Hi Folks,
I'd like to make a passive summing mixer (basically the same as the one at DIYRE) however I'd like to add adjustable make-up gain. See here:
SB2 Passive Summing Mixer Kit – DIY Recording Equipment
I'm struggling to find a complete schematic of a suitable make-up gain stage. I have a couple of TL074s and was hoping I could use them. I'd prefer the output to be balanced stereo.
One of the things I'm not clear about is how the addition of the make-up stage affects the output impedence.
Cheers,
Chris
I'd like to make a passive summing mixer (basically the same as the one at DIYRE) however I'd like to add adjustable make-up gain. See here:
SB2 Passive Summing Mixer Kit – DIY Recording Equipment
I'm struggling to find a complete schematic of a suitable make-up gain stage. I have a couple of TL074s and was hoping I could use them. I'd prefer the output to be balanced stereo.
One of the things I'm not clear about is how the addition of the make-up stage affects the output impedence.
Cheers,
Chris
The unit you refer to has 10k input impedance and 150 ohm output impedance, and 45dB of attenuation.
Its basically multiple 177:1 attenuators sharing common lower resistors. Since these are very low valued the output impedance is pretty low. You have to follow it with microphone preamps to restore the signal level by 45dB or so. The output impedance of these microphone amps would set the overall output impedance.
Its basically multiple 177:1 attenuators sharing common lower resistors. Since these are very low valued the output impedance is pretty low. You have to follow it with microphone preamps to restore the signal level by 45dB or so. The output impedance of these microphone amps would set the overall output impedance.
personally i would start again using active summing inverters on the inputs.
that way not only is there no losses but you can add gain.
that way not only is there no losses but you can add gain.