Bottlehead Forum

General Category => Technical topics => Topic started by: JamieMcC on May 10, 2014, 06:01:38 AM

Title: input selector switch
Post by: JamieMcC on May 10, 2014, 06:01:38 AM

I have been investigating line stage input/output switches and noticed two types which deal with the grounds differently and would like to know if there is any consciences of opinion or preference between the two?

1st switch assumes a long ground strip connects all the RCA input jacks grounds, so there is no need to connect the individual grounds along with the hots at the switch.

2nd switch takes both the signal hots and grounds to it so that only the individual signal source and its ground is selected and neither its outputs nor its ground make any connection to the line-stage amplifier ground or other connected components grounds.

All thoughts & opinions welcome.

Jamie



 

Title: Re: input selector switch
Post by: Grainger49 on May 10, 2014, 07:37:46 AM

The second type was one of the many improvements from the FP 2 to FP III.  It keeps any ground noise from an unused input from causing problems with the other inputs.

Title: Re: input selector switch
Post by: mcandmar on May 10, 2014, 07:55:42 AM

I would also prefer to switch the grounds, i.e. if a device isn't in use take it out of the circuit.

I believe one potential drawback is a pop or thump when switching if the grounds between devices aren't at exactly the same level.

Title: Re: input selector switch
Post by: JamieMcC on May 10, 2014, 08:40:28 AM

Thanks guys that's helpful.  Having to keep pulling and swapping round my RCA inputs is becoming very irksome. I have tried a couple of types of splitters but results have not been very satisfactory so now looking at components to make a proper switching box with multiple outs though not sure if I am going to combine it with the quickie or try my hand at a passive pre.

If I can pick your brains a little more is there any reason why a multi line stage input switch can not be used back to front to get selectable outs, this is what I'm pondering over.

selectable line stage input switch -> stepped attenuator -> selectable line stage input switch (but wired in reverse/ mirrored) to give selectable analogue out?

I'm not to sure if my terminology is correct but hopefully you can get the drift.






 

Title: Re: input selector switch
Post by: Paul Birkeland on May 10, 2014, 08:51:22 AM

I can't see anything wrong with doing that. 

Title: Re: input selector switch
Post by: mcandmar on May 10, 2014, 09:43:29 AM

I knocked up a similar arrangement with two four position four pole switches, idea being i could switch between four inputs, and then four outputs but gave up on it due to the extra cabling needed.  Switches i used were these style little Russian surplus items http://www.ebay.co.uk/itm/281321318545 (http://www.ebay.co.uk/itm/281321318545) smaller than the regular ceramic ones you see listed, and have a nice smooth switch action.