Princeton (NR) phase inverter tube type

[HBamps]

I recently picked up a Silverface Princeton non-verb. It's a great sounding little amp. Perfect for home use and those low volume jams.

I was messing around with tubes and was comparing a 12AX7 to a 12AT7 in the PI position. I think the 12aT7 sounds great (clearer, punchier tone) but the tremolo suffers with it.

the 12aX7 made the amp sound a little more 'congested' but the trem works so much better with it. I didn't try too many 12ax7's here. maybe a lower gain x7 would do well. 5751?

I read somewhere about a tube type that's one half "T" and one half "X". Anybody try that or know what tube it is? I have searched and cannot find it.

Thanks for looking

[MWJB]

12DW7 is one half AU one half AX, but I don't recommend it. The reason that you are having issues with the trem is because on a non-verb princeton V2 is half the trem tube & half the PI tube, the PI's gain stage is half of V1. Either put up with the tube you like in V2 and live with the poor trem, or try 5751/12AT7 in V1. However, in V1 a tube sub affects 2 triodes rather than just one, so even 5751 might be too much of a drop?

[tubeswell]

I read somewhere about a tube type that's one half "T" and one half "X". Anybody try that or know what tube it is? I have searched and cannot find it.

Aside from the 12DW7, JJ do an equivalent (1/2 12AU7 and 1/2 12AX7) they call an ECC832, and an 'opposite' one that they call an ECC823.

[Amp Kat]

Haven't seen a 1/2 T and 1/2 X in a duo triode. Not saying they don't make one but another big factor is the plate impedance difference of the 12AU vs the AT & X are way different. Think the 5751 would probably be the best fit.

[TheTinMan]

Based on your experience with this amp, you need the gain of a 12AX7 in the triode used by the tremolo. It's pins 1-2-3 of V2. Unfortunately, that's the "12AU7" triode of a 12DW7: data sheet. Didn't know about the JJ mules but whichever one has 12AX7 gain on the 1-2-3 section (called #2 for some unknown reason) would be worth a shot.

If you don't mind mangling the amp, you could rotate the tube socket and try a 12DW7. I'm not sure I'd go that far to experiment though.

Cheers,

Chip