Need 'stereo expander' circuitry for boombox - diyAudio
Go Back   Home > Forums > Source & Line > PC Based

PC Based Computer music servers, crossovers, and equalization

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 1st November 2011, 02:09 PM   #1
7V is offline 7V  United Kingdom
diyAudio Member
 
7V's Avatar
 
Join Date: Feb 2003
Location: North London
Default Need 'stereo expander' circuitry for boombox

Well not really a 'boombox', I'm attempting to build a classy portable stereo system to play MP3s, etc.

Both speakers will be fixed in the cabinet and non-detachable (for simplicity). Therefore they won't be as far apart as I would like. I am therefore looking for a circuit that can expand the stereo image so that the music appears to come from beyond the speakers.

Can anyone advise?
Also, should this be posted in another part of the forum? Things are getting complicated around here?

Regards
Steve
  Reply With Quote
Old 2nd November 2011, 08:22 PM   #2
dangus is offline dangus  Canada
diyAudio Member
 
Join Date: May 2004
Location: Vancouver Island
I've seen a circuit someplace. I think it just used an opamp to subtract a variable amount of each channel from the opposite one. Lout=Lin - (some fraction of)Rin. The pot could be wired to offer a range from full blend (mono) to normal to full wide (the blend range might be good for headphone listening). A quad op-amp wired as two inverting buffers feeding two inverting virtual-ground mixers.

Here you go:
Stereo Width Controllers
If the driving impedance is reasonably low, it should be OK to omit the non-inverting buffers and just use a quad opamp.

It's possible that someone like Rohm made a chip that did this. It was a fairly common feature for ghetto blasters, and might be found in some TVs.

Bass tends to be essentially mono, so making it wider will tend to reduce the bass in both channels. This might be a good time to consider biamping with a mono subwoofer. (Use a DVC sub so both sides of a T-amp can drive it.) Inserting a high-pass filter in the crossfeed signals should work... just a couple of series caps. Presumably the image information is mostly in the high frequencies.

Last edited by dangus; 2nd November 2011 at 08:47 PM.
  Reply With Quote
Old 2nd November 2011, 08:46 PM   #3
7V is offline 7V  United Kingdom
diyAudio Member
 
7V's Avatar
 
Join Date: Feb 2003
Location: North London
Thanks
  Reply With Quote
Old 1st April 2013, 04:50 PM   #4
diyAudio Member
 
MeTarzan's Avatar
 
Join Date: Mar 2013
Quote:
Originally Posted by dangus View Post
Here you go:
Stereo Width Controllers
If the driving impedance is reasonably low, it should be OK to omit the non-inverting buffers and just use a quad opamp.

It's possible that someone like Rohm made a chip that did this. It was a fairly common feature for ghetto blasters, and might be found in some TVs.

Bass tends to be essentially mono, so making it wider will tend to reduce the bass in both channels. This might be a good time to consider biamping with a mono subwoofer. (Use a DVC sub so both sides of a T-amp can drive it.) Inserting a high-pass filter in the crossfeed signals should work... just a couple of series caps. Presumably the image information is mostly in the high frequencies.
The circuit is simple enough but does anyone know of a chip available? I have an old EQ with this effect and have not ripped into it yet.
Attached Images
File Type: gif p21_fig1.gif (2.8 KB, 70 views)

Last edited by MeTarzan; 1st April 2013 at 04:53 PM.
  Reply With Quote
Old 1st April 2013, 09:11 PM   #5
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Quote:
Originally Posted by MeTarzan View Post
The circuit is simple enough but does anyone know of a chip available? I have an old EQ with this effect and have not ripped into it yet.
Just use an a pair of dual or a quad opamp's of your choice!!
I still use the TL082's and TL084's even to this day for great quality and low price !!!

jer
  Reply With Quote
Old 1st April 2013, 09:48 PM   #6
diyAudio Member
 
MeTarzan's Avatar
 
Join Date: Mar 2013
Quote:
Originally Posted by geraldfryjr View Post
Just use an a pair of dual or a quad opamp's of your choice!!
I still use the TL082's and TL084's even to this day for great quality and low price !!!

jer
In that case... I think I already have all the parts.
Thanks, Ron
  Reply With Quote
Old 1st April 2013, 11:18 PM   #7
diyAudio Member
 
sofaspud's Avatar
 
Join Date: Nov 2005
Location: San Antonio
Philips made a TDA3810 IC. It's likely there were other similar chips, but I'm not sure of their current status or if the function has been entirely moved to DSP.
__________________
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
  Reply With Quote
Old 1st April 2013, 11:28 PM   #8
diyAudio Member
 
Saturnus's Avatar
 
Join Date: Jun 2005
Location: Copenhagen, Denmark
Any reason you can't use the built-in DSP in the source? Doesn't matter if it's a laptop or mobile phone you have as source, they're still capable running professional DSP software.
  Reply With Quote
Old 2nd April 2013, 12:08 AM   #9
diyAudio Member
 
MeTarzan's Avatar
 
Join Date: Mar 2013
Quote:
Originally Posted by Saturnus View Post
Any reason you can't use the built-in DSP in the source? Doesn't matter if it's a laptop or mobile phone you have as source, they're still capable running professional DSP software.
That is a great idea if it is available. The source will be an iPhone broadcasting to a bluetooth device in a battery powered boombox type system for outdoor use. Nothing as fancy or well planned out as the Boominator, but along those lines. The speakers will be close together so I figured I would put something to give the illusion. I started off thinking BBE Sonic Maximizer, moved on to stereo expander but the software route would be great. Would be nice though if anyone with bluetooth had the effect built into the box. I took the stereo widener card out of a Realistic EQ and might be able to wire it in. The longer I delay starting this project the more simplified it is becoming. Went from 24v to 12v. From woofs, tweets, xo's and ports to full range closed box. Will be using 4 5x7 4ohm Ford speakers and a 4x100 t-amp. I don't expect greatness but should dazzle the crowd I tend to spring it on. Any suggestions on specific apps?
  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
Dynamic Range Expander systemerror909 Everything Else 16 31st May 2012 02:42 PM
Expander meconlen Analog Line Level 2 17th May 2010 02:19 PM
8" stereo ceiling speaker/MP3 boombox nordhaven Multi-Way 3 22nd January 2008 10:18 PM
DIY Expander/Sampler??? AudioAngel Instruments and Amps 10 16th November 2005 05:00 PM
Dynamic Range Expander CarAudioMage Everything Else 0 26th October 2003 02:24 AM


New To Site? Need Help?

All times are GMT. The time now is 09:19 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