Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

rotary mains switch and snubbers
rotary mains switch and snubbers
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 26th October 2005, 08:15 PM   #1
spendorspain is offline spendorspain  Spain
diyAudio Member
Join Date: Apr 2005
Location: Spain
Default rotary mains switch and snubbers


I’m going to connect a rather complex system (a valve amplifier and a home theatre amp both sharing the same main L&R loudspeakers, and a headphone amplifier). The small headphone amp and the relay-switching system for selecting the amp to drive the loudspeakers will be built into the valve amp case (there is room for them), and the neatest arrangement is to use only one front rotary mains switch with enough positions to select which amp to use: amp#1, amp#2 (relay PSU on and coils energised to connect amp#2 output to loudspeakers) and headphone amp.

There are many toggle switches available for mains use, rated at 6A, 15A or even 30A, but with not enough positions (on-off-on max). I’ve found in Mouser a high capacity NKK rotary switch (HS16-2N) that just fits in the available space. It has 2 pole-11 positions (!) phosphor bronze (movable) and Ag-plated brass (stationary) contacts and is rated at 12A/125Vac and 6A/250Vac (this is the relevant value in my case). Is it appropriate?

The original rotary mains switch of valve amp is only 4A rated, but it is protected from the high voltage “on-off” transients by a “snubber” RC circuit (a special cap with “0.022uF+100 Ohm” marked in its body, connected from ac-in to ac-out switch contacts for both live and neutral). Is this “snubber” also necessary for the new higher quality 6A-rated mains switch? (perhaps only for the valve amp contacts, as the mains transformer of headphone amp is small and the PSU for powering the relays is a very small switch-mode type). If I have to use “snubbers”, what is the correct type of capacitor for mains voltage and current? The 100 Ohm resistor wired in series with the cap must be also a special type (and what power rating)? As we are dealing with mains, I’d like to clarify these doubts before any action.

Thank you

  Reply With Quote
Old 28th October 2005, 09:35 AM   #2
Geoff-AU is offline Geoff-AU  Australia
diyAudio Member
Join Date: Sep 2005
My amp uses a 220nF mains cap and 100R 1W resistor in series, between the switched active and switched neutral.

The capacitor you use MUST be mains AC rated. Mains caps are sold as such and normally have a rating on them like "275V AC". Don't use anything else. The resistor can be a standard 1W type (I used 5W because I had one lying around). The leads should of course be suitably insulated so that they can't accidentally touch the chassis or a curious organic unit (human) poking around inside the amp.

I would definitely still use the RC snubber, it protects the switch contacts.
  Reply With Quote


rotary mains switch and snubbersHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
rotary switch woodturner-fran Parts 5 9th February 2008 09:04 AM
Never try to switch 450V DC at 3A with a conventional mains switch... Eva Power Supplies 28 1st November 2006 09:24 AM
Rotary on/off switch kestrel200 Parts 2 23rd April 2006 09:23 PM
Rotary switch Freddie Solid State 1 30th August 2001 07:55 PM

New To Site? Need Help?

All times are GMT. The time now is 08:15 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio