5-Tube PSU Schematic - Xformerless - Simpler is Better?

[beatpoet]

This is a PSU from an old 5-tube radio.

Is this too noisy for the heaters? Any drawbacks other than losing the whole set because of one filament?

I was thinking of small mixer circuits - this could accomodate 10 amplifiers at 12VAC per HT whilst using a semiconductor rectifier for the B+

I suppose you could add legs of 5 tubes from the hot of the mains.

How about an 8-channel NYDAVE mic/line mixer with stereo mix bus? Probably enough gain left over for a short but sweet EQ.

what the hey - it's simple.

 

[beatpoet]

What if you added a HV bridge rectifier from mains hot to neutral, using true ground for reference at the tail end of the series heaters. Perhaps you could accomodate 10 tubes on one leg?

I'm wondering about the initial turn-on's effect on the filaments or rectifier too. I have a few 1,000V high-amp rectifiers I've been looking to use on something.

I'm confusing myself now, I've had a long day.

 

[mich]

Probably enough gain left over for a short but sweet EQ.

-do you have the schematic for this EQ?i'll buy you a beer.. :sam:

 

[PRR]

Stick your finger in the wall outlet. It is a quicker way to die.

This scheme worked on radios, because there were NO external connectors. Radio waves came right through the case, sound waves came out, all knobs were plastic.

Even so, a lot of people were killed by these radios.

Do not do it.

 

[beatpoet]

That's what happens when ya learn from old, old books.

Next I'll be eating selenium rectifiers like potato chips.

[quote author="mich"]
-do you have the schematic for this EQ?i'll buy you a beer.. :sam:[/quote]

Is that a promise? :guinness:

 

[Mailliw]

[quote author="PRR"]Stick your finger in the wall outlet. It is a quicker way to die.

This scheme worked on radios, because there were NO external connectors. Radio waves came right through the case, sound waves came out, all knobs were plastic.

Even so, a lot of people were killed by these radios.

Do not do it.[/quote]

Could you elaborate for curiousity's sake please? I've been told it was because the chassis was the return path and they used non-polarized plugs, letting you put wall AC onto the chassis if you plugged it in backwards.

 

[beatpoet]

I am wondering if there are ANY instances of safely using power directly from the mains...

I was attempting to get an easy out for my heater supplies ONLY, as I have a couple of 1:2 transformers for B+

 

[NewYorkDave]

I wouldn't do it even if the heaters were totally floating, which would be a very noisy arrangement anyway.

Filament transformers are cheap. Even plate/filament transformers can be cheap if you look around. Better to spend a couple of bucks and do it the right way.

 

[Guest]

Even better, rectify a filament voltage and regulate it by a voltage regulator that limits output current on the level a bit higher that is needed to power already hot filaments. In such case you'll get no hum from filaments, and tubes will live longer because of slow start of heating.

 

[ciminosound]

[quote author="Mailliw"][quote author="PRR"]Stick your finger in the wall outlet. It is a quicker way to die.

This scheme worked on radios, because there were NO external connectors. Radio waves came right through the case, sound waves came out, all knobs were plastic.

Even so, a lot of people were killed by these radios.

Do not do it.[/quote]

Could you elaborate for curiousity's sake please? I've been told it was because the chassis was the return path and they used non-polarized plugs, letting you put wall AC onto the chassis if you plugged it in backwards.[/quote]

Series heaters DIRECTLY off the AC line. If something goes wrong there's no isolation, not very safe. It's like sticking your fingers in the wall socket.