Stev eH wrote:
ken scharf wrote:


I really don't see any advantage in his circuit over a conventional
zero bias grounded grid amp, at least not with the 4-xxx series of
tubes. With the 4CX250 series it makes some sense since these tubes
CAN'T be run in zero bias grounded grid due to the fragile grid
structure in these tubes.
You only needed 20W of drive power and a single HT supply. I have one
using a pair of 813s, 10W from my TS-120 drives it to about 200W output.

It looks to be exactly the same layout as the one on Ian's site but has
had the valve rectifiers replaced with solid state at some time.

Steve H
200W from a PAIR of 813's? You must be running them with less than
1.5KV on the plates. That's the problem with 813's, they don't live up
to their potential (pardon the pun) unless you run them with lots of HV.
The point though is that in conventional grounded grid (all three
'grids' grounded) you still don't need a SG supply and the drive power
should be about the same.