Conrad Johnson Owners & Discussion Thread

[muon*]

It's a simple job really.

The ultralinear connection from the output tube's screen to transformer is removed and that screen gets connected to the tubes anode via a resistor instead.

 

But you want someone competent doing the work, hopefully they remove the GNFB if there is any at the same time, It's not needed once the output tubes are triode strapped.

 

This is a Pentode strapped.

[evil c]

TUBE ROLLING:

Both my current Conrad Johnson, 

GAT preamplifier and ET250S power amp use 6922 tubes or equivalents. 

 

I've found the best results using old NOS 1974 Amperex Holland 6ES8 ECC189 tubes with my GAT, and very happy with JJ E88CC Gold pin tubes in the power amp. 

The Amperex are very smooth, holographic and detailed to my ears, and the JJ a good match with a bit more brightness to balance.

 

I've used many of the better known  variants , like Genalex and Sovtek Reflector plus NOS  6922 / 6ES8 tubes of various types.

 

I'm interested in other CJ owners impressions on tubes they've used and prefer (?)

[Ian McP]

Evil C

 

GE5670 as 6922 (adapter rearranges a few pins) as used by iFi

 

https://www.stereonet.com/forums/classifieds/item/1570-ifi-audio-premium-nos-6922-tubes-valvestubes/

 

back story on oddball substitutes for 6922, a great read!

 

https://www.audiocircle.com/index.php?topic=148150.0

[evil c]

20 hours ago, Ian McP said:

Evil C

 

GE5670 as 6922 (adapter rearranges a few pins) as used by iFi

 

https://www.stereonet.com/forums/classifieds/item/1570-ifi-audio-premium-nos-6922-tubes-valvestubes/

 

back story on oddball substitutes for 6922, a great read!

 

https://www.audiocircle.com/index.php?topic=148150.0

Very interesting indeed Ian.

I am well acquainted with the 5670 JAN tubes, used them very successfully in my Melody SP1 amplifier and a very sweet sounding tube ! 

Would l trust using a non compatible pin tube with a converter on an ultra exxy pre like the GAT? 

Not a chance, unless my CJ tech gave me the go ahead !,

It would most likely be ok, but couldn't live with the slightest doubt in damage occurring! 

Edited June 1, 2024 by evil c

[La scala]

Yesterday eve , scratched a big itch to experience Pre Amps predictions..... , the CJ Premier 7b Pre vs Pass Labs x2.5 Pre amp for a quick comparison , one being  a half decent solid state offering vs a tubed state of the art vintage glamour. Let some music play ....
My God the CJ made music , so engaging , realistic , coherent and just took you away.

Amazed how otherwise poorer recordings just come to live , it’s retrieval of details and textures simply amazes.

Poor pass pre amp performance is not worth mentioning, not even remotely fair to compare.

It goes to show how easy it is to go on the Power Amp swaps merry go around when the heart is in a beaut Pre amp , the audio difference is spellbinding. 
V from studio 23 

Edited June 17, 2024 by La scala
Error

[La scala]

A very exciting second preamp comparison with the imho Devine CJ Premier 7B vs my lovely Supratek base model Pre which also elevated my system to new heights more than ever expected , just adore tube preamps.

The Supratek this time was in the running at least , and as nice as it is , the CJ delivered much more , and as it should  with a 4x higher price tag.

Listening this time to the more basic modded Klipsch  La Scala workhorse single amp system ,  juiced by CJ Premier 5 mono blocks  , the CJ Pre once again had me in awe with greater separation , greater realism and such lovely captivating musicality. 
Lower bass was perhaps a tiny hint shy as one highly respected fellow observed. 
I could have listened to it forever but the CJ is sadly going to a new home I am told  , darn I’d really love one, darn they are still so pricey, darn I can’t get that sound out of my mind...

 

If any similar sounding CJ Pre Amp are known to be for sale , I am very keen to get my hands on one.

Happy days V - studio 23

 

[cafe latte]

I have quite a few amp, but in my collection I have a Premier 4 power and and a Premier 3 preamp with a rather special story attached.

My good friend Keith who used to own a hifi shop, he actually got me into this hobby was talking about this Premier 4 he had that was broken. He said three repair shops had tried to fix it and it was still at thr last shop where it had been for a couple of years. I told him to see if he could get it back. The shop owner found it and gave it back to Keith a few weeks later.

I was in the UK on holiday so I had a look, it was a real mess, tracks had vapourised and worse the people who had looked at it had removed and changed things.

I googled and found a circuit diagram, repaired the tracks and the blown components and it worked!

Keith was made up he had his amp back. I came back home to Aus, unknown to me at thr time Keith had terminal cancer, he was taking marijuana for pain when a bias light came on and he decided to bias it stoned with a metal screw driver.

He slips with the screw driver.... BANG!!

He posted the boards to Aus and I repaired thrmem again. The sad part is he never got to hear the CJ again.

We spoke four times on his last days just before Christmas a few years ago, thr last day he could not talk it was just me, then he passed..

He left the amps to me so they are rather special to me. It was seriously expensive to get thrm posted from thr UK too but we'll worth it.

Anyway that is my CJ story.

Chris

[Dinu]

Hi Thelastjedi,

                            Good Day!!! I realize this topic is two years old, but I'm new to stereonet, having joined just a few weeks ago. First, congratulations on your CJ LS17 preamplifier! Which power amp do you have connected to it? I also own a CJ LS17 SE preamp, and it sounds beautiful when paired with the right power amp. I've noticed that CJ preamps perform best with their own power amps. I've had some success matching them with Manley and VTL power amps, but I haven't found any solid-state options that work well with CJ. If you or any other experts have had success with different power amps, please share your experiences.

 

Dinu

[jon96789]

My MV-60 "sparked" and the left channel went out.  The sound from that side is soft and distorted. Atech took a look at the amp and said the only thing he could find was that the fuse blew. He has been running the amp for a couple of weeks and he says its been fine.  My question is what would cause this issue.  Apparently it is not unusual as some others have told me that they encountered the same problem so they keep spare fuses around when this happens. 

[evil c]

2 hours ago, jon96789 said:

My MV-60 "sparked" and the left channel went out.  The sound from that side is soft and distorted. Atech took a look at the amp and said the only thing he could find was that the fuse blew. He has been running the amp for a couple of weeks and he says its been fine.  My question is what would cause this issue.  Apparently it is not unusual as some others have told me that they encountered the same problem so they keep spare fuses around when this happens. 

Sounds like it could be a "bad" tube.

They will blow the fuse and often a resistor.

Get a tech to test all your  tubes to find the dud one, or replace all 4 output tubes if a few years old and don't mind spending. 

[cafe latte]

24 minutes ago, evil c said:

Sounds like it could be a "bad" tube.

They will blow the fuse and often a resistor.

Get a tech to test all your  tubes to find the dud one, or replace all 4 output tubes if a few years old and don't mind spending. 

I agree,

On my Premier 4, when the valve failed for my friend it took out bias resistors and vaporised some tracks which i managed to fix. He left the amp to me when he passed away, I make sure I replace valves ahead of time as a damage preventative.

Cheers

Chris

[jon96789]

I popped all four tubes into another amp and they biased fine.  I ran them for about a hundred hours with no issues so it can't be the tubes.  They're Groove Tubes EL34-M tubes that Brent Jesse raved about as being close to the real Mullards in sound and I agree.  

[xlr8or]

8 hours ago, jon96789 said:

My MV-60 "sparked" and the left channel went out.  The sound from that side is soft and distorted. Atech took a look at the amp and said the only thing he could find was that the fuse blew. He has been running the amp for a couple of weeks and he says its been fine.  My question is what would cause this issue.  Apparently it is not unusual as some others have told me that they encountered the same problem so they keep spare fuses around when this happens. 

 

It could be due to a number of reasons as others have shared below. I've had the same thing happen on my MV-50.

 

I would be checking the carbon composite cathode resistors and measuring their values. Also, check the fuse holder to ensure it's in no way loose in retaining the slow blow fuse and that no cold solder joints are apparent at both ends of the fuse holder. You may also want to remove the fuse and use a DMM in AC current mode set with the maximum peak feature to check the in-rush current on boot up to ensure it's around 4.2A or lower. Mean after that should stabilise to be 2.75A.

 

 

Edited December 28, 2024 by xlr8or

[billstevenson]

I am new here.  Please allow me to introduce myself, I live in Florida, have been a C-J fan for a number of years.  Currently in my main system of interest here:  ART 27A, ART 88, and ART Phono.  It has been a progress of steps to get here.  Basically when Jeff comes up with new stuff, I have been an early adopter.  That will continue until my 76 year old ears can't hear the difference, but so far that hasn't been a problem.  My current project is slated for our summer home in New Hampshire.  I found a NIB pair of B&W 802 D Diamonds for less than half price and they will be powered by NIB Marantz PM10 and PA10 combination also acquired for half price.  We are leaving to go up there next week to put it all together.  In the meantime I have been comparing Class A to Class D here with my Sony SS-AR2s.  Sort of, they don't need much power and I have to say there is not much difference in the power amps at least at low power demand levels.  Pre-amps are another story with the ART 88 night and day better than the preamp section of the PM10.  The PA10 is surprisingly good too, comparing quite well for the most part to my reference Luxman D10-X on Redbook CDs, but less so on SACDs.  Neither holds a candle to my phonos, through the ART Phono regardless of TT or cartridge.