Archived from groups: rec.audio.pro (
More info?)
steve-o <swildey@bellsouth.net> wrote:
>Has anyone heard of or had experience with changing out the stock tubes
>in the ART Pro MPA and if so, which make of tubes would be used in
>place of the stock? I was told that by doing so you can greatly improve
>the over all performance of the unit...? True or False...?
See, the "tube" stage in the Pro MPA isn't like a normal tube stage. It
isn't operating the tube anywhere near the envelope where it's designed
to be working.
So if you change the tube, you don't know WHAT will happen. It might be
better, it might be worse. Normally you can use the characteristic curves
in the tube handbook to tell you what will happen with a given tube in
a given circuit. But these guys are running the tube with only 50V on
the plate, for exaggerated distortion. The tube handbooks won't even HAVE
a line on the plot for such a low plate voltage, because the 12AX7 was
never designed to work that way.
I can't imagine anything is going to improve the overall performance of
the Pro MPA other than a trash compactor, but it won't hurt to get a
selection of inexpensive 12AX7 types and see what they do. Don't expect
anything predictable, though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."