Below is the schem of a twin power amp board I got ,
I didnt like the 100 v cap on the screen of the 6AU6 , that could easily be destroyed if the tube wasnt in its socket .
They also dont give a value for the cap in the feedback network , of course they dont have a clue what op tx your going to use .
I understand the basic function of the component , to ensure the feedback path remains negative at very high frequencies , and prevent oscillation .
I have my output transformers 3.5k - 4,8 ohms , whats the best approach to finding the correct value , maybe some small math to get me in the right ball park then adjust on test for final value ?
Maybe someone could explain the advantages of a diode in the screen supply , I will most likely add a choke to decouple the screen /driver and output stage . the main reason being for the limiting action at or around max output/clipping and more favourable harmonics , at least thats what my ears tell me , hopefully I can confirm this more scientifically with REW's dist analysis later.
So far Ive matched from bags 10 pieces 1% 1 watt metal film resistors and got very close pairs for left/right channels , seeing as the gain of the amp is controlled by feedback can I hope to get good left right balance ?,
in any case I have 100 6AU6's which I can select from , but Im not sure exactly what to select for ,closest agreement on dc electrode voltages across the two valves or the ones that give the closest match in terms of output voltage ?
I didnt like the 100 v cap on the screen of the 6AU6 , that could easily be destroyed if the tube wasnt in its socket .
They also dont give a value for the cap in the feedback network , of course they dont have a clue what op tx your going to use .
I understand the basic function of the component , to ensure the feedback path remains negative at very high frequencies , and prevent oscillation .
I have my output transformers 3.5k - 4,8 ohms , whats the best approach to finding the correct value , maybe some small math to get me in the right ball park then adjust on test for final value ?
Maybe someone could explain the advantages of a diode in the screen supply , I will most likely add a choke to decouple the screen /driver and output stage . the main reason being for the limiting action at or around max output/clipping and more favourable harmonics , at least thats what my ears tell me , hopefully I can confirm this more scientifically with REW's dist analysis later.
So far Ive matched from bags 10 pieces 1% 1 watt metal film resistors and got very close pairs for left/right channels , seeing as the gain of the amp is controlled by feedback can I hope to get good left right balance ?,
in any case I have 100 6AU6's which I can select from , but Im not sure exactly what to select for ,closest agreement on dc electrode voltages across the two valves or the ones that give the closest match in terms of output voltage ?
