I have bought a ready Audio Amplifier using TDA7498 chip and now I need some AUX input other than default one. Is there any circuit for this?



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    \$\begingroup\$ Add a pre-built mixer module. \$\endgroup\$ – Andy aka May 19 '20 at 9:53
  • \$\begingroup\$ Could you expand what you mean with "AUX input other than default"? Using AUX jack is much more a mechanical consideration than an electrical one. You could just use copper wires wrapped around an AUX connector for example, but it would be an extremely flimsy setup. \$\endgroup\$ – Vicente Cunha May 19 '20 at 9:57
  • \$\begingroup\$ I do not mean mechanical. I mean some mixing \$\endgroup\$ – Kamyar May 19 '20 at 9:58
  • \$\begingroup\$ Then I'd recommend rephrasing the question to exclude the "AUX" term, since it's pretty closely associated to the specific audio connector and that's not really what this question is about. \$\endgroup\$ – Vicente Cunha May 19 '20 at 10:03

Impossible to see what's optimal because we do not know the exact schematic. If you are a beginner, do not dig anything on the board, insert a mixer to the input as already suggested by others.

The simplest possible mixer is to connect 2 signals to the same input through few kOhm resistors. You lose easily 50% of the input signal voltage, but that can still be fixable by cranking the volume upwards. I have used 3,9 kOhm resistors in series when two line level signals had to be connected to the same input. The signal sources gave about 2Vpp and less than half was needed, so the caused 6dB attenuation wasn't a problem. I made a cable which had the series resistors.

Using 2 different resistors you can get some control over the balance of the combined signals. But the sum of the resistors must be a few kOhms.

If you need continuous adjustability, you can use a few kOhm linear potentiometer instead of 2 resistors. The viper is connected to the amp input. A stereo potentiometer adjusts both channels.

If you cannot understand what the text above means, do not try it. Get some local help!

A properly designed summing mixer with independent volume potentiometers and possible tone controls, too, gives much more flexibility, but the cost of home made 2 resistor cable is unbeatable.


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