I've been thinking my head off about this and still can't figure out what to do. I'm referencing the "Handbook for Sound Engineers" by Glen Ballou and various websites for information. Here are the questions that I can't figure out.
1.How important is it to build an attenuator with both constant input and output impedance (with the setup mentioned above in the thread, specifically, Rosetta 800 -> Dynaudio BM6A)?
2.What are average output and input impedances for devices like these? I was guessing 500 and 50,000.
3.If I did build a stepped potentiometer or ladder attenuator, how significant will signal degradation be if I'm working at an attenuation level that inserts 15 resistors into the signal path?
4.Dave, if you're reading this, my book has a diagram similar to yours of the ladder attenuator, but additionally shows a resistor between the input and switch wiper. It also states that a ladder attenuator only reflects a stable impedance to its source. Is there an explanation for this difference?
Other comments: I have a four deck ELMA switch to work with.
I calculated out values for an attenuator using a separate balanced Pi for each step, and even when I have a 1:5 ratio of Zi:Zo (as opposed to a 1:100 like if it were 500:50.000, which has a minimum loss of more like 25dB) there is a minumum loss of ~13dB, so it seems like a balanced Pi won't really work.
For various reasons, I think I'd like to build an attenuator that has a separate attenuator for each step.
This will not just be a snap to construct, so I'd like to do it right the first time and not have to buy new resistors and start all over. What kind of attenuator would be the best to use in this design? There is a lot of (too much) information out there, and I don't have enough experience to make my own informed decisions here...