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Tubes for Nagra VPA

I have just bought used pair of Nagra VPA power amps.
I found that there are 3 tubes are in the input stage, One E182CC by Mullard and two 12AX7 by EI. (But the JS's review for VPA in Stereophile, there are two tube in each monoblock, one 12AU7 and one 12AX7).

My Question,
1. Any VPA user help me what is the real tube nagra originally provided (12AU7 or E182CC)?
2. If nagra stock tube was 12AU7, can E182CC be used without any troble ? I know that 12AU7 and E182CC(7119) is totally different.

In the picture provided by Nagra USA (http://www.nagrausa.com/nagra_VPA.htm), one tube looks like E182CC, because it is taller than the other two 12AX7 tubes.

Any information would be highly appreciated.

JWK
bwv1004
kleech
129 posts
 
You have the factory tubes installed. There was a mistake in Scull's review and even the owner's manual where they describe the small tubes as ECC82 and ECC83. You should use an E182CC and NOT the ECC82/12AU7 as mentioned in the other sources as they are not interchangeable as far as I know.
bwv1004 OP
3 posts
 
Thanks for your kind information.

I have some more questions for my used VPA.

1. The tubes life of 845 and E182CC and E83CC in VPA ? In case of Nagra PL-L preamp, 5000 Hours of each tube(ECC83 & ECC81) life is specified in the manual. But for VPA, I could not find any information for the tubes life.

2. So, I consider changing tubes bacause my VPA have used a couple of years. How to set the bais ?? The owner's manual did not provide full infomation of setting the bais.

Thanks in advance,

JWK
kleech
129 posts
 
I've been told well over 5000 hours for both the small tubes and the carefully selected stock Sino 845's. I doubt that you would need to change your tubes at least from the perspective of tube life.

I agree that the owner manual's description of the biasing procedure is less than helpful. Please email me through the Audiogon system for further details if you like.
tangram
18 posts
 
maybe i have a newer pair than you guys mine have ballanced and single ended input, also there is a black button to the side of the volt meter for reading bias, there are recessed adjustment screws on the left hand side for adjustment.I find the manual to be very informative for these adjustments
i understand the 845 to last around 2000 hrs.

what speakers are you guys using.
bwv1004 OP
3 posts
 
Thanks for you guys help.
I have just bought used pair of VPAs and have listened only 3 days, actually around 10 hours, and using them with Meridian G08 CDP & Clearaudio TT, Nagra PL-L preamp and B&W Signature 805 speakers. And also, My VPA has only XLR input and they provided adapters to use single ended input.
Up to now, the performance of VPA is a little fall short of my expectations. therefore I doubt tubes life and want to know how to set the bais.
To "Kleech", please send an email to "[email protected]" regarding setting the bais. I found a black button to the side of the volt meter and 4 screws in the left panel, but I do not know hot to used them to set bais.
Thanks again you guys help and look forward to further information to set bais.

JWK
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