I can generally get simple circuits to work, but to call me a noobie would be generous.
I am trying to do something I thought would be simple: connect an audio amplifier (this one: 20W Bridged Audio Amplifier ) with a balanced input circuit (this one: Balanced Input/Output Assembly Guide – DIY Recording Equipment see schematic below).
I have the two circuits connected to the same 12volt power supply (this one: RS-35-12 - MEAN WELL - TRC Electronics ) pins 4 and 7 of U1 are connected to the 12V+ and 12V- of the power supply. Pin 1 of U1 is connected to the ground of the power supply. U1 is this chip: http://www.thatcorp.com/datashts/THAT_1240-Series_Datasheet.pdf
I hope someone experienced will be able to suggest what's going on from my description of what's happening.
I find that when I connect the OUTGND and the OUT+ of the balanced input circuit to the +/GND inputs on the amp, I get a buzz out of the speaker and the audio signal is very distorted and is only just audible. When I disconnect the OUTGROUND from the GND input of the amp so that only the OUT+ is connected from the balanced input, I get fairly clear audio out (there is some AC hum, but I'll leave that issue aside for the moment).
My question is: why does the audio sound better when only the OUT+ is connected?
My presumption is that is has something to do with the how the power supply is connected to both circuits, but I really don't understand how/why and would really like to know.
Can someone please explain what they think might be going on. I hope is that it's obvious to someone with more experience. The amp circuit itself does not seem to be an issue because I get the same behavior if I swap in a completely different amp.
Many thanks is advance for solving/explaing this puzzle.
I am trying to do something I thought would be simple: connect an audio amplifier (this one: 20W Bridged Audio Amplifier ) with a balanced input circuit (this one: Balanced Input/Output Assembly Guide – DIY Recording Equipment see schematic below).
I have the two circuits connected to the same 12volt power supply (this one: RS-35-12 - MEAN WELL - TRC Electronics ) pins 4 and 7 of U1 are connected to the 12V+ and 12V- of the power supply. Pin 1 of U1 is connected to the ground of the power supply. U1 is this chip: http://www.thatcorp.com/datashts/THAT_1240-Series_Datasheet.pdf
I hope someone experienced will be able to suggest what's going on from my description of what's happening.
I find that when I connect the OUTGND and the OUT+ of the balanced input circuit to the +/GND inputs on the amp, I get a buzz out of the speaker and the audio signal is very distorted and is only just audible. When I disconnect the OUTGROUND from the GND input of the amp so that only the OUT+ is connected from the balanced input, I get fairly clear audio out (there is some AC hum, but I'll leave that issue aside for the moment).
My question is: why does the audio sound better when only the OUT+ is connected?
My presumption is that is has something to do with the how the power supply is connected to both circuits, but I really don't understand how/why and would really like to know.
Can someone please explain what they think might be going on. I hope is that it's obvious to someone with more experience. The amp circuit itself does not seem to be an issue because I get the same behavior if I swap in a completely different amp.
Many thanks is advance for solving/explaing this puzzle.
Your power supply is single rail only and suitable for the amplifier but not the balanced line receiver which requires both a +ve and -ve supply and would have an associated common. You have been misled by the power supply output terminal marking which states +12V and -12V .The -12V terminal is just the negative of the +12V output . The ground of the power supply is just a protection ground .
The amp input ground is actually an extension of the -12V terminal .
The amp input ground is actually an extension of the -12V terminal .
You are not shorting the output .With the grounds unconnected the balanced receiver ground is probably floating around +6V and is able to give the full waveform output . When you connect the grounds you inhibit the bal. rec. from giving the negative part of the output waveform .
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