Stupid question check regarding switches

[swilliman]

So I've been rethinking my current hybrid mixing setup which is a Quantum 4848 into a Soundcraft series 600 (32 input channels).

Problem is there's only one line input for each channel so there's no way for me to easily switch the desk from 'tracking/monitoring' (using mics into XLR's and synths into Line In's) to 'mixing' (Quantum 4848 outputs from my DAW running to line ins). Currently I have to use the first 16 tracks for tracking and tracks 17-32 for mixing, but this mod would allow me to use all 32 for tracking or mixing.

The solution which I've thought of is just adding an extra switchable line in for each channel so that I could quickly flick a channel from 'track' mode to 'mix' mode.

This way I could have all of my mics, synths, DI's etc. permanently plugged into one Line In, and all of my DAW outputs permanently plugged in to the new Line Input.

Easiest way would probably be to put some switches on the meter bridge of the board, maybe 1 switch for every group of 8 channels to make things simpler. Maybe a small cap over the switch to prevent popping?

Anyone see anything wrong with this?


Any input or critiques very much welcomed...

 

[abbey road d enfer]

The solution which I've thought of is just adding an extra switchable line in for each channel so that I could quickly flick a channel from 'track' mode to 'mix' mode.

Ideally you should do that before the 30dB pad on the RearCon PCB. Doing it in buckets of 8 is a good option. Then you would need relays. For preventing relays from popping, I would suggest you use an additional separate supply, not connected to the other rails.

 

[JohnRoberts]

Welcome to rudimentary console design. To maintain signal integrity you will want to pay attention to circuitry on the sending end and destination. I like to use differential circuitry, perhaps on both ends.

Back in the early 80's I switched an entire console with a single logic control voltage using CMOS transfer gates (not simple). Relays would be simpler (not cheaper) but take care with inductive noise spikes.

JR

 

[ruffrecords]

Here is what I wrote in a very similar thread a few hours ago.

Back in the70s, some Neve consoles were fitted with separate mixdown line ins. These were in addition to the regular line ins. One huge relay, a T-bar relay, switched all line inputs over to the mixdown inputs at the push of a single button. Mixdown inputs were usually wired to a christmas tree at the back of the console.

I use a simpler version of this in the current design of my Mark 3 tube mixer. Instead of one big relay, each channel has a separate remix input which is switched in/out by a relay in the channel module. The dc to operate this relay comes from a bus so that one switch in the control section can operate all the relays at once. To add flexibility, each channel module has a switch that determines when and how the dc operates the relay. In the centre AUTO position the dc bus operates the relay. When overdubbing you want to be able to listen to track already recorded so you set the switch to PLAY on those tracks which operates the relay directly. Lastly during mixdown you may not want all channels switched to the mixdown inputs. You might want to use a couple for FX returns. In this case you set the switch to REC(ord) and it prevents the dc bus from operating the mixdown relay.

Cheers

Ian

 

[swilliman]

Ideally you should do that before the 30dB pad on the RearCon PCB. Doing it in buckets of 8 is a good option. Then you would need relays. For preventing relays from popping, I would suggest you use an additional separate supply, not connected to the other rails.

Thanks all for taking the time to reply, really good advice for me to be working on.

Using a schematic I found online for a simple relay switching system between audio sources, I came up with the attached.

A separate 12v supply (not sure where I'll pull that from but crossing bridges and all that) that feeds a 2 position rotary switch and connects to a SPDT Form A relay (not sure which one yet)

In it's unenergised state the relay allows recorded signal through and when energised only the mix audio coming from my DAW.

Each input channel on my console will need a relay, and each rotary switch will be responsible for 8 channels so I'll need 4 switches.

Oh and the grounds for the signal and power supply will be separate.

Does the attached schematic look like it would work?


- JR, I'm afraid I'm not sure what you mean when you talk about differential circuits. Would using a power supply separate to the one feeding the input channels reduce the likelihood of inductive noise spikes?


- Ian, I was having a read of your blog regarding your tube mixer, amazing project. I'm sure the way you've implemented switching with buses is better, but this seems like the easiest (and quickest) way for me to achieve what I want.
Good point about FX returns, I hadn't thought of that. With this system if I wanted them I'd have to turn the last 8 channels on my console to 'record' mode, which would leave me 8 less tracks to mix with.
I guess a way round it would be to just print the FX returns as their own track in my DAW when ready.

 

[abbey road d enfer]

separate 12v supply (not sure where I'll pull that from but crossing bridges and all that) that feeds a 2 position rotary switch and connects to a SPDT Form A relay (not sure which one yet)

You need DPDT for switching balanced lines.

In it's unenergised state the relay allows recorded signal through and when energised only the mix audio coming from my DAW.

Each input channel on my console will need a relay, and each rotary switch will be responsible for 8 channels so I'll need 4 switches.

You need an individual defeat switch, as Ian explained, for allowing overdubs.

 

[ruffrecords]

Your Quantum 4848 outputs are balanced so you will need to switch both hot and cold so you will need a DPDT relay.

Cheers

Ian

 

[swilliman]

Now you both know why I titled my post stupid question I've done a decent amount of DIY kit builds before but never designed a circuit myself so apologies for the obvious mistake there!

I've thought it through and now understand what you mean about a kill switch for individual channels.

So there will be a 'master' switching switch that can switch 8 channels, and then each individual channel will have it's own kill switch which stops voltage going to it and reverts the relay to it's unenergised state therefore allowing you to record with that channel again.

Is that sort of what you meant Abbey?

cheers again guys for the help, really appreciate it. Have ordered some relays and switches to play around with on veroboard.

 

[swilliman]

These pics show the two empty panels I have on my desk. Should be enough space for the four rotary switches and the 32 toggles.

 

[ruffrecords]

I think the kill switch position that does not operate the relay needs to be left floating. The reason is that if you ground it ic can then operate the relay in the other channel(s).

Cheers

Ian