How to combine the left and right channels with out making everything mono? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 12th November 2010, 07:02 PM   #1
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Default How to combine the left and right channels with out making everything mono?

I want to combine to left and right channels for my sub while keep the left and right remaining for my bookshelfs.

How do I do this?
  Reply With Quote
Old 12th November 2010, 11:24 PM   #2
parb is offline parb  United States
diyAudio Member
 
Join Date: Dec 2009
Location: Asia and United States
you need a filter and a summing amplifier (i assume low levek signals). possibly a buffer to phase shift the signal depending on the rest of your system.

this page seems decent based on a quick google search: Op Amp Summing Amplifier
  Reply With Quote
Old 13th November 2010, 12:03 AM   #3
diyAudio Member
 
Join Date: Oct 2010
Location: UK
If your sub is powered and only needs a line level signal and your power amp isn't operating in bridge mode, ie, has a common connection for the ground end of both main speakers, you could probably get away with just summing the channels via a pair of high value resistors and feeding that to the sub.

Does the sub expect a line level input? Does it have internal lowpass filtering?

We need more details to work with really.

Last edited by Slipstreem; 13th November 2010 at 12:07 AM.
  Reply With Quote
Old 13th November 2010, 12:03 AM   #4
diyAudio Member
 
Join Date: Mar 2010
Location: Santiago, RS/ Brasil
Send a message via MSN to smartx21 Send a message via Skype™ to smartx21
Here http://www.diyaudio.com/forums/solid...ml#post2350577 you will find a complete preamp schema. Look at the upper right corner. There is a very simple circuit that adds both channels and filters the signal, in order to feed the subwoofer (mono) output only with lower frequencies.
__________________
Regards,
Andres
  Reply With Quote
Old 13th November 2010, 12:07 AM   #5
Xoc1 is offline Xoc1  United Kingdom
diyAudio Member
 
Xoc1's Avatar
 
Join Date: Nov 2008
Location: Devon UK
Some stereo car amps have a phased output on one channel, this allows easy bridging of the amplifier This also means that a 2.1 speaker system can be used, the 2 speakers in stereo, and the sub in mono bridge.
You can get cheap passive crossover kits for this use, usually with a pair of caps for the stereo hi-pass and a single inductor for the sub.
To get a 2.1 system you would need to invert the signal phase to one of the amplifier channels, You probably need an op amp circuit for this, or maybe you could get some signal transformers and rewire one out of phase.
The stereo speakers are wired as normal but with one channel reversed, The sub is wired across both the amplifier outputs as a bridge mode.
Note Don't try this with a 4 ohm sub....
__________________
My daughters music
http://soundcloud.com/zoey-phillips
  Reply With Quote
Old 13th November 2010, 12:34 AM   #6
llwhtt is offline llwhtt  United States
diyAudio Member
 
Join Date: Jun 2008
Location: SoCal
My cheap Sony sub uses a 2.7KOhm resistor for each channel to combine the signals to mono. For example, left channel to a 2.7KOhm resistor, another 2.7Kohm resistor for the right then join the two ends together and there's your mono signal.

Craig
  Reply With Quote
Old 13th November 2010, 10:16 AM   #7
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Okay thanks for the advice, the sub is already filtered and is 4 ohm. So I'm thinking of just using a couple of resistors. That schematic, is it just the cap and that resistor or does it go further?
  Reply With Quote
Old 3rd February 2011, 10:09 AM   #8
diyAudio Member
 
Join Date: May 2010
The "Generic" method used in pro audio (usually, creating a mono signal from a line level single-ended source, such as a CD player's analog RCA output jacks, for sound checks, etc while saving a console input, which are always in demand) goes like this:

Hot lead Line Level CH1 --> 47K ohm resistor -->
Hot lead Line Level CH2 --> 47K ohm resistor -->

[Solder the two resistor leads together] --> Hot lead Line Level Mono

Normally you can sum the Ground leads together without problems since they are common internally at your stereo line level output source; that's your ground lead Line Level Mono.

There are other ways, eg a DI Box which will be either transformer coupled or use a buffer circuit but it's not necessary for what you're planning to do, plus the "good" ones will run you $200+.

There may be good reasons to use a different value for the resistor, but the 47K is the value to use if you are unsure. Preventing DC with a capacitor is usually not needed for component audio equipment, but should be considered if your line level source is non-component gear, such as a portable mp3 player.
__________________
" ... Go back to the beginning of a technology before the priesthood was established; that was the time when people were communicating information, not proving why there needs to be Priests. This is why the old texts tend to be so good. ..."

Last edited by Johnny2Bad; 3rd February 2011 at 10:30 AM.
  Reply With Quote
Old 3rd February 2011, 11:51 AM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by Johnny2Bad View Post
The "Generic" method used in pro audio
if you are correct that this is the normal "pro" method, then the "pros" are partially mono-ing their stereo signals.
One should use a summing circuit to create a mono that does not affect the two halves of the stereo signal.
__________________
regards Andrew T.

Last edited by AndrewT; 3rd February 2011 at 11:58 AM.
  Reply With Quote
Old 5th February 2011, 09:34 AM   #10
diyAudio Member
 
Join Date: May 2010
Quote:
Originally Posted by AndrewT View Post
if you are correct that this is the normal "pro" method, then the "pros" are partially mono-ing their stereo signals.
One should use a summing circuit to create a mono that does not affect the two halves of the stereo signal.
It works fine for sound checks, doesn't hurt the line-level source (first rule ... don't break stuff). I don't know where else the stereo signal would be going, so I don't really see what's "affected". If they want a "real" mono signal, like in a radio station, there is a preamp or mixer there that has the summing circuit built in. Or, they can use two inputs to the console and use the console's summing circuit (pan each channel to centre for 2-ch mono out, or pan both left and send to 1 channel out, for example). But that extra input is probably useful doing something else.

Like I said, you can always buy or build something more elaborate, but there won't be out-of-phase information at the frequencies the sub cares about. A lot of subs with stereo line level inputs have exactly that kind of configuration right behind those two RCAs before it goes to the line level mono amp. Horses for courses.
__________________
" ... Go back to the beginning of a technology before the priesthood was established; that was the time when people were communicating information, not proving why there needs to be Priests. This is why the old texts tend to be so good. ..."

Last edited by Johnny2Bad; 5th February 2011 at 09:52 AM.
  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
Combine left & right for sub wicked1 Tubes / Valves 6 25th March 2008 12:52 AM
Combine 4 amplifier channels into one? thylantyr Solid State 5 4th March 2008 08:43 PM
Merging left and right channels into one Rory Everything Else 9 17th August 2007 06:56 PM
2SK389 for left and right channels antomas Solid State 13 25th May 2007 09:13 PM
hook the left and right channels together? x. onasis Chip Amps 4 26th August 2006 03:23 AM


New To Site? Need Help?

All times are GMT. The time now is 01:38 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