Subwoofer circuit: Going from speaker level to line level - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, 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 16th December 2011, 08:47 PM   #1
champ04 is offline champ04  United States
diyAudio Member
 
Join Date: May 2009
Default Subwoofer circuit: Going from speaker level to line level

Greetings,
Most modern sub-woofers have both speaker level (high) and line level (low) inputs.

My sub does not have the speaker level inputs. This was not a problem while I was using a pre-amp in my system. But now that I've gone direct from the source, I need a way to include my sub in the system.

I was thinking about creating a circuit that would allow my sub to get it's signal from the main amp.

But before I go any further I am wondering, what's the opinion here on how complicated this might be and degree of difficultly to implement.

All I need is a circuit that takes me from the output level of my amp back to a workable line level that my sub amp can a handle.
Seems simple enough.
Any ideas?

Thanks!!
  Reply With Quote
Old 16th December 2011, 08:57 PM   #2
frasco is offline frasco  Finland
diyAudio Member
 
Join Date: Nov 2011
Location: Finland
I'm by no means an expert but wouldn't it be more logical to take the signal from the amp input instead of the output?
  Reply With Quote
Old 16th December 2011, 09:07 PM   #3
champ04 is offline champ04  United States
diyAudio Member
 
Join Date: May 2009
Quote:
Originally Posted by frasco View Post
I'm by no means an expert but wouldn't it be more logical to take the signal from the amp input instead of the output?
Perhaps.
I am using a shunt attenuator connected at the back of the amp.
So in order for it to work, the signal would have to branch off between the shunt circuit and the amp.

I'm not certain how this would effect the various impedances.

As it is, my source output impedance is 5ohm. The amp input impedance is 100Kohm. And the shunt circuit has a 2kohm for it's series resister. (technically, 1k per balanced leg.)
I haven't looked yet to see what the input impedance of the sub amp would be.

I'm just assuming that the input impedance of the sub amp would be a lot more benign parallel to the speaker load. It also keeps as much out of the primary signal circuit as possible. (though I may be naive in this thinking.)

Last edited by champ04; 16th December 2011 at 09:11 PM.
  Reply With Quote
Old 16th December 2011, 09:25 PM   #4
frasco is offline frasco  Finland
diyAudio Member
 
Join Date: Nov 2011
Location: Finland
I have no idea TBH, let's wait for the experts to answer.
  Reply With Quote
Old 16th December 2011, 10:02 PM   #5
ODougbo is offline ODougbo  United States
diyAudio Member
 
Join Date: Aug 2011
Location: Maryland USA
Sounds like you want to build one, however there are a lot of different models for sale.

e.g. Amazon.com: XANTECH SLLC1 Speaker Level To Line Converter: Electronics

I've used them here and there, they seem to work okay/fine.
  Reply With Quote
Old 16th December 2011, 11:51 PM   #6
champ04 is offline champ04  United States
diyAudio Member
 
Join Date: May 2009
Quote:
Originally Posted by ODougbo View Post
Sounds like you want to build one, however there are a lot of different models for sale.

e.g. Amazon.com: XANTECH SLLC1 Speaker Level To Line Converter: Electronics

I've used them here and there, they seem to work okay/fine.
I would prefer the experience gained in building one. But it is nice to see that there is something to fall back on. Didn't even cross my mind that such a product already existed.

Thanks!!!
  Reply With Quote
Old 17th December 2011, 12:45 AM   #7
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
If your amp is not bridged (so that black=ground) you just need two resistors in series over the speaker output, with the output to the sub taken from the middle. This will divide the voltage from speaker level down to line level when the two resistors are choosen right. What is right, is not critical when your sub has a volume control, so a ball park figure to start off with could be 10KOhm and 1KOhm, with the large value connected to speaker + and the small one to speaker ground. This will give you 20dB attenuation. If you can't get your sub to play loud enough, move from 1KOhm to 2KOhm.

Take 1 Watt resistors, that would keep you safe unless your amp delivers more than 1750 Watts ,

vac
  Reply With Quote
Old 17th December 2011, 06:11 AM   #8
rabbitz is offline rabbitz  Australia
diyAudio Member
 
rabbitz's Avatar
 
Join Date: Jul 2003
Location: Newcastle, Australia
This may help.... comes from Linkwitz.
Attached Images
File Type: gif attenuation speaker to RCA.gif (30.9 KB, 371 views)
  Reply With Quote
Old 17th December 2011, 08:05 AM   #9
UV101 is offline UV101  England
diyAudio Member
 
UV101's Avatar
 
Join Date: Dec 2008
Location: Oxford
But how does this effect the speaker that is still connected to the amp?
Are you intending to drive you main speakers and this circuit at the same time?
__________________
When Bitstream came out, I thought, “my God, what are we going to do...?” Ken Ishiwata http://www.hifisounds.co.uk
JA-88D Class A, Audio Aero Capitole MKII, Focal and Kimber "Leave Nothing as Standard"
  Reply With Quote
Old 17th December 2011, 10:39 AM   #10
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
Quote:
Originally Posted by UV101 View Post
But how does this effect the speaker that is still connected to the amp?
Are you intending to drive you main speakers and this circuit at the same time?
This does not affect the speaker still connected to the amp, because the speaker has a much lower resistance than the voltage dividing network. Therefore, the resistance of the resistors in this network should not be choosen too low. Linkwitz I feel is on the low side with his 1000/50 Ohms.

vac
  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
(minimal) speaker level vs. line level high pass filter noviygera Analog Line Level 1 15th October 2011 09:43 AM
trouble matching line level to guitar amp input level...any help? mondogenerator Tubes / Valves 5 19th December 2009 10:00 AM
Speaker level to line level converters qguy Subwoofers 2 9th December 2007 03:58 PM
speaker level input vs line level question crippledchicken Subwoofers 4 17th July 2007 03:36 AM
Speaker to line level adapter circuit question. Flatlander Parts 5 10th May 2006 12:33 AM


New To Site? Need Help?

All times are GMT. The time now is 02:39 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