Audio Patchbay relay board

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bobkatz

Well-known member
Joined
Jun 25, 2006
Messages
138
Location
Orlando
Has anyone got a PCB done with or without relays stuffed suitable for an electronically-controlled analog audio patchbay?

I'm looking lots of 4PDT relays... Simple, but nice project, eh?

In the end I'd have some front panel switches, one would be "serial", for use in mastering where the analog gear is patched in series, with bypass switches that insert various pieces or remove them from the chain, the other would be parallel, for use in mixing, where the analog gear is connected to multiple D/A/D chains for use with a digital console and analog outboard on aux or bus sends.

BK
 
There were some "relay bypass" boards for sale on the black market.
One board houses two 2pdt relays and two xlr's and some...
I guess that with a couple of these you're sorted, although they might need a slight modification.
Other than that I don't know ...
 
[quote author="RogerFoote"]Bob

That would be a really nice project!

I did some mono bypass boards that would work for serial uses, but would be pretty useless at the parallel function.

Were you thinking of having both in one multi purpose unit, or 2 seperate units?

If the boards were shallow enough, you could mount the whole mess as "apron" boards to build up enough density to satisfy a number of studio sizes.[/quote]

It would all be in one box, or defeat the purpose. Imagine that you have 8 stereo compressors/equalizers that you either want to master with or mix with, and you want a "programmable patchbay" to deal with that. The ideal unit would have a bunch of XLRs on the back, front panel simple programmability (or, go wild and use a PIC and an LCD) and be totally passive with no active audio electronics.

I agree it would be a great project for a manufacturer or a kit-maker. Crookwood makes a programmable model that's very expensive for my budget and my goal would be a do-it-yourself that's a bit less funky than a box with a bunch of multiple rotary switches on it. Ironically, in the end the R&D might be so costly it'll cost as much as a Crookwood to sell anyway. But if I built it myself it would not, if you don't count the cost of my hourly wage :)
 
relays or ssm2402? Jfets? Mosfets?

lots of possibilities!

Relays are nice for a while until the contacts give or get nasty.

ssm2402 is pricey but will work forever and without pops..

JFETS and mosfets have distortion that can be gotten around and are cheap..
 
[quote author="Svart"]relays or ssm2402? Jfets? Mosfets?

lots of possibilities!

Relays are nice for a while until the contacts give or get nasty.

ssm2402 is pricey but will work forever and without pops..

JFETS and mosfets have distortion that can be gotten around and are cheap..[/quote]

As a purist I have to do relays. Sealed gold contact relays are long life and don't add any distortion of their own. As a mastering engineer I don't want to have my patchbay have any coloration.

BK
 
I have an old AKAI DP3200 digital controlled matrix patchbay. its 32 inputs x 32 outputs and can be MIDI programmed. The MIDI is actually labelled "serial port" and its a XLR , but just making a XLR-5pinDIN cable you can control it for saving "snapshots" ;)

The one I got comes from the BBC studio and I keep it for installing once I move in my new studio next year.

Bob, try to find one in USA those are cheap. The DP1000 its also a combined video/audio patchbay. The audio part is a 16x16 matrix.

Best Regards,

Synthi.

PS. I think I have the schematics somewhere...
 
[quote author="synthi"]I have an old AKAI DP3200 digital controlled matrix patchbay. its 32 inputs x 32 outputs and can be MIDI programmed. The MIDI is actually labelled "serial port" and its a XLR , but just making a XLR-5pinDIN cable you can control it for saving "snapshots" ;)

The one I got comes from the BBC studio and I keep it for installing once I move in my new studio next year.

Bob, try to find one in USA those are cheap. The DP1000 its also a combined video/audio patchbay. The audio part is a 16x16 matrix.

Best Regards,

Synthi.

PS. I think I have the schematics somewhere...[/quote]


This is very very interesting, synthi. I doubt the audio switching parts are relays. If you think you have the schematic, please let me know.
 
hile doing investigations of existing pieces out there in this style, I found a "highly rated" programmable (by USB) box that does analog 8x8 and 8x16 (I believe), is balanced audio, and reports to use technology that doesn't use a "digital matrix switch" to avoid leakage and crosstalk. But there are no specs of crosstalk, distortion, headroom, or signal to noise ratio, and at the least I'd like to know those. As a card-carrying audiophile who does not want anything in my chain that affects transparency, my experience with the various active technologies that do analog switching has been unhappy.

They talk about an "analog devices" (not capitalized) analog matrix switch which I suspect is "Analog Devices" so I should be able to look up this part.

Even simple FET switches give me pause.

I fear I would not be 100% satisfied with the sound of the unit at

http://www.violetaudio.com/upm88.htm

but this particular active unit strikes me as probably being one of the best in its class. I get a good feeling just from their literature. I'm a sucker for the word "purist" :). And the real problem is that I need AT LEAST 16 x 16, and this box can only be expanded to 8 x 16.


Oh, and here's the URL for a PDF on a 16x16 eval board for one of Analog Devices analog matrix switches. It's unbalanced and configured for video at 75 ohms with BNCs and uses a + and - 12 volt supply, but it's a ready-made solution and after removing the 75 ohm resistors, you'd have an analog, unbalanced, parallel-port-controlled 16x16 matrix "active" patchbay in a weekend if you're industrious!

http://www.analog.com/UploadedFiles/Evaluation_Boards/Tools/294226281AD8113EB.pdf

Here's one of the specs of this part AD8113:

Excellent Audio Performance
VS = ±12 V
±10 V Output Swing
0.002% THD @ 20 kHz Max. 20 V p-p
(RL = 600 Ω)

Hmmmmm..... almost makes you want to use it, or at least test it... at least your patchcords won't get dirty. Does anyone know the best way to purchase an Analog Devices Eval board?

And this is a NEW evaluation board, must be a new part, "available 6/30/2006" for $395. Sure fits my "do it yourself" sort of nature!
 
Hey Bob,

This is what I'm working on. I design a mastering console with transparent sound in mind (minimal path). The PCB will be directly soldered to the XLR (audio will not leave the board, no wires ) and will use only relays for routing and relay based stepped attenuators.
I'm still not sure about one thing, and had the intention to ask mastering people at Brad's forum, but had no time to draw the diagrams I need for my question.
Now I'm more motivated to draw it and will post very soon.

chrissugar
 
By the way, Bob, what relays did you find that do not degrade audio signal. Any specific model you have experience with?

chrissugar
 
I'm on a whole different route.

First I'm building a new console with source selectors, mono switching and all, all passive. It will have a send/return loop path for the router.

This router will be totally passive too, built of good quality rotary switches. Say, 5 switches in a row = five inserts. Each switch position represents a piece of equipment, 1=EQ, 2=compressor and so on. Each switch sends and returns signal.

Here it'll be just a matter of turning knobs to route the chain. The only drawback in the all passive arrangement is that you could put inserts 1 & 2 to route to the same EQ => feedback. For this purpose, I will implement a "kill all" -switch (that will also serve as a chain bypass switch!), which simply cuts the inputs of the equipment (relays). From here it will only be a thing of muscle memory teachment, before routing, "kill all" to avoid squelches. :cool:

The router will also have an internal M/S matrix that could be put between inserts 2-3 and 4-5, for example.. Maybe a parallel processing chain, too.
 
[quote author="chrissugar"]By the way, Bob, what relays did you find that do not degrade audio signal. Any specific model you have experience with?

chrissugar[/quote]

Well, as long as the contacts are new and good, there's no more degradation than any audio connector and probably less than most.
Omron was my last venture into relays. I'd probably be quizzing you guys on that, the stories I hear is "sealed, double bifurcated contacts" and other such gibberish. I need to study what's current.
 
[quote author="[silent:arts]"]Bob,
if you want fully passive relay switching you should have a look at the SPL MasterBay:
http://www.spl-usa.com/indices/mastering_E.html

the 8 x 2 box uses 146 realays, the 8 x 8 box 584 ...[/quote]

SPL has an incredible pedigree and charges accordingly. It's not very cost-effective for me, and 8x2 barely scratches the surface. In fact, I did a little check on what I could accomplish with 16x16 and the answer is "barely enough" if you need to have multiple sends/returns to analog devices. If I were not trying to configure a studio for both mixing and mastering, then a simple 8x8 for serial stereo patching (a chain of multiple processors) would do the trick.
 
[quote author="bobkatz"]the stories I hear is "sealed, double bifurcated contacts" and other such gibberish. I need to study what's current.[/quote]

That is good gibberish! "Gas filled" is also good, unless it is describing me after a couple of tacos :grin:

Omron makes great DIP DPDT relays. G6A, G6E, G6S offer increasing reliability and price. I have remote speaker switchers in use for 15 years with the previous generation of "S" which was yellow. And there are SMD and through-hole available.

I go relay and not SSM. You caint show me the same response through semiconductor as with metal. SSM or DG silicon switches are used in large consoles purely for cost, density, and current considerations. For simple speaker or patchbay switching, I use what the telecom companies use for their mission-critical points: mechanical relays.
Mike
 
[quote author="sodderboy"]



Omron makes great DIP DPDT relays. G6A, G6E, G6S offer increasing reliability and price. I have remote speaker switchers in use for 15 years with the previous generation of "S" which was yellow. And there are SMD and through-hole available.
[/quote]

This ebay seller is selling large quantities of SMD stuff. Here he offers 3 factorie reels of Omron G6S (Watch out, this is the SMD version) relays .....1200 pieces :shock:
They usually go for less then $100,- . I bought 800 pieces for $80 from him.

http://cgi.ebay.com/1-LOT-1200-PCS-OMRON-G6S-2G-Y-TR24VDC_W0QQitemZ260003573380QQihZ016QQcategoryZ42897QQcmdZViewItem

Everything will be with a relay from now on..... :grin:
 
Well, I'm this close to buying a Violet UPM88 for Studio B, the price is very right. He implements the Analog Devices switches he says with +/- 18 volts, which scares me becuase the max I see is 12 on their data sheet... but anyway, he uses a 16x16 matrix in an 8x8 balanced configuration, so you could do 16x16 unbalanced which would suit me.

Wire up the XLRs with pin 2 as left channel, pin 3 as right.

I'll check it out first in Studio A and if I deem it "transparent enough" I'll keep it there. All the applications would be for D/A to processing and back to A/D so there is already a loss there. If the combined loss is unnacceptable I'll move it to Studio B, which is less critical. Tough call from the guy (me) who "insists on relays". We shall see. I have to give it my listening eval to be honest with myself. Every piece of electronics has some signature, but the fact is that each compressor, equalizer and other piece that I'm using in that chain has a signature, too, and is not transparent, but VERY close to that!

So, still in the market for a programmable, 16x16 relay switching system!
 
Wow, I'm doing some math and you'll need quite a few relays! :shock:

You basically want to be able to route each patchbay input to each box connected to the patchbay (# of inputs * # of boxes), each box to every other box (# of boxes * (# of boxes - 1)), and each box to each output (# of boxes * # of outputs). That's Boxes(Ins + Outs + (Boxes - 1))...

So if you have 8 inputs, 8 boxes and 8 outputs, that's 8(8+8+7)=8*23=184 relays! 16x16, you say? that's 16(16+16+15)=16*47=752 relays!!!

Like somebody else pointed out, of course, good quality Omron relays can be found cheap on eBay. So it's more an issue of the PITA of soldering 800 relays, than an issue of price...

And you'd probably want an AVR or a PIC controlling all those relays, too. Maybe even a little 2x16 LCD, so you can name your loops and know what box is connected to what...

Nice project idea! :thumb:

Peace,
Al.
 
Old timers!

I doubt very seriously that the ssm parts could be picked out of an A/B with relays.

As for relays on ebay.. those are damn good prices. Something like that would make me go with relays too!

In fact those are 5$ a piece at digikey..

:green:
 
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