thank you!
Yes, i should have mentioned. I actually plan to have 12 steps from say 15 to 65 db, and a second stage with around 0 to 6db of gain.
Maybe with a pot for the second stage, or somehow nicer, with a second 12 pos switch. Or spend some money on a 40pos switch.
Or maybe just one stage, sonce the ina can drive 600r loads and is most happy with gains around 100-1000.
So maybe the two switches could be combined for that first and only stage, although it might be impossible to get a usable law.
btw, here´s the datasheet. I came across this chip in some hifi forum because it´s used in some very nice phonopres.
http://focus.ti.com/lit/ds/symlink/ina103.pdf
anyone know what that "shield driver" thing is good for?
With the relais, it should be possible to do the stepping with much less than 12 relais, if you include some logic and switch in different combinations of a few resistors. Think the Emitter has a volume control that works like this.
I counted 6 or 8 relais if i remember right.
Thinking about this, i see a lot of efford, and i am not sure if it´s worth it.
But i might just as well mount the switch directly onto the pcb, so that distances are really short.
The contacts of the switch may be an issue, but i don´t belive in that too much. Don´t think i can hear the difference between a rotary switch and some relay.
The Ina103 is an instrument-amp, the basic three opamp design. It has two pins for the gainsetting resistor. If that is left open (and it will be for a moment inbetween two switching positions) the gain drops to 1.
No idea if that is going to cause any clicks.