Rear mounted phantom power switch on Control 24

[stardancer]

Clearly, the placement of the 48V phantom power switches on the BACK of the Control 24 represents an ergonomic design flaw. There; now that I've got that off my chest, has anyone attempted (with success) to MOVE the switch to the front panel, or REPLACE it with a different latching switch installed on the front panel? The gizmo's long since out of warranty. How much damage can I do taking it apart (and how do I find the resources to learn how to do that?), locating the wiring and switches, and relocating them to somewhere on the front panel. Cheers!

[netnoggin]

Originally Posted by stardancer

Clearly, the placement of the 48V phantom power switches on the BACK of the Control 24 represents an ergonomic design flaw. There; now that I've got that off my chest, has anyone attempted (with success) to MOVE the switch to the front panel, or REPLACE it with a different latching switch installed on the front panel? The gizmo's long since out of warranty. How much damage can I do taking it apart (and how do I find the resources to learn how to do that?), locating the wiring and switches, and relocating them to somewhere on the front panel. Cheers!

No disagreement here. It's a real pain. I suspect though that it was a design advantage that put them there instead of design ignorance. There are too many pieces of gear that have the same arrangement. I suspect it has to do with not extending the wires too far from the inputs or something like that. I know of some gear with front-mounted switches that actually drive relays close to the inputs, which adds fuel to my theory. And relays are expensive from a mass-production standpoint, so avoiding them in the design saves money.

Flip the Control 24 so it's laying on its face and remove all the screws (a bunch) on the bottom. That will give you the access you seek, or at least get you close enough to see what else needs to be done. But you may find the switch is PC board mounted, not wired. That's not a showstopper, but it does change the level of difficulty a bit.

Good luck!

[CoolBlueGlow]

Some comments about moving the Control 24 phantom power switches.

1. The power supply in the C24 is a switching type power supply, outsourced by Digi to one of the typical switcher supply makers from China. It is value engineered to a particular price point for digi. (readers may decode that themselves.)
2. The phantom power portion of the supply is a board kludged onto the main supply. It appears to be a design add-on (a kludge, either by Digi, or by the vendor in response to the specialized requirement for a low current 48 volt supply.) They probably fitted this onto one of their standard designs to hit the price point digi specified.
3. It has been my observation (based on 9 years of regular use of two Control 24) that the phantom supply can get noisy, especially under higher loads. (poorly regulated or poorly designed, can't figure which right now.) Other threads discuss the noise / harness interconnect problems experienced by Control 24 users, etc.

re: Relocating Phantom Power switches

CAVEAT: I'm flying from memory here - so use common sense, double check my from memory schematic and if this seems too deep for you, it probably is. If you haven't already thought of unplugging the console to start this work, you are already disqualified for the job, o.k? You have been warned.

4. The dual banks of 8 XLR connectors receive their 48 volt feed from the kludged on board 48vdc supply via a two-wire (red black) harness rather carelessly dressed, which traverses across the innards of the console from the supply to the switches, daisy chaining to them. That harness can easily be followed from the power supply to the switch. open up the bottom of the unit, find the switches and follow the red/black wires to the supply. It goes from supply to each backplane phantom switch and then to its distribution points on the backplane pcb, which contain the XLR and TRS inputs (and the DI inputs on ch 1-2)
5. The 48VDC itself is blocked from the preamp dif amps by a pair of 63v electrolytic caps located right next to each of the discreet transistor sets for each preamp. One pair of blocking caps per preamp, so are sixteen of these per 8 ch. board. They are found on each of the two preamp PCB assemblies. Seems like they are 250uf, as I recall. (sorry, really working from memory here)

6. a.) Moving the switch would be easy enough. Here's a suggested approach. First, acquire a pair of quality spst switches. Not big automotive toggle switches, either. Little SPST bat handle, rocker, or push button...As you choose, carefully consider the size of the switch. The front plane of the Control 24 is pretty busy. You won't find lots of extra room to add two switches. p.s. I do not recommend Radio Shack. Try Mouser or Digikey.
b.) Locate them at your desired point of convenience on the front panel, keeping a.) in mind. Yes, you'll have to drill a hole...TWO holes in fact, one for each bank of eight channels. Chooooose wisely, Luke...you are drilling holes in your console. (aooohmmmm) p.s. Manage your drilling chips well. They make wonderful short circuits when falling between PCB surface mount components.
I recommend that you FIRST solder and dress your new switches with 22ga twisted pair flying leads. Make them about 4' long. make BOTH wires red. If you are anal, stripe code one of them on each switch. Normal people can use two identical red wires on each switch. Whether or not you are anal, shrink tube the bare solder points on the back of the switches! After prewiring the switches themselves, install them at your desired front panel location. This is much easier than trying to solder on the back of the switches after you put them in the board! Use a nut driver to tighten them, so you won't scratch the console face with your cheap made in China adjustable wrench. Line the switches up so that when you flip them they aren't crooked. Crooked switches scream AMATEUR WORK!
c.) Neatly route and dress the 22 gauge twisted pair flying leads you soldered onto your new switches (you DID do that, right?) from your switch location to a location near each of the two backplane switches' location. Untwist enough wire to make it easy to split them to the various locations. Each wire in each new switches' two wire harness will be slightly unequal in length, for reasons that will be obvious to those who get this when they do the work. Careless workers will just push them in there willy nilly. Careful folks will neatly cable tie them.
d.) Now, intercept the RED lead currently going to EACH the existing backplane switches. It terminates at a plastic connector right at the back of the switch. Cut those wires, leaving enough to solder to later.

TECH STUFF: For you electrical engineer types, we're installing an additional SPST switch in SERIES with the + side of the supply harness for each of the two phantom power switches. Remember that the OEM harness presents power to the Digi phantom switches in daisy chain fashion. Consequently, the SUPPLY to BOTH of the new switches must intercept the 48volts BEFORE the first OEM switch. That's the harness feeding the OEM switch NEAREST the power supply, NOT necessarily the lowest numerical bank! To make a parallel intercept to the new switches will mean THREE red wires soldered at that location. One from Digi harness feeding each of your two switches in parallel. In essence, you are installing a parallel intercept at the wire coming FROM the power supply, sending it to two new switches, and then returning two independently switched leads, one to each of the OEM switch feed points. Remember - you are intercepting the 48 volt BEFORE the first Digi switch, and then paralleling it to EACH of your two new switches. IF this already doesn't make sense to you, you're probably not up to the job...no offense. Have a tech do it for you. If you do this wrong, then one switch will turn on both banks, and the other will turn on only eight...The truly ignorant will simply blow the power supply.

For those of you who are getting this, just solder the remaining two wires of your new harnesses (one from each, which are now the "output of 48V" from each of your switches) to each of the red wires you cut near the each of the OEM switch harnesses. You want the short OEM lead you cut at the digi switch harness. That will be fed by the 48vdc from your NEW switch. One new switch feed to each of the original digi switch red wires Got it?

ERGONOMIC ALERT: When you wire up your new switches, decide in advance which one controls which bank. Make sure you pick the most physically logical switch to control each bank, e.g. Left switch is bank 1, right switch is bank 2, or whatever you think makes most sense. Remember, you're flipping the console upside down to work, so everything is backwards.

Worrier's Caveat: Note that this installation will leave a "leftover" red wire from Digi harness at the second daisy chained switch, as well as a short length of unused red lead from the digi harness between OEM switch A and B. That's because you have made it redundant by the new harness you just installed that includes your two switches. Oh, Don't forget the shrink tubing over each and every solder connection! Remember, this if 48vdc. If you short it out, you will blow the supply. Don't kid yourself...you are working in FRONT of the phantom supply's current limiting resistors, so a short here is fatal to the power supply. p.s. The replacement supply is $795.00 and is available from Avid.

Draw a schematic first, after you look at it, and double check your work at least twice, o.k? and Don't whine to me or digi if you blow it up. Idiots and careless charlies beware. You can kill yourself if you are stupid about this. Otherwise, it's as safe as handling snakes...

Put it back together, turn on the stock switches and leave them on. Now flip your front panel switches. Voila! front panel phantom power control! Your clients will now be impressed with your "customized" Control 24. I can supply you with a small gold logo stating that this console is "customized" for only $699.95. Let me know on that

p.p.s. I see no reason to be concerned about the small additional run of wire from the existing switch to your new front panel switch. The phantom power lead dress is very careless already, and an additional 10-12" of 22gauge twisted pair carrying filtered DC at low mv should make zero difference in circuit performance.

Good luck.