Its quite often done in band power amplifiers on the front end.
12AX7's can interfere with each other between the triodes (as I have found) and work better in parallel.
I have often ditched 12AX7 due to instability problems and just used lower gain 12AU7.
Here is picture of Simm-Watts front end. 100Watt valve 4 channel PA amp.
12AX7's can interfere with each other between the triodes (as I have found) and work better in parallel.
I have often ditched 12AX7 due to instability problems and just used lower gain 12AU7.
Here is picture of Simm-Watts front end. 100Watt valve 4 channel PA amp.
An externally hosted image should be here but it was not working when we last tested it.
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As best I can interpret that schematic (parts of which are missing), none of the triodes are paralleled; the anodes aren't connected to each other, and neither are the grids all connected to the same input signal.
Rather, each of those input triodes is used as a separate and individual gain stage, with a separate and individual input signal. The circuits appear to be active mixers.
-Gnobuddy