I wouldn't be surprised if he also gets to listen to the local AM radio broadcasts with that construction technique.
I like this construction idea as well. It sort of reminds me of the builds that you see on the Bartola Valves site. Very cool indeed.
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To demodulate AM you need a non-linear element, I don't see any tubes with suitable operating points or any p-n junctions around
Beside, I rather like the construction myself too, although for safety it does need a cage or something.
Beside, I rather like the construction myself too, although for safety it does need a cage or something.
The system is dead quiet. There is a very slight hum if I put my ear "glued" to the speaker cone.
As far as the system is not grounded, one can touch the plate caps. But the RCA plug and plate cap are close. I don't have kids in home and nobody else uses my system, this is why I didn't think so much of safety.
The construction concept was born with the idea that the amp should be modification friendly. Today it could be D3A/6P45S, tomorrow it could be 471A- 300B 😉
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Wow, y'all just don't get the concept of RFI and EMI protection for electronic circuits, do you?
If you're going to fool around with VHF pentodes, you'd better be prepared to shield it from RFI!
If you're going to fool around with VHF pentodes, you'd better be prepared to shield it from RFI!
Uh, I ain't talking about that tube... The D3A is a VHF small signal pentode intended for use at the front end of radio receivers....
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It's not easy to design a VHF amplifier, even if such signals found their way in, they will for the most part end up being dissipated to ground because the parts he is using are not designed to work at VHF (e.g. chokes will likely become capacitive).
It's one reason why tubes are good at the front end of an amplifier, as opposed to a bipolar transistor which has a pn junction that can demodulate r.f. signals - and so you definitely want to have an r.f. filter at the front of a bipolar transistor amplifier.
It's one reason why tubes are good at the front end of an amplifier, as opposed to a bipolar transistor which has a pn junction that can demodulate r.f. signals - and so you definitely want to have an r.f. filter at the front of a bipolar transistor amplifier.
Uh, I was referring to the unintended consequences of using very high bandwidth parts in a chassis that has NO RFI or EMI shielding. That "hum" he hears may be the D3A oscillating it's little heart out.
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ah, yes, now I understand you concern. I don't worry about the chasis for that though, but I would worry if there were no gate stoppers and small cap from heater to ground. Since he has no O'scope he could use a small portable radio to sniff out local rf oscillations. Not sure if they would produce audible hum but then I've no experience with using high gm tubes (yet).
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