CJ: New 40th Anniversary ART Amps

LL21

Active Member
Dec 26, 2010
10,573
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#1
Anyone know more about the new 40th Anniversary CJ ART amps?

conrad_johnson_art_amp.jpg

From The Audio Beat: http://www.theaudiobeat.com/news/conrad_johnson_art150_art300.htm

Fortieth-Anniversary Amplifiers from Conrad-Johnson

by The Audio Beat | April 13, 2017

Conrad-Johnson has marked its 40th anniversary with two new amplifiers, both of which use KT150 output tubes, the first time these tubes have been used by the company.

A single pair of KT150s produces 150 watts per channel from the ART150 stereo amplifier ($18,500), while two pairs of the tubes produce 300 watts from each ART300 monoblock ($36,000/pair). In addition to utilizing the KT150 output tubes, the ART150 and ART300 have new input and inverter stages that use 6922s for voltage gain. The amps' main power-supply reservoirs have a more than tenfold increase in total capacitance compared to Conrad-Johnson's earlier ART and ARTSA amplifiers. The 40th-anniversary amps also feature a new regulator circuit for the input-stage power supply.

New styling puts the output tubes behind a clear window spanning the full width of a protective tube cage, while the input tubes are encased in a clear protective block.

As with earlier Conrad-Johnson anniversary electronics, production will be limited: 250 of the ART150 and 125 pairs of the ART300.

© The Audio Beat • Nothing on this site may
 
May 30, 2010
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#2
Anyone know more about the new 40th Anniversary CJ ART amps?
(...)
It is a turn face in their current ART. They are taking a lot of power from a quartet of KT150's - the ARC REF150 for example uses a quartet of KT150s to get 150W. Also they are returning to the 6922 tube - in the GAT2 they were using PCC88's to replace the 6922's. The ten fold increase in power capacitance suggest they are also changing the type of power capacitors.
 

bonzo75

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Feb 26, 2014
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#3
It is a turn face in their current ART. They are taking a lot of power from a quartet of KT150's - the ARC REF150 for example uses a quartet of KT150s to get 150W. Also they are returning to the 6922 tube - in the GAT2 they were using PCC88's to replace the 6922's. The ten fold increase in power capacitance suggest they are also changing the type of power capacitors.
Ayon Orthos uses 10 kt 150 per mono to get 300w triode, 400 pentode
 

XV-1

Active Member
May 24, 2010
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Sydney
#4
Quite weird for the conservative conrad johnson to be leading edge in using a lot less KT150's than others to produce 150/300 watts of power.

Proof will be in the sound. But no doubt Lew and Conrad have tested reliability of less power tubes to produce more power and also the sound quality vs the magnificent ART 6550/KT120 amps. Paradigm shift indeed for cj. :cool:

can't wait for the first review's.
 
Feb 3, 2012
614
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Melbourne
#6
Yes no doubt, heading towards a major change for CJ with this one particular tube, and looks like CJ certainly took their time.

I have auditioned an Ayon integrated with KT150's, it was an "overblown" sound driving a pair of Dynaudio's. We then switched over to stats- ML Ethos, Summit-X and the Montis, just to see if stats would reproduce the sound any better. If anything, it was actually worse!
Ventured back to a Pass Labs combination and preferred that by a huge margin. This was during a demo at the ML dealer's just as I was closing the purchase on the Ethos, last year.

I had a similar experience with some of ARC's new gear, as well as a REF75se fitted with KT150's. Again that sort of fat and over the top artificial hifi sound. It was no doubt very dynamic, thunderous impact, all the transient response required with plenty of slam but it just didn't have that musicality factor. Compared to the KT120, with almost similar specs, I actually prefer the KT120. However, in terms of pure musical bliss and that magical midrange, my overall preference is the EL34.

I am eagerly waiting to audition CJ's new Classic amps- version 2; delivering 120w in EL34 or KT120 config but nothing has arrived in Melbourne as yet. I was told they are waiting to sell off the old stock first, as this makes perfect sense. Apart from that, forget the price! This is for the "top dollar earner" no doubt!
The starting tags on the Classic 60 and 120 version two's start at 10 grand and go upto 15 grand depending on which tubes you want. The tags on these anniversary amps will be around 45 - 50 grand, let alone the ART amps which are now offered at 38 grand.

So, yes I will be the one very keen chappy to audition this, since I have a long term relationship with CJ. Having said that, we just celebrated our 16th wedding anniversary last Sat, and since that is also a somewhat "longish" relationship, if I want it to continue "happily ever after," I don't think I will be heading towards CJ's new line up! I'd probably get me butt kicked to a galaxy far far away...

Having said that, the boss did allow a small peek towards the Classic 120 (in EL34 version) just for curiosity, and to keep me looking eager... after all 16 years of marriage, sometimes the enthusiasm drops a tad...

As for now, she reckons the CAV45 is more than adequate! Oh well, I guess she's right. It's 11:15pm, I've got the next 2 days off, so now I'm heading towards that musical bliss, might as well just sit down and enjoy the music!

For those lucky chaps and fellow audiophiles who get a chance to audition these beauties, please do let us know. Looks pretty cool especially with the clear cage, nice touch.
Cheers, RJ
 

Marcus

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Oct 5, 2012
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#7

LL21

Active Member
Dec 26, 2010
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#8
May 30, 2010
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#9
I think Myles Astor will be the first to review ART300. You can already read his first impressions on AN.

https://www.audionirvana.org/forum/...n-40th-anniversary-art300s-monos-in-the-house
You guessed it right - he was the first and really liked them. We can read it at PositiveFeedback. https://positive-feedback.com/audio-discourse/conrad-johnson-40th-anniversary-art300-monoblock-tube-amplifiers-part-1-forty-years-and-still-going-strong/

The interview with cj Jeff Fischel also brings some new details about the KT150's. I was particularly interested on his view on reliability

"JF: We took a wait and see approach. We first made a prototype amplifier and tested that for a year. That amplifier ran for 60 to 70 hours a week for 52 weeks straight. We wanted to test the KT150's for long term reliability. Out of 100s of KT150s, we've had one fail so far."

Really good news for KT150 users!
 

LL21

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Dec 26, 2010
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#10

LL21

Active Member
Dec 26, 2010
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#11
XV1, Micro, Big Dog RJ...any new news on the ART 300s? Just curious if any of you have heard it, or spoken with someone besides Myles who has? Thanks for an update.
 
Feb 3, 2012
614
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#12
Hey LL, how's it going mate;
Not yet on the ART300's but the ART150 yes, taking place soon.
The top bloke who has the ML Ren15A, pairing with his GatS2, which was the one I heard on both versions (GAT & GAT S2) was also using the classic 120 in both versions standard & SE plus using EL34's. Now has ordered the ART150 and will arrive Sept according to him, the chappy travels an awful lot... The audition will take place only around Oct, an initial invite has been sent my way, to justify the purchase. He further states that if the Art150 can't handle the Ren15A's panels, he will then settle for the Art300's.

Oh well, I guess something's along the way, I'll have to wait till he's in a great mood for sound...
Will keep you posted.
Cheers RJ
 

tonytsui

New Member
Apr 21, 2014
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#13
Hi everyone, I have been reading this forum for quite some time, but think it's time to contribute my experience. I have been using the ART300 since last August, together with the GATs2, EMM Labs TX2 and DA2, Magico Q7 with Nordost cabling. Compared to the ART, the 300 is a much better amp, with staggering micro and macro dynamics, lots of details and a big big soundstage. Unlike some highly touted SS amps, at high volumes the ART300 doesn't change character and maintains its composure. However, I suggest user tests the tubes which come with CJ. One EH6922 and KT150 had measurement problems. And similar though for a lesser extent, there's still a problem with the H to K leakage of the KT150s. This leakage was a major problem with the KT120s when I had the ART. Unlike the ART which uses M8080 and 6H30p, the ART300 uses two 6922s and has great opportunities to tube roll. I have tried many brands and am now using two sets of Mullard E188s. The ART300 requires hundreds of hours of running in and requires the best of cabling. Together with Odin 2 speaker cables, I was finally able not only to tame the highs of the Q7, but produce beautiful strings which I had thought the Q7 was not able to.
Tony from Hong Kong
 

Marcus

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Oct 5, 2012
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#14
This leakage was a major problem with the KT120s when I had the ART.
Tony from Hong Kong
Hi Tony. Can you describe this problem you had with KT120 tubes and how did you solve it?
 

tonytsui

New Member
Apr 21, 2014
16
0
1
#15
Hi Marcus, it's a long story. I use an Amplitrex to test all tubes, and the Tung Sol spec of H to K leakage of the KT120 is not more than 30uA. However, for a new tube after a few months use this spec could exceed 30 to over 100. Knowing little about the effect of a higher than 30uA spec, I did ask Tung Sol and others but received no satisfactory answer. The fact is the failure rate is very high. There's no way to solve it except to replace the tube with a new one, and I can tell you I have dozens of used KT120s with high H to K leakage but good emission and transconductance. This did not just happen to me - same applied to friends using the ART with KT120s. Was it the ART? I don't think so.
 
May 30, 2010
14,145
86
48
Portugal
#16
Hi everyone, I have been reading this forum for quite some time, but think it's time to contribute my experience. I have been using the ART300 since last August, together with the GATs2, EMM Labs TX2 and DA2, Magico Q7 with Nordost cabling. Compared to the ART, the 300 is a much better amp, with staggering micro and macro dynamics, lots of details and a big big soundstage. Unlike some highly touted SS amps, at high volumes the ART300 doesn't change character and maintains its composure. However, I suggest user tests the tubes which come with CJ. One EH6922 and KT150 had measurement problems. And similar though for a lesser extent, there's still a problem with the H to K leakage of the KT150s. This leakage was a major problem with the KT120s when I had the ART. Unlike the ART which uses M8080 and 6H30p, the ART300 uses two 6922s and has great opportunities to tube roll. I have tried many brands and am now using two sets of Mullard E188s. The ART300 requires hundreds of hours of running in and requires the best of cabling. Together with Odin 2 speaker cables, I was finally able not only to tame the highs of the Q7, but produce beautiful strings which I had thought the Q7 was not able to.
Tony from Hong Kong
I do not have the diagram of the circuit of the ART's with me, but as far as I remember the cathodes are grounded through 20 ohm resistors - I can't see why heater to cathode leakage should be a problem? Usually leakage becomes a problem if there is a significant negative voltage difference between heater and cathode. At what voltage does your tester measure leakage?

I have used many tens of KT120s in ARC and cj amplifiers, including LP275m and ART. They were mainly sourced from German suppliers, surely not burned-in, and I would rate failure rate at less than 5% - usually grid current or noise.

BTW, perhaps it is just superstition when applied to KT120's or KT150's, but I use Ralph Karsten burn-in techniques - before applying HV I burn-in the filaments for 100 hours. If it was good for the 6AS7s it should be good for the KT's!
 

Marcus

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Oct 5, 2012
212
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#17
Hi Marcus, it's a long story. I use an Amplitrex to test all tubes, and the Tung Sol spec of H to K leakage of the KT120 is not more than 30uA. However, for a new tube after a few months use this spec could exceed 30 to over 100. Knowing little about the effect of a higher than 30uA spec, I did ask Tung Sol and others but received no satisfactory answer. The fact is the failure rate is very high. There's no way to solve it except to replace the tube with a new one, and I can tell you I have dozens of used KT120s with high H to K leakage but good emission and transconductance. This did not just happen to me - same applied to friends using the ART with KT120s. Was it the ART? I don't think so.
Thank your Tony for the answer. How did this problem affect the sound quality?
 

tonytsui

New Member
Apr 21, 2014
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#19
Thank your Tony for the answer. How did this problem affect the sound quality?
A tube seller advised high H to K leakage would induce hum but I didn’t hear any. To me the midrange and upper midrange became a bit coarse and slightly bright in a bad sense.
 
May 30, 2010
14,145
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#20
Hi Microstrip, the test parameters are : eP 400, eG2 225, eHTR 6.3, iP 140, iG2 10, GM 12.6
Thanks - I looked at the Amplitrex manual and the cj diagram. In the LP275m cj uses a floating secondary for filaments and uses a resistor divider to keep it at around +100V - this should avoid any leakage, unless it is ohmic (perhaps poor insulation). Theoretically if the cathode is negative relative to filament there is no electron emission.

Can you try burning the filaments for a few hundred hours and repeating the measurement with the Amplitrex? Do you measure any finite resistance with an ohmmeter between filament and cathode?
 

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