Idea for a balanced switch box...

[Allanmarcus]

Well, I haven't built this box yet, but I'm thinking about it. I'm thinking a 4 position box with one 4-pin XLR output and three 4-pin XLR inputs, and one TRS input. The idea is to be able to connect multiple amps to the box and one headphone, then be able to switch between the amps.

This assumes there is a way to get the same input into the amps. In some case, some amps have pass-through. Some DACs have multiple outputs. At worse, I would use my other switch box to split the DAC output. Then, with a two handed switch, I could still switch amps with very little time for the switch.

Cross talk between amp inputs might be an issue.

I listed out a complete BOM on my site, and the cost comes out to $111 for a 4 position box, and $71 for a two position box. Given how much I compare amps, which is way less than some, but more than most, I think it would be worth it to me. Plus the fun of building it

Update: I’m thinking of just having the cables hard wired. That would save some money on jacks and plugs.

Pricing for hard wired option is 4-way: $78.06 and 2-way: 61.88

It's the cross talk I'm worried about. Any thoughts?

 

[Speedskater]

What's with the 4 pin XLR connectors? If you are going to run two channels thru one interconnect, then you don't want a star-quad cable. Shielded Cat5 would be better but not very robust.

In the past, I made a DIY pre-amp with permanent interconnect cables. It saved adding a lot of unnecessary connectors.

 

[Allanmarcus]

4-pin XLR is the standard in most amp for output to balanced headphones. I can't change that.

Star quad cable is also very commonly used for headphone cable, and since this is just a headphone switch box, it seemed to make sense.

 

[Allanmarcus]

Now I'm thinking I might want a better switch. Maybe a DACT CT3 type switch, since they are "audio quality".

update; YIKES. I just saw how expensive they are. Maybe not.

 

[Speedskater]

Oops, I was thinking about balanced interconnects from the DAC.
And I saw shielded mic cable, why a shielded cable for headphones?

 

[Allanmarcus]

Oops, I was thinking about balanced interconnects from the DAC.
And I saw shielded mic cable, why a shielded cable for headphones?

Quad cable is relatively cheap and works well for headphone cable. For actual headphone cables, most of us DIYers strip the shielding off of quad mic cable, and just the the inner conductors. Sometime we sleeve the wire individually, or just twist or braid it , then sleeve it, or sometimes just braid it and leave it un-sleeved. See my DIY page to see a number of cables I've made all these ways. Stripping off the shielding and outer insulation and just using the conductors makes the resultant cable more flexible.

For this switch box project, using the whole cable as-is is probably good enough. I don't need the extra flexibility of stripped wires. The shielding just comes with the wire.

 

[penmarker]

A chip controlled switch with relays might yield better results. Stereo relays can be used for single channel XLR and can maintain the integrity of the audio. Ebay has some kits and they're cheap too. Since the only thing physically making the connections are the relays, you can find audio grade ones for replacement.

One caveat is it requires power. But a small 12V walwart could be sufficient.

 

[Allanmarcus]

Thanks.

I've already purchased everything for a passive switch box, and soldered almost everything. I'm just waiting on some "Nylon Cable Glands" to run the cable through from inside the box to outside the box, and then I will solder the final connectors.

I will run the wires out the opposite side from the input jack.

I will look into some relay based switch boxes. I don't understand what advantage that had over a passive box.

 

[Paladin79]

Passive should be fine for this application IMHO and star quad would be the way to go for me as well. If you take the cables directly through holes in the side of the box, I probably have some rubber grommets laying around that are the proper size. There are also some nice Neutrik plates that mount between the four pin xlrs and case that allow for nice labeling of each connection. I used them on a few of my amp builds. I can probably get a photo this weekend, it is a little hard to describe them otherwise.

https://www.markertek.com/product/n...ack-d-series-xlr-lettering-and-id-plate-black

 

[Allanmarcus]

Passive should be fine for this application IMHO and star quad would be the way to go for me as well. If you take the cables directly through holes in the side of the box, I probably have some rubber grommets laying around that are the proper size. There are also some nice Neutrik plates that mount between the four pin xlrs and case that allow for nice labeling of each connection. I used them on a few of my amp builds. I can probably get a photo this weekend, it is a little hard to describe them otherwise.

https://www.markertek.com/product/n...ack-d-series-xlr-lettering-and-id-plate-black

DAMN! That would have been useful when I was drilling the "D" sized hole to use as a template. I ended up using a dremel and a flex shaft attachment. First time using the attachment, and it was really easy and helpful.

Thanks. I have some of these arriving today:
Yongcun Nylon Cable Glands Waterproof Cable Gland Joints PG9 Wire OD 4mm to 8.0mm ($5.00)
My hope is to just drill four 6mm holes in the back of the box, and use these "glands" to secure the wire to box, which should offer some strain relief.

 

[Paladin79]

Nice, waterproof even. I will have to keep those in mind, on occasion I have to build water proof enclosures and search for waterproof connectors for specific applications.

Very cool idea by the way.

 

[Allanmarcus]

Thanks. I'll post here it they work or are POSs
For $6 not much risk.

 

[Allanmarcus]

Done! I learned that one has to look inside the dos, as well as outside, when figuring out where to drill the holes for the cables. The "glands" things work great, but they require some clearance, and I made one hole too close to the pillar inside the box. I had to hot-glue that one. Other wise, the box came out exactly how I wanted it. I have a buddy with a cricut, and he will print some white numbers. For now, here it is! I will be taking it to a meet tomorrow.

 

[Paladin79]

Very nice work, I did wonder about the size of the glands but like the idea they lock the cable in place, to be waterproof they have to fit snugly. I have a device that prints water proof labels, black on a white background if your other labeling scheme does not work. They wrap around the cable and have a clear coat over them so the numbers never smudge and the white portion does not get dirty.

On my list of things to do is a box that has only one input, and one output and a switch that controls the selection of cable within. It will be a fairly large box because inside will be 2.5 meter coils of braided cable. The person being tested will only see numbers as they switch between high end OCC copper, silver coated copper, ofc , and litz wire. I will most likely use knurled fasteners to allow for easy access and quick changing of cables inside the box or replacing certain cables. I will most likely go TRS for this application for size purposes and keep all wire gauges the same. Basically a test subject will be able to switch back and forth between four types of wire, ceteris paribus (with all things being equal). All I will need to do to change cables is open the box and plug in another cable and suddenly they are testing seven strand hookup wire as well. End result, listening to the same amp, same headphones, with different wires as close as I can get them to being identical in construction. Now if a person under test chooses the same cable as their favorite no matter where it is located in the box, I will certainly be impressed with that ability. Another way to do it would be having three cables of the same type, and a fourth of different materials. The test subject would only have to consistently say which cable is different. It would be a fun thing to send to people to try out, just so they know which type of cable they might enjoy more than another type.

Tests could be done with say one eight strand cable compared to three other four strand cables of the same material but running the same trs configuration. This is not exactly a fair test because if all strands in an eight wire cable were 24 awg, the overall gauge would increase, pass a signal more easily, and be a bit louder than the other three.

 

[Allanmarcus]

So here's my balanced switchbox in action. DAC to RCA switchbox to four amps to balanced switchbox to one headphone.