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| Audio distribution amp. |
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| SNGLinks:
Hi I have an stereo audio switch unit. I wish to feed this to, up to, 5 stereo domestic amplifiers. Instead of just paralleling the inputs I want to build a distribution amplifier. I was thinking of using two power amplifiers such as an LM380 and feeding each amp input via a series resistor. What do you think of the idea and what value resistor is required? |
| Audioguru again:
Why use an LM380 POWER amplifier when the inputs of five domestic audio amplifiers use almost NO power? The LM380 is not hifi. Instead us a simple audio opamp as a distribution amplifier that will have a high input resistance and an output that can drive hundreds of domestic audio amplifiers. A dual audio opamp like a stereo OPA2134 has extremely low noise and distortion. |
| SNGLinks:
Thanks for your reply. I have loads of TL072s so could use that. What value resistor should I use? I want some isolation between outputs so a short on one line cannot effect another. |
| DaJMasta:
Any good audio opamp should be able to be configured as a follower amp so you can drive however many lines from a single source (a follower amp driving each) without any gain. If you want over-current protection, you just need to look at the output spec of your chosen opamp and add a series resistor that keeps the full scale output below that current - probably on the order of 50-100 ohms, depending. If you're talking about ground isolation to eliminate added hum, you're going to need transformer coupling or some similar method - much more complicated and harder to get right, especially if your device has its own power supply, and may be less of an issue with your own installation. The devices you are running are high impedance (high resistance even to AC signals like sound waves), so in normal operation, the opamp will drive very little power through the load to maintain signal levels. You only need amplifier ICs for very high voltages or, more commonly, low impedance drives (like an 8 Ohm or less speaker), a line level input is designed not to need much power to be properly driven. |
| awallin:
one op-amp per output, if you want some isolation. see e.g. https://electronics.stackexchange.com/questions/266872/active-audio-splitter-line-levels |
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