Wonder if this is safe? would it give my pedals a tad more gain and bite? It may be my new speakers but seems like my pedals have a little less gain with the 68 twin. Might be the tone stack.
Think its safe then? I have all the head room I need lol got to experiment loud though. I do have a At7 in the v3 reverb and one in the PI12AT7's have a gain factor of around 70% vs an AX which is around 90-100mu
More important an AT7 also has a higher current rating (which makes it an ideal reverb tank driver). The lower gain is a factor but the larger factors are:
We have almost 10 times the current available to drive the output tube grids before the phase inverter starts to break down and clip (in the same PI/amp)
We have a transconductance of 5500 vs 1600 of the 12AX7. Keeping this simple, it means it takes a lot less input signal for a given output signal.
With this said an AT7 in the PI of a push pull AB amp w/ LTP PI will drive the grids harder and give you more clean headroom than an AX will which will clip sooner and generate more harmonic character (crunch).. PI distortion is different (not as smooth as in a regular gain stage) so some people like that sound and others do not!..Also going from a 12AX7 to a 12AT7 in the PI (phase inverter) will yield a change in output tube distortion, touch, and output dynamics in most amps. (The AX being slightly more dynamic!!) due to added harmonic content....
BTW.. IMO a more ideal (dynamic) setup for a 12AX is altering the PI values by changing the tail from a 22k to a 10k and 820 cathode to 470..Typical Marshall/5f6a Bassman design..Fender designed theirs for the cleaner/headroom of an AT not an AX...Just sayin
Wrong, some amps have higher current levels at certain points, if the amp is designed in a manner where it's pushing current the tube will fail quicker. Read up on it a bit more. For example reverb on a Fender one is the driver, if you don't have current capacity it won't be correct.I don't think it's an issue as far as doing any damage to the tube or amp by going to a 12AX there!..They just operate at different parts of the curve..One breaks down faster and clips harder than the other..12AX's can handle up to 300v on the plates with no problem.. Purely a taste thing!!..Have at it..
As far as killing the tube faster..Look at how many Marshalls and hundreds of other amps out there use 12AX7's in the LTP PI with no issues or show any signs of wearing out any faster...
Try this!I cant to seem to find the tube layout and what they drive, fenders email wont open!
If we take a look at Merlins (Valve Wizards) Respected web siteWrong, some amps have higher current levels at certain points, if the amp is designed in a manner where it's pushing current the tube will fail quicker. Read up on it a bit more. For example reverb on a Fender one is the driver, if you don't have current capacity it won't be correct.
Hey thanks a lot! I did put a GE WA in 2 days ago, much better! I do have RFT, LPS sitting around 803 is in there now