|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
|
|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
In Reply to: While we're on a roll... posted by Joe Murphy Jr on January 5, 2002 at 21:37:20:
Based on your info, I'm considering two Shallco rotary switches: the 121-CM and 121-DM. The resitors that I would like to use are the Vishay S102 types. Do you know if they will be applicable (specifically, will they fit?!!!) for either of these switches (2-pole, 2-deck)?After considering just how the thing would have to be wired up to produce a ladder attenuator, it'd be an absolute mess trying doing it with this type of switch configuration. All of the series resistors would have to span across the deck and they'd all have to be stacked on top of each other. And then you'd have all of the shunt resistors you'd have to squeeze between the decks on the one attenuator.
Mmmmm.
Are you SURE you want a ladder attenuator? :)
How 'bout the J series? Four decks, one pole per deck. That'd give you 12 positions and you said you didn't need more than that. That'd still be a bit of a mess for a ladder attenuator, but at least it's doable. That's what's nice about the Elma switches. They make this kind of wiring a piece of cake using a circuit board.
From a web article about the Marchand PR-41 passive volume control, the author seemed to think that the increasingly poor channel separation (as the frequency increases) was due to the Elma switch that was used as a source selector. Do you think I can get "dual-mono" channel separation -- or at least 120dB -- from a single Shallco switch (from 20Hz - 20kHz)?
The channel separation performance is due to the capacitive coupling between switch contacts. And it's this capacitive nature that causes it to degrade with increasing frequency as a capacitor's impedance decreases with increasing frequency.
Seeing as this is a DIY project, one way to significantly improve crosstalk performance is to wire your inputs to every other contact and wire the intermediate contacts to ground. What this does is use the intermediate contacts as an electrostatic shield. The drawback is that you have to switch through the intermediate contact to get to the active contact.
A manufacturer might refrain from doing something like this on a commercial product as most people are used to one click per input and they could lose some sales because of it, but for a DIY project, it's perfect if you don't mind the one drawback.
se
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Re: While we're on a roll... - Steve Eddy 22:36:22 01/05/02 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
