2. amps-preamps
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tube rolling first-timer

So I bought some NOS tubes to try in my preamp. It is my first piece of tubed equipment, and this is my first time switching out the tubes for something different. The pre is a Nagra PL-L. It comes with some Sovtek tubes. The tube complement is two 12AX7's and one 12AT7.

So, I've done a fair amount of reading about different tubes, and decided to start with some Telefunkens. I found a good deal on a matched pair of Telefunken smooth plate 12AX7's and a Telefunken 12AT7.

Here are my questions:

(1) when you are first learning about tube characteristics and your preferences in your system, is it best to stick with all one kind of tube and swap them all out, or should I first switch out the AX7's (leaving in the Sovtek AT7)... I'm just curious if people think there is a "right" way to go about it.

(2) Does one generally switch to all of the same brand tube, or do people tend to mix and match brands to their preference? Of course I recognize you need to use the same brand (and closely matched) tubes for the L/R channels, so I would stick with the same brand for the AX7's.

(3) Do folks have particular preferences or combinations of tubes that they have like for the Nagra PL-L and would recommend?

Thanks for your advice and recommendations.
dgaylin
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drrsutliff
861 posts
 
I would always keep your pairs the same as they usually effect each channel (one tube operating in each channel's circuit)and you want the same tone or signature sound from each channel. Change out the 12AX7 to the Tele. pair you have and leave in the Sovtek pair of 12at7 and listen to see if you like the change. That is what tube rolling is about. Find another 12at7 Tele to match up with your single.

Rick
dgaylin OP
255 posts
 
Hey Rick, thanks very much. The PL-L only takes a single 12at7. Maybe that means it's not in the signal path and is just used for for volume attenuation? So I can switch all of the tubes to the Telefunkens (the two ax7s and the one at7) or I could try just switching the pair of ax7's first, and then try all three or try just the single at7 first....

any thoughts?

Thanks again,

--dan
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drrsutliff
861 posts
 
Sorry for not investigating the curcuit first. I would still roll the 12ax7s first and note the change. Possibly trplace the original 12ax7s back in and then change the 12a7t. This way you can hear what affect each one can have. Finally roll all and again listen at each stage for a while. Possibly use a familiar album or set of music and repeat with each change. Its fun to listen to the changes.

Rick
dgaylin OP
255 posts
 
Thanks again Rick. Much appreciated.

--dan
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