UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

kalee20 · 14th Jul 2011, 6:42 pm

They're not. DAC32 (triode) - in 1.4V battery series valves - common enough.

In the 2V-heater battery valves there are oodles of triodes: HL23DD comes to mind as it's used in one of my battery radios. Triode detectors and twin-triode output valves were common.

I do agree that last-generation battery valves (Dx96) didn't include a triode - pentodes provided greater gain including for the AF voltage amplifier.

The 6146 is a tetrode, but it's a power amplifier not a small-signal amp. In this application, the benefits of a triode (no partition noise) are not needed. A triode would require neutralising (unless used in grounded-grid, which for a power amplifier would require LOADS of drive power). And as it's frequently used in Class C, the tetrode provides greater efficiency and requires less grid voltage swing.

14th Jul 2011, 6:42 pm	#23
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: Triode vs Pentode They're not. DAC32 (triode) - in 1.4V battery series valves - common enough. In the 2V-heater battery valves there are oodles of triodes: HL23DD comes to mind as it's used in one of my battery radios. Triode detectors and twin-triode output valves were common. I do agree that last-generation battery valves (Dx96) didn't include a triode - pentodes provided greater gain including for the AF voltage amplifier. The 6146 is a tetrode, but it's a power amplifier not a small-signal amp. In this application, the benefits of a triode (no partition noise) are not needed. A triode would require neutralising (unless used in grounded-grid, which for a power amplifier would require LOADS of drive power). And as it's frequently used in Class C, the tetrode provides greater efficiency and requires less grid voltage swing.