Schematics is attached.
I am wondering if I can add two signals coming from RCA inputs and XLR inputs? Will something like what I have makes sense to do in order to support both unbalanced and balanced inputs? I am trying to avoid to switch them with the manual switch.
First stage allows for gain adjustment.
Bias resistors R3, R4 were selected at 10K to set input impedance. Feedback resistors can be 15K or 47K and determine R3 and R4 values as 15K||47K = 11.3K and 15K||15K = 7.5K.
Second stage is balanced signals driver.
Unity buffer for the positive swing signal. Inverting unity gain opamp for the negative swing signal with bias resistor = 2K||2K = 1K. Current sharing resistors of 100R at each end to adjust for offset differences. Output signal doubles in value which is what I want. For example Topping DACs have 2Vrms output level for RCA outs. I will need to double that to drive my next stage at the amplifier end.
Balanced input stage is two impedance matching buffers to be able to drive the next stage at the amplifier end wich has input impedance of 1K.
I am assuming that connecting both RCA and XLR inputs at the same time and play music at both sources will add those two signals together and I will hear both sources?
Each opamp has decoupling capacitors, but those are at different sheet for schematics.
Any suggestions will be appreciated.
I am wondering if I can add two signals coming from RCA inputs and XLR inputs? Will something like what I have makes sense to do in order to support both unbalanced and balanced inputs? I am trying to avoid to switch them with the manual switch.
First stage allows for gain adjustment.
Bias resistors R3, R4 were selected at 10K to set input impedance. Feedback resistors can be 15K or 47K and determine R3 and R4 values as 15K||47K = 11.3K and 15K||15K = 7.5K.
Second stage is balanced signals driver.
Unity buffer for the positive swing signal. Inverting unity gain opamp for the negative swing signal with bias resistor = 2K||2K = 1K. Current sharing resistors of 100R at each end to adjust for offset differences. Output signal doubles in value which is what I want. For example Topping DACs have 2Vrms output level for RCA outs. I will need to double that to drive my next stage at the amplifier end.
Balanced input stage is two impedance matching buffers to be able to drive the next stage at the amplifier end wich has input impedance of 1K.
I am assuming that connecting both RCA and XLR inputs at the same time and play music at both sources will add those two signals together and I will hear both sources?
Each opamp has decoupling capacitors, but those are at different sheet for schematics.
Any suggestions will be appreciated.
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