Tube Rolling a 7-Pro
This amp is medium sensitive to a tube swap; maybe not as sensitive as a WA but you can actually here a real audible change unlike my experiences with SWR or a 3Pro.
I have lot of older used 12AX7 tubes.
During a really long test with a WA awhile back, I found my favorites were:
Telefunken, Amperex, Mullard, and National (long plate and does not have nearly the reliability of the other 3). I also checked these against the stock JJ tube.
This was the order of preference in the WA and remained the same for the 7-Pro.
The Tele just had a bit more detail and air; a clear soundstage and 3-D
The Amperex sounded great but slightly different. Maybe not as wide but a slightly tighter bottom (insert joke here).
The Mullard seemed to have a more focused sound and not as 3-D; not a bad thing just not my thing.
I like the National tubes but I have been told that they are spotty on performance (mine are NOS from the later 70's early 80's). I think these can be found cheap and the others are about $40 each if you buy rebranded tubes like Dynaco, Eico, Baldwin, and Fisher to name a few. The real deals are just a bit more.
What's cool with Dynaco (made by Tele) is they ran lower voltages than many applications so one might surmise the will last longer although mine are from the 60's.
The J&J was fine but not as refined or detailed. It should be noted that this tube had more gain than all the rest. It also has really short plates.
I'd welcome any reports that others have found with a preamp tube swap in a 7-Pro.
Details of the last few tubes and my test rig.
Johnk did some pre tube swapping in his. Used four, forget what all he used but one was a Mullard, and it was the brightest and middiest of the four as far as I remember. And the JJ he used did sound darker and less detailed. Surprisingly, I did some tube rolling in my Heritage SVT-CL and V4B and ended up preferring the JJ's they came with in V1 because it sounded more like my 69 with an Amperex 12dw7 in V1.
Another amp test and a cool Hot Rod.
I've got a Mullard in mine right now. I've gone through JJ, Tung Sol, Telefunken, GE and the Mullard just puts everything in the right place. The GE ran a close second, but I'd use any of them in a pinch. They just all add a different feel to a great sounding amp.
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