Thanks all for your responses. The valves looked NOS therefore I searched for specs to be able to make a small PA with them. Now it looks I will put them back on the shelf for another twenty years in
Hello Marco, You are so kind. Thank you very much. My tubes look exactly like 4B/551B(D). I will measure the dimensions to be sure as soon as I can. It looks convenient that the filament voltage is t
You are so kind. Thank you very much. My tubes look exactly like 4B/551B(D). I will measure the dimensions to be sure as soon as I can. It looks convenient that the filament voltage is the usual 6.3