech support and they recommend replacement at 1500 hours for my ART monos and ARTsa. I have lost count of the hours on my ART monos, so I am a little nervous for the future. I am not sure how common it is for tubes to take down an amp or have something more serious happen. I guess I am a little paranoid. but I will get over it. It sounds too good to worry.

Hi Joe,

Normally, when a power tube goes south catastrophically on the c-j amps I've had (11A and 140) it'll take out one of the plate fuses. More common, I think, is for the amp to lose its sparkle and sound kind of "meh" as the tube(s) age. What do you have in there now, KT120s?

Regards,
Joe

Hi Joe,

I still have KT-120's in the amps. CJ said emphatically no to KT-150's but I'd be willing to try them in my ARTsa and see how it goes. The KT-120's are one half the price of the KT-150's to replace. The KT-120's sound wonderful in the amps, can't imagine how good the KT-150's could sound.

Joe Appierto wrote:
Hi Joe,

Normally, when a power tube goes south catastrophically on the c-j amps I've had (11A and 140) it'll take out one of the plate fuses. More common, I think, is for the amp to lose its sparkle and sound kind of "meh" as the tube(s) age. What do you have in there now, KT120s?

Regards,
Joe

I think the plan is to check all the tubes at the one year anniversary. The small tubes might need to be replaced with the big tubes needing to be replaced about every other time. My dealer has a tube tester. I will let you know when the time comes.

Thanks Bill. I'd appreciate the update.

I am so impressed with KT-150's in my Jolida Fusion 3502, I just may take a chance in my ARTsa.

I love my CJ gear. It sounds amazing.

I'll be standing by to see how it goes with the 150's. I switched to 120's in my Premier 8's over a year ago and upgraded the electronics at the same time to be close to the newer Art amps. I've had El34's and 6550's in these amps and they are greatly improved with the upgrades and 120's but if there is more to be had by simply swapping tubes, thats a very tempting proposition. Especially since I'll be replacing the 120's eventually anyway.

Also as a side note, I've got a pair of Carver 305's that sound very much like my Premier 8's; same power, same 120's, and now Carver is selling their amps with an optional upgrade to 150's for an extra charge. I've got very limited knowledge about electronics but if Carver is using 150's in a similar amp, it seems they might also work well in my CJ amps? Right now I've got my GAT as the preamp in that system with a pair of custom built Quads Another great addition has been Herbie's tube dampers on all the tubes in my system. These cost $30 each so it adds up, but the improvement in clarity was stunning. http://herbiesaudiolab.net/rx.htm.

Wow! Beautiful system Jasper, thank you for posting.

Thanks Joe! You might have noticed my obsession with blue tape. I just slid those 2" maple platforms under the speakers and lifted them up on brass footers with incredible results. My project for this weekend is to replace those old 2" with 4" platforms and heavier footers. Not so easy to get them in the exact spot but well worth it! Happy listening.

Well done! Looks great.

Any idea if the KT-150’s would work in a CAV-50 (which normally takes EL34’s)? I doubt it but would like to know. Thanks! Eric

Sorry mate, the CAV50 or CAV45 or any amp that incorporates the EL34 will not take in KT series as a direct replacement.

EL34's are more triode based, with very different values at factory settings on voltage and amperage ratings. These are factory set and bias adjusted to match the transformers. Replacing with KT150's or any KT series tubes, operating in ultra-linear mode with push-pull topology will cause the amp to damage, let alone a nice wonderful display of colors!

One of my very old customer's did this with his premier 11A, after getting CJ to order the Prem 11A in triode version which was referred to as the "XS" model. These XS versions were also offered on the Prem 12 & Prem 8, halving their full output. This modification had to be done at the CJ factory and no where else, unless it was fully authorized by CJ. This basically halved the output on the Prem 11A from 70w to 35w but the resolution and musicality were superior to the 6550's. He then later bought inefficient Apogee's and wanted more power from the amp, so dropped in some KT120's and hoped for the best, and boy did new year fire works come earlier than the 4th of July!

CJ does not conduct a mod on the CAV50 or CAV45 for larger tubes, that would cause the mains transformer and output transformers to be modified as well. This type of mod is mostly done on their stand alone power amps, which can be modded according to customer requirements for extra cost.

If you wanted more power from your CAV50, then I'm afraid it will no longer be a CAV50. You can try the new CAV45, which was my all time favorite CJ amp I have ever owned, and it does have more oomph compared to the CAV50. If you are going for more power, then you are venturing into MV60, LP70S, LP66S or Classic 60 territory, and this is a totally different level in sonic performance from power amplification. Also, in which case you will need to acquire a separate preamp as well.

There are a number of previous power amps for a very good price, if you were interested to go down that path. I think in your part of the woods it would be Spearit sound, since they're shutting down, they're getting rid of all CJ gear, and the prices are remarkable!

Cheers mate and all the best!
RJ

Thanks for the info! I didn’t think they would work but I figured it was at least worth a question, as some amplifiers (primarily those with autobias) will work with almost any octal power tubes, whether they are EL34/6CA7, 6550, KT88/90/100/120/150, 6L6/5881, 6V6, KT66, KT77.

Yes that is correct, and you do make a valid point.

Unfortunately, CJ doesn't do this with their EL34 based topology, I don't know why though?

Perhaps they want to control the factor of tube replacements and try to direct their valued customers towards them for re-orders. Makes more business sense, after all the main gentlemen, Lew & Bill are economists, they now how to survive in a competing, ever changing environment...
Cheers to that! RJ