Direct from the mains?

Jonathan Bright · 12th September 2008, 09:42 PM

I live in a country with around 240V ac as mains power. I notice that some PSU for small signal tube circuits require around that voltage prior to retification/sabilization etc.. Given that we get 240ac straight "out of the tap", is it possible to dispense with the power supply transformer in these designs? Now be polite please. There may well be very good and obvious technical/legal/safety reasons etc.... it is just an innocent enquiry....ok?

I think my negative ion generator (built from a local mag' design) does this.

ray_moth · 12th September 2008, 10:24 PM

Jonathan,

This is not meant as a flame, but in a DIY forum such as this no one with any sense of responsibility is going to agree with doing what you suggest. It's dangerous (and possibly illegal where you live, anyway). If you do a search you'll find it has been discussed here already.

Bottom line: always use a transformer, even if it's only a 1:1 isolation transformer to give the same voltage as the mains.

SY · 12th September 2008, 10:36 PM

It is DEADLY DANGEROUS. Don't even think about it. That's why we have a forum rule against it.

12th September 2008, 09:42 PM	#1
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Direct from the mains? I live in a country with around 240V ac as mains power. I notice that some PSU for small signal tube circuits require around that voltage prior to retification/sabilization etc.. Given that we get 240ac straight "out of the tap", is it possible to dispense with the power supply transformer in these designs? Now be polite please. There may well be very good and obvious technical/legal/safety reasons etc.... it is just an innocent enquiry....ok? I think my negative ion generator (built from a local mag' design) does this. __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

12th September 2008, 10:36 PM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	It is DEADLY DANGEROUS. Don't even think about it. That's why we have a forum rule against it. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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12th September 2008, 10:24 PM	#2
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Jonathan, This is not meant as a flame, but in a DIY forum such as this no one with any sense of responsibility is going to agree with doing what you suggest. It's dangerous (and possibly illegal where you live, anyway). If you do a search you'll find it has been discussed here already. Bottom line: always use a transformer, even if it's only a 1:1 isolation transformer to give the same voltage as the mains.

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