audio input line problem

I have a problem with my audio setup where the audio input line signal is to strong to the point where it distorts audio.

My audio setup looks like this:

Pc -> usb dac -> amp

So far the only solution is to lower the pc volume down to 50% (and this solution isnt OK for me, i need my volume in windows at 100% !). The signal is still way to strong and i would like it lower, but at least the distortion is gone. All components were tested elsewhere and it came down to amp being the culprit.

So since lowering the pc volume to 50% solved the issue, i thought it should be easy enough to just put a resistor on each channel between dac and amp. I had to use a 50k resistor to actualy remove distortion. But for some reason this completely ruined the sound quality, it became muddy, like someone cut certain frequencies. I fail to understand why because lowering the pc volume should be basicaly the same as if i put a resistor on the L and R line and lower the volume like that, right ?

As for the reason why that is so, someone on this forum i belive, said that probably the amplifier is designed with mobile phones in mind and the signal i get from DAC is a lot stronger than what my mobile phone can supply. Meaning it overpowers the amp and distorts.

On the attached image you can see the amp and how it's connected. I soldered the input wires directly to 3.5mm female input jack on the amp for the sole reason to not have a 3.5mm male jack sticking out near volume pot. Just to make sure there is no misunderstanding.
 

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How 'bout a simple potentiometer before the amp? That way you can adjust the level for optimum quality. A 50K audio-taper pot (stereo) ought to do the trick.
This way you have a constant impedance on the input side (whatever the value of the pot is).

Ackshooly, on further thought, you probably don't want a big old pot hanging off your circuit, so just connect one temporarily, adjust it for optimum performance, then take it out and measure its resistance. Both ends. Then put in two resistors of about those values (close enough is close enough), since what you want is a voltage divider, not just a single resistance.
 

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Thanks ! Attached is the image how its connected right now. How would i connect the pot ? Never tried doing that, but im pretty sure i got some laying around if u show me on the scheme.

Just curious .. why did the single resistor not work and produced such bad quality audio ? Always love to learn something new
 

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Oh, i think i got it. Pretty simple. I did it just for 1 channel, just to verify if i got the idea. And i dont mind a pot on top of the amp, its temporary setup anyway and looks interesting

If u dont mind, i would still love to hear why a single resistor ruined the audio. And how i would connect 2 resistors ?
 

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So it sounded OK with your pot? Not sure why it didn't work before; what value resistor did you use? Probably needed a voltage divider rather than just a single R.

Connect it just like any voltage divider; basically the same as your pot (think of the pot as having 2 segments, with the wiper--connected to the output--at the common point between them).

 
Just so you might learn something from this, here's how a voltage divider works:



It's a basic electronic concept used in a lot of places, so worth knowing about. Like the name implies, it divides a voltage (on the input side) into two voltages. The output side is at the voltage at the lower end (V2). The voltages are proportional to the ratio of the resistances. If R1 is a large value and R2 small, then V2 is a small voltage (and vice versa). Imagine turning your pot from one side to the other and think about what those 2 resistances are doing as you do that.
 
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