I (stupidly) bought some phonograph at a yard sale, after briefly observing it had "tubez". First thing I noticed after getting it home - no PT.
No 12AX7 either - A 50C5, a 35W4 - a resistor in the heater string - and of course, a death cap from one side of the NP plug to the chassis. The piezo cartridge drove the 50C5 directly.
I've seen Zenith radios where much care was taken to isolate the hot chassis from human contact. But this thing has a turntable that's made of metal. I suppose as long as the insulation holds on those fine wires up through the metal tone arm. Volume and tone - yeah, tone a pot and cap across the OPT primary - were isolated primarily by their plastic knobs.
Another $15 down the toilet, another 2 cu ft for the junk yard. People sell 'em on ebay I see. Selling just the amp would be a no-no in my book. I was thinking of snapping a pic of the schematic for a "who has done worse in audio as a commercial product" thread -
No 12AX7 either - A 50C5, a 35W4 - a resistor in the heater string - and of course, a death cap from one side of the NP plug to the chassis. The piezo cartridge drove the 50C5 directly.
I've seen Zenith radios where much care was taken to isolate the hot chassis from human contact. But this thing has a turntable that's made of metal. I suppose as long as the insulation holds on those fine wires up through the metal tone arm. Volume and tone - yeah, tone a pot and cap across the OPT primary - were isolated primarily by their plastic knobs.
Another $15 down the toilet, another 2 cu ft for the junk yard. People sell 'em on ebay I see. Selling just the amp would be a no-no in my book. I was thinking of snapping a pic of the schematic for a "who has done worse in audio as a commercial product" thread -
But that is a Mains transformer.
Are you clickbaiting or pulling our legs with the thread title?
Please change it to "SMPS powered tube amp".
As-is, it sounds like you are making fun of Forum rules.
Connecting 2 "just legal" 48V supplies in series creates a "beyond the limits" potentially deadly 96V one.
Your thread continues trying to surpass safe limits.
It is much lighter- much smaller transformer -- better regulation.
Ok -- I will change title -- but the benefit will be there -
Original idea bad -- sorry
Ok -- I will change title -- but the benefit will be there -
Original idea bad -- sorry
No different than the 300VDC normally used -- it has the same situation -- the output transformer protects you from the internal 300VDC
Thanks.
The moderation team take a dim view of mains connected audio devices. Generally we do not allow the posting of such projects here.
However, since this thread has now taken this into consideration and changed direction, we will let the thread stand.
From the forum rules.
3. Working on live and non isolated power supplies as well as high voltage equipment carries risk. Much of today's equipment uses power supplies derived from circuitry that is both live at all times and that also has no isolation from the incoming mains supply. This can be lethal to those unfamiliar with this mode of operation. Even probing the circuitry with mains powered test equipment carries an immediate and lethal risk. It is therefore the responsibility of the person working on such equipment to ensure that they are fully conversant with safe working practices which include (but are not limited to) powering both the item being worked on and the test equipment from an isolated supply. Tube/valve circuitry also poses a lethal shock hazard due to the high voltages typically encountered. Again, the person working on such projects should be conversant with safe and good working practices.
As a concerned Forum member I'd ask to have thread name changed to "SMPS powered Tube Amp"
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