Thread: Any thoughts if this will get me into trouble (KT-150 related)?

So here I am thinking about trying to sell my ARTsa stereo amp. I absolutely love the CJ sound, but paid more for the amp than the sale price.

I do love KT-150 tubes in my little Jolida Fusion 3502 amp. Granted it's not a CJ amp but it does alright.

I know from friends and others that Audio Research finally "authorized" KT-150's for their KT-120 based amps. Eventually they offered an "SE" upgrade that changed the tubes and made available some circuit changes (supposedly) to take better advantage of the KT-150's. There is still some speculation on any transformer updates with no concrete answers that I know about.

Soooooooo, my thinking tells me that our CJ amps (especially the ART series) are capable of drop in replacement with KT-150's from the KT-120's. Of course they are not "optimized" for the tube, but I suspect there will be better performance and since the KT-150's are not run as hard (bias being the same as the KT-120), with longer tube life just like in the ARC amps.

I am SERIOUSLY considering ordering 8 (maybe 10 so I have 2 spares) matched KT-150's from a reputable dealer, drop them in my ARTsa, bias as usual and enjoy it/them until either the tubes need to be replaced or the amp need fixing.

What are your thoughts?

CJ refuses to discuss anything KT-150 related and I have been a fan since I can remember.

Are they gonna cover the warranty, Joe? if any problem occurs ?

Originally Posted by Paul

Are they gonna cover the warranty, Joe? if any problem occurs ?

Warranty? Hahahahahahahahahaha What warranty?

I'm a gambling kind of guy.

Joe.......I have to ask these questions. What is it you want to gain? What is the KT150's will provide that the KT-120's do not? Are you prepared to replace any hard parts that may fail from the tube change that might include transformers? If you're tinkering just for the sake of doing so, then have at it, but don't be surprised if everything doesn't come up roses.

I would try to contact and speak directly with a repair tech at CJ and ask your questions of this person before I would make the assumption that just tossing KT150's in your amp will automatically be a good thing. Forewarned is forearmed.

Originally Posted by joeinid

Warranty? Hahahahahahahahahaha What warranty?

I'm a gambling kind of guy.

Joe...have you listed the amp in Agon and for how long? Since it's only been a day since you listed it on AS, you might want to give it time to sell. You are offering a very good price so whether on AS or on Agon you should be able to get a buyer at that price (frankly I would list it at least at your cost and I think it would still sell eventually). Since you have the Monos, I think the stereo amp will give you similar sound but depending on speaker probably less dynamics and smaller staging cues (these are guesses), so you might as well stay with the monos and recoup your cost on the Stereo amp.

I have to agree with Dan, I would not just drop the KT-150 into the amp without checking with CJ. And if they are adamant on not responding to the question (which is kind of weird), then call a reputable tube tech/repair center (maybe the folks at Audio Classics even though they are primarily a McIntosh focused shop) and see if you can get them to opine on the possible dangers. My guess is though you need someone who is familiar with the circuit and transformers being used in the ARTSa to really be able to get an accurate opinion on doing this. Also, this is purely a guess, but my bet would be the KT-150s will give you perhaps a bit more bass slam and dynamic headroom than the KT-120s but the sonic signature should be very similar to the KT-120s, so what really do you get by trying this experiment out?

I don't mean to be a party pooper but in this scenario I would go better safe than sorry....

Thank you Dan for the reality check.

I have though of these questions. I like what the KT-150's sound like in the Jolida and from what others say too. I know ARC amps were not originally designed for the KT-150's but they gave their blessing.

I feel the CJ amps are of sufficient quality that yes, if there is an issue, just replace any broken parts, but I don't "expect" trouble, but am prepared for the consequences.

I know, leave well enough alone, but I have confidence in the gear. I would not do it in the ART monos, only the ARTsa stereo if it does not sell.

Originally Posted by Double-D

Joe.......I have to ask these questions. What is it you want to gain? What is the KT150's will provide that the KT-120's do not? Are you prepared to replace any hard parts that may fail from the tube change that might include transformers? If you're tinkering just for the sake of doing so, then have at it, but don't be surprised if everything doesn't come up roses.

I would try to contact and speak directly with a repair tech at CJ and ask your questions of this person before I would make the assumption that just tossing KT150's in your amp will automatically be a good thing. Forewarned is forearmed.

Cyril,

It's listed at the usual spots. I do think it will sell, but I am prepared to play if that price is not met. I will do a little more research once I decide to buy that many KT-150's. I appreciate your concern.

Joe.......Just because ARC amps tolerated KT150's in place of KT120's before the manufacturer bestowed a blessing has no bearing on how the CJ amp will fare. As for CJ's silence, no answer IS an answer if you read into it. Perhaps it will be smooth sailing and you may have Murphy at your back. Then again......

I agree with Cyril and Dan. Curiosity killed the cat....or something like that.

Leave it in the box, sell it, move onward.

I'm not concerned in the least with the K150's not working in the CJ amp. BUT, if you want to go KT-150, you need an amp that's been designed specifically to take advantage of the new tube.

Here is the deal: ARC has not changed output transformers or the power transformer on the Ref 75SE version of their amp. If an amp can safely run KT-120s, it should safely run KT-150s as well. The KT-120 tubes are designed to draw 1.7-1.95A of heater current. The KT-150s are 1.75-2.0A. Neither the KT-120s or KT-150s will output more power than the circuit they are in will allow. That is why the power output ratings didn't change when ARC switched over to the KT-150 tubes. They would need a bigger power transformer to supply the higher voltages both tubes are capable of accepting and then the output transformers would need to be changed as well to accommodate the higher output power. Both the KT-120 and KT-150 tubes are loafing in circuits that were never designed to come close to the max ratings of these tubes. Remember that ARC and others routinely claimed 75 watts of output power for their amps that had a pair of 6550 tubes.

As someone who has experience listening to the KT-120s and the KT-150s in the Ref 75, I can tell you the KT-150 is the better sounding tube from top to bottom.

Originally Posted by Mike

I agree with Cyril and Dan. Curiosity killed the cat....or something like that.

Leave it in the box, sell it, move onward.

I'm not concerned in the least with the K150's not working in the CJ amp. BUT, if you want to go KT-150, you need an amp that's been designed specifically to take advantage of the new tube.

I understand what you are saying Mike. I have a few serious inquiries, so keep your fingers crossed.

Originally Posted by mep

Here is the deal: ARC has not changed output transformers or the power transformer on the Ref 75SE version of their amp. If an amp can safely run KT-120s, it should safely run KT-150s as well. The KT-120 tubes are designed to draw 1.7-1.95A of heater current. The KT-150s are 1.75-2.0A. Neither the KT-120s or KT-150s will output more power than the circuit they are in will allow. That is why the power output ratings didn't change when ARC switched over to the KT-150 tubes. They would need a bigger power transformer to supply the higher voltages both tubes are capable of accepting and then the output transformers would need to be changed as well to accommodate the higher output power. Both the KT-120 and KT-150 tubes are loafing in circuits that were designed to come close to the max ratings of these tubes. Remember that ARC and others routinely claimed 75 watts of output power for their amps that had a pair of 6550 tubes.

As someone who has experience listening to the KT-120s and the KT-150s in the Ref 75, I can tell you the KT-150 is the better sounding tube from top to bottom.

Mark,

Thank you for the explanation. I had pulled up the tube data and you more than confirm what I was reading. I sincerely appreciate your perspective as it relates to ARC.