REAMP BOX (original) - Fixed with schematic

[Mikaeel]

According to the posted schematic (linked above) the signal driving into the XLR sees a 17.6 Ohm load via R2/R3/R4.

Even old vacuum tube line-level sort of load.gear (RCA, WE, Etc) could never drive that load.

Something is amiss with those resistor values in the posted schemo...

Bri

You're absolutely right. The owner has sent me new pictures:



I have updated the schematic in the above message with the correct resistor values.

 

[Mikaeel]

Here's something I don't really understand:





A = 20log10(R4 + R2 * R3) = 20log10(620+2 * 470620) = approx −8.02db
Zin = R1⋅(R2+Zout) / R1⋅(R2+Zout) = 492300/1560 = 315.58 Ohm
Zout = 620 Ohm
In the case of impedance matching by voltage, the maximum source impedance will be 315.6 / 10 = 31.6 ohms.
Or should be equal to 315.58 ohms.
This is odd because most popular line-outs have impedances from <10 ohms to 600 ohms.
How will the impedance mismatch affect performance in this case? Or will the U-pad just attenuate linearly?