Fader-start for Multiplay

[david.elsbury]

Hey

Hoping to pick your collective minds for a wee DIY project.

 

For those of you familiar with radio systems, they quite often use fader-start, so when the DJ raises the fader for (say) a CD or cart machine, the track automagically starts to play.

 

 

I want to build a box that has a fader with a fader-start contact (normally a microswitch) that I will wire to trigger Multiplay (probably a butchered keyboard). The audio from the computer will pass through the fader into the audio console.

 

Problem is, I'm having trouble finding a fader... Ideally I would like to build 2 of these. Anyone got any suggestions? Pot has to be log (audio) taper, prefer dual gang. Suppliers that ship to NZ would be preferred... or if anyone has any that they can post my way? :)

 

Cheers

David

[timd]

I'd do it with an Alps K type fader. Standard on radio desks and come with a microswitch fitted for you. RS stock them, eg this one.

[david.elsbury]

The one on the RS site, apparently isn't the microswitch variant. Just called RS and been rebutted.

 

How are these things so hard to find!

 

Any more suggestions?? :)

 

Thanks

[Bobbsy]

According to the ALPS data sheet linked from the RS site, all the faders marked with a * do indeed have a microswitch--this is roughly two thirds of the faders.

 

Have a look at http://docs-europe.electrocomponents.com/webdocs/0124/0900766b8012457a.pdf

[david.elsbury]

Yep, saw that. Very confusing! I've just spoken to the local trade counter, and will pop in on Thursday (when I'm next free) to take a look and hopefully purchase.

 

Cheers :)

 

It really *does* have to be log taper, doesn't it, from memory using a linear fader will just give a really small area of useful travel on the fader?

[dbuckley]

It really *does* have to be log taper, doesn't it

 

For volume, yes. Assuming you are using the pot as a straighforward attenuator, and not using a VCA or somesuch.

 

Level control on linear pots is... strannge.

[david.elsbury]

Yep, basic audio attenuator. Thanks for confirming that for me.

 

I'm having an exciting time ordering my switches on eBay, and designing a panel on Vectorworks, got to find somewhere to do cheap laser cutting/engraving now!

 

:D </nerd>

 

David

[Bobbsy]

 

It really *does* have to be log taper, doesn't it, from memory using a linear fader will just give a really small area of useful travel on the fader?

 

Looking at the scale beside the fader on a mixer kinda confirms this! The part up by 0dB would be a bit small if the part down by infinity was the same scale!

[dbuckley]

got to find somewhere to do cheap laser cutting/engraving now!

 

That would be http://www.frontpanelexpress.com

[david.elsbury]

Much obliged :)

[Oldradiohand]

You might find some P&G faders on ebay out of an old sound desk - most of these come with microswitches but they can be extortionately expensive. They don't really wear out and can be refurbished fairly easily, just don't use switchcleaner on the tracks, distilled water is the stuff.

[dbuckley]

Ha, talk about a missed opportunity. All the kit from a radio station that was damaged in the 'quakes was flogged off on trademe (local eBay equivalent) a little while ago, including boxes of spares for radio consoles, spares including faders with start capability, and these bits went for very little money.

[cedd]

Thinking outside the box, could you instead build a fader start module to fit around an existing fader? I'm thinking some kind of horseshoe shaped casing housing an IR LED and a light gate. When the fader's at the bottom it sits in the middle of the U and blocks the light. Such an item could be attached simply with magnets and could fit any fader on the existing mixing desk you want. It'd need power but for such simple electronics you'd get away with using the desk's phantom supply I'm sure.

 

Just a thought.

[david.elsbury]

Had considered a opto-isolator, ruled out because the fader cap would foul on the parts at the bottom of the fader. Also considered a hall effect sensor with a modified fader cap with magnet, but it's easier in my mind to just have a microswitch.

 

Went into RS, definately no microswitch-enabled faders. Ended up purchasing a microswitch and will retrofit to the fader. Emailed Alps, their NZ distributor contacted me, and says that they don't do faders with microswitches !?! I replied with a link to the datasheet, still waiting for replies.

 

So here is the basic concept: 3 general purpose assignable buttons. "advance" and "previous" buttons above the fader, "pause" and "stop" beneath. Raise fader for cue go.

 

I'm stashing a 4 port USB hub inside, to connect the keyboard and a USB stick to store stings and software etc.

 

Any thoughts or suggestions? Front panels being ordered shortly :)

 

Cheers

David

 

http://i45.tinypic.com/2hq9vko.jpg

[Paul TC]

Slightly off topic, but a mixing desk, custom built at a hospital radio station a good few years ago,(CD's hadn't been invented :) ), had the studio monitor speakers muted when a microphone was faded up, by micro switches mounted on top of the panel at the bottom end of travel. Pulling the fader cap against the microswitch enabled the studio speakers. Small piece of perspex screwed down over it, hellerman sleeves over tags, and wires routed through panel.