I want to learn more about how my amp works. I have a Sun Audio SV-2a3 clone. 2a3, 6SN7, 5U4 tubes. Schemes are all over the net. Can you explain (if that is even possible for a layman to understand) how the tubes and transformers participate in the amplification? I am keen to understand the stages rather than how things technically work in detail.
in a nutshell....
1. the power transformer and associated rectifier/psu converts meralco to dc needed by the tubes plates and ac low voltage to power the filaments..
2. the output transformer matches tube plate resistance to a level that can feed or drive the speakers...
3. more than the tubes, the irons used in any tube amp is the deal maker, my reasoning is that tubes are easy, just get another and replace and you're done. but transformers are set once you stick them in...
4. once the power tube operating points have been decided, like for the 2A3, that's 250 volt plate at 60mA cathode current, you need to drive its grid to get output swing, the power tube plate current is maximum at near 0 volt grid and minimum at about -45 volts and beyond. we will need another tube to provide this grid voltage swing...
at the chosen operating point, the 2A3's plate resistance is about 800ohm, so that a 2.5k ohm plate load is consistent with low distortion and reasonable power output...
5. the voltage amplifier is used, it can be a triode like the 6SN7 or a pentode like the EL84 or a D3a. the voltage amplifier converts a 1 volt input to a 45volt peak output.
6. the 6sn7 has an amplification factor of about 20, so 2 stages makes a maximum gain of about 400, but in reality voltage gain is much lower than 400, 100 is a realistic figure, the 2A3 has a gain of 4 so that your amplifier tubes has a gain of about 400, divide that by the turns ratio of the OPT at about 18, so that your gain structure is about 23.
7. what this means is that a 1 volt peak will give 23 volts peak at the speaker terminal...
tubes are easier to figure out than SS, up to now, heated debates are on-going at diyaudio....
