ED8000 tube amplifier schematic

When I'm talking about NOS Telefunken tube amplifier, it gets me excited and makes me sleepless! 

For those that are unaware of the previous article, please visit:  
http://jandkaudiodesign.blogspot.my/2018/03/ed8000-tube-amplifier.html

Here goes revision 1 of our proposed ED8000 tube amplifier design. There are tonnes of methods to build ED8000 tube amplifier. Below ED8000 tube amplifier schematic is just one of them, a simple one in fact. It needs only 1pc of 5687 to drive both Left and Right channels, with the use of 1:2 step-up input transformer to provide sufficient gain to drive ED8000 tube to full power.

P/S: circuit has not been tested yet, further fine tuning may be required.

Other than the usage of 1:2 input transformer, there is the innovative use of a 200H plate choke for 5687 as load to keep the B+ low to match the B+ of ED8000, where B+ is quite low compare to other tube amplifiers such as 2A3 or 300B. If resistive load is used for 5687, then the Vplate of 5687 needs to be lower so that the B+ needed does not exceed 177V. 

Or, use interstage transformer! With interstage transformer, ED8000 grid leak resistor can be removed, together with the coupling capacitor, which is an even more elegant and better sounding design. Of course, interstage transformer comes with a slightly heftier price tag.

All the components for the ED8000 single ended tube amplifier schematic are carefully calculated for the best effects and are not simply plugged from the sky. If you copy the design, please do not change the values of the components used. If you change it, and it does not sound good, blame yourself! LOL. 

The B+ can be slightly tuned by adding a small capacitor of 0.1U - 0.68U after 5U4 rectifier tube rectifier. This converts the choke-input rectification to pseudo capacitor-input, and raise the B+ slightly.

If you build it and like it, let us know! If you need the irons, let us know too! If you see errors in the design, let us know. It was designed in a matter of minutes.

Enjoy!

J&K Audio Design
11/3/2018