monitor controller switchboard

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Rocinante

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Jan 17, 2014
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I am building an active monitor controller equipped with a few bells and whistles like minor DAW control and volume metering and display.
The layout so far is 2 in and 3 out.
So you can select from two sources and send to three sets of monitors. 
I'm using JLM Dingos to unbalance and then balance each L and R.
The unbalanced L and R are then brought via relays to either an 10k encoder using pga2311 for volume control (and display) and/or a stepped attenuater. 
After leaving the volume control the L and R enter a switchboard.
The switches provide mute left, mute right, reverse, dim and stereo to mono.
It would then eave the switchboard then through three switches back through  the JLM Dingos  to the desired out.
I used several circuits I found on Elliot Sounds.
Eventually I am going to try to use spst switches or tact so the layout may be different but for the moment I am using dpdt push button switches.
I would love some suggestions on the switchboard.
Attached are the schematic and board.

https://postimage.org/

https://postimage.org/

 
Rocinante said:
I am building an active monitor controller equipped with a few bells and whistles like minor DAW control and volume metering and display.
The layout so far is 2 in and 3 out.
So you can select from two sources and send to three sets of monitors. 
I'm using JLM Dingos to unbalance and then balance each L and R.

I assume you are going to do up a PCB, so why bother with those kits? Just use INA217 or THAT1280s for the differential receiver part.

The unbalanced L and R are then brought via relays to either an 10k encoder using pga2311 for volume control (and display) and/or a stepped attenuater.

I used PGA2320 in my design -- it has +/-15 V analog rails. The 2311 has +/-5 V analog rails.

It would then eave the switchboard then through three switches back through  the JLM Dingos  to the desired out.
I used several circuits I found on Elliot Sounds.

Again, why use that board? Put DRV134 or THAT1646 on your switch board (minding that they require low-impedance input).

Eventually I am going to try to use spst switches or tact so the layout may be different but for the moment I am using dpdt push button switches.
I would love some suggestions on the switchboard.

The schematic is too small, so I can't tell what's going on.

The thread for my monitor controller design is here. Not mentioned in the thread is that I've built the user interface remote part (the buttons and encoder) and I use the thing daily. There are a couple of things I would fix if I was doing it again. One of the suggestions was that it was "over engineered," in that it has an individual PGA2320 per output. Half of me agrees with that assessment; the other half likes the flexibility. The PGA2320 is by far the most expensive part in the design.

The main issue is that the analog muxes I used spec crosstalk as -100 dB down. I verified that. The problem is that 100 dB isn't enough for the worst case, so if you have something playing into channel 1's input while you're listening to channel 2, the potential for channel 1 to bleed into 2 exists. That said, to actually see the crosstalk, you need to run a very hot signal into the unselected input -- I didn't start to see the crosstalk until that signal was at like +15 dBu. In practice, I think you wouldn't have anything playing into the other inputs.

I like the idea of DAW control. I assume you mean Play/Stop/Record/FF/REW.
 
Andy thanks for replying. 
All good stuff.  I re-uploaded the schematic after resizing it, hopefully its better.
2320 sounds great.  I am already using 5v for the digital end but I like the idea of keeping things in the 15v range.
I suppose you are right with using the DRV or That op amps.  I had the Dingo's so I used them. 
I plan on building a blue tooth remote and yeah you got it;  Play, Stop, REW, FF, REC as well as Next and Prev Track.

 
Being able to switch in a sub is a nice feature for a monitor controller. You could potentially use one of the outputs for it as long as you can use outputs simultaneously.

How are you implementing the machine control, is it HUI, MMC, something else?
 
For now its open through hui but I plan on making it be seen as a generic controller e.g. a qwerty keyboard.  So they'll be no device driver to be seen. I hope to have all of the features (all 7) automatically mapped upon opening the daw.
I thought about subs.
And so here we go..
What do i have to take into consideration?

I'll post the front panel layout soon but i am trying to keep it 1u.
I was going to use .96 oleds for parameter and volume level metering but i broke them wayyy to easily.
So maybe a tft for volume level, track, and pan display.
I'd like to have a 3 digit seven segment display for volume level as well and yeah its a lot to swueeze in but its doable.



 
Rocinante said:
For now its open through hui but I plan on making it be seen as a generic controller e.g. a qwerty keyboard.  So they'll be no device driver to be seen. I hope to have all of the features (all 7) automatically mapped upon opening the daw.

If you use a USB connection, you can make your controller look like an HID class of type keyboard, so it doesn't need a custom driver. It's up to you to map the button presses into the desired key presses, and that can be configurable.

If it speaks HUI, isn't that basically a MIDI interface? You can do MIDI over USB, if you're so inclined, as it too is a standard USB class and you don't need a custom driver.

A lot of inexpensive micros have Full Speed USB support, and you can roll up the button scanning and display driving and the SPI port for the PGA2320 into one part. Get a micro with an ADC and there's your metering, too.

-a
 
Andy your controller is awesome.
I should have been clearer as yes i plan to make it hid class although right now i have it using midi as i was trying to see what i could implement.
Is there a micro with adc like your describing you could suggest i look into?
 
Rocinante said:
Is there a micro with adc like your describing you could suggest i look into?

I am a big fan of Silicon Labs parts. We've been using their 8051s forever, and are starting to use the ARMs. The software tools are free, they run on Windows, Macs and Linux, and the debug pods are $39. Of course -- which to choose! Look for number of digital I/O you need, digital peripherals, and such, and usually in the family there are variants which have ADCs.

My monitor controller uses the C8051F314, which does not have ADCs. I decided that metering wasn't all that important. I suppose that using an LM339 quad comparator for signal present and peak indicator would be sufficient.

(Actually there are two '314s in the design. One is on the board with the switches, muxes and I/O, and the second is in the user interface. It was cheaper to put another microcontroller in the user interface board to do the button scanning and encoder read and LED drive than it is to use an I2C expander chip!)
 
Thanks for the suggestions Andy. I looked up a lot of the components you guys discussed on your monitor thread and got sucked into the digital world again.  Funny, its unfamiliar so I'm reluctant to delve too far (even though I want too) and every time after hours of reading I feel like I've retained next to nothing.  No matter what there's a lot to learn and I need to learn a lot more.

Regarding the switchboard, I think it could be a pretty great little  utility board for several  projects.
I couldn't find an agreed upon mono/stereo or dim (pad) switch circuit other than the passive ones I am using. I'd like to possibly incorporate relays then maybe have a ribbon connected daughter switchboard that can mount along the front panel.
I'm open to suggestions.
 

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