Conrad Johnson ART amplifier fuse blown

[admin]

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

https://conradjohnson.com/conrad-johnson-art-amplifier/

KT120's.

[roberto]

Oh! What a big mistake,

Definitively I'm getting old. The new model says the tube, Art150 (Stereo) and the mono blocks Art300. (KT-150).

The ones that you have to my ears, are the ones!. I did listen for over a month, a pair of Art300. Big sound, but my liking is the KT-120s, not the KT-150s. The exaggeration of the musical notes while the dynamics occurs, is not my liking. That's the reason why I am using the Classic One Twenty SE. This is a monster amp too, and I do not envy the owner of those two big monsters. They were exhibiting a problem while dynamics happened. There were a kind of stress and a little dirt on some instruments, specially with winds ad voices.

Believe when I tell you that the problem was his AC line conditioner. I plugged them with my BPT BP-3.5 Signature Plus and I could not hear a thing...everything was BIG ...and the level that I usually use...clean with the signature of CJ magic of course. A pair of big monsters, but they are not for me. That's the reason I said before that perhaps your AC conditioner was causing a problem. I do believe in you're ears and they told you that the sound is perfect, no stress at all.

Remember, this is my liking and not necessary must be yours!

Happy listening!

[Big Dog RJ]

Spot on there Robbo mate!

Don't want to hijack this thread, afterall we're here to help Admin with his tooobs and fuses...

I'll just mention though briefly, that the ART150 has been ordered. It's been a few months now, and still waiting. Most probably Oct end. If I like it, I'll keep it but if not I'll return it. I'm sure there will be quite a few interested but not too sure since we're talking around 30grand! Just for a power amplifier, that's top dollar.

My experience with the new ART series amplifiers have been very interesting. It was a great learning curve no doubt. The ART150 and 300's are capable of delivering serious pressure levels, as long as the speakers are up to par. JF uses top line Zellatons with the ART300's so that's basically saying something. They are able to drive efficiently to the point of where the limitations would be in the speakers and room, basically nothing else. They can hold strong, with no break up and zero distortion, absolutely flawless! In other words, they can play really really loud. So if you're into that kind of presentation, full orchestra, rock concert or massive stage affects, and want the full scale delivered, these ART amplifiers can do exactly that! No other CJ amplifiers can do that under those kind of parameters, simply because it's the KT150 topology that enables this extra thunderous bloom.

I'm definitely not one of those who even likes this sort of presentation. I just prefer a more relaxed, softer approach with an intimate setting. My listening sessions are way past midnight, whiles I'm typing this it's now 1:41am. So my need for that kind of volume is totally unnecessary. With the amplifiers I've already got, having 125w of Class AB plus a modded 60w of Class A, during these late night sessions, I don't think the amps deliver more than 10w! So why bother?

However, if you're into that type of performance and huge presentation, and have the speakers to handle that kind of power plus the large room, then it doesn't get any better than the ART300's.

So, just to try out how better or worse the CLX's can deliver scale, I will give it a go. I highly doubt it that I would prefer that sound, I've achieved what I'm looking for and that's about it. So we'll see how it goes just for fun.

Similarly Robbo mate, you've found your liking with the Classic 120se, that's your preference and it's more than plenty of power and current to drive the CLX's to their full potential. Trust me, I know!

Just sit back and enjoy those fine tunes!
Woof! RJ

[admin]

Go ahead with the hijacking, I love tangents like this!

I emailed CJ two days ago but have not heard back. I also tried calling but it went to their voicemail but I didn't leave a message as I was at work. I'll probably give them another call on Monday if I don't get an email response. I'm sure they are pretty busy.

In the mean time. I did order some fuses (this time the correct values, 10 amp slow blow) from mouser. Again, I just want to have some spares for diagnostic purposes and to hold me over until I get the official ones from CJ. They are made by a reputable electronics manufacturer (Littlefuse) so they should be up to their spec requirement.

I'm still considering a full new set of tubes but I actually wanted to talk with CJ and see what they recommend. Also, maybe get a quote from them if I buy directly.

The stereo is sounding great, but now I know I'm running the wrong fuse type I am paranoid! I'll keep you guys updated.

[Big Dog RJ]

For what it's worth mentioning Admin,

I wouldn't change those original ART's for anything! Simply because I just happen to love the 6N30P and M8080 tubes in those amplifiers. They're one of the most musical and satisfying combinations, and this is what C&J's team decided to use.

With the newer SOTA offerings, these tubes are no longer used in any of their applications, so that's the main reason for that specific change in sound/presentation. I guess it's a highly personal thing! It really is.

Just sit back and enjoy those fine tunes matey
Best, RJ

[AnotherJohnson]

The KT120s are the way to go.

CJ’s prices will be high … you’re paying for their expertise and they do not have the turnover of Upscale.

Buy from CJ to support CJ’s continued existence.

Save money without worry with Kevin.

Save more money with Bobby’s supplier.

[admin]

So I'm still waiting to hear back from CJ about the fuse replacements.

But the plot thickens. So I got my "replacement fuses" from mouser and as soon as I saw them I was "this can't be right." The size of the fuse the manual calls for is not the same size as what is in the unit. The back fuse is a much larger fuse, not 5x20 mm but more like 10x38mm or so.

Any chance that the manual could be wrong as I'm pretty sure my unit is not modified? Here are the pictures of the two fuses, the left which came from the unit and the ones I ordered and the manual calls for.

20211004_174533a.jpg

[AnotherJohnson]

Did you email, or call?
Calling persistently (couple times a day) is the best bet.
Small shop, small staff.

I was surprised at the manual. The fusing looks significantly different from the fusing in the LP275M. (Edit: turns out it’s not. Neither manual describe the plate fuses.)

Usually there are a couple of plate fuses. The 10 amp fuse looks like it’s on the power input.

In any event, you could also call the CJ Flagship dealer in NYC. Personally, I’d stay after JF by calling at different times. Don’t be bashful… let him know you’re running the CJO forum and you need his help.

[AnotherJohnson]

Mine are KTK-2, but that’s not what’s called out in the Art OM.

[Joe Appierto]

I think AJ has this one nailed. The one on the right if it's like my CA200 is for the IEC inlet and it's in a little drawer either above or below where you plug in the female end of the power cord. You pop out the drawer to replace the fuse.

The other 4 fuses are internal,

[AnotherJohnson]

Conrad-Johnson Flagship Dealer - Audioarts NYC
210 Fifth Avenue New York, NY 10010
Call 212.260.2939

https://www.audioartsnyc.com/

Something has happened. They do not list CJ as their product anymore. But CJ still has them listed as their flagship.

NYC has been crippled by cuomovid_diblasiovid-19 and perhaps they’ve parted ways with CJ.

Steve Javaherian might know what’s correct, or he may know how to get a quick response from JF.

[admin]

I sent CJ an email a few days ago. I did try to call twice last week (but didn't leave a message) and then I called this afternoon and did leave a message for call back. I'm not in a rush and I'm sure they are busy so I'm patient.

I have to believe that the manual is a mistake as the fuse holder on the back certainly does not fit a small 5x10 mm fuse. It's held by a screw in holder that is easily accessible on the back of the unit.

AJ, the fuses that were in there were also KTK-2 which makes me think that that would be the correct fuse but I want to get confirmation from CJ first before ordering anything else. Maybe the original owner did have the correct fuse types in?

[Big Dog RJ]

Yes, that's the correct fuse in your case KTK-2. In my case KTK-1. These fuses are the ones that sit behind protecting the output trannys.

The other plate fuses are pretty much standard type. You can get standard versions, audiophile grade versions and so on... as long as they are of the correct type of fuse. Same goes with the mains plate fuse that's located next to the IEC power cord inlet (AC mains on the amplifiers).

It is this special type of fuse that's only located at the back to protect the output transformers, which only CJ supplies. You can source these special types of fuses from other suppliers and they are available, it's a matter of finding the right supplier. However, since CJ stocks and offers these on their amplifiers, it would make more sense to order directly from them.

In past, within the owners manual, CJ used to provide two spare fuses of these specific types. They were offered within the plastic sleeve that came along with the owner's manual and plastic wand for biasing tubes.

However, now CJ doesn't offer these fuses for free... and I'm not sure of these specific large type of fuses are used in their newer designs. I know the ART amplifiers do use these fuse types and in the LP series amplifiers. Not too sure about the other Classic series and new ART series amplifiers. I think they just use standard ceramic type now, since most of these fuses are not easily accessible. You have to actually turn the amp upside-down or onto one side and take off the bottom plate to access these fuses, and there you will see pretty standard fuses but mostly ceramic type. I could be wrong in regards to CJ's newer offerings, simply because I've never had to change fuses.

However, this large type of output transformer fuse are the ones that every CJ amplifier used within the Premier series all the way upto the LP and original ART series amps. They are housed in its own screw-type cradle which has an associated LED to it. When that LED lights up, it's basically a fuse blown which results in a bad output tube... which was tge case in Admin's amplifiers.

In the case of CJ's newest offerings, they no longer use this srew-type cradle. Rather, the fuses are all located at the bottom, hence you have to take off the bottom plate... it was much easier then, not now.

Here's a pic, looks similar but my monoblocks are less in power. The number on the far right indicates the Amperage value. In the case of KTK-2 (2 Amps). The rest of the fuses in my amps are standard ceramic type. There's only one of these huge buggers in each amp.

Cheers, RJ

[Big Dog RJ]

I'd be very surprised if the owners manual is incorrect. That's a serious issue relating to amperage... not something to mess with. I think you need to contact JF asap!

Wondering why they're not responding, which could also relate to the very slow response from our CJ Aus end... I reckon two things here:
1. Thanks to covid, everything and everyone's out of whack
2. Maybe they all went fishing

Usually owners manuals are required to be correct, with a few grammatical errors, which I've found in CJ's manuals as well. I've sent them numerous notes about this but back then they all actually went fishing. By that time, C& J retired and transferred ownership to JF, so I didn't bother since. It's just grammar and nothing life threatening

Hope it all works out well Admin. Don't stress too much, eventually you'll get there.
Cheers, RJ

[admin]

It is unusual. But a 5x10 mm fuse is really tiny to be mounted on the back of the unit with a twist cap holder and considering the KTK-2 seems a much more appropriate size, the the previous owner had KTK-2's in there, and the fact that your picture of the KTK-1 is so similar it really does make me believe that the manual is in error.

I left a message on CJ's voice mail late yesterday afternoon so I do want to give them 24 hours to respond before calling again, but I will call tomorrow morning if I don't hear anything.

[AnotherJohnson]

The owner’s manuals are woefully short of useful info.

It’s the same drivel that was in the manuals 35 years ago.

If the Art came with KTK-2 fuses on either side of the back, then those are the plate fuses, and I don’t see them in the OM.

Those are the fuses notoriously difficult to find, and so replaced by other amperage by exasperated or cheapskate owners.

I guess we all need a video to watch what’s actually happening during troubleshooting.

I guess admin’s got his amps up and running. That’s good.

As for CJ, and many other small shops, I’d stay after them on the phone. You need to randomly catch them answering. Messages will be summarily ignored.

[admin]

AJ,
Yup, the amps are up and running with the replacement KTK-2 fuses I had as extra from the previous owner. I'm really thinking that these are the correct fuses but I'm waiting to talk with CJ to get the official word.

The manual mentions nothing about these fuses but seems to indicate wrongly that they should be 10 amp slow blow instead.

I've found manuals for many high end audio very lacking as you mention. Not sure why this is but it seems true. Even my most recent Holo Audio May DAC came with a very paltry few page manual that illustrates button function but really doesn't go into any detail about what the different modes are doing specifically. It is however nicely laminated... I'm ok with this as I rarely go reading the manuals but I am a little surprised that the ART manual would have the wrong fuse descriptions.

[AnotherJohnson]

Just for grins I looked at my LP275M manual. As you know, the Art descended from the LP275M.

It is the same spiel as in the Art manual. No mention of the plate fuses.

The plate fuses are installed on each side in tubular compartments on either side.

These KTK-2 fuses blow when a tube runs away.

I’d bet a buck that the Arts use the KTK-2 in this application too. The power level and tubes are essentially the same.

[AnotherJohnson]

And, more importantly, since they are not readily available for local purchase, this supports my advice to replace the tubes after the constant hazard rate regime has run its course. If you buy good tubes, and replace them every 2000 hours, you may never need to replace the KTK-2. One or two spares are plenty.

[AnotherJohnson]

It isn’t that they list the wrong fuses.

It’s that they don’t mention the KTK-2s.