Line Level attenuation - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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 7th May 2003, 12:18 PM   #1
habana is offline habana  United Kingdom
diyAudio Member
 
Join Date: May 2003
Location: Cardiff
Default Line Level attenuation

Does anyone know the resister values needed to attenuate the CD line-in on my amplifier. I want to attenuate it by about 12dB.

Thanks.
  Reply With Quote
Old 8th May 2003, 09:09 AM   #2
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Do you know the input resistance of your amplifier?
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 8th May 2003, 09:19 AM   #3
habana is offline habana  United Kingdom
diyAudio Member
 
Join Date: May 2003
Location: Cardiff
Default attenuation

Hi EC8010

I'm sorry I don't. Is that important? I was thinking along the lines of the Kimber attenuators, they are general purpose units so I understand.
  Reply With Quote
Old 8th May 2003, 11:30 AM   #4
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Make a voltage divider with the ratio 1:4

=>

10 k + 3.3k these values will work if the input impedance is >10 kohm (most likely) and if not lower the values, 5.6k + 1.8 k maybe?
__________________
/Per-Anders (my first name) or P-A as my friends call me
Tube Buffered Gainclone in work |Thread || Diamond buffer |Thread for the group buy | Wiki
  Reply With Quote
Old 8th May 2003, 02:26 PM   #5
habana is offline habana  United Kingdom
diyAudio Member
 
Join Date: May 2003
Location: Cardiff
Default Line attenuation

Thanks for the reply.

I've actually built a passive pre amp using stepped attenuators and so the CD output goes straight into the power amps. Does this make any difference?

Excuse my ignorance but in the example you gave (10K, 3.3K) which value goes on the line and which on the return to line?

Thanks.
  Reply With Quote
Old 12th May 2003, 09:35 AM   #6
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
The 10k goes in series with the line. The 3k3 goes from across the input of the preamp.
  Reply With Quote
Old 12th May 2003, 10:20 AM   #7
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
It helps if you know the input resistance. The resistor values suggested will work, but the input resistance loading your CD player will be roughly 10k. Most CD players use an op-amp output stage, and most op-amps produce higher distortion into lower resistance loads. Admittedly, 10k should be just outside that range, but if you can have a higher input resistance, why not? If you had known that the input resistance of your pre-amplifier was 10k (for instance), you could have simply added a 30k series resistor, and your new input resistance would have been 40k. You might prefer to keep the input resistance constant when adding attenuators, just in case the input resistance affects the sound.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 12th May 2003, 10:24 AM   #8
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Default atten

Don't forget that adding these largish resistors in series does worsen your signal-to-noise ratio (which will be worsened anyway by the attenuation).
I don't know any CD output stages (except possibly weakish tubed ones) that are hurt by a couple of kilo-ohms load. I would go even lower, 3k series and 1 k to gnd.

Jan Didden
  Reply With Quote
Old 12th May 2003, 10:43 AM   #9
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Default A final point...

The attenuator should be at the destination end of the cable.

Cheers,
  Reply With Quote
Old 12th May 2003, 10:45 PM   #10
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Default Brrr...

Hi,

Quote:
A final point...
All data given is way too vague but I understand D'haen's point when he suggested the attenuators at the end of the cable.

All in all a middle of the the road decision is called for here, vere to either end and you'll face a frequency abberation.

I agree with D'haen, best put the attenuator at the amp input.

Poor Q poor A I'm afraid,

P.S. Yet another case for transmissionline transfer theory.
__________________
Frank
  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
Convert Line Level to Electric Guitar Level miallen Solid State 4 16th May 2010 01:22 PM
speaker level input vs line level question crippledchicken Subwoofers 4 17th July 2007 03:36 AM
lesser of two evils, high level -> line level, digital volume control mazurek Solid State 3 19th November 2006 12:25 AM
how to bring down line level signal to preamplifier level deji Solid State 15 15th April 2004 04:13 PM
Line Level, Balanced Voltage Level... dkemppai Solid State 3 10th December 2002 11:04 PM


New To Site? Need Help?

All times are GMT. The time now is 06:23 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