Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

How to DIY Attenuated Interconnects?
How to DIY Attenuated Interconnects?
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
Thread Tools Search this Thread
Old 27th January 2010, 01:43 AM   #1
lgreen is offline lgreen  United States
diyAudio Member
lgreen's Avatar
Join Date: May 2003
Location: San Diego, USA
Default How to DIY Attenuated Interconnects?

My office system is way too loud. It is a cd player (no volume control) to BOSOZ preamp to amp to speakers. I can only get 1 click on the preamp volume controls and its still too loud. I need background music at low volumes and some vol control wiggle room.

What I'd like to do is install some attenuation into my CD->PRE or PRE->AMP interconnects without messing up the treble response. Seems a series resistor in the + lead and a resistor to ground should do it (talking about the RCA connection here). But what should the values be and where should I install this?
Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.
  Reply With Quote
Old 27th January 2010, 03:27 AM   #2
Peter Daniel is offline Peter Daniel  Canada
diyAudio Member
Peter Daniel's Avatar
Join Date: Jul 2002
Location: Toronto, Canada
How to DIY Attenuated Interconnects? Send a message via AIM to Peter Daniel
You can calculate the values here: 50-Step Shunt Attenuator Resistor Calculator - Neville Roberts

Normally, you should only need appropriate value series resistor as the shunt resistor is usually already inside the equipment.

Here's the adapter I made for a customer (using Cardas parts) who needed additional attenuation with my amps: 22k series resistor (nude Vishay) will add 6dB of attenuation with 22k shunt that was in the amp.
Attached Images
File Type: jpg aten.jpg (176.2 KB, 175 views)
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 27th January 2010, 04:44 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
if you want -20dB then the resistors are in a 9:1 ratio. -40dB requires a 99:1 ratio.

For this to hold true the input impedance (Rin) of the amp must be much greater than the grounding resistor (Rg).

Take a 9k and 1k pair. At first sight this gives the 9:1 ratio and should give -20dB.
attenuation = 20 * log [1 / (9+1)] gives -20dB.
Now take the input impedance of the amplifier into account.
attenuation = 20 * log[1//100 / (9+1//100)] gives -20.1dB. not too much of an error.
attenuation = 20 * log[1//10 / (9+1//10)] gives -20.7dB. the error is 7times bigger.
The closer Rin to Rg the worse the error gets.
The pre-amp/source sees the attenuator and the 22k amp as a 10k001 load.

Using 9k1 and 1k the attenuator has an output impedance of 901r and creates -20.35dB when Rin=22k
You can check whether that 901r source impedance causes an HF roll off problem.
The pre-amp sees the attenuator and 22k amp as a 10k001 resistive load in parallel with the the cable capacitance.
regards Andrew T.

Last edited by AndrewT; 27th January 2010 at 04:55 PM.
  Reply With Quote


How to DIY Attenuated Interconnects?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
My new DIY interconnects cjkpkg Parts 7 31st August 2009 04:13 PM
DIY Interconnects mhouston Everything Else 61 29th June 2007 12:38 AM
DIY Interconnects RyanW Solid State 13 18th December 2006 11:58 AM
cd input too loud can it be attenuated? homertooties Solid State 14 4th December 2006 05:06 PM
diy interconnects graeme uk Everything Else 18 17th May 2006 10:06 PM

New To Site? Need Help?

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

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio