Greetings, This is my first post. I know a fair amount about electronics but am still clunky at times. My project needs help. The project is a musical organ device. The object is to replace a magnetic wheel with pickup per sound or voice with an electronic file player. The original organ has 91 wheel/pickups that play through switch contacts to allow the sound out (wheels are always spinning). The "handful" of tones that let the sound through as music is played arrive on a buss that simply feeds the primary of a matching transformer. The combined tones (or single toones) leave the transformer and go on to more amplification, etc.
In my design, I have made digital recordings of the wheel outputs and put them each on a micro sd card. THey are played by a stereo player circuit from china that is probably only a PIC of some kind streaming the wav or MP3 data converted to PWM. Each circuit is only about a buck and replaces two of the tone wheel outputs. The problem I have is that as the outputs of these travel through the key contacts to the transformer, the combined signals interact to the various circuit board player's outputs, loading them down and causing volume to decrease.
The original wheel pickups are low impedance and the input to the transformer primary is low impedance. The wheel pickups do not exhibit the loading problem. I assume the output of the circuit board player does not like the near short circuit (the tranny input is only about 20 ohms measured).
So I thought making some kind of cheap and easy buffer was in order. I tried an LM324 quad op amp because it seemed good, being able to be single-side powered from the same 5v rail as the circuits. I need the buffer to be cheep and easy because there are like 78 channels of them to build! The LM324 did not work. I tried a small mosfet but no configuration worked. The player board does have surface mount caps on the two outputs but they are not electrolytic, etc.
So the help I need is something that can buffer each output, hopefuully with 5v single-sided supply, and only provide unity gain (the outputs are already at good volumes) but not be unhappy when stright-wire bussed. In other words the outputs will not interact with each other level-wise. I hope this makes sense enough for some ideas from you great forum members!
Jeff
In my design, I have made digital recordings of the wheel outputs and put them each on a micro sd card. THey are played by a stereo player circuit from china that is probably only a PIC of some kind streaming the wav or MP3 data converted to PWM. Each circuit is only about a buck and replaces two of the tone wheel outputs. The problem I have is that as the outputs of these travel through the key contacts to the transformer, the combined signals interact to the various circuit board player's outputs, loading them down and causing volume to decrease.
The original wheel pickups are low impedance and the input to the transformer primary is low impedance. The wheel pickups do not exhibit the loading problem. I assume the output of the circuit board player does not like the near short circuit (the tranny input is only about 20 ohms measured).
So I thought making some kind of cheap and easy buffer was in order. I tried an LM324 quad op amp because it seemed good, being able to be single-side powered from the same 5v rail as the circuits. I need the buffer to be cheep and easy because there are like 78 channels of them to build! The LM324 did not work. I tried a small mosfet but no configuration worked. The player board does have surface mount caps on the two outputs but they are not electrolytic, etc.
So the help I need is something that can buffer each output, hopefuully with 5v single-sided supply, and only provide unity gain (the outputs are already at good volumes) but not be unhappy when stright-wire bussed. In other words the outputs will not interact with each other level-wise. I hope this makes sense enough for some ideas from you great forum members!
Jeff
