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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    VALVE ELECTRONIC

    avi.inc
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    avi.inc


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    • Post n°1

    VALVE ELECTRONIC Empty VALVE ELECTRONIC

    Post by avi.inc Sat Jan 02, 2010 7:21 pm

    Hi all

    I was reading here on line about the valve electronic cv4024 and it seemed like a easy thing to try in my VTA ST120 amp. So i ordered one and replaced my center tube a JJ 12at7 and i really wanted this to be GREAT you know NOS made in JOLLY OLD ENGLAND and all, but not so much kind of flat. and the other two tubes are JAN 12AT7WC

    Anyone have a thought?

    Also i'm looking at a set OF Matched Quad ElectroHarmonix KT88 tubes Valves 6550 EH i have now a set of
    sovtek KT-88 that sound good and are about 6 mouths old. I'm just looking if this would be a good move.


    Last edited by avi.inc on Sat Jan 02, 2010 7:34 pm; edited 1 time in total (Reason for editing : More INFO)
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    Bob Latino
    Bob Latino
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    • Post n°2

    VALVE ELECTRONIC Empty Re: VALVE ELECTRONIC

    Post by Bob Latino Sat Jan 02, 2010 10:31 pm

    Hi,

    The Valve Electronic CV4024 (which is a 12AT7 equivalent tube) is made by Mullard even though it may not say "Mullard" on the tube. These were made for the British military in the 1980's and are in good supply. They are a very durable tube. The price on these is reasonable at $20 - $30 a tube. In an ST-70 or ST-120 with a VTA driver board that center 12AT7 (initial voltage amplifier for BOTH channels) is the most important one and either the Valve Electronic (Mullard) or an NOS RCA black plate are the best here.

    The JAN (Joint Army Navy) Phillips 12AT7's are easy to source, relatively inexpensive ($8 - $12 a tube) NOS tubes and work very well in the two side (phase splitter/phase inverter) positions on the VTA driver board. The JAN Phillips 12AT7's are also military grade tubes and usually have fairly close matching triode sections which is important in the this position. Altering the two side 12AT7's on the VTA driver board has much less influence on the sound of the amp than changing out the center 12AT7.

    The Sovtek KT88's are reasonably priced, sound good and have proven themselves to be very durable in the ST-120. The Genalex Gold Lion KT88's are the best tube I have personally heard in that amp but they are expensive tubes at $200 a quad. If you are planning on upgrading your Sovteks I would consider the Genalex KT88's.

    Bob
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    avi.inc
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    • Post n°3

    VALVE ELECTRONIC Empty Re: VALVE ELECTRONIC

    Post by avi.inc Tue Jan 05, 2010 11:39 am

    Thank's Bob

    I'm getting the Genalex KT88's and i will try the Valve Electronic CV4024 in the center again to see if it is better than the JJ 12at7 i have now. With the Sovtek KT88's it was a step back.
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    avi.inc
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    • Post n°4

    VALVE ELECTRONIC Empty Valve Electronic CV4024 in the center now with the new Genalex GoldLion kt88

    Post by avi.inc Fri Jan 08, 2010 10:45 am

    WOW now that works very well, before having the jj's in the center with the sovteks was good but overly brite with the gold lions. And CV4024 was flat with the sovteks. The CV4024 and the gold lions is well GOLDEN!!

    Nice call Bob
    Thanks again
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    Bob Latino
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    • Post n°5

    VALVE ELECTRONIC Empty Re: VALVE ELECTRONIC

    Post by Bob Latino Fri Jan 08, 2010 11:07 am

    Hi,

    The best price I have seen on the Mullard (Valve Electronic) CV4024 (as I have mentioned before on this forum) is from "bnb_tubes" an Ebay vendor who sells them for $19.50 each in pairs. Most other places sell the same tube for $25 - $30. This price is very reasonable for a genuine NOS Mullard built tube. Because Mullard made so many of these for the British military in the 1980's, there are many still in warehouses. It's strictly a supply and demand thing. Because the supply is still fairly good, the price is still reasonable.

    The 7199 tubes that the stock ST-70's use on their driver boards is an opposite situation. The 7199 tube is no longer made by anyone and the only ones left are those in circulation now. If you have a stock ST-70, IMHO, you should pick up a spare pair of 7199's NOW if you plan on keeping your amp playing with its stock driver board. The good thing is that these 7199 tubes as supplied by Dynaco with the original amps were made by RCA and Sylvania. These tubes were well made and do last long. The story at the time was that Dynaco always tried to supply their amps with the Sylvania version because the Sylvania tended to be quieter than the RCA version of the 7199.

    Bob
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