Conrad Johnson ART amplifier fuse blown

[admin]

So I only have a single spare fuse now so I figured I go and buy some extra to have available. After all, fuses don't cost too much. The fuses in the amps and what I had spares of were Limitron KTK-2 fast blow fuses (ceramic). But these are rated for 2 amps. The CJ manual says they should be "5x20mm 10 amp T-type if configured for 100 or 120V". Is it possible that the previous owner was running the wrong type of fuse? Although I am not putting the unit in danger by having a 2 amp fuse instead of 10 amp fuse as the only downside is that it could blow prematurely well in the safety limits of the unit. Still, it seems like an odd mistake to make.

I'm thinking of picking up some of these: https://www.parts-express.com/10A-Fast- ... ck-071-315 in case the I blow another tube as I will destroy at least 1 fuse just confirming the bad tube. In this particular event I blew 2 extra just to diagnose the problem and the tube so I figure having some cheap fuses on hand to blow would be a good idea. What are your thoughts?

[roberto]

follow what the operating manual says. If you found a different fuse, the previous owner might changed it. Make sure it is the same rated fuse on the manual.

Happy listening!

[admin]

I agree, I think I'll get what the manual recommends. Even though I have not had any premature blowing of fuses with the current ones, I'll probably switch the fuses to the recommended value ones once I get them.

By any chance, does anybody know or have a picture of the original fuse that is included with the CJ ART amps?

[admin]

Ended up buying these: https://www.mouser.com/ProductDetail/576-0216010.HXP

It came out to $22 for 10 pieces (shipping included).

[AnotherJohnson]

It is not only possible, but likely, that a former owner would/could put in the wrong fuse.

Note that the 2 amp fuse isn’t regularly blowing … you are mostly operating the amp at under 250 Watts in, which translates to maybe 100 watts useful out tops. The point being that you’re not challenging the amp with either source or load.

As for what fuses to use, I’ve bought them from CJ. If there are any problems down the road, it’s the sure way to know that they’re not self inflicted. And it supports Jeff.

YMMV … mine does most of the time.

[Joe Appierto]

Ended up buying these: https://www.mouser.com/ProductDetail/576-0216010.HXP

Any reason why you ordered the fast blow 10A when the manual has them listed as the slow-blow (a/k/a T for timed) type?

[admin]

T type is fast blow. Pretty sure that is correct. I'm going to order some fuses from CJ directly and use the ones I just ordered as "diagnostic fuses" if another tube goes bad.

[admin]

Correction Joe. I ordered the fast blow because I'm an idiot and when I looked at the fuse that was in there by the previous owner it was a fast blow fuse! Since the manual says "T type" and the other fuses it says "slow blow", I presumed T type was fast. Wow, this thing is really getting messed up. So instead of a slow blow 10 amp fuse, they were fast 2 amp fuses in there (as it is currently as well). Oh, boy. Time to call and cancel an order. I'm going to order from CJ directly and look at what they are using to be sure.

[Joe Appierto]

CJ will send you the correct fuses for sure. Why the previous owner was using under-rated fuses and fast blow at that is surely a mystery. I know diddly about electrical stuff but I'm amazed anyway that the fuses he had in there ever survived the current inrush when the amps were turned on.

The only reason I know a little about fuses is because the CA200 (or at least the one I have) is not kind on fuses when it goes from standby to on due to the current inrush. A couple of weeks ago there was an electrical storm that caused the power in my apartment to flicker on and off a number of times before it finally went off for about three hours. When it came back on around 1 AM I stupidly decided to power-up the CA200 from standby and the XLT (extra slow blow) fuse I had in there popped. One thing I should've known from past experience is to never fully power it on when the demand on the electrical grid is low like early in the morning before work starts and the electrical demand on the grid hasn't ramped up as yet. But nooo, I had to play Russian Roulette. So please believe me, you aren't alone.

[admin]

I was able to cancel the order so no issues. The representative from mouser was super nice on the phone so I may order some correct backup fuses from them once this is all settled and I confirm the CJ specs.

I have no idea how the previous owner got the fuse specs so wrong? Luckily, he errored on the side of caution as the only side of going to lower amp and fast blow is premature blowing of the fuse. Much safer than going the opposite direction.

I hear you on the grid unreliability. That is one of the reasons I use a power condition and voltage regulator. Don't trust the power here.

[Big Dog RJ]

Ah! Welcome to the world of high powered "tube" monoblocks! That's pretty much what they are, and the main reason why I've settled for monoblocks that have only 4 output tubes per side. More the tooobs more the maintenance...
I'm no expert, still learning and have had my fair share of major disasters (VTL, Manley, Melos, Carver, Sonic Frontiers, Jadis etc.) I guess that's the way we all learn. One thing for sure is CJ's designs have never given me any major problems, only very minor and most due to voltage issues from the AC mains, other than that all tickety boo. AJ certainly knows his stuff and I'm sure that's where experience comes in

Similarly, I would replace ALL output tubes, for three basic reasons:

1. When a full set has been installed and that set has been properly matched, tested and burned in, they should all degrade around the same time. As long as no one has messed around with tube rolling...

2. CJ typically recommends 2 - 3 years of usage on average listening hours (2000 - 3000hrs) and then recommend a full tube replacement. I've always followed their advice and have never encountered anything bad regarding output tubes. Small signal tubes (input & driver) are slightly different, and must be used according to spec. Again when tube rolling is overdone, we have mucked around too much. Just replace it with the original tube, if it works that's all that matters, really!

3. Which leads to point 3; always better to install properly matched tube sets, especially output tubes. Confirmed that CJ and Upscale do this, without a doubt, and that's the price we pay. There are quite a number of other reputed suppliers that also offer this but sometimes I have my doubts, hence the price variance...

In CJ's owner's manual it clearly states how to identify bad output tubes; lightly tap each tube with the plastic wand, look for white flashes etc... this is all good if you have absolutely nothing else to do. I've got hardly any time to even take a leek... let alone enjoy a beer, so I just change all tubes when the time is up!

Fuses are not cheap either, these are top notch high grade ceramic fuses 600vdc something, can't remember since I've not looked at one for a while now. The primary function of these fuses are to protect the output transformers not the tubes. So a fuse blowing associated with distorted sound from that channel, pretty much involves a bad output tube.
Identifying which tube and replacing that tube is best, however in high powered amplifiers there are quite a lot of tubes to go through...

When it comes to those fuses, and especially those fuses, I've always ordered directly from CJ, no where else! Afterall, CJ are the ones that designed, calibrated and made these amplifiers, so in all do respect, there's no point cutting corners. They know their stuff in & out, and will only recommend and supply the best. Afterall, they want their customers to be very very happy

Obviously we all have different budgets and varied life circumstances to deal with. Therefore, we must make choices that suit our financial needs.

I'll say one thing though, when going for high powered amplifiers, and especially tube amps, you have to have the means of maintaining them, otherwise there's really no point in trying to make it work. Pretty much the same thing of a Lamborghini owner who doesn't want to spend the extra on top grade fuel, the super car still drives on normal fuel, in the long run is it the right fuel...?

As for me, I think once I can no longer afford to maintain my humble monoblocks, I'll most definitely just get a simple CAV45 or whatever version CJ may offer down the road and just settle with that! With a pair of mini ProAc's and a simple Rega TT, either way I'll be still enjoying those fine tunes!

Not to worry about it too much Admin, just get the matching ones and you'll be rewarded for life! It is what it is, and btw those are not one but two Lamborghini's you have! They deserve only the best mate, there are no compromises at this level. Believe me, I know.

Cheers, RJ

[Big Dog RJ]

Admin,

Nah mate, don't go there bud. I just saw the pics of those fuses... they're no where near the original quality of the fuses that come with the ART's, let alone even my own LP series amplifiers.

There's just no comparison by even looking at them, which concerns me about the quality sound... I don't think you should use these fuses at all mate. Just my sincere advice, that's all. Afterall, it's your decision and choice to use whatever suits.

Best, RJ

[AnotherJohnson]

I hope they listen to you. I didn’t bother to comment on the crummy wrong fuses … seemed futile.

As for “Why was the previous owner using the wrong fuse?

1. It was available at Walmart and it was the right geometry.

2. He was not cautious. He was buying the cheap stuff. If 20 amp were on sale, you would have found those.

3. It was too much trouble to get the right thing.

Some people know the price of everything and the value of nothing.

[admin]

I'm going to get the official CJ fuses to use in the amp. I already sent CJ an email. Hopefully, I'll hear back soon or I'll just give them a call.

I was thinking of getting those spare fuses from mouser.com only for using when I blow a tube and I have to put in a new fuse to find the bad tube again. In other words, it's not for listening (those would be the CJ supplied fuses), but rather for finding the bad tube (which seems like requires blowing an extra fuse or two).

[AnotherJohnson]

Yes, it could be good to have LOTS of spares if you are going to wait through one by one failure of the 16 tube set .

I keep a few in stock myself. But just a few. If you replace the tubes on a 2 to 3 year schedule, and they were 90th percentile tubes when they were installed, you may never need any.

[AnotherJohnson]

FWIW, I would not look for a tube failure by tapping.

It can work for some types of failures, but it has the downside of causing failure too.

I don’t think CJ offers this advice anymore… but I could be wrong.

Many of the tube electronics manufacturers suggested this at one time (EL34 era).

As for tube testers, they’re not especially reliable as 60 year old units. They don’t typically load the tubes as an audio amp would. I had a military surplus unit for many years, but gave it away as a curio about 10 years ago.

[roberto]

I'm confused, The Art amps use the KT150 tubes or am I wrong?

[Big Dog RJ]

Roger that AJ!

As always, spot on matey! That's basically vast experience and prior ownership of the best CJ has to offer. Very wise words indeed, and I learnt all this the very hard way... many many fingers burnt, sometimes still burning with after shocks!
When I saw those fuses, I nearly fell off my seat... was listening to Sarah Vaughan, Laura Fygi (however you spell her name) and Carmen McCrae, last night. BTW superb recordings all on SACD by Supreme Jazz.
That's why I replied to Admin straight in good faith... I hope he understands and doesn't take it the wrong way.

The ART's are basically CJ's SOTA! It really doesn't get any better than this. A few years ago, I was very fortunate to take on loan an ARTSA amplifier, whiles the owner went overseas for nearly 6 months! It was an absolute marvel! It drove my Quads and Maggie's so effortlessly as if it were horns! The owner had the ML Ren15a hybrid stats, and it was superb on that system as well.

The ARTsa is the stereo version and what Admin has are the monoblocks! These are way superior to the legendary Prem8A's which I also owned when we had the Apogee Diva's. So I'm not quite sure why on earth that previous owner used crappy fuses, other than the reasons you've outlined... still makes absolute nonsense to me, especially at this level???

I truly hope Admin will eventually get back to the right stuff and just let it settle down to full spec. Afterall, these deserve the best, like I said, there are absolutely no compromises in this league.

Attn: Robbo mate,

These are the original ART amplifiers that CJ offered just after the top of the line LP series amplifiers, which were the LP275M's ( same amplifiers that AJ has). These ART amplifiers came fitted with a choice of 6550C's, KT120's or EL34's based on the customer's preference. They are absolutely superb amplifiers!

After that, CJ didn't offer a statement product for a while. Then came along the GAT and the rest followed; GATS2, Classic series amps (60/se, 62/se, 120/se) and then CJ offered another new limited edition- ART series amplifiers, ART27A & ART150 (stereo amps) and ART300's (monoblocks). Only these latest generation ART amplifiers use the KT150 topology, with the exception of the ART27A that uses KT88's. No other CJ amplifiers use the KT150. Hence, these new ART amplifiers are quite different to the original ART's. In fact, I would say very different sound. Only previous owners of original ART's who have moved on to the new ART's would understand this difference.

Having extensive experience in auditions on both types, also with speakers and systems I'm quite familiar with, such as CLX's and ML Statements, I wouldn't say that the latest ART's are far superior but just unique in their own regard.

BTW, the only pair of monoblocks that CJ offers now are the ART300's, nothing else! The rest of their line up are all either stereo versions, integrateds or control amplifiers. I guess JF will narrow it further in time to come... might as well, afterall the brand's already operating in the ultra-high-end arena. Having secured several top awards, such as "amplifiers of the year," might as well be on a roll!

Whether or not CJ decides to continue with the Classic series amplifiers is upto JF. At this stage, I would highly recommend those who have LP series amplifiers, just hold onto them for long as possible, simply because this series was also CJ's SOTA but very very rare!

Cheers, and enjoy those fine tunes!
RJ

[roberto]

Thats correct, RJ,
My mind tricks me, I remember now that I had one mono block, and forgot it was the ART. The problem was a tube with Led on all the time. The bias resistor was fried, and the amp was playing...once I changed the 6550C and the resistor (5Watt 20 ohms), all led ok.

Thanks for the explanation!

Happy lisgening!

[roberto]

I found this on the Art Manual:

The ART Amplifier power transformer is protected by a fuse on the ac power line (F5, located in a compartment in the ac line-cord receptacle mounted on the back of the amplifier), and by four separate internal fuses on the secondary circuits of the transformer (F1 – F4) located on the bottom of the pc board. A failure of any of these fuses is a symptom of a more serious problem, and a competent service technician should be consulted. In no event should fuses be replaced with a value or type different than that originally supplied. The correct fuse values and types are:

F5: 5x20mm 10 amp T-type if configured for 100 or 120V:
5x20mm 6.3 amp T-type if configured for 220 or 240V.
F4: 3AG type 4 amp, slow blow
F1, F2, and F3: 1/4 amp, slow blow

Happy listening!