Digital Patchbay?

[abechap024]

Hi I have an idea for a Digital(ly) (controlled) Patchbay.
Like 24-48 TRS plug ins in back and then some sort of digital sorcery inside that makes the signal path completely analog (just bare wire) and lets the user have complete versatility ( TRS "1" can got to "2-48") The TRS could only be sent to one other TRS at a time to avoid a much more complicated design. The unit should be one rack mount space and a simple to use front interface, and mybe a simple usb connectivity? Wouldnt that be sweet to point and click how you want everything interfaced?!? that would rock my world. Anyone know of a product already designed like this?? Any ideas?
Thanks!
Abraham

 

[abbey road d enfer]

TC Electronic Digital Konnekt x32
Frontier Design APACHE
M-Audiodigipatch (discontinued)

 

[JohnRoberts]

This still requires a rather extensive switch matrix whether relay or SS.

I designed a product a couple decades ago (MAP8x4)  that was digital (midi) controlled insert patch bay, with 4 sets of effect processor input and output jacks, that could be electronically routed (inserted) into 8 insert points. Any one or all of the 4 effects could be sent to any one of the 8 inserts. Multiple effects could be sent to any one insert, in any order. Noiseless electronic  switching allowed you to move a single effect around onto different tracks, or even in different order in the same insert, based on midi cues. A single midi controlled reverb could do different effects on different tracks at different times during a single song.

This was complex enough for a simple 4x8 matrix. Expanding to more inputs and /or more destinations expands the complexity exponentially.

It was a clever product (IMO) but perhaps a little too cool for the room at Peavey/AMR.

These days with digital reverb so cheap, there is less incentive to move around a single effects unit.

JR

 

[abechap024]

No sorry I guess I didn't do a very good job of explaining myself. What I'm looking for is a totally analog patch bay, but instead of using patch cables to make the connections I use digital Switches. know what I mean? So there is no A/D D/A conversion at all. Only a matrix of switches. I know we have the technology available because some consoles do it. I just have not seen or heard of a rack mount version. Patch bays seem like they should be a thing of the past! (dont get my wrong I love patchbays, I'm just to broke to buy a nice TT patch bay with 10$ a piece cords) Imagine 4-8 DB-25 connectors on the back, and complete digital control, along with digital recalbility....nice!
I dont have much experince with the logic side of consoles, but It isn't tooo too complicated. I would like to DIY a version anyone game, that mybe knows a little more that can push me in the right direction...or mybe just of a clifff> ???

 

[abechap024]

Hi John
That sounds exactly what I'm looking for. You don't have a schematic for that do you? however complex the internal curcuitry is it would make my studio work flow much much lesss complex. what chips did you use?
Thanks!

 

[jdbakker]

http://messageboard.tapeop.com/viewtopic.php?t=65179
http://www.aaroncramerengineering.com/Senior%20Project.html

The AD chip he used looks okay if not stellar. Haven't looked too closely at his layout, and he does point out that (at the time of writing) he hadn't gotten around to doing THD or noise tests.

I'm just to broke to buy a nice TT patch bay with 10$ a piece cords

I would be very surprised if a digital patchbay would be cheaper.

JDB.

 

[JohnRoberts]

Hi John
That sounds exactly what I'm looking for. You don't have a schematic for that do you? however complex the internal curcuitry is it would make my studio work flow much much lesss complex. what chips did you use?
Thanks!

Sorry no schematics I did this a long time ago... not that I save schematics from my old gigs. I would be surprised if even Peavey has one, this product was  mid/late '80s and before full CAD for PCB/schematic capture there.

I used cmos TG technology for the actual audio routing.. IIRC not the 4016/4066, but 1x4 or other variants.

I had to use a +/-8V rails, and used some other tricks to reduce clicks. I recall some fancy mutes used with the CMOS switching so it was always switching to or from a ground mute, again for less switching noise.

The digital side was handled by a common 8051 board that the digital group used inside several other products, so not only are there no schematics I think that one PCB was hand taped and from much earlier designs.

I don't see huge utility for this today, but for very high performance to mimic an analog patchbay, i'd use relays, but we're talking a lot of relays for even a modest number of cross points.  In my design I recall some 12 daughter PCBs to accomplish the 4 x 8, plus 1 digital PCB, and the mother board, and front display board... lots of stuff in a 1u product.

JR

 

[abechap024]

Sweet! Thats totally what i had in mind. looks great. Thanks for that link ;D

 

[stickjam]

That's easy, if you can (or get help to) program in C.  

For a 48 x 48 switching network*, all you need are nine of these and a PIC microcontroller.  I'd stick with the 16-bit PIC24's (the 8 bit chips can be a pain).  A lot of these chips tend to be SMT, but if you prefer thru-hole, the PIC24 comes in DIP and that crosspoint switch chip comes in a PLCC package which can be socketed.

It's a couple Franklins worth of switching chips, but they run dual-rail analog + digital supply and it's a heck of a lot smaller and cheaper than 2304 relays or 576 CD4066's (and 288 8-bit latches to drive 'em).

(addendum
*that's unbalanced.  There are dual 16-by-16 crosspoint chips to directly switch balanced, but those are SMT only.  I'd use this to only switch line-level signals, so with that in mind, I'd throw in 48 apiece of THAT balanced input buffers and OUTSMARTS chips on the outputs.  You don't want to switch mic cables with 48V phantom over those crosspoint chips.

 

[stickjam]

--and you probably COULD cram it all in a one-rackspace unit if it was entirely USB controlled.  Well, that depends on whether USB, power and 12 Tascam-pinout DB25F connectors will fit on the back,  ;D

 

[TheGuitarist]

If it helps at all Igor's CRM kit does this on a small scale. If anyone makes one, i'd be interested in it if its fully balanced switching (the less stuff in the signal path the better)

And maybe just have a 48v on the back end of each channel or something, so you wouldn't risk damaging anything if you're sensible, and 48v supply.

2ru with say a button on each input, so say you had a mic input 2 compressors and an output, have a button on the input, that when you press it, lets you choose where you want it to go, so you then select the first compressor. Then you select the first compressor, and then you press the button for the next compressor. then you press the button for the second compressor and select an output.

Just some ideas. Igor might be able to help out.

 

[Rochey]

That's easy, if you can (or get help to) program in C.  

For a 48 x 48 switching network*, all you need are nine of these and a PIC microcontroller.  I'd stick with the 16-bit PIC24's (the 8 bit chips can be a pain).  A lot of these chips tend to be SMT, but if you prefer thru-hole, the PIC24 comes in DIP and that crosspoint switch chip comes in a PLCC package which can be socketed.

It's a couple Franklins worth of switching chips, but they run dual-rail analog + digital supply and it's a heck of a lot smaller and cheaper than 2304 relays or 576 CD4066's (and 288 8-bit latches to drive 'em).

(addendum
*that's unbalanced.  There are dual 16-by-16 crosspoint chips to directly switch balanced, but those are SMT only.   I'd use this to only switch line-level signals, so with that in mind, I'd throw in 48 apiece of THAT balanced input buffers and OUTSMARTS chips on the outputs.  You don't want to switch mic cables with 48V phantom over those crosspoint chips.

I'd be a little nervous about the ADI chips. They look pretty good (don't get me wrong), but the 0.01% THD bothers me.
Maybe I'm being silly. I'd personally prefer switched relays for everything.

However, that gets big and expensive really quickly

If you assume that each output can only come from one input, then on an 8x8, you'd need 7 DPDT relays for each output. 54 relays. ouch.

let me chew on this one a little more.

/R

 

[jdbakker]

I'd be a little nervous about the ADI chips. They look pretty good (don't get me wrong), but the 0.01% THD bothers me.

That's for a relatively old chip, which I presume stickjam suggested as it comes in PLCC, and you can easily get through-hole adapters for PLCC. The newer ADI chip used in the design I linked to a few posts earlier (the AD8113) has an internal buffer and claims a 0.002% THD at 20kHz/20V.

Maybe I'm being silly. I'd personally prefer switched relays for everything.

However, that gets big and expensive really quickly

No kidding, http://www.spl.info/index.php?id=91&0=&L=1 f'r example has 576 relays!

Plus relays are relatively unreliable, so you'd have to make the beast easily serviceable too.

However nice it might sound to have total recall and fast A/B-ing in an automated patch unit, I suspect it would take a lot of engineering effort and money to approach the flexibility and robustness of a simple wired patch panel.

JDB.
[for studio applications I would sooner suggest one big 32 or 64 channel AD/DA box, with built-in routing and possibly automatic latency hiding, so all paths appear to be equally long in terms of path delay]

 

[jdbakker]

--and you probably COULD cram it all in a one-rackspace unit if it was entirely USB controlled.  Well, that depends on whether USB, power and 12 Tascam-pinout DB25F connectors will fit on the back,  ;D

One word: heat.

JDB.
[ah, but you didn't say how deep this 1U box would have to be]

 

[abbey road d enfer]

Hey! This guy wants to switch DIGITAL signals...

 

[abechap024]

no no, I don't want to switch Digital signals. I want to switch analog signals digitally. This is great info ;D I say if there is enough interest we should try to get something like this going DIY. I'm still digesting all this great info

 

[jdbakker]

I say if there is enough interest we should try to get something like this going DIY.

Right.

A project that either requires upwards of a hundred relays @$4ea (unless you get an eBay bargain, but that's no good if multiple people would want to build it)...

...or a number of single-sourced crossbar switch chips @$40ea, which come in 100-pin TQFP packages with 0.5mm pitch, on a forum where most people are hesitant to solder much larger SMD components.

JD 'not holding my breath' B.

 

[abbey road d enfer]

no no, I don't want to switch Digital signals. I want to switch analog signals digitally. This is great info ;D I say if there is enough interest we should try to get something like this going DIY. I'm still digesting all this great info

OK, my mistake. I have difficulties with your Ute (or is it Utopian?) accent
You may find a second hand 360 Systems Audio Matrix (16x16 under MIDI control) or even a BSS Soundweb.

 

[justanalogue]

Maybe I am silly but I have the idea of an old Sonic Solutions setup with 3 Lucid 8824's to use as a patch bay.
Any one thoughts about this?

Willem.