I just got myself some stuff that needs fixing, but hopefully it will be golden shiny pieces of hifi heaven after a while.
Got the ART preamplifier wich there is only 250 made. The right channel is silent, so need to find and fix the problem. Also got a pair of Premiere Twelve where the left amp is not working correctly, no bass, only top-end.
So hopefully this is fixable and look forward to get this great gear up and running
Last edited by ThomasN on Mon Feb 22, 2021 3:48 am, edited 1 time in total.
Congratulations on the nice finds. It is all straightforward and repairable.
If you’re in the US and want service, the best thing to do is call CJ. There is a minimum bench charge to work up the estimate. Plus the two way shipping. But if you go for the bench estimate, at least you’ll know they’re up to full potential.
If you can’t (or don’t want to) send them off, you can try to get schematics (maybe on this site -some are posted here) and/or find someone technically trained to trouble shoot them (possibly you?).
In an event, it’s part of the fun. I hope they’re sorted soon. Welcome to this forum.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
I'm located in Norway, so hope to get schematics for the ART, but think the problem is found already, so waiting for parts to be delivered. Since it's two mono pre's and amps and one of each are working properly it's a bit easier to measure values to compare as well.
Hopefully these beauties will be up and running in perfect condition soon.
I guess that was Norwegian, unless it was a bad spell...
Ah! The legendary ART preamp. That was the reference statement for CJ back then and launched them on par with the big boys.
With the ART pre we ordered, and later used in our personal reference system, comprising of the Prem 8A's and Apogee Diva's, we did not have access to the 6922 tube variants that are available now. I believe that if we tried the Genalex Gold Lions, that would have enhanced with performance and overall tonality of the ART by a good margin. However, the only tubes that came with the unit were EH6922's, standard no gold pins.
Note to ThomasN: once you get the ART pre back in order, try out the Genalex Gold Lions E88CC/ 6922 tubes. The ART requires 10 of these gens, 5 per chassis, so keeping spares can get costly but once you hear this thing sing, be ready for a wonderful ride of a lifetime!
It also weighs a lot, nearly heavier than most power amps, just make sure those dual chassis are well ventilated and well away from the monoblocks, otherwise things can get pretty hot!
With your Prem12's, another fantastic combination, will match very nicely with the ART. With the Prem 12's just check that all power supply caps are in good order and tubes are operating as normal. Those monoblocks can deliver some serious power, and in the majority of installations, 140w of tube power with plenty of current capacity is all you really require.
BTW, what type and brand of speakers are you using?
I have the Piega Classic 80.2 speakers, so I think this will be a great combination.
The ART has Phillips ecg 6922 tubes installed, that seems to be in good condition. They should be of great quality.
Wondering a bit more about the JJ Electronic 6550 that are in the Prem 12, how they are quality wise for the Prem 12.
Thinking about Genalex Gold Lion KT88 for the Prem 12, but not sure how KT88 are instead of 6550 on this unit.
The choice of output tubes on power amplifiers is a personal preference. There's no one special tube that's better than the others.
Now since you have the Prem 12 mono's, you would need 8 output tubes, 4 per monoblock. Therefore, trying out 8 output tubes just to check your liking is going to cost a fair bit. If there was a way to trial or audition a similar setup using KT88 tubes then you could make a fair comparison but it won't be an accurate measure compared to your own system at home.
Some would actually just prefer the standard 6550C Russian tube made by SED (Svetlana electron devices) which was the tube CJ used for several years on all their premier amplifiers, including the Prem 8's that I had.
Some would prefer the KT88, others would prefer the KT90, and others would prefer the KT120 (which is my personal preference). So to answer your question on which tubes are good, is upto you ThomasN!
You could always get a set of KT88's and try them out, if you don't like them you could always sell them off on ebay or something. Then there's that sweet magic of EL34's that you cannot directly replace. The amplifiers need internal adjustments before you can do this. However, it also reduces the power output by half, so instead of 140w the Prem12's will generate about 70w max if you decide on using EL34's. That's a whole different ball game, not sure if you really want to go down that path... but you never know you may actually prefer it!
It's all an interesting learning experience and can be very enjoyable. Just remember to obtain matched pairs of output tubes as these will yield the best results. You can also order matched quad sets that come in fours. So all you need is two sets of four output tubes.
All the best with this journey, and do let us know how it goes. Cheers mate, RJ
They do make good space heaters, don’t they. I turned my LP275Ms on a couple of hours before a planned listening session yesterday. They dulled the impact of the air conditioning.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
Take those same amplifiers with similar output tube topology or even more, and place them in the tropics, you're sweating! Then wait few minutes and do a bias adjustment and you're really sweating. I think CJ supplied the magic wand to accommodate the tropics... biasing CJ amplifiers is such a breeze.
Having onwed a few other monoblocks where a multimeter is required for biasing, you have to get right on top of tubes, trim pots were located behind the tubes. Biasing 16 output tubes with a multimeter isn't even funny. Let alone taking care that no sweat drops into the amplifier or worse still onto a tube!
It's like a surgeon, asking the nurse to "wipe " before and after procedure... (each tube bias).
I remember nearly every owner's manual used to state warm up time, and generally recommended about 15mins to half hour. In the heat of the tropics, this was clearly not the case. Warm up happens as soon as the amplifiers are powered up! Everything around you is virtually warmed up!
ThomasN;
Good to hear your Prem 12's are working fine. Just make sure you have the phase connected in absolute phase from preamp to power amplifiers leading upto the speakers.
Sounds like you'll have the system up and running in no time.
Cheers, RJ
Just checking in on how the ART preamp is coming along... and the Prem 12's should be up and working well by now?
Any changes or improvements in sound, what are your findings so far? How have you been experiencing the best recordings, is there good control and drive from the Prem 12's?
ThomasN wrote: ↑Wed Sep 23, 2020 10:40 am
Yay, all things are good now Both The Premiere Twelwe and the ART Pre is singing along...
The ART ave ony been up for a couple of hours, so will need some time to listen before making any statement... except that it sounds promising
CJ.jpg
Wow, that looks incredible. Tell me, how do you like the MBL speakers? How does the sound compare to traditional speaker designs? I've never heard them myself in person but as soon as I saw a picture of one in an audio magazine I was like, "what the heck are those." I then read a little about the "radialstrahler" technology and thought it was really cool. It's kind of unique in the sense you get sound produced in a 360 degree fashion.
-admin Home Theater in Member Gallery Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
Nice one ThomasN,
Well laid out system and those Prem 12's are looking mighty fine! Obviously the ART preamp will always have that legendary presence, great stuff mate.
Are those KT88's on the Prem 12's? Perhaps I missed it... what brand of output tubes did you finally decide on?
I ended up with Genalex Gold Lion KT88 for the prem 12s, and Gold Lion 12AU7 instead of 5751 and BLACK SABLE RCA Clear Top 6CG7
But the ART has some minor Buzzz noise that I'm not sure what is causing, but It's constant in volume no matter what the volume is set to Except that it's totally quiet when using mute. Maybe new tubes there as well... hmmm?
EDIT: It was a ground loop issue.
Last edited by ThomasN on Wed Sep 23, 2020 4:26 pm, edited 1 time in total.
ThomasN wrote: ↑Wed Sep 23, 2020 10:40 am
Yay, all things are good now Both The Premiere Twelwe and the ART Pre is singing along...
The ART ave ony been up for a couple of hours, so will need some time to listen before making any statement... except that it sounds promising
CJ.jpg
Wow, that looks incredible. Tell me, how do you like the MBL speakers? How does the sound compare to traditional speaker designs? I've never heard them myself in person but as soon as I saw a picture of one in an audio magazine I was like, "what the heck are those." I then read a little about the "radialstrahler" technology and thought it was really cool. It's kind of unique in the sense you get sound produced in a 360 degree fashion.
The MBL's are great, but quite power demanding. So I'm using a Vera Audio P400/1000 on the low input (up to 170 hz) and the Premier 12 on the mid/high. When startng the CJ project I had some Piega Classic 80.2 that had 93db sensitivity and the prem 12 did just fine.
The MBL's are 83db, but the bi-amping are doing he magic. Getting the superfast tight low end, and the smooth mid/top from CJ. Just loving it
MBL's must be experienced, hard to describe, but it's just so much more live feeling. Instruments are not as directional in real life as traditional speakers usually are. These are the MBL 116 F
ThomasN wrote: ↑Wed Sep 23, 2020 3:08 pm
But the ART has some minor Buzzz noise that I'm not sure what is causing, but It's constant in volume no matter what the volume is set to Except that it's totally quiet when using mute. Maybe new tubes there as well... hmmm?
EDIT: It was a ground loop issue.
That is so often the case. That’s great that you got it sorted out.
Leaking or failed power supply cap, and transformer insulation failure seem to the other two issues that can come up and create some hum or audible buzz.
Ground loop is the best possible outcome.
It’s just stuff. I like mine. I hope you like yours. I probably like yours too.
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