Ways to sum stereo to mono before the power amplifier?

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Hi all,

I've been building a few test boomboxes with class D chip amps and for my next one I'm looking at a single woofer/tweeter config, so a mono amp is required for maximum power benefit.

There are plenty of mono boards (3116/3118 etc) available, but I want to know how to best sum a stereo aux signal to mono before it hits the power amp.

I know it's possible (but not recommended) to just twist the L & R wires together, but what's a better way to do it?

Cheers all,

Jim
 
Hi, In most cases it simply will not do at all, very wrong, rgds, sreten.

This has often puzzled me. Why do so many places sell "Stereo to Mono" adapters and cables etc. that are simply just that? For example - the attached?
 

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This has often puzzled me. Why do so many places sell "Stereo to Mono" adapters
and cables etc. that are simply just that? For example - the attached?

Hi,

You don't know whether it has internal resistors or not, it should.
It probably does, as shorting two output channels is very inane.
I'd guess around 4.7K per channel.

rgds, sreten.
 
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You don't know whether it has internal resistors or not

Yes I do. I tested it with my multimeter. It doesn't.

I used to use them to connect a CD player and a Minidisc into a small tape-based HiFi that only had one Aux input. It was crap anyway. I have a better one now that actually has proper inputs and speakers that don't sound like they're made of cereal boxes.

Here's an approach.

Excellent, thank you!
 
I don't know why people get so worked up about a trivial issue.

It's annoying to think that shops which sell HiFi equipment give bad advice that could damage equipment, Potentially damaging your equipment isn't really a trivial issue, is it?

I can't find a single Y connector that says it's only for connecting one output to two inputs and not the other way around. Shouldn't that really be on the packaging?
 
You said "aux" signal (i.e. line level), not headphone signal. A proper line level output should have resistors. A headphone output may not, but that is a different issue. In many cases a headphone output will have come from a small (and probably filterless) Class D amplifier, so may need HF filtering before feeding into other audio equipment.

It surely figures though that there are millions of people driving amplifiers from phones, tablets and laptops etc - possible more so than people using preamps etc?
 
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