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A/B xlr selector
Old 15th March 2014
  #1
Gear Nut
 
dimebucker5's Avatar
 

A/B xlr selector

Im thinking of building a peddle like this for use with a dynamic microphone

Radial HotShot™ ABo - Line Ouput Selector

after a bit of internet research there seems to be a lot of different methods some using 3PDT some 2PDT, some powered, some not... so im a bit confused as to what to go for...

any ideas?


would something this simple work?
Old 15th March 2014
  #2
Lives for gear
 

Hi
As a basic 'switch' box yes that is fine and would work with both dynamic and phantom powerd mics. It will also work if you wanted to use 1 monitor amplifier/speaker and switch between 2 'sources'.
There is no harm in this circuit but you should turn the gain or 'fader' down for the switching process as it will cause some 'click' or other noises simply because at the moment of switching there will probably be a short period where the preamp input is connected to 'nothing'.
If the switch were a 'make before break' type you could lessen the 'click' BUT would have both mics on together for the duration of the switching. Circuitry to prevent noises would be unnecessarily complicated and require a power supply (probably) as you would 'mute' the output before actually changing the 'switch' which would probably need to involve a relay. All in all FAR too involved!
Matt S
Old 15th March 2014
  #3
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Richard Crowley's Avatar
 

Yes everything that Mr. Syson said. Note that even if you are using it with a dynamic mic, if one of the inputs has phantom power on it, there is an excellent chance that you will get a pop when switching.

Note that many mixers/boards have "global" phantom power switches so you can either turn the phantom power ON or OFF for ALL the inputs. Now, if you were direct-connecting a dynamic mic into a mic input with phantom power applied, it would typically not be a problem. But "hot-plugging" (which is what your simple circuit is doing) can be dangerous to both the microphone and to both mic inputs.
Old 15th March 2014
  #4
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dimebucker5's Avatar
 

Thanks for the informative answers

i intend to use this in a live situation, so turning down the gain on the input wont be an option...

How does the 'Radial Hotshot' get around this click problem and remain passive??
Old 15th March 2014
  #5
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Richard Crowley's Avatar
 

Quote:
Originally Posted by dimebucker5 View Post
How does the 'Radial Hotshot' get around this click problem and remain passive??
Two possibilities. (In order of my expectations)

1) It probably doesn't. They are used in such noisy (rock music) environments it isn't a big problem. or...
2) They use a 4PDT switch which shorts (mutes) the unused output.
Old 15th March 2014
  #6
Gear Nut
 
dimebucker5's Avatar
 

We are a fairly loud band so perhaps it will be ok? The application is to switch between vocals going direct to FOH and vocals going through a laptop (via soundcard) and then to FOH.


I literally have no idea how to wire a 4PDT switch into that circuit!!
Old 15th March 2014
  #7
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Quote:
Originally Posted by dimebucker5 View Post
I literally have no idea how to wire a 4PDT switch into that circuit!!
That is the easy part. The hard part is actually FINDING a 4PDT alternate-action foot peg switch.
Old 15th March 2014
  #9
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Quote:
No. That switch is plastic and wouldn't last the night.

This is what you are looking for...

Pedal Parts Plus: 4PDT True-Bypass Footswitch

I am assuming this is an "alternate-action" (aka. "push-on, push-off") switch since it doesn't say one way or the other.
Unless you wanted momentary (which you didn't say, either)



Your diagram shows two poles: 1-2-3 and 4-5-6

Add two more: 7-8-9 and 10-11-12 NUMBER THE PINS IN THE SAME ORDER AS IN 1-2-3

Connect pins 8 and 9 of the switch to pins 2 and 3 of the LOWER XLR output (pins 1 and 4 on the switch)
This mutes the lower XLR when the upper XLR is selected.

Connect pins 10 and 11 of the switch to pins 2 and 3 of the UPPER XLR output. (pins 3 and 6 on the switch)
This mutes the upper XLR when the lower XLR is selected.
Old 16th March 2014
  #10
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brianroth's Avatar
 

Hell...just use a XLR patch panel, unless you need immediate "A versus B" gratification.

Bri
Old 16th March 2014
  #11
Gear Nut
 
dimebucker5's Avatar
 

Quote:
Originally Posted by Richard Crowley View Post
No. That switch is plastic and wouldn't last the night.

This is what you are looking for...

Pedal Parts Plus: 4PDT True-Bypass Footswitch

I am assuming this is an "alternate-action" (aka. "push-on, push-off") switch since it doesn't say one way or the other.
Unless you wanted momentary (which you didn't say, either)



Your diagram shows two poles: 1-2-3 and 4-5-6

Add two more: 7-8-9 and 10-11-12 NUMBER THE PINS IN THE SAME ORDER AS IN 1-2-3

Connect pins 8 and 9 of the switch to pins 2 and 3 of the LOWER XLR output (pins 1 and 4 on the switch)
This mutes the lower XLR when the upper XLR is selected.

Connect pins 10 and 11 of the switch to pins 2 and 3 of the UPPER XLR output. (pins 3 and 6 on the switch)
This mutes the upper XLR when the lower XLR is selected.
THANKYOU, i will get started on this right away!
Old 16th March 2014
  #12
Gear Nut
 
dimebucker5's Avatar
 

Just to minimize confusion here is a crude sketch including the 4PDT.




I hope it's correct! so to mute an XLR you just short pins 2 and 3?
Old 7th April 2014
  #13
Gear Nut
 
dimebucker5's Avatar
 

Thanks Richard!

Built this the other day and it works really well




Although, there is a small high frequency "tick" type noise when engaging the pedal..

Would this pose a problem on a bigger P.A.? I mean, it's by no means a "thump" and it's perhaps an 1/8th of the volume of the voice going into the mixer..


Any suggestions for a fix, or is this unavoidable with a mechanical switch?
Old 7th April 2014
  #14
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Hi
It is largely unavoidable with a mechanical switch although adding 'pull down' resistors to 'ground' MIGHT help but only if it is a signal with no phantom or any 'stray' voltages.
One possibility might be to add a 'momentary' press switch which simply shorts the output which you would press BEFORE operating the changeover (and released after the main switch) however it is hardly an 'ergonomic' solution. More specialised ways of doing this would be possible but gets quite serious in terms of hardware and complexity and nowhere neas as 'universal' as your simple version.
Matt S
Old 7th April 2014
  #15
Gear Nut
 
dimebucker5's Avatar
 

Hmmm, i see... that's interesting

I wouldn't ever be using phantom power, so maybe il give the 'pull down' resistors a go.

I know in guitar pedals you put the pull-down resistor at the input to the circuit board, but where would they go in this situation? from the hot AND cold of each XLR output to ground?

Thanks for the help
Old 8th April 2014
  #16
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Richard Crowley's Avatar
 

Yes, from pin 2 back to pin 1 (ground) and from pin 3 back to pin 1 (ground).
Old 8th September 2015
  #17
Gear Head
 

I've been looking for a simple sketch for making this exact thing.

I'm going to use it as an A/B switch for choosing if a condenser mic or an active DI box is going in to a preamp.
I don't really care if it pops/clicks - I'll drop the volume down when switching.

Can someone tell me if my sketch for this is correct?
Attached Thumbnails
A/B xlr selector-mic_selector_01.jpg  
Old 8th September 2015
  #18
Lives for gear
 

Hi
Yes that is great and yes it will pop when switched, but so would simply pulling the plugs in and out. Go for it!
Matt S
Old 8th September 2015
  #20
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Hi
The first and third would be good. The second is a bit 'large' and the contacts are rated for much greater current so not quite as suitable for low level audio signals. It would work initially but may 'tarnish' over time unless switched frequently.
Matt S
Old 8th September 2015
  #21
Lives for gear
 

Hi
Just looked up the thread and you have posts 13 which show how it can be wired and my comment #14 about a momentary switch to 'short' the outgoing signal so it would 'mute', allowing relatively quiet switchover even with phantom power on. Probably not 'silent' however, just not massive!
Matt S
Old 8th September 2015
  #22
Gear Head
 

Thanks, Matt. The momentary mute switch sounds like a good idea.
How do I wire that?
Old 8th September 2015
  #23
Lives for gear
 

Hi
Just so it 'shorts' pin 2 and 3 of the outgoing XLR. A simple 2 pin switch is sufficient although many have more contacts available.
Matt S
Old 8th September 2015
  #24
Gear Head
 

Is this correct?

With something like this:
http://www.electrokit.com/productFil...sort=price_asc
Attached Thumbnails
A/B xlr selector-mic_selector_02.jpg  
Old 8th September 2015
  #25
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Hi
Yes and yes!
Matt S
Old 8th September 2015
  #26
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would be nice to source a "make before break" action switch that is a push button instead of rotary switch for this application..

then there will not be any pop.
Old 8th September 2015
  #27
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Hi
It would still 'pop' with a make before break action switch as you are powering up a phantom powered mic or DI.
Matt S
Old 10th September 2015
  #28
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Quote:
Originally Posted by Matt Syson View Post
Hi
It would still 'pop' with a make before break action switch as you are powering up a phantom powered mic or DI.
Matt S
that is true matt. but in the application of phantom power mics, by my recommendations, it would be preferred if phantom power was applied on both inputs independently before the circuit (like one or both inputs are plugged into an external phantom power supply block)
Old 10th September 2015
  #29
Lives for gear
 

Hi
That is as may be BUT the OP wants to switch conveniently between 2 'sources' so any 'preference' to mess about with any of the pieces of gear involved is not on the cards.
As had been said by myself and others there are some compromises to be made, which have been highlighted.
From applying power to a Phantom powered circuit, practically all will take a moment or two to stabilise and start to work correctly. The result of this is the various pops and bangs that will be 'heard' through the system.
Matt S
Old 25th September 2015
  #30
Gear Head
 

Just wanted to pop in and say that I succesfully built this little switch the other day.
It works brilliantly.

Thanks for all the help/info and sorry for hijacking the thread.
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