Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Is this acceptable?
Is this acceptable?
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
Thread Tools Search this Thread
Old 12th December 2012, 02:16 AM   #1
weinstro is offline weinstro  United States
diyAudio Member
weinstro's Avatar
Join Date: May 2003
Location: N. Cal
Default Is this acceptable?

I need +- 24 Vdc and perhaps 700-800 ma.

Can I take two laptop power adapters rated at 24 Vdc and connect the outputs in series? Should I avoid providing an earth ground connection at the center node?


  Reply With Quote
Old 12th December 2012, 06:15 AM   #2
palstanturhin is offline palstanturhin  Finland
diyAudio Member
palstanturhin's Avatar
Join Date: Jun 2011
Is quite likely to be possible.
Depends on the supply type.
If output is floating you are good to go...

Measure it with DVM between both supplies. If you get 0 reading, you most likely can serial connect them...

(Been there, done that...)
  Reply With Quote
Old 12th December 2012, 07:03 AM   #3
jan.didden is offline jan.didden  Europe
diyAudio Member
jan.didden's Avatar
Join Date: May 2002
Location: The great city of Turnhout, BE
All adapters I have ever used had fully floating secondaries, they have to for safety reasons.
And if you use the ones with the 2-pin mains lead, it's even impossible for them NOT to be floating.
So yes, just put them in series and ground whatever node you want.

Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.
  Reply With Quote
Old 12th December 2012, 10:53 AM   #4
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
Unless the two adaptors are identical it might be good to put a diode in series too. Under normal conditions this will just drop 0.7V. On switch-off or some fault conditions it may stop one supply from driving current backwards through the other one, which could cause damage.
  Reply With Quote
Old 12th December 2012, 11:34 AM   #5
FoMoCo is offline FoMoCo  United States
diyAudio Member
Join Date: Dec 2012
Every laptop adapter I have used has had the barrel (usually "minus") connected to earth through the ground pin on the AC plug. This would make it impossible to easily series them.

Most likely the secondary of the SMPS is indeed isolated, and you could just not connect the ground pin, but it's one of those "if you have to ask, you shouldn't try" kind of things.

So. The short answer is "No."
  Reply With Quote
Old 16th December 2012, 08:56 PM   #6
weinstro is offline weinstro  United States
diyAudio Member
weinstro's Avatar
Join Date: May 2003
Location: N. Cal
Default Power Supply Question

Thanks for the previous answers.

I've located two 24 Vdc power supplies which are likely to support a series connection. These are inexpensive SMPS, rated at about 2A each, and are a open frame rather than wall wart style case with barrier strips instead of barrel connectors.

However, they are described as "constant voltage, LED power supply". How is that different than a "DC power supply"?

I do need constant voltage rather than constant current. Application is for a small Class A headphone amp.

Also, for Class A, current load presented to the power supply should be constant, therefore step load response should not be a major concern, correct?

Thanks and regards,

  Reply With Quote
Old 17th December 2012, 08:16 AM   #7
gmphadte is offline gmphadte  India
diyAudio Member
Join Date: Jul 2003
Location: Dona paula, Goa
Your application will suffer with these SMPSs. Better construct a linear power supply with some low noise voltage regulators.

Gajanan Phadte
  Reply With Quote


Is this acceptable?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How much noise is acceptable? matherp Chip Amps 10 4th December 2010 04:56 PM
Acceptable Acceptable Load for Lite 60 DAC 6922 Output Tubes dtm1962 Digital Source 0 14th November 2010 01:03 AM
Acceptable F3 UNDERSTANDIN Multi-Way 0 21st September 2005 03:23 PM
CapacitorsReplacing the old with the new. What is acceptable? naimgame Solid State 11 4th July 2004 07:35 PM

New To Site? Need Help?

All times are GMT. The time now is 06:34 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio