Another Wall wart question - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 26th November 2003, 02:55 PM   #1
JCoffey is offline JCoffey  United States
diyAudio Member
 
Join Date: May 2003
Location: Atlanta, GA
Default Another Wall wart question

OK, I'm really trying to build on a budget for a simple LM1875 pc amp, and I have a pair of Netgear router wallwarts that on the back have this info:
I\P: ac120v 60hz 22w
O\P: AC16v 1000ma

So what do you think? With the right rectifier, could a wallwart run a 1875? I know it would be a little underpowered, but since its for a PC speaker (Gonna build the Elf 1.0) It would be perfect to run a pair of wallwarts for a pair of 1875s
  Reply With Quote
Old 26th November 2003, 03:11 PM   #2
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
It should work. You could use a single supply and output cap, or you could create a virtual ground and run it from split rails. I have done this successfully with a steady 500mA load; at 1000mA of dynamic load, YMMV. Maybe someone else will comment or go single-supply if you want a sure thing.

You will only get about 4W into 8 ohms.
  Reply With Quote
Old 27th November 2003, 10:03 PM   #3
diyAudio Member
 
tlmadsen's Avatar
 
Join Date: Aug 2003
Location: Roskilde - The vikingships
Jcoffey

You don't need to do single supply or output cap. Have a look at

http://sound.westhost.com/project05.htm

You should do something along those lines.

This project if for pre-amps, but with your tranformaer size, it should work fine.

You don't need the regulators unless you capacitors are very small..............on the other hand with your small transformer it should also work fine with them included.

Your 16 V AC should give you something like +/- 20 V DC witch should be fine for your LM1875 and your PC-speaker.

Regards

Thomas
  Reply With Quote
Old 27th November 2003, 10:11 PM   #4
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
there is a schematic for single ended operation of the LM1875/3875 on Nat Semi's web site -- after all, it is an op-amp
  Reply With Quote
Old 27th November 2003, 11:01 PM   #5
JCoffey is offline JCoffey  United States
diyAudio Member
 
Join Date: May 2003
Location: Atlanta, GA
Quote:
Originally posted by tlmadsen
Jcoffey

You don't need to do single supply or output cap. Have a look at

http://sound.westhost.com/project05.htm

Regards

Thomas
Just so I understand you correctly, by using one of these boards, with the wall wart connected to it, gorund to the chassis and run the outputs to the 1875. If it's that easy, then sweet! but will it really only put out 4 watts?
  Reply With Quote
Old 1st December 2003, 03:05 PM   #6
JCoffey is offline JCoffey  United States
diyAudio Member
 
Join Date: May 2003
Location: Atlanta, GA
ttt
  Reply With Quote
Old 1st December 2003, 04:35 PM   #7
diyAudio Member
 
tlmadsen's Avatar
 
Join Date: Aug 2003
Location: Roskilde - The vikingships
To JCoffey

What does "ttt" mean ??

Thomas
  Reply With Quote
Old 1st December 2003, 04:49 PM   #8
macboy is offline macboy  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Ottawa, Canada
The power supply shown in project 5 uses half-wave rectification since the transformer has only a single output rather than two or a centre-tapped output. You can certainly do the same thing for your amplifier, but omit the voltage regulators. Basically, you just need everything up to the first pair of 100nF caps. You might want to increase the filter caps to more than 4700 uF though - since this is half-wave recitified, the caps only charge half as often, so they'll need to store twice the energy as the caps in a full-wave rectified design. I'd start with 10000 uF and see how that works.

Or, instead of using one walwart and a half-wave rectified supply per channel, you could use both walwarts together to make a full-wave rectified supply. This should save you a few bucks on filter caps. Treat the output of each walwart as one output of a dual-secondary transformer.
  Reply With Quote
Old 1st December 2003, 06:57 PM   #9
JCoffey is offline JCoffey  United States
diyAudio Member
 
Join Date: May 2003
Location: Atlanta, GA
hehe ttt means To the top, if a thread is getting stagnant and you need peopel to read it you type that to bring it back up.

I'm not quite sure I follow your idea with using both wall warts as one ps. If I am, I should just pretend that both wall warts are 1 toroid transfo and use a rectifier bridge as one normally would? If I do, what kind of DC Voltage should I be seeing?
  Reply With Quote
Old 1st December 2003, 07:09 PM   #10
JCoffey is offline JCoffey  United States
diyAudio Member
 
Join Date: May 2003
Location: Atlanta, GA
And if I go with the project from the link, this is all I should need to see 20v Dc correct?
Attached Images
File Type: gif p05_fig1.gif (3.4 KB, 294 views)
  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
wall wart and basswood BluesMagoos Analogue Source 6 9th September 2007 09:54 AM
Wall Wart for testing bal704 Chip Amps 6 23rd October 2006 01:47 AM
best wall wart for t-amp, where? gychang Class D 3 2nd October 2006 12:06 PM
Using unregulated AC wall wart ezkcdude Power Supplies 146 17th July 2006 11:43 AM
2 Wall Wart PS Question Sherman Chip Amps 13 22nd February 2005 09:25 PM


New To Site? Need Help?

All times are GMT. The time now is 09:30 PM.


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