Hi everybody, I'm fairly new to the forum looking for some help from you experienced people.
I'm trying to build a simple two-channel mic preamp, powered off a 9V battery to go with the accordion of a friend of mine. His accordion has two built in mics with a trs jack for each. My plan is to build a small box which can be mounted to the belt/strap of the accordion. I would like to be able to control the volume of each mic independently and mix the signals to a mono-signal OR leave them separate and use two mono outputs, one for each channel.
I thought I'd use the simple mic preamp presented by ESP (https://www.abcelectronique.com/annuaire/montages/cache/1034/preamplificateur-pour-microphone-faible-bruit.html), one of those for each channel.
How can I mix the two channels with their own volume control? My idea was to put a 10k volume pot to the output of each channel and mix them using an opamp. What would be the best way to do so? I have tried some configurations and simulated them in spice but the results don't look very promising. I think one problem is that the volume pot interferes with the feedback-network used to set the gain of the preamp.
The configuration that can be seen in the attached schematic is what seems to work best so far. I think I would have to reference the non-inverting input of the opamp to half the supply voltage, right? But this gives weird results unfortunately.
I would like the output of the whole circuit to be able to drive a long unbalanced cable going to a mixer or something.
Are there any other ideas on how to mix the two signals with each having their own volume-control? The gain will be set by a trim-pot once we have figured out what works best with those old mics.
Any help would be highly appreciated. Thank you very much!
I'm trying to build a simple two-channel mic preamp, powered off a 9V battery to go with the accordion of a friend of mine. His accordion has two built in mics with a trs jack for each. My plan is to build a small box which can be mounted to the belt/strap of the accordion. I would like to be able to control the volume of each mic independently and mix the signals to a mono-signal OR leave them separate and use two mono outputs, one for each channel.
I thought I'd use the simple mic preamp presented by ESP (https://www.abcelectronique.com/annuaire/montages/cache/1034/preamplificateur-pour-microphone-faible-bruit.html), one of those for each channel.
How can I mix the two channels with their own volume control? My idea was to put a 10k volume pot to the output of each channel and mix them using an opamp. What would be the best way to do so? I have tried some configurations and simulated them in spice but the results don't look very promising. I think one problem is that the volume pot interferes with the feedback-network used to set the gain of the preamp.
The configuration that can be seen in the attached schematic is what seems to work best so far. I think I would have to reference the non-inverting input of the opamp to half the supply voltage, right? But this gives weird results unfortunately.
I would like the output of the whole circuit to be able to drive a long unbalanced cable going to a mixer or something.
Are there any other ideas on how to mix the two signals with each having their own volume-control? The gain will be set by a trim-pot once we have figured out what works best with those old mics.
Any help would be highly appreciated. Thank you very much!