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
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,
3-10Kohm in series with each channels +, commoned to the + input. Common
each - channel. Do it at the amplifiers input or the end of the stereo cable.
rgds, sreten.
3-10Kohm in series with each channels +, commoned to the + input. Common
each - channel. Do it at the amplifiers input or the end of the stereo cable.
rgds, sreten.
This question, or something like it, comes up every few months. Forum search might give you the answer.
In most cases just joining the two wires will do. If not, add a resistor to each output, then join the wires together.
In most cases just joining the two wires will do. If not, add a resistor to each output, then join the wires together.
Hi, In most cases it simply will not do at all, very wrong, rgds, sreten.
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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?
Attachments
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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Those are one output to two inputs adapters.
Don't use them for:
Two outputs to one input.
See the "Why not Wye?" paper, linked above.
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.
Excellent, thank you!
Well-designed sources will already have build-out resistors - a direct connection is fine. If not, add some resistors. 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?
Hi-Fi shops have always given bad advice, just like hi-fi magazines.
People buying Y connectors broadly fall into two groups:
1. those who would ignore any warning, and would not know how to check for resistors
2. those who don't need a warning
People buying Y connectors broadly fall into two groups:
1. those who would ignore any warning, and would not know how to check for resistors
2. those who don't need a warning
Hi,
I can believe that.
It makes it a phono output splitter rather
than an a exceedingly poor input combiner.
rgds, sreten.
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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?
Millions of people can be wrong, or confused, or not notice the problems sometimes caused by sending HF into an unprepared audio amp. The fact remains that a headphone output is not a line level output, even though the voltage levels may be similar.
Shorting channels works well on the output of my stereo USB DAC.
Sounds excellent.
It depends on the driving circuit.
Shorting output of 2 op amps together isn't recommended.
But if they have resistors on the outputs then shorting them should be fine.
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