I have 2 AMP11 (see http://www.41hz.com/forums/showthrea...d-an-AMP/page2).
I decided to build a volume control. After some research I found the PGA2311 (http://www.ti.com/product/pga2311) that says "Using high performance operational amplifier stages internal to the PGA2311 yields low noise and distortion, while providing the capability to drive 600Ω loads directly without buffering.".
The input source impedance must be less then 2 KOhm ("A source impedance of 600Ω or less is recommended. Source impedances up to 2kΩ will cause minimal degradation of THD+N.").
I think this is enough for input protection of AMP11: "Given VA+ = +5V and VA− = −5V, the maximum input or output voltage range is 7.5Vp-p.".
With the PGA2311 I will have the analog grounds of both AMP11 connected. Unless I use 2 of them.
1- Is 7.5Vp-p enough for avoiding damage to the AMP11?
2- Do I need an input buffer before the PGA2311? I donīt know exactly what are the input sources: CD, DVD, etc.
3- What about the connection of the two AMP11 grounds? Any problem?
For the digital pot I found a nice 10 bit absolute magnetic rotary encoder. I am buiding the mechanical part of the pot.
Both ICs have a very simple serial protocol so any microcontroler can interface them. I will use an AVR
ATmega. I am looking also for a display (maybe 16x2) with serial comm.
The power will be from a little transformer (2x9V).
Who want to comment? Someone working on this?