Author Topic: Conrad-Johnson Premier Three pre-amp  (Read 961 times)

Online MusicMan_ZA

Conrad-Johnson Premier Three pre-amp
« on: March 21, 2021, 06:52:52 PM »
I am the very lucky new owner of an almost-40-year-old CJ P3 valve pre-amp.

I really like the look and feel of it, and I love the sound!
It honestly is everything I have always wanted from a pre-amp to drive my various valve power amps.

I do, however, have 3 questions about this pre-amp.
(I do the have very basic CJ user manual, which does not seem to answer my questions).

1. What does the MODE switch do?

On Phono input (the only way I am using the pre) I usually have the MODE set to STEREO.
However, turning it to Left or Right makes no difference (both channels still play) and REVERSE also does not seem to make a difference.
Only MONO changes the sound a little (for the worse, on a stereo LP.)

2. Phase Invert?

I have read that the P3 is a phase-inverting pre-amp.
But this seems to be only on line-level inputs - so not PHONO input?
Does this then mean I have to switch my Red/Black speaker connections "the wrong way" round for line-level inputs but not for PHONO input?

I am sure I am missing something here?

3. One channel "acting up"?

Usually - like right now - the amp plays perfectly.
However, every now and then, the one channel goes very soft / has buzzing and distortion coming through the speaker.
Always the same channel.

A. I first suspected a valve mono block issue, so switched them around. This moved the problem to the other mono block/speaker.
B. I then suspected the one (L) RCA cable (Jones plug to RCA for my Quad II amps), and swapped that out for another cable. Things immediately sounded 100%. This made me think I have solved the problem...
C. Then, at the start of my next listening session, it happened again - on the same pre-amp channel, where I was now using a "new" RCA cable. I unplugged the cable, and then plugged it back in again, and the problem went away. Right now still playing perfectly.

What could my problem be here? Maybe a dodgy RCA L-channel "OUT" on the pre? Or what else, given my description of the problem?
What other tests could/should I do?
Unplugging and re-plugging the Jones/RCA cable seems to sort out the issue every time?

Playing as perfectly as it is right now, I cannot believe there is a real issue (valve / cap / etc.) with my pre. But what could it be?

As always, all advice / comments will be greatly appreciated. Especially from anyone who has owned one of these beauties!

Thanks,
Johan


 

 
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Agaton Sax

Re: Conrad-Johnson Premier Three pre-amp
« Reply #1 on: March 21, 2021, 07:27:03 PM »
I had one. I loved it.Most of the techs in the country repaired it at one stage or another.

You are aware you can download the manual?

From that manual

Phase: phono and high level stages are each phase correct (non-inverting)


https://conradjohnson.com/vintage-conrad-johnson-products/
« Last Edit: March 21, 2021, 07:29:44 PM by Agaton Sax »

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #2 on: March 21, 2021, 07:41:14 PM »
/\/\/\ Thanks A.S.
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Agaton Sax

Re: Conrad-Johnson Premier Three pre-amp
« Reply #3 on: March 21, 2021, 08:10:18 PM »
Sorry, I was scrounging around for my printed manual as it has the circuit diagram  but I seem to have mislaid it.

The mode switch: This was fairly standard at the time. Stereo is obvious. Reverse is left input to right output and vice versa. L or R is channeling either the left or right input to both outputs.

The importers at the time was Phonovox. I was told most of the pres were modified by them. Mine certainly was with all sorts of bypass caps on the bottom of the pcb. It is quite possible that someone bypassed the mode switch and possibly the balance control as those were popular mods at the time. Schalk Havenga worked on mine and others and may be able to give you tips.

Offline Hi-Phibian

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Re: Conrad-Johnson Premier Three pre-amp
« Reply #4 on: March 21, 2021, 08:11:45 PM »
Afaik

Left.
Left input signal sent to both left and right outputs, right ignored.
Right.
Right input signal sent to both outputs.  Left ignored. 
Mono
Left and right inputs summed.
Rev
Left input sent to right output and right input sent to left output. 
Stereo. 
Left in to left out
Right in to right out. 
Croak Audio
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Conrad-Johnson Premier Three pre-amp
« Reply #5 on: March 21, 2021, 08:16:59 PM »
Sorry, I was scrounging around for my printed manual as it has the circuit diagram  but I seem to have mislaid it.

The mode switch: This was fairly standard at the time. Stereo is obvious. Reverse is left input to right output and vice versa. L or R is channeling either the left or right input to both outputs.

The importers at the time was Phonovox. I was told most of the pres were modified by them. Mine certainly was with all sorts of bypass caps on the bottom of the pcb. It is quite possible that someone bypassed the mode switch and possibly the balance control as those were popular mods at the time. Schalk Havenga worked on mine and others and may be able to give you tips.


Very likely.   Mr Polydorou was the original SA tweak master I believe. 

I have never yet for eg seen an Alphason 100 arm with the original external wire in SA yet I have seen well over a dozen.
Croak Audio
Analogue by birth, digital by design. Mostly a StereoType though known to enjoy some Mono too  http://www.croak.co.za https://instagram.com/croakaudio?igshid=1wzr83vlqtbyy

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #6 on: March 22, 2021, 08:01:00 AM »
Thanks for this information.
My biggest incorrect ass-umption was that
R will mute the L channel, and L will
Mute the R channel.
I will play a test record and try this out again.
The Balance control works perfectly.

I did find a copy of the circuit diagram online,
And have downloaded the user manual from
The CJ site - nothing about the mode settings in there!
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #7 on: March 22, 2021, 06:34:32 PM »
Quick update: I hope I am not jumping the gun, but I think all my issues have been sorted out!

1. I have tested the MODE switch with a youtube stereo speaker test video, and everything works as it should.  :thumbs:

2. Answered by A.S. and yes, RTFM!  :thumbs:

3. I lifted the lid, stared at the components, and scratched around in my valve box.
As I have tested with CD/DAC input earlier today, I knew the problem was not specific to
the Phono input stage, so I suspected a valve in the pre-amp section.

Of course, I had no 5751 valves in my box.
However, I found a lovely NOS Mullard ECC81 (yellow writing, old badge, from the 60's).
As the manual states that the single 5965 valve may be replaced with an ECC81 with only "subtle degradation" of sound,
I did just that, and fired up the system.

Now, 4 hours later, it is still playing perfectly, and the sound (on both channels) is much better than before!
Probably because the "new" ECC81 has a bit more gain, but most probably because the (almost 40-year) old
5965 was shot!?

I will play, monitor and report back.
And start looking for a few 5751 valves...  :groovy:


 

 
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #8 on: March 24, 2021, 06:19:23 PM »
I am really not having a great time - audio wise - at the moment.

My CJ P3 is "broken".

Actually, it often works, and then it sounds like a band of angels singing in heaven... :-)
(What really boggles my mind is how it can both work perfectly (some of the time) and be broken (some of the time).  :headbanger:

But it often just stops working, as well. On one channel. Always the same channel.

Sometime, when this happens, I unplug the RCA cable on that channel, and plug in another RCA cable, and everything works well - for a while. Then the channel "dies again". (a while can be 2-3 hours, or sometimes 30 minutes).

I have replaced the one 5965 valve with an ECC81, and everything worked well - for a while. Then the channel "died again".

I have moved one 5751 valve from the phono stage to the pre-amp, and everything worked well - for a while. Then the channel "died again".

Sometimes I just switch everything off, and then back on again (source - pre-amp - power amps), and everything works well - for a while. Then the channel "dies again".

I have NOT yet tested all the valves.

Until then - any ideas what I should be looking at?  :( :( :(
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Hi-Phibian

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Re: Conrad-Johnson Premier Three pre-amp
« Reply #9 on: March 24, 2021, 07:47:57 PM »
Perhaps swap left and right inputs around and run the pre in Rev mode. 

If the same channel fails it would appear to be electronic, if the problem moves, itís switchgear. 


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Croak Audio
Analogue by birth, digital by design. Mostly a StereoType though known to enjoy some Mono too  http://www.croak.co.za https://instagram.com/croakaudio?igshid=1wzr83vlqtbyy

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #10 on: March 25, 2021, 07:02:15 PM »
Please note: I bought this on the forum, for a fair price,
and it arrived exactly as described and working 100%.

It then went on working perfectly for a few months, before I started having issues.
Whatever has gone wrong (I still suspect old and failing valves) was on my watch.

So please do not see my posts as "complaining" or "buyers remorse" - it is not!  :thumbs:

I would just like to get this working 100% again, and enjoy the superb sound!  :groovy:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Agaton Sax

Re: Conrad-Johnson Premier Three pre-amp
« Reply #11 on: March 26, 2021, 12:26:09 PM »
Do bear in mind that the Premier3 has separate plate supplies for each channel. Thinking the problem can not be in the power supply as only one channel is affected may not be true here.

IIRC, in my P3 breakdowns were always in the psu. 
« Last Edit: March 26, 2021, 12:31:56 PM by Agaton Sax »

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #12 on: March 26, 2021, 01:04:38 PM »
/\/\/\ Thanks for that info; I will bear it in mind.  :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Online MusicMan_ZA

Re: Conrad-Johnson Premier Three pre-amp
« Reply #13 on: April 11, 2021, 05:30:09 PM »
I will never pretend to understand or "know" electronics, but sometimes I am more
confused than others!

I put my CJ3 away in a cupboard almost 3 weeks ago, because one channel had "stopped working".
It used to be intermittent, then became almost all the time.

Tonight, on a whim, I took it out of the cupboard, dusted it off, plugged it in and switched it on...

It has now been playing perfectly, on both channels, for over an hour, driving my QUAD II mono block amps absolutely beautifully.  :Whoohoo:

How is that even possible?  :nfi:


I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Agaton Sax

Re: Conrad-Johnson Premier Three pre-amp
« Reply #14 on: April 11, 2021, 08:25:07 PM »
I have written this 3 times over the past 3 weeks and every time deleted it. It is not for me to spoil another person's fun but it is in my ethos to warn so here goes:

My cj Premier 3 was behaving in a similar fashion. On a Sunday evening 26 years ago, on an evening just like tonight, my Premier 3 went into oscillation. My system was tri-amped then ,so that incident totally destroyed a much loved Threshold Stasis 3, severely damaged an Audio Research D160, Audio Research D90 and  a pair of Magnepan Tympani 3 speakers. Of these the ARCs could be repaired ,the other components were gone.

Please do have this pre checked out before similar happens?