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Circuit Board Question - Jukebox/Speaker related

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Category: Technical
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URL: http://www.ukvac.com/forum/forum_posts.asp?TID=373087
Printed Date: 31 Mar 2020 at 2:29pm


Topic: Circuit Board Question - Jukebox/Speaker related
Posted By: Purity
Subject: Circuit Board Question - Jukebox/Speaker related
Date Posted: 09 Oct 2019 at 8:01pm
Just a quick question for you tech savy guys

I have two jukeboxes - one vinyl and one cd, but I only want to use one set of speakers for both, so I thought I would wire up a speaker switcher box to switch between both units.

I was thinking about a circuit something like this (apologies for the crude drawing)

In this I was thinking of using a couple of DPST rocker switches to switch between the speakers, as below or a single DPDT toggle switch to flick between the two, but essentially the circuit would remain the same.

Would this work ok?  Can you forsee any issues?  Any better ways to do it?








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Replies:
Posted By: SUPERSPRINT
Date Posted: 09 Oct 2019 at 8:07pm
Dpdt looks like the best way to do it. It isolates the input from the other pole so should cause no issues.


Posted By: stevebm1
Date Posted: 09 Oct 2019 at 8:38pm
have you asked Duncan?,he's the jukebox specialist

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Posted By: Purity
Date Posted: 09 Oct 2019 at 10:36pm
I think this would do it with a DPDT toggle switch



No I haven't asked Duncan.  I guess it's more of a wiring/circuit question than a specific jukebox related question?

I'm sure he will pipe up if he has an opinion or view to share.


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Posted By: tin
Date Posted: 10 Oct 2019 at 9:22am
I would just use something like this but in reverse. And remember to not have either juke powered on when the speakers are disconnected.  http://www.ebay.co.uk/itm/Radio-Shack-4-way-Speaker-Selector-Switch-Box-Control-Center-Black/293213730189" rel="nofollow - https://www.ebay.co.uk/itm/Radio-Shack-4-way-Speaker-Selector-Switch-Box-Control-Center-Black/293213730189


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Posted By: John Bennett
Date Posted: 10 Oct 2019 at 1:47pm
Would it be a problem to put another relay/switch circuit on the negative lines too? 

You've got the grounds of two separate pieces of electronics joined together there - I don't know the specifics of the kit, but I'm thinking about avoiding earth loops and unwanted noise.


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Posted By: Purity
Date Posted: 10 Oct 2019 at 7:20pm
yea probably not a bad idea to completely isolate the speakers from each other


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Posted By: stevelup
Date Posted: 10 Oct 2019 at 8:16pm
Before you do this, put a meter between the both negative terminals on the JB and check you get zero ohms. Same on the CD.

Some amplifiers run in bridge mode and if you short the grounds together, you will destroy them. It's not common, but it's also not all that unusual either.

As long as you see a short circuit between the ground terminals, you can be sure that the amps are conventional and not bridged, then Purity's drawing is fine and you only need a single DPDT switch.



Posted By: Purity
Date Posted: 13 Oct 2019 at 1:35pm
There does seem to be some resistance between both the CD and Vinyl grounds, when I set the meter on 200 Ohms

Vinyl Jukebox:



CD Jukebox:


Would this cause issues?


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Posted By: SUPERSPRINT
Date Posted: 13 Oct 2019 at 1:50pm
Likely, as there will be a potential difference in voltage if there is resistance. Will
the switch, switch double pole? Isolating the positive and negative? That’s what you need really.


Posted By: Purity
Date Posted: 13 Oct 2019 at 2:24pm
I think I would need 2x DPDT switches or 1x 4PDT switch to isolate both - and + terminals.

I do have 2x DPDT switches - one (On)-On and the other On-(On).  I think if one deals with the - and one deals with the + this will work?  The only problem is I don't know when both switches are in the correct position

I may end up with the - active on the vinyl juke and the + active on the CD juke.  Although I'm not sure if this would cause issues and both are not connected at the same time

EDIT: I'm going with a 4PDT switch to isolate both jukeboxes


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Posted By: tin
Date Posted: 14 Oct 2019 at 12:14pm
Just get a speaker switchbox! they've got all the requisite switches inside without any dicking about.


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Posted By: Purity
Date Posted: 14 Oct 2019 at 12:53pm
Originally posted by tin tin wrote:

Just get a speaker switchbox! they've got all the requisite switches inside without any dicking about.


True, but where's the fun in that :-)

I already had most of the parts to make a switchbox, so that's why I didn't buy one, but thanks for the link.

As far as I can tell the 4PDT will work fine.  It has 12 pins, so 4 for the output in the middle pins, and then each device on the left and right Thumbs Up


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