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What do you call this piece of gear that I need to have built?

Postby DC-Choppah » Tue Aug 06, 2019 12:50 am

I would like a thing built for me, but need your help calling it by the right name when I ask to have it made.

This thing will accept 16 microphone (XLR) inputs from around the project studio in two groups of 8. Some signals will be mics, some signals will be the output of DI boxes. The thing has only 8 microphone outputs. The thing has a switch and I can set it to send the first OR the second group of 8 mics out.

This allows me to connect 16 inputs to an 8 channel mixer/interface and switch them all in 2 groups without moving cables around. This is meant to be sort of permanent.

There will be phantom power on these mic inputs coming from the mixer.

The distance between the inputs to the outputs is about 4' and needs to run inside of a permanent cabinet.

The switch can be on the input or the output side. Either is OK.

What is that called? A mic-switcharoony?
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Re: What do you call this piece of gear that I need to have built?

Postby MOF » Tue Aug 06, 2019 2:00 am

Have you seen such a device? It sounds like a custom job to me, alternatively there are these two options:

If your mixer has D-sub connectors such as this https://www.bhphotovideo.com/c/product/ ... Cable.html
then you can plug in 8 mic cables, one at a time, just by un-screwing the multiway plug of one 8 way loom and then screwing in the next one.

The other way to do this is with a jackfield where all the cables are wired to it and all the mixer inputs too, then you use 8 jack to jack cables to plug which ever xlr cable you want to which mixer input you choose, this is more versatile since you can mix different sources from both looms.
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Re: What do you call this piece of gear that I need to have built?

Postby DC-Choppah » Tue Aug 06, 2019 5:11 am

MOF wrote:The other way to do this is with a jackfield where all the cables are wired to it and all the mixer inputs too, then you use 8 jack to jack cables to plug which ever xlr cable you want to which mixer input you choose, this is more versatile since you can mix different sources from both looms.

That is brilliant! 8-)

And those are all pieces I can easily find.

Jackfield: 8 inputs, choose from any 16.

Thank you kindly




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Re: What do you call this piece of gear that I need to have built?

Postby ef37a » Tue Aug 06, 2019 7:28 am

It might no matter for your application DC but I am not happy with
phantom power on jacks (you will know of course not to patch around with monitor/cans fader up!) .

You can accomplish the same thing with XLRs but the result will be bigger and a bit more expensive. You can buy pre-punched XLR panels, not sure how many you can get per "U"? (was looking the other day for pre-punched TRS panels and Google KEPT finding XLRs!) .

But, less versatile would be 16XLRs to 8 XLRs and 8 DPDT mini switches. Then you can have "XLR 1 to input 1 or XLR 2 to input 1. Di-da.....

DPDT assumes all with be well with a common ground but you can get Three pole and four pole switches if you are worried? Phantom power all goes back to a common -ve anyway so I doubt there would be a problem.

I bet that clever chap at Orchid Elecronics has been there, got the T shirt?

Oh yes! Name! Best I can come up with is a "16 to 8 microphone router". Catchee.

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Re: What do you call this piece of gear that I need to have built?

Postby Hugh Robjohns » Tue Aug 06, 2019 10:23 am

What you're seeking is a multi-channel microphone change-over switcher... or router...

I'm not aware of a commercial 2x8 into 8 channel version (although there are two (A/B) and 4 into 1 mic switchers around), so your requirement would indeed be a custom build.

However, it's not quite as trivial as it first appears because of the presence of phantom power, as Dave has noted.

The traditional solution is a patch-bay of course, but patching on TRS (or any form of jack plug) with phantom present on the line is a recipe for blown mic preamps and mics... so don't do that! And before you say, "But I'll always switch phantom off before I patch"... you won't! You'll forget one day, or a friend will patch without realising... it's just not worth the risk, trust me!

Patching on XLRs is safe, though, albeit a little more bulky. You can get rack-mount XLR patch panels with 8, 12 or 16 XLRS per strip, so it would be easy enough to make up a patch with two sets of 8 male XLRs carrying the outputs from your studio wall boxes, and then patch with short XLR cables into 8 female XLRs to feed the desk. Lots of versatility that way and not a huge expense. Just a bit of soldering involved...

An alternative that might be quicker to patch would be to use AES59 D-subs, since these will patch all eight channels in one go -- and you can buy ready-made boxes with XLRs on one side and D-subs on the other... but D-subs aren't really designed for lots of plugging/unplugging -- they are really installation connectors, and they are a bit fiddly and prone to damage, too... so that wouldn't be my favourite solution.

The custom build idea would probably be best with a box full of change-over relays to select either of your two input routes to feed the output. Easily done, all passive switching, phantom-power tolerant, and easy to remote control as well... It would just need a small power supply to energise the relays which could be a simple wall-wart or line lump. Could be a nice DIY build if you're handy with tools...

Coleman Audio make something along these lines already. There's a 2x6 into 6 channel switcher (the AB5.1), or there's a 7.1SW model which is a 4x8 into 8 switcher. Both are passive, balanced, relay-switched boxes, and can be used in either direction.

They are intended for switching between 5.1 surround sources/destinations with balanced line-level signals, but they'd almost certainly be fine with mic signals too. I have the 5.1AB box here... I'll give it a go when I get a chance.

http://www.colemanaudio.com/

Not cheap boxes... but then a custom build job wouldn't be cheap either! Orchid Electronics would be my recommendation to, if you were in the UK -- and it might still be cost-effective to Canada. Worth a call, anyway!

H
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Re: What do you call this piece of gear that I need to have built?

Postby ef37a » Tue Aug 06, 2019 11:54 am

https://www.pennelcomonline.com/en/gb/P ... 2AQAvD_BwE

There ^ you go. Then all you need is a bucket of XLR plugs and some cable.

Ooops! Sorry, you need another 16 XLRs!

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Re: What do you call this piece of gear that I need to have built?

Postby Hugh Robjohns » Tue Aug 06, 2019 12:02 pm

Nice find, Dave. That would make the ideal XLR patch panel.

I'd probably have the top row 1-8 as the A outputs (male XLR), and the bottom row 1-8 as the B outputs, and then top 9-12 as mixer inputs 1-4 (female XLR) and bottom 9-12 as mixer inputs 5-8. Eight patch XLR patch cables and the job's a good'un! :-)
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Re: What do you call this piece of gear that I need to have built?

Postby MOF » Tue Aug 06, 2019 12:05 pm

It might no matter for your application DC but I am not happy with
phantom power on jacks (you will know of course not to patch around with monitor/cans fader up!) .
I hadn’t thought of that , it was late and I was trying to come up with something that wouldn’t be too expensive, hence the first suggestion.
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Re: What do you call this piece of gear that I need to have built?

Postby ef37a » Tue Aug 06, 2019 1:12 pm

MOF wrote:
It might no matter for your application DC but I am not happy with
phantom power on jacks (you will know of course not to patch around with monitor/cans fader up!) .
I hadn’t thought of that , it was late and I was trying to come up with something that wouldn’t be too expensive, hence the first suggestion.

Heh! We've all been there! I don't think any solution is going to be cheap.

Dave.
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Re: What do you call this piece of gear that I need to have built?

Postby CS70 » Tue Aug 06, 2019 1:40 pm

DC-Choppah wrote:This allows me to connect 16 inputs to an 8 channel mixer/interface and switch them all in 2 groups without moving cables around. This is meant to be sort of permanent.


Much more fun to have a custom box of course, but an ADAT-enabled 8 channel interface and an octopre or something similar would allow you to have 16 inputs - you then have just to route in software all of them to the same 8 outputs in pairs (but only once) and you'll be set?

With RMEs and TotalMix you may also save mixer setup snapshots so it's easy to load the one you want (inputs 1-8 enabled or 9-16) - which is pretty much the same effort as flipping a switch. Surely other interfaces allow something similar. There is also a Tascam 20 i/o interface - I am not sure how good the software mixer is tough.

All undoubtedly less neat, but it could be less expensive.
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Re: What do you call this piece of gear that I need to have built?

Postby ef37a » Tue Aug 06, 2019 2:13 pm

Y'know..If I was doing this and wanted the flexibility to route any of the 16 mics to any 8 mic input I would use a passive RJ45 rack patch panel.

You can get 24 RJ45s to a 1u panel. 16XLRs above and wired down to the network jacks. You have 4 pairs per jack so, redundant audio on 2 prs and redundant phantom power neg on the third..Shoot! you could even have LEDs!

The 8 outs could just go on a cableform and save more sockets.

Even shielded RJs are earth isolated so the whole of the metalwork could just go to a good ground with no association with any signal or gear grounds.

No chance of spook juice getting to anything vulnerable.

https://www.fs.com/uk/products/69181.ht ... 5YQAvD_BwE

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Re: What do you call this piece of gear that I need to have built?

Postby DC-Choppah » Wed Aug 07, 2019 1:26 am

I was going to have these guys build it, but I have to figure out what it is first.

https://www.redco.com/


I am a bit confused on the phantom power concern. And it has to be safe to switch as we will never remember to turn off the phantom power. Phantom power is just a little red light that always happily glows as we make music.

Increasing digital channel count is mot an option. We have a nice analog mixer that has to fit in the cabinet. So I will be tracking in groups of 8 through the same mixer. Need the mixer to get the mix right for tracking while doing all monitoring in the analog domain.
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Re: What do you call this piece of gear that I need to have built?

Postby MOF » Wed Aug 07, 2019 2:50 am

You need two boxes with eight female xlr sockets on them soldered to an eight way balanced multiway cable of sufficient length to go from your recording areas to (for simplicity and cost reasons) a 2U high panel with a sufficient number of xlr connectors - 16 male xlrs i.e. two lots of 8 and then 8 female xlr connectors wired to the 4’ multi-way with 8 balanced wires with male xlrs that plug in to your mixer.
You then need 8 short (long enough to stretch along the 2U strip) male to female balanced xlr cables permanently plugged into the xlr sockets going to the mixer and then plug the other ends into the sockets from the studio.
The reason patch cords are a bad idea is because the tip and ring can short out the phantom power on the patchbay metal surround that connects to the sleeve, not the case with xlrs. Still, keep the faders down while re-patching though.
If re-patching is not desirable you’re going to have to incorporate double pole, double throw switches/relays on each pair of mic channels per mixer input i.e. mic 1a or mic 1b to mixer input 1.
Make sure you get label strips on the panel and make sure you cover any areas where the multiways are a trip hazard with rubber strip mats.
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Re: What do you call this piece of gear that I need to have built?

Postby DC-Choppah » Wed Aug 07, 2019 5:08 am

OK, building this up on the Redco site to make a 16, pick 8 channel jack field using XLR plugs is getting to be pretty darn huge and eating up too much rack space and is like $450.


MOF wrote:If your mixer has D-sub connectors such as this https://www.bhphotovideo.com/c/product/ ... Cable.html

Sadly, the mixer only has XLR connections.


But to build the '16 to 8 microphone change-over switcher' , if I have 3 of these cables and a db25 A/B switch box, I think that might work.

https://www.showmecables.com/2-way-manu ... switch-box

So the 8 'A' mics go into one db25 and the 8 'B' mics into another db25 using this cable. Both dB25s go into the A/B switch box. The output goes db25 back to 8 XLRs into the mixer.

Cables are bundled and tied off, all I need is room for the switch.

Is it OK to use a db25 switcher like this for microphones? What is going to happen to my phantom power???
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Re: What do you call this piece of gear that I need to have built?

Postby ef37a » Wed Aug 07, 2019 7:10 am

If you want I can draw up a schematic of the switcher I suggested?

I would only draw 4 ins to 2 outs to show the principle and show all the pin ones tied together since I cannot see that being a problem as it is how it goes inside mixers etc? Doctor Robjohns might like to comment? I would also suggest there be no ground from the mixer conneted to the metalwork? That would find earth from a different path. My preff' being a mains earth pin. That is the way IT comms cabs work. They are just made part of Mother Earth and signal grounds are isolated. Maybe 10nF to tie grounds at RF?

I think a switcher is the most compact and cost effective solution? Yes, you only get the choice to send either mic 1 or 2 (say) to mixer input one but of course, you can choose WHICH mics go in 1 or 2.

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Re: What do you call this piece of gear that I need to have built?

Postby Hugh Robjohns » Wed Aug 07, 2019 10:20 am

DC-Choppah wrote:I am a bit confused on the phantom power concern. And it has to be safe to switch as we will never remember to turn off the phantom power.

The only issue with phantom is if you try and patch mics using a TRS-style patch-bay. In that situation, as you insert (or remove) the plug, you can very easily accidentally short one side of the balanced line to ground, and if phantom power is turned on that can produce voltage spikes that have been known to damage preamps and mics.

There's no threat to life or anything like that -- the voltage is way too low -- but there is a real risk to equipment.

Hence all the advice not to use TRS (or PO316/B-type, or TT/Bantam) patch-bay for plugging mic circuits!

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Re: What do you call this piece of gear that I need to have built?

Postby Hugh Robjohns » Wed Aug 07, 2019 10:34 am

DC-Choppah wrote:OK, building this up on the Redco site to make a 16, pick 8 channel jack field using XLR plugs is getting to be pretty darn huge and eating up too much rack space and is like $450.

That's bonkers! It requires a 2U panel -- like the 24-hole model Dave found, and 24 XLRs, so the total for that would be around £125 tops. If you can't do the soldering yourself you'd have to add that, obviously... but it would be a really good project to learn how to solder with!

On top of that you'd need the studio end boxes, of course... If you don't already have something, I'd buy two 8-way stage boxes, populate them yourself with female XLRs, and a length of 8-way multicore.

You should be able to do the whole thing for under £250 if you can do the wiring yourself.

Regarding the D-Sub switch box... No! Not suitable! Sorry. Not wired correctly and inappropriate switch.

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Re: What do you call this piece of gear that I need to have built?

Postby Stratman57 » Wed Aug 07, 2019 10:49 am

Why not just buy a Behringer XR 18? 16 XLR inputs, 18 channel Audio interface. You wouldn't need to do any switching.

Regards, Simon.
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Re: What do you call this piece of gear that I need to have built?

Postby blinddrew » Wed Aug 07, 2019 1:53 pm

Better part of £400 though. Might be worth it if the rest of the functionality is useful to you but otherwise...?
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Re: What do you call this piece of gear that I need to have built?

Postby DC-Choppah » Wed Aug 07, 2019 2:05 pm

Stratman57 wrote:Why not just buy a Behringer XR 18? 16 XLR inputs, 18 channel Audio interface. You wouldn't need to do any switching.

Regards, Simon.

A want all mics to switch into the mixing board to provide a surface to control the mix while tracking in groups of 8.

Yes if I had more space for the mixing surface that would work but I don’t.
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