The circuit is confusing to me, the transistor on the left I think the are two filters, one is active by switching transistor.
Not understand
The 22k resistor (3675,3676) before the two transistors mute funcion, I seem to make a voltage divider, more leaves to very high output impedance.
I was thinking of using the OPA2134, The opamp OPA2604 would be a better option?
Is to put the preamp and CD player in even GND to avoid a ground loop, see figure.
Attachments
The 22k resistors reference the output electroylitic and mute transistors to ground. Common practice to do that. The resistor is high enough to have no effect on the output at all as it's fed from the opamp output.
The mute transistors, two are used per channel to get a "deep" enough level of muting in conjunction with the 470 ohm resistors. These two 470 ohm in series define the output impedance of the player.
The deemphasis transistors are the two in front of the opamp that change the hf filter characteristics.
All the transistors and diodes at the top are used to provide the logic levels required to operate the mute and deemphasis circuits.
The OPA2604 is just a personal favourite I find works well
The mute transistors, two are used per channel to get a "deep" enough level of muting in conjunction with the 470 ohm resistors. These two 470 ohm in series define the output impedance of the player.
The deemphasis transistors are the two in front of the opamp that change the hf filter characteristics.
All the transistors and diodes at the top are used to provide the logic levels required to operate the mute and deemphasis circuits.
The OPA2604 is just a personal favourite I find works well
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