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Old 17th April 2009, 08:23 AM   #1
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Default Upgrading the Conrad Johnson Premier Fourteen preamp

Dear tube experts,
I have upgraded my old Conrad Johnson Premier Fourteen preamp with teflon Vcaps, tantalum (Yamamura, Shinkoh, Audio Note) resistors, Infineon diodes, HiFi Tuninig fuses, Faber's Magik Marker and so on. I would like to share my finding, which I have posted in details here:

http://digilander.libero.it/agostino...premier14.html

and ask you possible comment/suggestions.

Sorry very much if I will be late in answering, but I don't have a flat Internet connection...

Tino

http://digilander.libero.it/agostino...dio/audio.html
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Old 17th April 2009, 10:57 AM   #2
SY is offline SY  United States
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Very imaginative writeup!

I'm particularly interested in the capacitor salesman's directions that ended up costing you another $1000 to prevent the timing being off. Though the marker (how much does it cost?) that prevents static on conductors is quite remarkable itself.
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Old 17th April 2009, 11:25 AM   #3
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Dear Tetsujin,
about the "timing problem" which can appear bypassing the original CJ polystyrene caps with smaller teflon caps, I can only say that I trusted this suggestion of the "salesman", which -BTW- is also the teflon Vcap maker (Chirs VenHaus). I have not tried the other way (a 0.02uF teflon cap in parallel), so I can't compare the two results. I can only add that an audio engineer which I trust told me the same thing...
About the untistatic Faber's Magick Marker, I know that Faber's cable sell it directly to some italian audiophiles at 50 Euro. I think that it is an "amateur product", not already a commercial product, at this stage, but if you are interested I can give you the Faber email and you can ask him.
I was very skeptical about this product, how I was initially skeptic in replacing my original CJ power cords with Faber's cable power cord (see this link if you are interested in the power cord topic:
http://digilander.libero.it/agostino...ber_visit.html ) but I had to recognize that the effect (at least on the CD disc) is very clearly audible as a better focus and larger soundstage.
Difficult to believe... you should try it.
In Italy there is a lot of discussion on the use of a ionizator dry
hair machine ("phon") which uses tourmaline salts to produce ions. I bought it (at about 30 Euro) and tried a double blind test with about 25 different CDs (some "treated" with the dry hair for about 20 seconds before audition and other not treated -placebo-, by an assistant which declared the truth only at the end) and have found a statistical evidence of a good effect. The Faber Magik Marker seems to me even more evident than the dry hair machine treatment...
Sorry if I spoke of these "vo-doo" esoteric accessories in a tube amp forum, it was just to explain more on the FMM...
Best regards,

Tino

http://digilander.libero.it/agostino...dio/audio.html
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Old 17th April 2009, 01:09 PM   #4
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Hi Tino

Thanks for posting this and for your very inspirational site.

IMO the volume control relays would be now the weakest link in the design. Of course it is also the most difficult to address. I have generally poor opinion of relays and R-2R volume controls but unless you dramatically change the design your only option is to use better relays. After so many years of use and especially assuming there has been some dc in the input signal these relays are ripe for replacement.
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Old 17th April 2009, 02:55 PM   #5
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Dear analog_sa,

thank you very much for your suggestion! I really hope that there is no DC in the incoming signal, since my CJ DV-2b DC-player has expensive 2-4uF polystyrene output caps, and similar happens to my EF-1 phono preamp. I'm not sure of the goodness of my Technics GT550 and Aiwa F350 tape, but I use them so rarely...

BTW, I also have the feeling that this volume is not very good, since at higher volumes it seems to me that it sounds much better, so there should be some effect in the volume circuit, but it seems to me very strange that the proble is due to the NEC relè (EA2-5NJ, golden pins) since I believe that CJ uses the same relé (maybe also the same circuit?) in their top models (ART, ACT,...) which are universally known to be well sounding. Anyone knows which type of relé are used inside the top CJ preamps?

Lastly, do you have any relé suggestion for upgrading these NEC EA2-5NJ with compatible pins but better "sounding" relè?

Thank you again,

Tino
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Old 17th April 2009, 03:44 PM   #6
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Hi Tino

Sorry, i'm definitely not a relay expert but there have been many related threads and some very interesting opinions on the subject. In the absence of any data on your relays i would suggest a simple (hopefully) experiment. Have a nice switch, per example a Shallco wired for a particular attenuation using only two resistors. Bypass the internal volume control and compare. I only suggest one set of resistors in order to minimise the cost of the test. It is also possible to have the attenuator external to the CJ and simply short-circuit the relays. This experiment will give you an idea of thescope of improvement that can be had by upgrading the relays.

It comes as no surprise that some attenuator positions sound better than others. If the topology follows the standard R-2R used in most relay attenuators some positions have multiple resistors and relay contacts in the signal path and others - just two.

The fact that CJ may use this in its top preamp doesn't mean much. ARC uses a pretty dreadful potentiometer IC in most of its preamps (not sure about the REF).
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Old 17th April 2009, 08:56 PM   #7
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Dear analog_sa,

thank you very much for your suggested test. I will not have the possibility to try it in a short time, but will consider it in future. I guess that the use of more than 2 resistors could affect the sound more than the NEC EA2-NJ relé (which datasheet you can find also here: http://www.datasheetcatalog.org/data...nec/EA2-3T.pdf ).

Unfortunately I don't know if the CJ volume topology is the R-2R (the same used in DAC?) or what logic they used. I only know that with only 12 resistors per channel (exactly: 2k58 5k56 12k0 25k8 55k6 120k 25R8 55R6 120R 258R 556R 1k20, plus the initial 25k8) they need to combine more than 2 (probably more than 3?) to obtain 99 different attenuations.

Also, using a simple 2R voltage partitioning with Shinkoh resistors instead that Vishay VS H1 will probably improve the result.

Thank you again,

Tino
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Old 7th January 2011, 07:44 PM   #8
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Hi Tino,

Very interesting post. I have plans to upgrade my CJ Premier 17LS which has very similar components (polystyrene caps in audio circuit and polypropylene caps for power supply). I will try to find tantalum resistors as well to follow your suggestion. I already received my Fairchild stealth 4A diodes to upgrade.

For the output coupling cap upgrade, I may opt for ClarityCap MR (a polypropylene cap). However, it is much cheaper to use a single 4.1uF per channel instead of two paralleled 2.2uF per channel). Have you considered to use a single cap per channel? Why?

Thanks to share your knowledge about CJ!
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Old 7th January 2011, 08:13 PM   #9
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Quote:
Originally Posted by fortinal View Post

For the output coupling cap upgrade, I may opt for ClarityCap MR

Those may turn out not to be an upgrade.

Depending on your power amp 2.2uF may be sufficient.
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Old 7th January 2011, 11:51 PM   #10
M Gregg is offline M Gregg  United Kingdom
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Just for interest,

If you are going to this degree of "synergy" the one thing you cannot change (without major work) is the dielectric between the PCB tracks (The circuit board).
Some people use Teflon PCB. Others use point to point

Have you tried bypassing fuses on DC supplies with film caps? It allows signal, however it will block DC should it blow due to a fault.

Relay contacts do tend to oxidize if they are not carrying current. Some are encapsulated or "mercury wetted" there many different types.

Mains cable that has platted L N E tends to be better than just screened. It's interesting that platted cable tends to sound better. Longer lengths seem better than short lengths.

All these things are personal taste.
Interesting write up!

Regards
M. Gregg
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