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Topic: Line Level mixer - Active vs Passive (Read 1551 times) previous topic - next topic
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Line Level mixer - Active vs Passive

I have a couple of setups which are always On and hooked to Alexa (Echo dot line out) and Airport Express (For airplay)
The setups are of moderate to high-ish resolution (KEF speakers and HK/Marantz amplifiers) and have reasonable amount of imaging present if I play back directly from a good source hooked directly to the line-in

The problem I have is that I need to have both the Alexa and Airplay output plugged into a single line-in at all times.
I am currently using a basic passive mixing circuit (Common ground, 1K resistors on L/R channels on both inputs terminating on line feeding into Amp)
Obviously there is some signal attenuation but I have enough head-room on the amps to balance that out.

However I am not sure if this is the right way to do it.
I  also perceive a loss in quality of stereo imaging (don't expect it from the echo dot but do on Airplay) - although it could just be a placebo effect

Question: Is this the right way to do this ? Or should I be looking at active mixers instead - and if yes, any recommendations?

Re: Line Level mixer - Active vs Passive

Reply #1 –
You could try an "auto" sensing/switching type box such as this https://www.amazon.com/5-way-Tilting-Auto-sensing-Stereo-Selector/dp/B00XQL6UEK
Whenever either output device (Alexa/Airport) becomes active, it should switch to them. I have neither of those nor this device, YMMV.
I do have a similar Sony switcher from a decade ago buried somewhere that did exactly that and worked fine.
Loudspeaker manufacturer

Re: Line Level mixer - Active vs Passive

Reply #2 –
I'd want to try an active setup, because with passive, matters of input and output impedance and cable capacitance can make or break your sonics.

Re: Line Level mixer - Active vs Passive

Reply #3 –
If you are building circuits with op-amps it's super easy to make a summing amplifier.   (Analog mixers are built-around summing amplifiers.)   

1K is a little low for a line-level output.   It's probably OK but I'd use 10K.

Quote
I  also perceive a loss in quality of stereo imaging (don't expect it from the echo dot but do on Airplay) - although it could just be a placebo effect
That shouldn't happen.   You might want to disconnect the left & right, one at a time, to see if there is any left-to-right (or right-to-left) leakage.

There are lots of mixers and as long as it's stereo (most are) and as long as it has at least 4 line inputs (or two stereo line inputs) it should be perfectly adequate.