DC offset figures - 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 4th February 2004, 11:21 AM   #1
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
Default DC offset figures

Hi everyone!!

Could someone please tell me what the max. level of DC offset from a source (in my instance a CD player) can be before the DC input cap is really necessary in the Gainclone?

Usign my multi-metre I put one probe inside the phono socket of my cd player, and the other touching the outside of the socket, with the player on, but no CD. measured about 0.54mv on both sockets. Is this acceptable, or should I use the 4.7uF input cap?

Thank you,

- John.

P.S. Nuuk i have read the section on DC offset on your site, but this is with a built Gainclone. I onyl want to build my gainclone once, so need to have the circuit/parts worked out before building. Cheers.
  Reply With Quote
Old 4th February 2004, 11:44 AM   #2
diyAudio Member
 
Join Date: Jul 2003
Location: Nottingham, England
Seems ok, you'll probably get an additional 10-20mV at the output of the amp which is quite acceptable IMO.
  Reply With Quote
Old 4th February 2004, 02:08 PM   #3
GregGC is offline GregGC  Canada
diyAudio Member
 
Join Date: Oct 2003
Location: Toronto
Default Re: DC offset figures

Quote:
Originally posted by johnm
Hi everyone!!

Could someone please tell me what the max. level of DC offset from a source (in my instance a CD player) can be before the DC input cap is really necessary in the Gainclone?

Usign my multi-metre I put one probe inside the phono socket of my cd player, and the other touching the outside of the socket, with the player on, but no CD. measured about 0.54mv on both sockets. Is this acceptable, or should I use the 4.7uF input cap?

Thank you,

- John.
Did you measure it when the player was playing or when in stop mode? I think you should be fine using DC coupled GC.
  Reply With Quote
Old 4th February 2004, 05:19 PM   #4
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Connect your source to the amp (with speakers disconnected and CD in PLAY) and then measure it on the amp. If it's less than 80mV (or so) it should be fine.
  Reply With Quote
Old 5th February 2004, 10:35 AM   #5
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
Thanks for all the advice guys! So - if I've understood this correctly - in order to measure DC offset properly the CD player MUST be connected to an amp, and must also be playing a CD then? can I not just measure the DC directly from the phono sockets on the CD player?
  Reply With Quote
Old 5th February 2004, 10:56 AM   #6
diyAudio Member
 
li_gangyi's Avatar
 
Join Date: Jun 2003
Location: Woodlands Circle
it is possilbe because the player has some DC out...if it's low then u don't need a DC blocking cap in front...however with an amp...the voltage will rise...due to gain and of course the opamp itself itself will have a little Offset...so you have to test for offset at the outputs as well to determine if your amp is working properly...but you wun need the DC blocking capacitor (usually 4.7uF) in front as your CD player seems to have low offset...
__________________
Kids in the back seat cause accidents...Accidents in the back seat cause kids...
  Reply With Quote
Old 6th February 2004, 12:51 PM   #7
johnm is offline johnm  United Kingdom
diyAudio Member
 
johnm's Avatar
 
Join Date: Sep 2003
Location: Hampshire
Hmmm.... I think I'll go without the input cap then. I'll just make damn sure to test it with an old pair of speakers first

I doubt - when all's said and done - that there can be a day and night difference between using either the cap, or the input resistor instead. when I've saved up more money I'll build a second one and try it with the input cap and compare the sound. So I gues it comes down to what sounds best - a 220r 2w carbon film resistor, or a 4.7uF Black Gate non-polar cap...
  Reply With Quote
Old 6th February 2004, 01:01 PM   #8
sss is offline sss  Israel
diyAudio Member
 
sss's Avatar
 
Join Date: Jul 2003
Location: Israel , haifa
Send a message via ICQ to sss
dont forget that the amplifier will amplify the offset of your cd player
  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
Distortion figures for analog muxes eplpwr Parts 39 26th June 2013 12:08 PM
Lissajous figures rtarbell Everything Else 1 28th October 2005 01:23 AM
Noise Figures northsiderap Solid State 12 7th May 2005 08:48 AM
Xmax figures to actual exurcsions? TRANSDUCEReng Subwoofers 20 21st September 2004 08:19 PM
help, need some figures Alex_B Multi-Way 54 9th December 2002 12:36 AM


New To Site? Need Help?

All times are GMT. The time now is 12:01 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