DIY remote audio switcher (RCA)

[rthorntn]

Hi All,

As always your help is much appreciated, say I wanted this:

http://wardsweb.org/misc/sw10.jpg

But with the switch replaced with something I could control with an MCU, a motorised switch, anyone seen something like that?

The idea is to preserve the audio quality but switch RCA sources remotely?

Thanks for looking.

Richard

[madires]

Pick your prefered solution:
- motorized rotary switch: expensive, requires motor driver and additional switch element for position feedback, gold plating strongly recommended
- relays: less expensive but would need push buttons (for each relay or an up/down pair), LEDs for feedback, use gold plated small signal relays
- CMOS switches: inexpensive but would need push buttons again, there are also dedicated audio switching ICs

[tooki]

Pick your prefered solution:
- motorized rotary switch: expensive, requires motor driver and additional switch element for position feedback, gold plating strongly recommended
- relays: less expensive but would need push buttons (for each relay or an up/down pair), LEDs for feedback, use gold plated small signal relays
- CMOS switches: inexpensive but would need push buttons again, there are also dedicated audio switching ICs

Why do you say that relays and CMOS switches need buttons and LEDs?? The goal here is MCU control, as stated in the OP. An arduino and a multi-channel relay shield board (to populate with your own relays if you reeeeeeeeealllly need gold, which I don't think you do) could do it with no additional parts beyond whatever inputs the OP wants to use.

[madires]

My understanding is that the OP wants local and remote control. If he's happy with remote only he doesn't need any push buttons of course. When you're switching small signals with standard relays youl'll get contact problems after a while. The contacts build up some tarnish and oxide layer with time, but the load current cleans the contacts usually. Small signals like audio line level don't provide sufficient current for cleaning, so the tarnish and oxide layer stay intact. It's a slow process and it might need several years. If you like to build something to last, you'd use small signal relays with gold plated contacts which nearly prevent the tarnish and oxide layer. Long time ago I was an intern in a small company designing and building high end stereos (proper engineering, not audiophoolery) and I learned a lot. After that I've seen problems with poor choices of relays and switches over and over again. Take Yamaha for example. They've put nice motorized switches from ALPS as input selector in their flagship amps 20 years or so ago. Most of those amps started to create problems (distorted or very weak audio) after a few years, caused by a bad input selector switch. The switch contacts were not gold plated.

[rthorntn]

Thanks, remote control is the most important thing, I could always add local control later using buttons attached to the MCU.

Can you please recommend a gold plated small signal relay for this application, I have no idea what to look for?

Also if there was a suitable arduino shield that could take the recommended relays that would be great.

If I was designing it to switch one of four input RCA's to one of two output RCA's how many relays of which type (SPDT, DPDT) would I need (I think 8 SPDT)?

I have used this in the past for switching motors polarity (maybe I could swap the relays if they used a common socket):

http://www.ebay.com/itm/DIN-Rail-Mount-8-SPDT-16A-Power-Relay-Interface-Module-OMRON-G2R-1-E-DC24V-Relay/371196733296

Come to think of it, the low voltage relays would probably be a lot smaller than those Omrons.

Thanks again.

Richard