MIDI Controlled Vari-Mu Compressor

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joe-electro

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2U_VM-1.jpg


Okay, this is still seriously in the development stage, but I couldn't wait any longer to show it off.  What we have here is an all tube compressor based on the Sta-Level/GE BA-9/CCA LA-1D lineage, but with *all* switches and pots controlled by an Arduino microcontroller.  I've been working on this project for a while but just made it real this week. I was originally going to use the PIC family of microcontrollers but decided to try out the Arduino platform after reading Owel's post on his digitally controlled preamp project. (http://www.groupdiy.com/index.php?topic=31185.0)  I have to say, the Arduino makes digital control really easy, and thanks to Owel for introducing me to it.

I took a little different approach to digital control with this project. I'm using Alps motorized pots for all the analog controls except the Time Constant, which is a 10 position rotary switch. The pots I bought have 4 gangs, and since the compressor circuit only needs up to two gangs, I could use the other gangs to sense the position of the pot by hooking it up to one of the A2D converters on the microcontroller.

The plan is to implement MIDI three different ways. First will be snapshots of all controls via a MIDI System Exclusive message. This is the main reason I wanted digital control. It will allow the user to store all compressor settings with the session data in their DAW. Second will be dynamic automation using MIDI continuous controller messages. Just dedicate a MIDI track to your tube compressor, and your software will record all your moves as you make them, just like any other MIDI instrument.  Third will be a mode using standard MIDI note on/off messages to change parameters. This would be useful if you want to user the compressor as an effect, allowing you to easily bypass the entire unit, just the compression, or switch ratio, attack and release very dramatically for effect.

Also notice the joystick to the the right of the LCD display. At first I thought I would use this instead of the little blue up/down/left/right buttons, but it occurred to me that it could also be used to control two parameters simultaneously. For instance, the X-axis could be attack and the Y-axis could be release, or X could be input level and Y could be output level. You get the idea. I'm going to play with it and see what combinations make sense.

I'd really like your feedback on several things. First, the feature set.  Right now, the automatable functions are:

Analog Pots and Rotary Switch:

Input Level, Output Level, Attack, Release, Time Contant and Mu-Point. The last one is my attempt to be cute, sort of a variant on Q-Point. It varies the bias voltage fed to the 6386/5670/6BA6 pair/6BJ6 pair (the circuit board is set up to accept any of the above, and is modifiable to accept other tube pairs as well).

Pushbutton switches:

Hardware bypass, sidechain bypass, sidechain external loop in/out, MIDI automation on/off (not automatable obviously) stereo link and tube or solid state diodes in the sidechain.

There will also be the provision to store the startup defaults in EEPROM. It will have a USB port for talking to the Arduino as well as the MIDI port.

I'll post some videos of the controller in operation later this week. I have a bunch of other ideas, but they will have to wait until I have the basic unit the way I want it.

Let me know your ideas for additional features.

The second thing I need feedback on is whether there's a market out there for a product like this. Do you think there's enough demand to put this thing into production?

Let me know your thoughts.

Thanks,

---Joe
 

emrr

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This will take some thought.  I feel like it's 1925 and you're asking me if I want to use the newfangled electrical recording process.  ;D 
 

joe-electro

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I know what you mean! My first reaction was "Nah! Why would anybody wanna do that?" But then I thought (to quote Professor Emmett Brown in Back To the Future) "Aw, what the hell!"

---Joe

emrr said:
This will take some thought.  I feel like it's 1925 and you're asking me if I want to use the newfangled electrical recording process.   ;D 
 

veermaster

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Wow! I think a box like this could be really usefull for compressing vocals. One could use different settings on soft and loud passages , for example a lower threshold with a higher output in a soft verse and then bringing the threshold up and the output down in the chorus. This way the louder sections would not be overcompressed in comparison to the softer.
But now that I think about it one could of course also level the different sections in the DAW so the compressor is always in the same GR range. ???
Anyway the automated output is a nice feature for riding the volume through the song for people who don´t have an automated desk, maybe mix everything in their DAW, but want to use a dedicated hardware compressor for vox.
Good luck and succes!
emre
 

Michael Tibes

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joe-electro said:
The second thing I need feedback on is whether there's a market out there for a product like this. Do you think there's enough demand to put this thing into production?

While I'm mostly mixing ITB I've been thinking about an analog master (maybe summing as well) chain which would be recallable and automatically be set up when a song is loaded. So it seems interesting to me - but the main qhestions are how much is it gonna be and how does it sound? It wouldn't make too much sense in the recording chain in my personal workflow.

Michael
 

joe-electro

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Yeah, that's the main reason I think it would be useful. In a busy studio you wouldn't have to write the settings down; they would be recalled automatically when the session is loaded. The dynamic automation aspect also has interesting possibilities. While it's easy to automate levels from inside the box, you can't change any of the other parameters. It will be interesting to see if this is actually useful or just a fun distraction. I'll post videos when the unit is closer to being finished.

--Joe

Michael Tibes said:
...While I'm mostly mixing ITB I've been thinking about an analog master (maybe summing as well) chain which would be recallable and automatically be set up when a song is loaded...

Michael

 

theblotted

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i think this is a great idea, and if well implemented, it could be the next future.

altho immediate real-world application wise, i think an MIDI controlled, automated EQ would make more sense to me - esp for vocals. seeing that there's so many vocalists move around when they record, and the on/off -axis effect always lead me to automate an EQ... but so far it's only possible with ITB (or without having to spend an arm and a leg).

i would seriously pay money for this...
 

joe-electro

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The EQ thing is next. And after that, an 8 channel console (cascadable up to maybe 32 or 64 channels?) with automated volume, pan and mute, and API 500 slots on each channel. Gotta crawl before I can run, so I'm starting with dynamics processors, which are my favorite. I want to develop an automation platform that could be applied to any piece of analog gear, within reason.

Thanks,

---Joe

theblotted said:
i think this is a great idea, and if well implemented, it could be the next future.

altho immediate real-world application wise, i think an MIDI controlled, automated EQ would make more sense to me - esp for vocals. seeing that there's so many vocalists move around when they record, and the on/off -axis effect always lead me to automate an EQ... but so far it's only possible with ITB (or without having to spend an arm and a leg).

i would seriously pay money for this...
 

helterbelter

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Cool....

Well, I know there are a lot of AV studio's bought a Focusrite liquidchannel, just for the midirecall. They usually work with the same group of voice over narrators.  so, when a narrator comes for the 2nd time to their studio, they only have to press a button to recall the settings, and then they're ready to start recording. This saves precious time.

So, I surely think there'll be interest in this compressor.
 
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