Changing the tube in the F1X

[keith_h]

To the best of my knowledge all 12AX7 tubes are built to the 7025 specification and have been for many years. However if you are buying new old stock from the 60's this is something to take into account when looking at 12AX7 tubes.  
 
There can be quite a bit of variance in tube quality even with the older stuff from the heyday of tubes. Even tubes within the same manufacturing run can vary quite a bit not to mention between manufacturers. This means if you are depending upon a tubes characteristics as part of your sound you should be prepared to try out several tubes. A lot also depends upon the design of the amp. Some amps like those from Eden aren't really affected by the 12AX7 itself as it serves as nothing more than a buffer. For others such as those based on Fender designs the tube can have a dramatic affect since it is part of the gain stage. This variance is one of the reasons sound equipment design using tubes is as much a holistic exercise as an engineering one.  
 
Keith
 
(Message edited by keith_h on November 29, 2014)

[sonicus]

Here is a must read as part of the terminology such as MU  differences   in  currently manufactured 12ax7/7025 ( tubes /valves ).
 
https://www.amplifiedparts.com/tech_corner/12ax7_comparison_of_current_made_tubes

[moongerm]

Interesting read Wolf, very informative.  I learn so much from all of you the past year or so I have been a member. The F1X is brilliant.  I have been playing through a 600 watt class d amp (acoustic image focus 2) for many years because of its flat sound and light weight.  But ever since I learned and  finally tried out Alembic gear, just over a year ago (Distillate, miss that bass) then a 2nd hand f1x, it warmed up and brought to life what would otherwise be a flat amp that is sterile, in a good way, but sterile nonetheless. I can't play without an f1x now without missing a big part of my tone. Addicted

[sonicus]

Brian , I am pleased if we can all help each other here . Yes , the F1-X is a fine piece of gear. The DI's are also very useful and quiet enough for recording .

[edwin]

When I had an F1-X, I tried a lot of different tubes. I didn't notice a huge variation in sound, certainly not as much as the F2-B.