12AU7 Tube in Shunt Regulator

[grufti]

What prompted the change to the 12AU7 in the Eros 2 shunt regulator? Can I still use the 12BH7 that used to occupy that spot in the original Eros Phono? The shunt circuit has now gone from 6CG7 to 12BH7 to 12AU7 over the life of the circuit. They're all similar, but the plate dissipation limit is definitely lower for the 12AU7.

[Paul Birkeland]

The dissipation is lower for the 12AU7, but still well above what we need.  The 12BH7 was only being used in the Eros, so we switched over to the 12AU7.  The 6CG7 was drawn in a really early schematic, but never actually provided with the kit (I did build one a long time ago with a 6CG7 just for fun though).

[grufti]

I still have some "new" old 12BH7 tubes sitting around. I'll use one of those unless you tell me that it's a bad idea. Everything else being equal the 12BH7 should last longer in that position than a 12AU7. Is there anything else that I should consider? Amplification factor is the same at 17. The transformer should be able to handle the heater current. Am I forgetting something? Does the 12UA7 shunt regulator sound better? You never know until you've tried. Do you have a preference?

[Paul Birkeland]

You are welcome to experiment to your heart's content.  The 12BH7 for us ended up being a redundant component that we had to stock.