Has anyboidy had any experience with an 833-A single-ended triode amplifier?


One weakness of the SET is you are limited to sensitive speakers because of low power. Some people have experimented with using radio station transmitting tubes, especially the 833-A. Once you know how to do it, it is not difficult to build an 833-A final amplification stage which will work with low sensitivity speakers such as Magnepans if you prefer the sound of planar transducers to cone in box speakers and you can still have the purity of SET.
I have had success with only 1000 Volts through Hammond 1642SE output transformers. At this voltage the 833-A only draws 120 ma with zero grid bias so you can drive the grid with a 45 SET through a Lundahl LL2756 step-down transformer. The 10 Volt 10 Amp DC needed to heat the 833-A cathode is slightly tricky to build and I use 4.5 Farads in the final filter stage to do this.
Building your own, with help from someone who had experience with how to do this safely if you need it is much less expensive than buying one from a factory.
128x128drbarney1

Showing 2 responses by drbarney1

I need help in how to put photographs in these answers.
The picture of the curves on the 833-A at 1kV have near equal spacing for grid voltages vs plate current so it looks linear. I do not have distortion measuring equipment but I understand second order harmonics are not easy to hear in music and it sounds very clear. Of course all 1kV wires must have thick insulation and the anode cap is modified with a collar to prevent the danger of anyone touching the anode, unlike a 3-500Z or a GM-100 which requires an air cooled finned anode cap. You do need to know how to make the power supply with a cage to prevent any access to the power supply parts and you need to ground the output transformer frame which is rated at 4kV. Here is a link to some pictures of it before I connected it to Magnepan 0.7s and replaced the driver transformers with Lundahl LL2765 driver transformers.
PS I just looked at Will Vincent's amplifier and it is a beautiful piece of art work.