HT regulator using 78xx

poynton · 9th February 2006, 06:31 PM

Hi.

Can a 78xx ( or other cheap regulator) be used to regulate a voltage of around 200v for a valve preamp??

or is a high voltage transistor with zeners adequate?

I'm not looking for anything sophisticated - just simple and working.

Any help appreciated.

Andy

SY · 9th February 2006, 06:33 PM

The 317 is suitable and cheap. Go to the National Semiconductor site and search for the applications note on this from Michael Maida.

triode_al · 9th February 2006, 06:39 PM

yes, as the thing is purely floating.
Though use a diode (250 PIV) across the unit as a safeguard against the countercurrent if the feeding supply might get lower than the destination...
I used this already in 1984!
It will give around 5-10 mV ripple/noise.
You can put a small capacitor on the voltage intersection (100 nF) to reduce noise. But then also this must be brigden with a diode to the destination to ensure the "ground termminal" never is higher than the Vout or the unit will break down when the output goes down too fast.

Whether the simple zener/transitor is ok depends on the feed: often a zener will hardly be 'quiet'.

poynton · 9th February 2006, 06:50 PM

Hi.

OK guys - enough info for now!!

Thanks for the quick replies - much appreciated.

Andy

9th February 2006, 06:31 PM	#1
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	HT regulator using 78xx Hi. Can a 78xx ( or other cheap regulator) be used to regulate a voltage of around 200v for a valve preamp?? or is a high voltage transistor with zeners adequate? I'm not looking for anything sophisticated - just simple and working. Any help appreciated. Andy

9th February 2006, 06:33 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	The 317 is suitable and cheap. Go to the National Semiconductor site and search for the applications note on this from Michael Maida. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

9th February 2006, 06:39 PM	#3
triode_al diyAudio Member Join Date: May 2004 Location: Westland Blog Entries: 1	yes, as the thing is purely floating. Though use a diode (250 PIV) across the unit as a safeguard against the countercurrent if the feeding supply might get lower than the destination... I used this already in 1984! It will give around 5-10 mV ripple/noise. You can put a small capacitor on the voltage intersection (100 nF) to reduce noise. But then also this must be brigden with a diode to the destination to ensure the "ground termminal" never is higher than the Vout or the unit will break down when the output goes down too fast. Whether the simple zener/transitor is ok depends on the feed: often a zener will hardly be 'quiet'. __________________ See my 2SK175/2SJ55 F5.. CS8412/SAA7220/TDA1541 ; SP-6 Light ; MC30 Super--> two stage RIAA 2SK240-ECC88/6SL7.

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9th February 2006, 06:50 PM	#4
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	Hi. OK guys - enough info for now!! Thanks for the quick replies - much appreciated. Andy

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