29-01-2021, 11:27 PM
Hi.
Can be done with auto bias if you float the filaments. Only means that you need a separate filament supply for the outputs.
I've tried it using a gardiners multitap transformer in a lash up.
Agree that stoppers are important. My lash up had both "cathodes" (valve filament centre tap) strapped, this supplied the bias without the need for balance etc and followed convention, with 130v power was around 3.5 Watts at 10% distortion. This was a total lash up on a piece of wood with nails!!!
Dismantled now but a definite one for a proper build.
We need to really follow the way our Soviet brothers made the units the valves were used in. You'll notice that the valves are often fitted through a metal plate separating anode from the bottom connections. They are then made into a box type of construction, this no doubt aids stability.
One thing too if you can is to run the filaments from a stabilised supply especially on the power stages, you may notice that when you run from a battery via a dropper resistor the filament voltage changes with cathode current so I use a stabilised supply for this, running the outputs at a nominal 1.1v.
Can be done with auto bias if you float the filaments. Only means that you need a separate filament supply for the outputs.
I've tried it using a gardiners multitap transformer in a lash up.
Agree that stoppers are important. My lash up had both "cathodes" (valve filament centre tap) strapped, this supplied the bias without the need for balance etc and followed convention, with 130v power was around 3.5 Watts at 10% distortion. This was a total lash up on a piece of wood with nails!!!
Dismantled now but a definite one for a proper build.
We need to really follow the way our Soviet brothers made the units the valves were used in. You'll notice that the valves are often fitted through a metal plate separating anode from the bottom connections. They are then made into a box type of construction, this no doubt aids stability.
One thing too if you can is to run the filaments from a stabilised supply especially on the power stages, you may notice that when you run from a battery via a dropper resistor the filament voltage changes with cathode current so I use a stabilised supply for this, running the outputs at a nominal 1.1v.
