SPICE Analysis of a 6922/300B DRD Amplifier
Author: Dmitry Nizhegorodov (dmitrynizh@hotmail.com). My other projects and articles
1. Introduction
In this article we use PSPICE to explore some of the properties of a 6922/300b varaint of Randall-2 amplifier, a design based on Jack Elliano Direct Reactance Drive (a.k.a. DRD) and Ultrapath ideas.
2. Schematic and parts
Randall-2 is a DRD Ultrapath topology that uses 6an4 for the driver stage and 300B as the power tube. For this article, we use 6922 as the driver and 300B as the power tube. At the moment we use PSPISE model of 6DJ8 in place of 6922. The models should be very close. Once we obtain exact 6922 model, we'll update this analysis. We tested 2 driver tube configurations - high dissipation and low dissipation.
High dissipation:
Low dissipation:
The transformer is 4K:8. Note that we run simulation with a single driver tube whereas Randall-2 employs 2 triodes connected in parallel, and for that reason the biasing resistor will be lower in reality.
Here is simulation with 2 6DJ8 in parallel, biased using 3 1.2V batteries. The B+ voltage is 500V, the output transformer is 3.5K:8.
3. References
[1] SPICE Analysis of Randall-2 DRD Amplifier
Author: Dmitry Nizhegorodov (dmitrynizh@hotmail.com). My other projects and articles
