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New member from Italy

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New member from Italy

Post by tube » Tue Jun 06, 2017 2:57 am

Hi all!
I live in Italy and my passion for music and hi-fi is since I was seventeen, something like forty years ago!
I have many components in my system and I have changed a lot of them in all of these years.....
I even have a passion for diy and I built several tube preamps and amps.
I have modified and upgraded many components of my CJ PV 10 line preamp and sounds great.
Now I would like to buy a CJ tube phono preamp or build one with CJ schematics but still haven't made up my mind... :D
I mainly use MC carts, and this complicates things a little.
Do any of you members have experience with Conrad Jonson tube phono preamps?
Thank you.
Kind regards.
Tube

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Re: New member from Italy

Post by admin » Tue Jun 06, 2017 7:29 am

Tube,
Welcome to CJO. Sounds like you have a lot of modding experience. Out of curiosity, what did you upgrade in your PV10?
-admin
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Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

tube
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Re: New member from Italy

Post by tube » Wed Jun 07, 2017 4:30 am

Thank you Amin, concerning the PV10 I first upgraded the output capacitors with Audyn cap plus, not 4,7mf but with 2,2 mf because with a standard 100Kohm load of a typical tube amp like CJ amps this smaller value is better.
CJ and other manufacturers use big values for the output caps because they don't know what power amp the custumer will use, but one thing is for sure, smaller caps are faster and better sounding.
Then I upgraded the caps in the power supply increasing the capacitance with C-R-C filter in order to have a cleaner DC entering the stabilazer.
After a while I realized that the preamp was stressing the tubes ( their life span was very short ) to much because they where using a single tube for the same channel.
The cathode follower needs elevation of the heaters in order to work correctly and even to prolong tube life.
In the same tube the other triode was used for the first stage of the same channel and it doesn' t need any heater elevation.
If you elevate the heaters using a triode in the first gain stage and the other triode for cathode follower you will create a conflict between the two triodes whith audible strange high frequency noises and short life.
I recabled the two tubes, one for the first stage of both cannels and the second for the cathode follower of both channels.
The strange noises disappeared, the preamp sounds much better and the tubes last for ever!
Why did CJ arranged the connection between the two stages of each channel in this manner I don't understand, maybe it was convenient concerning the design of the traces and the space at disposition.
At the end I modified the circuit changing the output tube from ecc82 to ecc81 eliminating the elevation of the heaters because the voltage on the cathode is much lower.
I am very pleased with the result, the preamp is dead quiet and sounds great!
Kind regards
Tube

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Re: New member from Italy

Post by admin » Wed Jun 07, 2017 7:11 am

Very impressive. Those are some pretty significant modifications. Thanks for the thorough explanation.
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Home Theater in Member Gallery
Conrad Johnson Owners.com Main Page

Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

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