Has anyone ever thought about designing a DIY Digital Patchbay?

[canidoit]

I have noticed that there is no digital patchbay DIY projects out there.

Why are they so expensive, like the Flock or Dangerous Music Liaison?

Would an 8 stereo matrix be very expensive or difficult to make that is mastering grade?

I have noticed some AV matrix out there for sale, but they have RCA or unbalanced TS connections for their audio. How bad would it be to put DI's on the ins and Line converters on the outs to make it work with balanced gear? Would this be ok for mastering?
XRL out of outboard > DI > AV Matrix > Line converter > XLR in of outboard

Thank you.

 

[pucho812]

I have noticed that there is no digital patchbay DIY projects out there.

Why are they so expensive, like the Flock or Dangerous Music Liaison?

Would an 8 stereo matrix be very expensive or difficult to make that is mastering grade?

I have noticed some AV matrix out there for sale, but they have RCA or unbalanced TS connections for their audio. How bad would it be to put DI's on the ins and Line converters on the outs to make it work with balanced gear? Would this be ok for mastering?
XRL out of outboard > DI > AV Matrix > Line converter > XLR in of outboard

Thank you.

I can’t speak for flock but I have seen inside the patchbay designed by fix audio. The number of relays inside the unit to do all the patching is pretty staggering. To me that is the expense right there.

FWIW flock and others are basically piggybacking off old tech used in telephony. Check old patents for such action.

Lastly things like the flock have a headroom. Decades ago with sear, it was calculated that an analog patchbay has a headroom of 50dBu which is a considerably loud signal. The flock seems to have much less. I can’t say how much less but I have been told by some that it does distort with loud signals. That has me guessing 24dBu before it starts to distort but that’s a guess.

 

[mrclunk]

Yeah an enormous amount of relays needed.
I built a ‘simple’ relay auto patch device for a 24 track and that had 72 relays!

 

[ccaudle]

I have noticed that there is no digital patchbay DIY projects out there.

Just to clarify, you mean a digitally controlled patchbay for analog audio, not a patchbay for digital audio signals (like a S/PDIF or AES/EBU digital signal)?

Would an 8 stereo matrix

By that you mean 16 channels which can be connected to any of 16 other channels, but always routed together in pairs?
Would you ever want one input routed to multiple outputs, or would it always be 1-to-1?

 

[ccaudle]

The number of relays inside the unit to do all the patching is pretty staggering.

Yes, it seems that the way to make the cost more reasonable is to drastically limit the allowed configurations. That way it is just what you need, but probably not general enough to be worth marketing.

 

[pucho812]

Yes, it seems that the way to make the cost more reasonable is to drastically limit the allowed configurations. That way it is just what you need, but probably not general enough to be worth marketing.

or buy used patch bays and reconfigure to your needs.
It's one of those, if it's not broke, do not fix it scenarios.

 

[scott2000]

I have noticed some AV matrix out there for sale, but they have RCA or unbalanced TS connections for their audio.

There are some balanced ones afaik. Not sure about the quality of some of the audio after passing through some of the active switch ics and circuits in some of the matrixes.....

 

[JohnRoberts]

For what exact purpose?

I have noticed that there is no digital patchbay DIY projects out there.

Why are they so expensive, like the Flock or Dangerous Music Liaison?

Would an 8 stereo matrix be very expensive or difficult to make that is mastering grade?

it's only money

I have noticed some AV matrix out there for sale, but they have RCA or unbalanced TS connections for their audio. How bad would it be to put DI's on the ins and Line converters on the outs to make it work with balanced gear? Would this be ok for mastering?
XRL out of outboard > DI > AV Matrix > Line converter > XLR in of outboard

Thank you.

Back in the 90's I designed a MAP 8x4 Midi controlled Patch bay (for Peavey's AMR division). In fact it was more like midi controlled insert points. It supported 8 controlled insert points and 4 EFX loops that could be cybernetic-ally routed inline with any one of the insert points. Further multiple EFX could be sent to the same insert in any order.

This was pretty powerful using midi controlled EFX in combination with SMPTE to midi program changes to allow one reverb to perform different tasks as needed.

This was designed for -10dBV bedroom recording performance. To make it mastering grade would be several X more expensive.

JR

 

[mrclunk]

Would an 8 stereo matrix be very expensive or difficult to make that is mastering grade?

There is used broadcast relay audio switcher / matrixes out there. Companies like Grass Valley, Miranda etc made them. Sometimes can be found cheap on ebay.

JLM does a handy relay board that makes life much easier if anyone wants to build their own. Its what i used in my box.
https://www.jlmaudio.com/forum/viewtopic.php?f=2&t=296&sid=76f79b251a85d8a1001cda8fb0c77dc8

 

[pucho812]

for a brief moment I thought you were talking about an aes patchbay like the z-sys detangler and not a digitally controlled patchbay

 

[Brian Roth]

In the 1990's into the 2000's I was involved with the design and installation of several "small" video production facilities. All had routing switchers for analog (later, digital) video and audio. The largest router I worked with was something like 64 in, 72 out (or maybe 72 x 64? it's been awhile). Sigma Electronics and Sierra Video were the vendors.

I've always been intrigued by routing switchers. To those unfamiliar, I'll try to describe the concept using an 8 x 8 matrix as the example.

Draw a grid with 8 vertical and 8 horizontal lines. The horizontal lines are 8 signal sources and the verticals are 8 signal outputs. At each intersection is a "crosspoint", so in theory 64 crosspoints.

Eight of the crosspoints are No Good...one device's output routed to it's own input is a bad idea! <g> Thus a total of 56 crosspoints.

In the systems I worked with, any given input could be routed to one or more outputs, but only one signal source could be routed to any particular output at a time....that would be "mixing" the multiple signal sources. The control logic prevented more than one source to be switched to any output.

Crosstalk was a consideration. One or more manufacturers would spec that figure in an interesting way: "- (whatever) dB with all other inputs Hostile". Hostile meaning there is some unrelated signal entering the router on the unselected inputs.

In my mind I can imagine an analog audio router using Panasonic TQ2 relays at each crosspoint.

https://www.mouser.com/ProductDetai...Devices/TQ2-2M-5V?qs=YINDDaGsG3G4XvXpbalQHQ==

That's $164 bucks in my simple 8 x 8 example. Shrug.

I'm intrigued by this discussion. And, earlier I mentioned a 64 x 72 as being in a "small" facility. Take a look at rear of one of many analog video routers at WRC television in Washington DC (where Meet the Press, etc. originate). For some reason I can't find a pic of the corresponding audio router.

 

[Brian Roth]

Here's a possibility for a crosspoint....drawn in RothCAD. <g>

 

[Brian Roth]

Lastly things like the flock have a headroom. Decades ago with sear, it was calculated that an analog patchbay has a headroom of 50dBu which is a considerably loud signal. The flock seems to have much less. I can’t say how much less but I have been told by some that it does distort with loud signals. That has me guessing 24dBu before it starts to distort but that’s a guess.

Like my RothCAD crosspoint idea (actually tested years ago) I also pondered what would be reasonable I/O designs, dynamic range, etc.

Most folks don't need something like a router to accept +50 dBu in/out levels or drive 50 Ohm destination loads. Is +24 dBu insufficient?

My goofy relay idea should work fine at +30 dBu or higher, but ya gotta get in and out of the Matrix (movie reference there...LOL!).

Bri

 

[pucho812]

Like my RothCAD crosspoint idea (actually tested years ago) I also pondered what would be reasonable I/O designs, dynamic range, etc.

Most folks don't need something like a router to accept +50 dBu in/out levels or drive 50 Ohm destination loads. Is +24 dBu insufficient?

My goofy relay idea should work fine at +30 dBu or higher, but ya gotta get in and out of the Matrix (movie reference there...LOL!).

Bri

Well the 50dBu of an analog patchbay was calculated max before distortion. Equipment will distort way before then. So it really was an exercise more so then anything else

 

[canidoit]

I mean patchbays are useful, but the convenience factor and sometimes I notice that I have to turn or re-insert plugs for a solid connection as sometimes I notice levels were not even. I like the idea of digitally controlled routing the outboard with recall for Mastering that I am trying to get into. Mixing would be nice as well, but that most likely become costly for so many input and outputs.

 

[Brian Roth]

Well the 50dBu of an analog patchbay was calculated max before distortion. Equipment will distort way before then. So it really was an exercise more so then anything else

I'm lazy so I used:

https://sengpielaudio.com/calculator-db-volt.htm

50 dBu = 245 VAC. Are ya plugging the electric stove power cord into the patchbay? lol

Bri

 

[Brian Roth]

I mean patchbays are useful, but the convenience factor and sometimes I notice that I have to turn or re-insert plugs for a solid connection as sometimes I notice levels were not even. I like the idea of digitally controlled routing the outboard with recall for Mastering that I am trying to get into. Mixing would be nice as well, but that most likely become costly for so many input and outputs.

I'm with you here. I have a similar problem here dealing with a custom console, built decades ago, for a disc mastering lathe.

Hence my current interest in a analog matrix design....and not just to replace an older system. When cutting lacquers, everything has to happen in Real Time....so some sort of "automation" would be the Cat's Meow.

Bri

 

[machprod]

FWIW: I dont see it in the docs, but SSL 4000s use CMOS (4051s) for the monitoring section. And they used FETs for the channel matrix on the 611 modules. I have a bunch of manuals somewhere here, I will go see if I can find them

edit I originally wrote 4053 but its the 8 channel version of that chip

 

[cdc3oo]

Kramer's older balanced analog matrix switchers are available on the second-hand market. For example, the VS-88A is an 8x8 with >80dB SNR, accepts more than 20dBu and can be controlled via the front panel with memories. It also features serial remote control (RS232 + RS485). If that's not enough, the VS-1616 offers double the capacity and can be expanded to 96 channels.

Seen the price asked for a 8x8, I doubt the cost of a DIY project will be so cheap. I don't even think about the time spent on design and build.

That said, I'm not sure it meets OP's requirements.

 

[scott2000]

Kramer's older balanced analog matrix switchers are available on the second-hand market. For example, the VS-88A is an 8x8 with >80dB SNR, accepts more than 20dBu and can be controlled via the front panel with memories.

Those probably aren't going to be as transparent as some other options. I believe I recall reading not favorable opinions on the chips used in these that handle the audio switching and, then you have the active output circuits . Not sure but sometimes the utility of something takes precedence over getting the most transparent results.