Nice. its a very simple idea. Probably won't be an issue at 150v however the screen on your valves should be current limited, and run at a slightly lower voltage than the plate. Learnt that one the hard way!!! Another safe alternative is you can run in triode mode by tying the screen directly to the plate.
I checked that it would be okay at 150V, I wanted the simplest circuit that would let me test the valves. I will probably try triode and ultralinear mode some time just to hear how it sounds, although the transformer taps aren't quite right for ultralinear.
No, it just uses a grid-leak detector then two stages of audio amplification - one stage in the same valve that does the detection, then more in the second valve. There's no regenerative feedback.
I tracked down the manual. Boat anchor now, but it must have been a cost-effective and versatile piece of kit in its day (and no doubt still is). Much better design than most Jack-of-all-trades equipment too - but what a horrible way they chose to draw the Darlington in the HV supply! Clever idea to use the op amp -15V rail as the below-ground reference, so the HV supply could get within a bee's dick of 0 V. (Have you tried making use of that to experiment with low-voltage valves working in space-charge mode? Many years ago I was an avid follower of Jeff Duntemann's "Structured Programming" column in DDJ. Head down the space-charge rabbit-hole with him if you're short of obsessions and want a lot of fun.) I'm guessing a good many Australian engineers cut their teeth on that BWD mini-lab.
Sweet. I went to school in the 1970's before White mother's gutted shop programs. No more electronics, wood shop or metal shop. Lot's of dance, though.
exactly where is the detection taking place? I see a TRF amplifier then an audio amplifier but not sure where detection is taking place other than maybe controlled conduction? Nice work and thanks for sharing. 73...
Detection takes place in the control-grid/cathode circuit of the first valve. That grid acts as the plate of a diode in its own right. The (rather inefficient) diode, capacitor and paralleled resistor form an envelope detector. The demodulated audio in the grid/cathode circuit is amplified in the cathode/plate circuit, then amplified more by the second valve.
@@whippoorwill1124 Ok, that makes sense now; would not have thought of the grid in that role. Thanks for responding and the excellent description! 😄 73…
@@SpinStar1956 You're welcome. If you have (potentially a lot of) time to spare, dive down the rabbit-hole of early research on valves (aka "vacuum tubes"). In the 1910s, and even into the '20s, they were objects of curiosity, poorly understood and undergoing rapid innovation. The people who came to be recognised as experts were mainly experimental physicists, and even gas-statisticians. They poked voltage and current at valves, at various frequencies and levels of vacuum, and reported their attempts at explaining what they observed. Grid-leak detection evolved gradually from circuitry that was much cruder. Like later demodulation methods, its development and eventual abandonment were driven by the constraints of growing numbers of radio transmitters, their increasing power levels, and the need to avoid both suffering and causing interference.
Nice. its a very simple idea. Probably won't be an issue at 150v however the screen on your valves should be current limited, and run at a slightly lower voltage than the plate. Learnt that one the hard way!!! Another safe alternative is you can run in triode mode by tying the screen directly to the plate.
I checked that it would be okay at 150V, I wanted the simplest circuit that would let me test the valves. I will probably try triode and ultralinear mode some time just to hear how it sounds, although the transformer taps aren't quite right for ultralinear.
Very nice
VERY NICE!⭐⭐⭐⭐⭐⭐⭐
cool radio
Nice! The tube sockets, where might I find those, please? Thanks!
Those are relay sockets. Great for breadboarding with octal tubes.
I had same idea using relays sockets in a guitar amp I made several years ago Compliments!
Nice 👍
This is a regenerative receiver?
No, it just uses a grid-leak detector then two stages of audio amplification - one stage in the same valve that does the detection, then more in the second valve. There's no regenerative feedback.
Useful-looking power supply, which I should perhaps recognise but don't. What make is it?
BWD 603B Mini-lab. www.radiomuseum.org/r/bwd_electr_mini_lab_603b.html
@@StephenMcNamara Thanks! And for the very prompt answer :-)
I tracked down the manual. Boat anchor now, but it must have been a cost-effective and versatile piece of kit in its day (and no doubt still is). Much better design than most Jack-of-all-trades equipment too - but what a horrible way they chose to draw the Darlington in the HV supply! Clever idea to use the op amp -15V rail as the below-ground reference, so the HV supply could get within a bee's dick of 0 V. (Have you tried making use of that to experiment with low-voltage valves working in space-charge mode? Many years ago I was an avid follower of Jeff Duntemann's "Structured Programming" column in DDJ. Head down the space-charge rabbit-hole with him if you're short of obsessions and want a lot of fun.) I'm guessing a good many Australian engineers cut their teeth on that BWD mini-lab.
Where did you get them tube bases? Thanks
They are 8 pin round relay sockets. Available lots of places.
Sweet. I went to school in the 1970's before White mother's gutted shop programs. No more electronics, wood shop or metal shop. Lot's of dance, though.
exactly where is the detection taking place?
I see a TRF amplifier then an audio amplifier but not sure where detection is taking place other than maybe controlled conduction?
Nice work and thanks for sharing. 73...
Detection takes place in the control-grid/cathode circuit of the first valve. That grid acts as the plate of a diode in its own right. The (rather inefficient) diode, capacitor and paralleled resistor form an envelope detector. The demodulated audio in the grid/cathode circuit is amplified in the cathode/plate circuit, then amplified more by the second valve.
@@whippoorwill1124 Ok, that makes sense now; would not have thought of the grid in that role.
Thanks for responding and the excellent description! 😄 73…
@@SpinStar1956 You're welcome. If you have (potentially a lot of) time to spare, dive down the rabbit-hole of early research on valves (aka "vacuum tubes"). In the 1910s, and even into the '20s, they were objects of curiosity, poorly understood and undergoing rapid innovation. The people who came to be recognised as experts were mainly experimental physicists, and even gas-statisticians. They poked voltage and current at valves, at various frequencies and levels of vacuum, and reported their attempts at explaining what they observed. Grid-leak detection evolved gradually from circuitry that was much cruder. Like later demodulation methods, its development and eventual abandonment were driven by the constraints of growing numbers of radio transmitters, their increasing power levels, and the need to avoid both suffering and causing interference.
Hola desde argentina.Ponele una mejor antena vas a ver una gran mejora.