At your risk. Take al safety precautions. Even 48V can be lethal.
2 Channels of this amp have been completed today. The sound is very nice and deep..
Description of schematic from left to right:
47KOmhs input potentiometer. Coupling capacitor. Grid (nothing else is connected to grid so it is at space potential, no grid current.. DC90 electron tube. 12KOhms anode load resistor. Coupling capacitor. Belclere 5666 output transformer (other terminal or primary connected to Vb in order to make schematic neat, it is unorthodox, more dangerous). Sennheiser HD580 headphones either to 2 secondaries in parallel or (in series, higher inductance gave deeper bass).
Vb=48V is made in a Bulgin 4AA battery holder, housing paper cylinders of AA size, each containing 2 4LR44 6V batteries.
Va=1.3V is made by an Eneloop rechargeable battery in series with switch, (a fuse should be also in series for safety).
It worked in stereo and sounded very nice.
As the anode field penetrates the grid, the grid negative bias (contact potential in electron tube terminology) due to electrons emitted from cathode becomes less negative and with above conditions ie VB=48V, Rl=12KOhms, Va becomes 36V, and since VRl=12V this means Ia=1mA.
Listening test signal path:
Skyfall - Adele from best of James Bond CD - Sony CD Walkman line out - Pleiades 2 DC90 48V line amplifier - Sennheiser HD580 2x300Ohms headphones
All connections have been done with Wago connectors and wire wrap technique, so no soldering iron was used. The amplifier physical layout is as close as possible to how the schematic looks like.
No comments:
Post a Comment