need help with adding active mixer

[login721]

Hello .i need help with adding a active mixer before the "MXR headphone amp" .

This is the original schematic

This is my new schematic

my question is :
1.will this circuit work properly ?
2.i need the gain of mixer = 1 , so Ra=Rb=Rc=Rd , but what value should i use ?
3.What value should i use for Ca,Cb,Cc ?
4.What value should i use for Rx

Thanks in advance!
sorry for my bad English!

 

[ruffrecords]

my question is :
1.will this circuit work properly ?
2.i need the gain of mixer = 1 , so Ra=Rb=Rc=Rd , but what value should i use ?
3.What value should i use for Ca,Cb,Cc ?
4.What value should i use for Rx
sorry for my bad English!

1.  Looks basically OK to me.
2. What input impedance do you want? Ra, Rb and Rc are equalt to the input impedance of this circuit.
3. Depends on the answer to 2.
4. 10K should be fine. You don't need R1 anym more because the dc bias for the second op amp is provided by the output of the first.

Why did you change the second op amp to an NE5532?

Cheers

Ian

 

[abechap024]

spice it up! plus do you need it to run off a 9v battery? thats not going to give you much headroom...and the output is mono...all these things im taking for granted are part of the grand plan?

I would get rid of that 10M resistor

 

[login721]

2. What input impedance do you want? Ra, Rb and Rc are equalt to the input impedance of this circuit.
3. Depends on the answer to 2.

Why did you change the second op amp to an NE5532?

Thanks !

2.i need 3 input .the first input for the sansamp Gt-2 .the 2nd for MP3 player left channel,the 3rd for MP3 player right channel.
I changed to Ne5532 because NE5532 is much lower noise than tl071,and NE5532 is a dual op-amp.

This is schematic of SansAmp

This is new schematic with volume control for each input ,and i removed the R1. Can you please help me find the good value for Ra-Rd ,Ca-Cc , and P1-P3 .
Thanks you very much !

spice it up! plus do you need it to run off a 9v battery? thats not going to give you much headroom...and the output is mono...all these things im taking for granted are part of the grand plan?

I would get rid of that 10M resistor

Thanks !
Yes, its mono .Because i want to reduce the size of the circuit board.My project is a portable headphone amp with Cab simulator(Sansamp gt2) for guitar input ,and an audio input form mp3 player.