Reducing CD player output: suggestions? - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, 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 6th June 2015, 02:35 PM   #1
Stabby is offline Stabby  Belgium
diyAudio Member
 
Join Date: Sep 2010
Default Reducing CD player output: suggestions?

I'm trying to find ways to attenuate my CD player's output for use with a vintage amplifier. RCA attenuators are too expensive (can't find cheaper than €50 to get a pair in Belgium). So I see only 2 cheap and easy fixes:

- Put in an Opamp with less gain. Are there any dual Opamps with 6dB less gain than for example NE5532?
- Add 2 resistors per channel (one in series, one to ground) after the Opamp stage. I'm fully aware that it's better to put these at the amplifier's input but what's the difference if I put them at the CD player's output? More high frequency roll-off? My hearing craps out at 16kHz so I'm not too worried about that.

CD players I have are Philips CD710, CD634 and CD620. The latter two have variable gain output so I could play around with that without any mods. The CD710 however does not and will require a mod.
  Reply With Quote
Old 6th June 2015, 02:58 PM   #2
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Putting in an opamp with "less gain" will make no difference whatsoever, as the circuit gain is determined by feedback components (usually resistors) and not the opamps.

Adding an attenuator will do the trick. This should be at the amp end, not the CD player end, unless you are happy to lose treble due to the cable capacitance. If the cable is short then this doesn't matter.
  Reply With Quote
Old 6th June 2015, 04:08 PM   #3
Stabby is offline Stabby  Belgium
diyAudio Member
 
Join Date: Sep 2010
Thank you. If I put the attenuator at the CD player end, how do you think treble will be affected? Will everything below 16kHz be untouched?
  Reply With Quote
Old 6th June 2015, 04:15 PM   #4
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Use something like 6k8 feed resistor and determine the second shunt element of the attenuator by listening until the level suits. Any CD player will drive loads down to at least 2K, in practice quite a bit lower.

The treble won't be materially affected.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 6th June 2015, 04:18 PM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
If you use 6k8 and have a cable capacitance of say 200pf then the -3db point is way over 100kHz. You can go lower than 6k8. Try a 2k2 and say 680 ohm as a shunt if your old amp is really sensitive.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 6th June 2015, 04:50 PM   #6
impuls is offline impuls  Yugoslavia
diyAudio Member
 
Join Date: May 2006
solder over 3304 and 3305 resistors another one 3k9
Attached Images
File Type: jpg cd710out.jpg (44.4 KB, 79 views)
  Reply With Quote
Old 6th June 2015, 05:13 PM   #7
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Nooo I wouldn't do that. The stage isn't a gain block, its an I/V convertor. What about the coil and the cap ?

What you could do is just add a resistor across the 1nf cap at the output. Adding 1k would cut the level in half.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 6th June 2015, 06:32 PM   #8
Stabby is offline Stabby  Belgium
diyAudio Member
 
Join Date: Sep 2010
Quote:
Originally Posted by Mooly View Post
If you use 6k8 and have a cable capacitance of say 200pf then the -3db point is way over 100kHz. You can go lower than 6k8. Try a 2k2 and say 680 ohm as a shunt if your old amp is really sensitive.
I saw your post before from a few years ago. Is that the recommended position for the resistors or can I put them after the coupling capacitor right before RCA outputs?

Quote:
Originally Posted by Mooly View Post
Nooo I wouldn't do that. The stage isn't a gain block, its an I/V convertor. What about the coil and the cap ?

What you could do is just add a resistor across the 1nf cap at the output. Adding 1k would cut the level in half.
Any disadvantages of that over the other method (with 2 resistors)? So 1k would be -3dB, 4k -6dB?

Also, does it make a difference if I use cheap film resistors vs more expensive ones?

Last edited by Stabby; 6th June 2015 at 06:35 PM.
  Reply With Quote
Old 6th June 2015, 06:43 PM   #9
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The earlier post was player specific, in just the same way that this one is

There is no disadvantage with adding a resistor across the 1nf cap, its achieving the same thing. In this case you have a nice 1k to use as part of the attenuator, in the earlier thread there wasn't anything suitable without changing those 100 ohms. I have spotted one thing though, and this would apply to an external attenuator as well, and that is that the coupling cap 2306 in the above diagram could do with increasing by a factor of 10 to 47uf. That will preserve the low frequency response of the stage.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 6th June 2015, 06:54 PM   #10
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The resistor quality will have no effect. Use standard 0.25 or 0.6 watt metal films.

The really important thing is for you to make sure your player really is the same as the one in the diagram. If the 1k resistor is different then the attenuator would not work correctly without altering. Once you know what you have then its only a minutes work to pick suitable values.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  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
dj cd player suggestions j_dunavin Digital Source 1 5th November 2008 03:36 PM
looking for cd/dvd player suggestions rtate Digital Source 5 4th May 2008 11:26 AM
Any good sounding cd player suggestions to buy used ? gaetan8888 Digital Source 6 31st July 2007 09:14 PM
suggestions for a new-used CD-player (to buy on e-bay) Antonio Tucci Digital Source 6 12th August 2006 02:35 PM
How do I use CD-Rom diy meridian 588 CD player and 800 reference CD/DVD player? jelou Digital Source 4 29th April 2004 03:48 AM


New To Site? Need Help?

All times are GMT. The time now is 01:36 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2