[dotashope]

Hi all,

Recently I got a friend needing help for wiring up a sound installation and there's only one transducer used. and I'm planning to use a dongle dac to power it. The question is can I simply short the left and right + for this purpose? Thanks!

 

[tomb]

Hi all,

Recently I got a friend needing help for wiring up a sound installation and there's only one transducer used. and I'm planning to use a dongle dac to power it. The question is can I simply short the left and right + for this purpose? Thanks!

The short answer is NO. You'll short the stereo outputs, because the music signal varies between the channels. A stronger music note in one channel will feed into the other channel and short it, if they are connected together.

The long answer is using some resistors to attenuate, then mix the signal through a single resistor (or it could be the impedance of the volume pot in a mono-connected amplifier). The resistor values will need to be different, depending on the load impedance at the mono connection.

Here's a non-technical discussion of the passive use of mixing resistors to convert stereo to mono:
https://www.instructables.com/Simple-Way-to-Convert-Stereo-to-Mono/

EDIT: I've read where transformers are better utilized to do this, but you probably aren't interested in going that far.

 

[dotashope]

The short answer is NO. You'll short the stereo outputs, because the music signal varies between the channels. A stronger music note in one channel will feed into the other channel and short it, if they are connected together.

The long answer is using some resistors to attenuate, then mix the signal through a single resistor (or it could be the impedance of the volume pot in a mono-connected amplifier). The resistor values will need to be different, depending on the load impedance at the mono connection.

Here's a non-technical discussion of the passive use of mixing resistors to convert stereo to mono:
https://www.instructables.com/Simple-Way-to-Convert-Stereo-to-Mono/

EDIT: I've read where transformers are better utilized to do this, but you probably aren't interested in going that far.

Thank you so much for the read! From the tutorial it seems like resistors are necessary although I think the source audio is mono as well so I'm not sure if joining left and right altogether would work. But in short she wants as small and simple of a solution as possible. I'd love to make a proper converter for myself but for her application I think either joining 2 channels or simply just using one channel of the amp :/

 

[tomb]

Thank you so much for the read! From the tutorial it seems like resistors are necessary although I think the source audio is mono as well so I'm not sure if joining left and right altogether would work. But in short she wants as small and simple of a solution as possible. I'd love to make a proper converter for myself but for her application I think either joining 2 channels or simply just using one channel of the amp :/

If the source audio is mono, then there's no issue at all.

 

[dotashope]

If the source audio is mono, then there's no issue at all.

I'm somewhat sure the audio played is mono from the mp3, so it would make passing the whole analog signal safe to combine? Thanks!

 

[tomb]

I'm somewhat sure the audio played is mono from the mp3, so it would make passing the whole analog signal safe to combine? Thanks!

Maybe not. You said "source audio." I took that to mean the audio from the source device. If you're referring to the source files, then you'd be taking a chance. If there is any signal at all that's not mono, even a blip from a spike in the circuitry (like a switch thump), then you could have a potential voltage back-feed from one channel into the other. It probably wouldn't hurt if it wasn't sustained, but there's also the entire issue of offset. Sometimes voltage offsets are present in amplifier outputs that may not be balanced from one channel to the other. An offset is straight DC and could short things out as soon as you connected the channels, whether audio was playing or not. At headphone and preamp levels, these offsets - when they are present - are probably in the millivolts, so not so potentially harmful. However, if you're dealing with an amp that supplies speakers, an offset can be much higher.

We don't normally think of offsets as being a big deal, but if you are dealing with vintage amplifier, receiver, or integrated amplifier equipment, they can be a very big deal. Many amplifier/receiver service manuals detail how to zero out the offset between channels with pots that are on the PCB. Offsets can drift over time and become very great - especially with vintage equipment. I probably should've mentioned some of this before, but you didn't really specify your equipment details.