power supple for valve pre-amp - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th December 2009, 02:08 PM   #1
cr0wl3y is offline cr0wl3y  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Default power supple for valve pre-amp

Hi there,

Been looking around for ideas on building a pre-amp and while looking into power supplies, I noticed that on a couple of designs, a 220V AC supply is "turned" into 250V DC using a network of diodes, a choke and some smoothing capacitors. One example is the one shown in this site:

OBTAINING 250vDC & 6.3vAC FOR VALVES by Harry Lythall

Does this also imply that you can essentially power a valve amplifier (excluding the heaters) using European mains and the aforementioned diodes-choke-caps circuit? Is it adviseable?

Thank you,
Nikos
  Reply With Quote
Old 8th December 2009, 03:07 PM   #2
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Yes. No.

My guess, nobody really wants to get into this because there are loads of safety issues and no-one really wants to encourage you because your post is a bit glib. We don't like glib where mains power is involved. There are legal issues too. All-in-all too much to go into into with someone with a bare grasp of the basics. 240VAC will give you plenty of DC to operate a valve but in general you should not operate any device other than a simple resistive load direct from the mains without an isolating transformer.

w

Last edited by wakibaki; 8th December 2009 at 03:10 PM.
  Reply With Quote
Old 8th December 2009, 03:47 PM   #3
diyAudio Member
 
Steve Dunlap's Avatar
 
Join Date: Sep 2008
Location: Here
Quote:
Originally Posted by wakibaki View Post
Yes. No.

My guess, nobody really wants to get into this because there are loads of safety issues and no-one really wants to encourage you because your post is a bit glib. We don't like glib where mains power is involved. There are legal issues too. All-in-all too much to go into into with someone with a bare grasp of the basics. 240VAC will give you plenty of DC to operate a valve but in general you should not operate any device other than a simple resistive load direct from the mains without an isolating transformer.

w
If you check the link he posted, you will see he does use a transformer.
  Reply With Quote
Old 8th December 2009, 03:52 PM   #4
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
Quote:
Originally Posted by Steve Dunlap View Post
If you check the link he posted, you will see he does use a transformer.
But if you read his post, you will see that he is asking if he can leave it out.

It must be stated even more emphatically than wakibaki did that this is a no go, an isolating transformer must be used for safety.
__________________
Aerodynamics are for people who can't build engines. Enzo Ferrari
  Reply With Quote
Old 8th December 2009, 04:05 PM   #5
diyAudio Member
 
Steve Dunlap's Avatar
 
Join Date: Sep 2008
Location: Here
Quote:
Originally Posted by leadbelly View Post
But if you read his post, you will see that he is asking if he can leave it out.

It must be stated even more emphatically than wakibaki did that this is a no go, an isolating transformer must be used for safety.
I missed that part. You are absolutely correct.
  Reply With Quote
Old 9th December 2009, 04:09 PM   #6
cr0wl3y is offline cr0wl3y  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
Thanks for the advice - transformer it is!

For the record, what does "glib" mean?
  Reply With Quote
Old 9th December 2009, 04:17 PM   #7
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Offhand, superficial, it means.
  Reply With Quote
Old 16th December 2009, 04:51 PM   #8
cr0wl3y is offline cr0wl3y  United Kingdom
diyAudio Member
 
Join Date: Sep 2009
One more question, if I may:

The schematic posted before (it's actually been mover to a new server, link posted below) starts with 220V AC, which is then rectified and smoothed to power the pre-amp. Assuming I have 230V AC instead, will I need to re-think the amp circuit?

The new link: OBTAINING 250vDC & 6.3vAC FOR VALVES by Harry Lythall

Thanks,
Nikos
  Reply With Quote
Old 17th December 2009, 02:01 PM   #9
Banned
 
Join Date: Jan 2008
Blog Entries: 2
No, the difference is not significant in this case. Lots of components used in valve circuits have tolerances of 5%. 1-in-22 is less than 5%. Depending on the design your last requirement may be to tweak some values for best performance once things are running, almost certainly you will want to check what quiescent currents you have ended up with.

w
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Shunt Cascode Power Valve Driver Rod Coleman Tubes / Valves 18 12th February 2010 12:02 AM
Swap Shanling CD-T80 valve CD player for Quad valve equiment johnm Swap Meet 2 24th September 2009 12:15 PM
Valve Power Supplies? soundbadger Tubes / Valves 2 8th October 2007 02:29 PM
Valve Pre Amp & Class D Power Amp Puffin Tubes / Valves 7 16th June 2006 04:41 PM
MOT valve power supply? Kilowatt Tubes / Valves 6 10th December 2001 05:13 AM


New To Site? Need Help?

All times are GMT. The time now is 08:46 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2