The source impedance issue is quite real and few opamps address it. TI has one (I forgot the number) that is optimized for minimal input C change with voltage. The relay solution I linked would be my first choice for a no compromise volume control. Frex's attenuator is very good but really addressed to a different task.
You are probably thinking of the OPA1642, which is described in this "Analog Applications Journal" http://www.ti.com/lit/an/slyt595/slyt595.pdf.
I assume that some of the later op-amps from TI use similar techniques, but I don't know for sure. I guess that is a question for @johnc124 .
I assume that some of the later op-amps from TI use similar techniques, but I don't know for sure. I guess that is a question for @johnc124 .
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.