Thrust me, you have the time. But at that age (I'm way ahead of you) it's mostly the motivation that's in short supply!
He is assuming the load is at least 500k, the input to the next stage, so wouldn't make much difference (his words).
Jan
You probably mean SEPP (Single Ended Push-Pull) OTL audio output stages, in combination with 800 Ohm loudspeakers. Philips used them in many of their televisions, radio's and a range of Hi-Fi amplifiers. Attached are some examples.
Sorry, I meant can you give me an example of a TV in which an SRPP was used for the speaker output.
Cheers
Ian
And of course not the HF303 😊
The upper tube is controled by the output current for a Serial Regulated Push Pull and can only function in classA.
In the HF303 the upper tube is driven by a phase inverter and can funtion in classAB for more output power.
Mona
The upper tube is controled by the output current for a Serial Regulated Push Pull and can only function in classA.
In the HF303 the upper tube is driven by a phase inverter and can funtion in classAB for more output power.
Mona
Yes the HF303 is in class of its own. Like 'the mother of all OTLs'.
It's also been an inspiration for combining (positive) internal feedback loop and overall feedback.
My own patent on a similar matter was conceptually very close but I didn't know the 303 at that time (end of the 90-ies).
If you know how to analyze the 303, you know circuit design!
Jan
It's also been an inspiration for combining (positive) internal feedback loop and overall feedback.
My own patent on a similar matter was conceptually very close but I didn't know the 303 at that time (end of the 90-ies).
If you know how to analyze the 303, you know circuit design!
Jan
The idea of positive feedback like in the HF303 goes back to the '50th I think.
Early '60th I have asambled the Philips HF308 kit (yes, I am very old 😀 ).
By the way, happy anniversery
Mona
Early '60th I have asambled the Philips HF308 kit (yes, I am very old 😀 ).
By the way, happy anniversery
Mona
Definitely not, the 309 is only the power amp. The 308 has a pre-amp + tone control.
Miller did the positive feedback to the grid from the inverter stage with all kinds of phase shift correction capacitors and the negative feedback to the cathode of the same tube.
Cathode to cathode feedback is more simple.
Here the explication of the positive feedback in the serial PP amp.
Mona
Ohh, yes the one I build was the HF 309, power amp only.
https://linearaudio.nl/sites/linearaudio.net/files/miller combined fb electronics march 1950.pdf
Jan
https://linearaudio.nl/sites/linearaudio.net/files/miller combined fb electronics march 1950.pdf
Jan
Like in the more eleborate SEPP circuits by Philips there is positive and (more) negative feedback going on in the HF309. But the HF309 is an ultra linear push-pull power amplifier, so it has little to do with SEPP or SRPP.
Instead of a couple of SIC diodes, I would try a known good sounding LED like a Broadcom HLMP-Q150, which will drop 1.6V and give it a listen. A low power LED isn't going to run across the knee, and I've found a combination of an LED + resistor can sound quite good. YMMV