Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 2nd January 2004, 03:18 AM   #1
Garbz is offline Garbz  Australia
diyAudio Member
 
Join Date: Dec 2003
Location: Brisbane
Send a message via ICQ to Garbz Send a message via MSN to Garbz
Default How can i use a noisy PSU ?

Hi all.

I recently built an OpAmp based headphone amplifier using OPA2134 chips from BurrBrown. The amplifier itself works perfectly and sounds pretty good considering the price and the cheap parts.

The problem is the amp is powered by a computer PSU and while it sounds great from a 9v battery, it sounds rather noisy when running in the computer. If i turn my fans on the amp sounds like a lawnmower!

Basically the amp doesn't draw power through a rail splitter because of the nature of a computer's sound design, and there's nothing fancy at all.

Currently the +12v rail of the PSU is connected 200ohm resistor (the original attempt to reduce noise). From there +12v and -12v connect in parrallel to a 1000uf capacitor, and then are connected straight to the power pins on the opamp.

The circuit and amp itself generate no noise at all, it all comes in on the +/-12v rails of the power supply.
How can i reduce noise in this situation? Currently the amp is utterly useless!
  Reply With Quote
Old 2nd January 2004, 11:04 AM   #2
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Default One setp back, then two forward..

Much of the noise will be common-mode.
IMO Fixing it will be more trouble that building a new (linear) power supply.
  Reply With Quote
Old 2nd January 2004, 12:16 PM   #3
diyAudio Member
 
Join Date: Oct 2002
Location: pittsboro, NC
Is the noise high frequency or 50/60 Hz ?

My 2cents is buy a wall wort PS and run it off that.
  Reply With Quote
Old 2nd January 2004, 01:57 PM   #4
Garbz is offline Garbz  Australia
diyAudio Member
 
Join Date: Dec 2003
Location: Brisbane
Send a message via ICQ to Garbz Send a message via MSN to Garbz
i was afraid something like that would have happened.

Like i said it sounds like a quiet lawnmower. I didn't think it would be an easy fix. It's just transformers cost the best part of $30AUD here.
  Reply With Quote
Old 2nd January 2004, 04:01 PM   #5
diyAudio Member
 
Join Date: Dec 2003
Location: Atlanta, GA, US
Send a message via ICQ to tpenguin Send a message via AIM to tpenguin Send a message via Yahoo to tpenguin
I'm certainly no expert, but I'll give you my thoughts anyway. When your computer is running, the fans are going to generate some fairly large, oscillating magnetic fields. Any inductive part prior to an opamp (or even inside one) is going to pick up a tiny bit of AC from these oscilations, and this includes the PSU's wiring. I would suggest putting the amp in a separate enclosure and powering it from a small Wall-mountable power supply with a couple of extra filtering caps to smooth out the ripple. This should make it sound better. If you have to have it inside your computer, I'd still recommend you use an external wall-mount PSU, and just run shielded power cables into your case. If that doesn't clear up the noise, try a shielded sub-enclosure inside your computer. I don't know if that will help or not, but that's what I would try.
  Reply With Quote
Old 3rd January 2004, 12:15 AM   #6
Garbz is offline Garbz  Australia
diyAudio Member
 
Join Date: Dec 2003
Location: Brisbane
Send a message via ICQ to Garbz Send a message via MSN to Garbz
thanks everyone but this is getting too hard.

The amp itself doesn't pick up the noise from the fans when i'm using a 9v battery. So i'm just gonna put the amp unshielded into the side of the case and simply run an additional powersupply into the computer.

Personally i'm not gonna worry about the ripple either since the sound is comming from a computer and is therefore quite substandard anyway!

Thanks again.
  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
Noisy ADC 5th element Digital Line Level 6 30th August 2009 10:29 PM
Noisy NAD 705 squirrel69 Solid State 6 7th April 2006 01:37 AM
noisy noisy noisy noisy noisy tube dsavitsk Tubes / Valves 50 20th February 2006 04:07 PM
help on P1.7 (Noisy) pamaz Pass Labs 9 26th August 2004 02:21 PM
ESP P3A amp, very noisy DaViruz Solid State 33 16th November 2002 06:07 PM


New To Site? Need Help?

All times are GMT. The time now is 02:27 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