Quantcast
DIY PTT desktop switch AND footpedal - Gearspace.com
The No.1 Website for Pro Audio
DIY PTT desktop switch AND footpedal
Old 5th March 2014
  #1
Lives for gear
 
superwack's Avatar
 
1 Review written
🎧 10 years
DIY PTT desktop switch AND footpedal

Hi,

I was wondering if anyone could point me towards a product or DIY schematic that would allow me to have a talkback mic (most likely a dynamic) connected through a PUSH TO TALK circuit where there was both a desktop button and also the ability to have a footswitch.

Basically, I am comfortable with the pressing the button to talk thing but, every once and a while, I need both hands and someone starts talking and I'd love to be able to step on a pedal and catch what they're saying. Obviously I could use a latching box but some clients and some producers aren't comfortable with the 'always on thing' or I could switch to a footswitch only but there are those client who will reach for the button so...

Mic in/out would be XLR and the footswitch would probably just be a 1/4" TS in so I could re-appropriate one of the many I have lying around. I did a search and found a simple schematic for a talkback switch for a phantom powered condenser, but didn't know how, where or if a second footswitch could be implemented in the design.

Thanks so much for any help you're willing to give.
Old 5th March 2014
  #2
Gear Maniac
 
🎧 15 years
This really shouldn't be a problem - have a push to talk (momentary operating) switch on the desk, with a foot switch in parallel.

Then you can use either - or both!
Old 5th March 2014 | Show parent
  #3
Lives for gear
 
Richard Crowley's Avatar
 
🎧 10 years
Quote:
Originally Posted by Mixermend ➡️
This really shouldn't be a problem - have a push to talk (momentary operating) switch on the desk, with a foot switch in parallel.

Then you can use either - or both!
That scheme seems OK on first inspection, but there are a couple of issues:

1) We typically mute a microphone (both dynamic and condenser balanced) by SHORTING across the balanced audio (pins 2 and 3). We use a normally-closed switch so that when you actuate the switch, you OPEN the switch and allow the audio to pass. If you put TWO normally-closed switches across the audio pair in PARALLEL, then you will have to actuate BOTH of them to un-mute the audio. (Logic "AND" function). This may be what you want for launching a weapon or a 10-ton punch press, but for un-muting a microphone, it is the opposite of what you need.

To make a proper logic "OR" function (which you are seeking), you would wire these shorting switches in SERIES so that opening EITHER of them will un-mute the audio. This means that you need to use a jack for the foot switch that "shorts" the circuit when no foot-switch is plugged in.

2) Since actual audio is present on the switch, using a typical foot switch may be unsuitable because...

a) They have unshielded wire which will allow interference to enter the audio path, sometimes severe.
b) They are unbalanced and use TS (tip-sleeve) connectors.
c) They are typically "normally open" and only close the connection when you activate them with your foot. This is the OPPOSITE of what you need.

Now all of these problems can be overcome by doing a very simple re-wiring job on the foot pedal. If you use a "balanced" TRS connector and 2-conductor shielded cable (as you would use for a mic cable), it would solve the (a) and (b) issues. And then, assuming the switch has a conventional SPDT micro-switch inside, you can connect the wires to the NORMALLY-CLOSED terminals instead of the normally-open terminals (which is the conventional way).

So, yes, you can do this with simple, passive switches, but you will need to take some extra measures to make the foot switch work properly.

Here is a schematic diagram...


Old 9th March 2014
  #4
Lives for gear
 
superwack's Avatar
 
1 Review written
🎧 10 years
Thanks so much! That schematic is perfect and very, very much appreciated!
📝 Reply
Topic:
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…

Forum Jump
Forum Jump