Can someone help me understand?
I understand what a Push Pull amplifier is, I understand Single Ended , I understand Single Ended Triode (SET).....So, are Triodes ALWAYS single ended? I have a Bob Latino ST120 and it has a switch to run it in "Triode" or "Pentode"......When in Triode, is it Single Ended?
Are ALL SET amplifier Class A?
Can Pentodes be configured to be Class A?
Thanks
I understand what a Push Pull amplifier is, I understand Single Ended , I understand Single Ended Triode (SET).....So, are Triodes ALWAYS single ended? I have a Bob Latino ST120 and it has a switch to run it in "Triode" or "Pentode"......When in Triode, is it Single Ended?
Are ALL SET amplifier Class A?
Can Pentodes be configured to be Class A?
Thanks
Then you should also understand that it is not the type of tube or how the tube is wired that makes it push-push.
If you have two tubes that are 'pushing and pulling', each delivering part of the output signal, it's push pull.
Jan
A SE amp has its output tube biased half way up its voltage supply. So it can go from zero to full voltage to make the signal(not really all the way to the limits!). A PP amp is biased to be on passed the switch on voltage to use a SS term. So you can get twice the voltage swing out of it which is four times the power. Distortion spectrums are different too making them sound different to many people. SE has more even order harmonics will PP is odd order. I like SE sound but listen to both and judge for yourself.
Single ended is class A, there is some current in the output tube during the complete musical signal cycle (positive voltage / air compression;
and negative voltage / air rarefaction).
Take a 300V B+ to the single ended primary, and increase the signal volume level to move the plate voltage swings to near 0 Volts, and then to near 600V.
When you turn the volume way too high, it can clip when the tube cuts off completely.
A tube that cuts off, is the Antithesis of Class A operation.
Take a 300V B+, move the plate to near 0 Volts, and then to near 1000V or more due to the cut off tube.
(especially if the load on the output transformer is light / or high impedance).
Ouch! Arcing tube, Arcing output transformer, and a terrible sound in the loudspeaker. That is Not music!
I have built single ended amplifiers with:
*** Pentodes; beam power tubes; DHT Direct Heated Triodes (no cathode); and Indirect Heated Triodes (they have a cathode);
Ultra Linear pentodes; and Ultra Linear beam power tubes; Triode Wired pentodes; and Triode Wired beam power tubes.***
Which tube type do you want to use?
For a single ended amplifier, which mode do you want the tube to be in?
Lots of possibilities.
A single ended output tube plate normally is very near to the B+ voltage, it is only an output transformer's primary voltage drop away from the B+ voltage (B+ 300V, primary voltage drop 10V, plate at 300 - 10 = 290V).
Push Pull amplifiers can use all the tubes and operating modes listed in * through * above.
Push Pull amplifiers can operate in Class A, Class AB, Class AB2, Class B, Class B2 . . . but Not in Class C.
and negative voltage / air rarefaction).
Take a 300V B+ to the single ended primary, and increase the signal volume level to move the plate voltage swings to near 0 Volts, and then to near 600V.
When you turn the volume way too high, it can clip when the tube cuts off completely.
A tube that cuts off, is the Antithesis of Class A operation.
Take a 300V B+, move the plate to near 0 Volts, and then to near 1000V or more due to the cut off tube.
(especially if the load on the output transformer is light / or high impedance).
Ouch! Arcing tube, Arcing output transformer, and a terrible sound in the loudspeaker. That is Not music!
I have built single ended amplifiers with:
*** Pentodes; beam power tubes; DHT Direct Heated Triodes (no cathode); and Indirect Heated Triodes (they have a cathode);
Ultra Linear pentodes; and Ultra Linear beam power tubes; Triode Wired pentodes; and Triode Wired beam power tubes.***
Which tube type do you want to use?
For a single ended amplifier, which mode do you want the tube to be in?
Lots of possibilities.
A single ended output tube plate normally is very near to the B+ voltage, it is only an output transformer's primary voltage drop away from the B+ voltage (B+ 300V, primary voltage drop 10V, plate at 300 - 10 = 290V).
Push Pull amplifiers can use all the tubes and operating modes listed in * through * above.
Push Pull amplifiers can operate in Class A, Class AB, Class AB2, Class B, Class B2 . . . but Not in Class C.
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???
SE Class A amplifier power tube's anode voltage is near to high voltage supply voltage (B++ minus Ia*DCR of output transformer primary) as 6A3sUMMER wrote.
It is half way biased if it is resistor or current source loaded, for max output.
With transformer or inductance loading Va is very close to B+ because there's very little drop across the wiring resistance of a coil. But it is the AC impedance that determines the signal load impedance and the output..
Jan
With transformer or inductance loading Va is very close to B+ because there's very little drop across the wiring resistance of a coil. But it is the AC impedance that determines the signal load impedance and the output..
Jan