I kept this thread title vague (DELUXE/PRINCETON) because my final build is both. Started as a Deluxe (cathode biased 6V6s) and, using only one input, freed up 1/2 of the preamp 12AX7, which I tried as an extra gain stage. Didn't need it, so used it for a tremolo (ala Princeton AA964). The Deluxe puts the 2nd gain stage in the PI tube (and I left it there), but the Princeton uses it for PI and tremolo. I went to fixed bias of course (ala Princeton) as part of the tremelo addition. The amp sounds great, but just wondered if it really matters what you "pair up" with the Cathodyne tube? One thing I realized is, you could change the preamp tube from an AX7 to an AT7 (or AU7), for less mu (and more headroom?), but still have an AX7 for your 2nd gain stage. You can't on the Princeton (both gain stgs are in the same tube). How it would affect the tremelo I don't know. I am now doing mods on my "final" build chassis, so made an Octal adapter to look at the 6V6s. I also (should have done it on the breadboard) realized I had been using a GZ34, so tried a 5U4 then a 5Y3 (which I want to leave in - the amp only draws 68 mA from the PT), but need to change the bias resistor (to keep my 10K bias pot in range, want 10-23mA). When do you stop modding and call it FINAL????
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NEVER lol, no amp is perfect keep going till it is.😀
I am also about to try a 12dw7 in my harp amp twin triode with uneven mu. one half is like a 12au7 the other is like a 12ax7. I'm going to run the mic into the low side then into the high side. less feed back more gain i hope.
ArcticBreaze is right on the money with this, you need a 12DW7, like stated it's half 12AX7 and half 12AU7. Just check data sheet to which section is which and make sure your first stage sees the AU7 section.
You guys are both correct, but what if you want to try a 12AT7 or 12AY7? I can just plug one into my preamp, the tremelo still oscillates fine, and leave the 12AX7 for the 2nd stage gain and phase inverter.
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