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MB MicroMixer - A Simple MIDI Controlled Audio Mixer idea... (+ renders)

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Recent developments with mios CV control & my other ponderings regarding automation & audio resulted in the following idea..

I figure that it might be really handy to have a Fully midi controlled compact Mixer for dealing with multiple synth outputs, getting them into the same 1 or 2 channels of audio...  and having the option to completely recall or automate the mix in a variety of ways.. without splashing out on a substantial digital desk to do the same...

Or at least make better use of the big desks inputs ;)

The basic design i've cooked up here should with abit of luck fit into a 1/3rd (rendered) or 1/2 1U rack module space. In this design i have gone for 8 mono channels in & 1 stereo output; although other people may only be intersted in mixing to one mono track (which halfs the hardware needed).

Also, with the inclusion of a built in user interface; iv'e designed it to fit onto a 16*2 lcd for economy ...and because in my view it'd work :)

mbmicro18by.jpg

Getting to the hows this proposed idea might work.. it'd probably be best adapted from the mios CV firmware; and the intention being to use the most economical AOUT solution possible (AOUT LC + S&H?) to control the 4 VCA chips (voltage controlled amplifers).

The proposed VCA is the Analog Devices SSM2164; which contains 4 VCA's (normal opamps are not easily controlled by voltage) which can be biased into class a easily, perform well & are available at RS for an okayish £4.70 a pop (somewhere else would probably be cheaper).

See this document for further information on SSM2164:

http://www.analog.com/UploadedFiles/Data_Sheets/15183786ssm2164.pdf

ancilliary components omitted from diagram; simply here to illistrate the overall configuraation.

mbmicro2b5qu.jpg

link for larger, legible version:

http://img96.imageshack.us/img96/5540/mbmicro25ov.jpg

Also following the same principle which is used to double up hardware to mix to two channels for stereo panning ..the same form of banking up can be used to add 'aux sends' ..to send a variable portion of each individual incoming channel to an effect processor.. etc.

The output levels could be depicted on the display as something like the three little bars below the pan icon. Also these could be used to depict basic equalisation settings for each channel. It would be possible to use these vcas to do this in a fashon... however its a battle against available hardware space & financial outlay.

Also as you may notice, this is a 20x2 lcd below rather than a 16x2... the extra space as illistrated could be used to display the value of the last edited perameter of the given channel without interfereing with the rest of the display.. as a possibility

mbmicro36nn.jpg

Another idea to still be able to see the fine detail of perameter trimming - without the extra characters; would be to have a one pixel wide bar appear one editing (hanging to the middle right, of the larger vol bar section) ..and have it cycle through the subincriments/single decibels.

(maybe this idea could be used to display fine perameter adjustment in other applications too ?)

This concept could also be completely integrated into the likes of the MBSID or MBFM firmware + hardware - as a way of mixing internally as a one box solution. This of course leaves the option open to saving levels and automation of this section as part of a sound patch too. 

Yup.. its another case of putting an idea out there..

views welcome..

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Getting to the hows this proposed idea might work.. it'd probably be best adapted from the mios CV firmware; and the intention being to use the most economical AOUT solution possible (AOUT LC + S&H?) to control the 4 VCA chips (voltage controlled amplifers).

The S&H chips would be way more expensive and tricky than multiple AOUT LCs.  S&H chips seem to have a short product lifecycle so picking one that will be around this time next year is a challenge.

My -in progress- layout for the AOUTLC board is fairly compact (too much so, I'm spacing it out better for a human to build) so if size is a consideration for you with the S&H we can work around it.

Yup.. its another case of putting an idea out there..
A very good idea at that!  Do you want help in the form of a custom board layout? Are you working on code for this yet?  Let me know if/how I can help.....I'll have time after the new releases.

Best Regards

Smash

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Ah, I 'd love to have such a unit! Really great idea!

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Best mixer proposal yet!  But not the only one.  Have you read some of the others?

This thread suggests using serial controlled audio mixer chips rather than AOUTs and VCAs. Could work out a lot cheaper, and simpler to build.

Pilo has already modified AOUT driver to work with PGA2311 volume control chip.

There's also this one which sources a 16x16 audio matrix chip' date=' with any input to any or all outputs (but no gain control).

Both threads then go on to discuss quite a few other chips.

I'm not dissing your design at all!  Personally, I'd love your front end attached to a simple to build and control mixer-on-a-chip, but I have no idea how the sound quality might be.  It looks like you are designing for quality.

Then again ... I found this external link which said

the PGA2311 from TI has a 120db sn ratio and 0.0004%thd
... and said many other interesting things

One more thought ... DCAs?

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Hi everyone :)

Interesting comments all round..

Smash TV:

The S&H chips would be way more expensive and tricky than multiple AOUT LCs.  S&H chips seem to have a short product lifecycle so picking one that will be around this time next year is a challenge.

My -in progress- layout for the AOUTLC board is fairly compact (too much so, I'm spacing it out better for a human to build) so if size is a consideration for you with the S&H we can work around it.

A very good idea at that!  Do you want help in the form of a custom board layout? Are you working on code for this yet?  Let me know if/how I can help.....I'll have time after the new releases.

Fair comment about the S&H chips, yes the best solution would be to use a compact stack of AOUTLC's for this idea. However as noted further down; someone has suggested an arrangment which maybe simpler to construct than a AOUT>VCA...

However in favour of this solution; it maybe able to execute lightning fast volume/modulation changes without any weird artifacts...

(Ie: ability to use as a shaping/gating tool; as well as a mixer)

Thinking this one through..

My programming skills are rusty to say the least. At one time i was quite fluent in Pascal, Basic & dropped C before i got accoustomed to it.

I would be more than happy to actually do the coding; however i will have to become familiar with the language & also the structure of the MIOS code in order to get some serious work done...

Part of the problem, is that looking at one small snippet of code/one file in the function set.. is that its hard to understand in context to the whole program structure without knowing what everything else is doing - which it relys on.

however, it is definately easier than tredgeing through raw assembler :))

As for juggling pcbs for the most compact layout - i feel i have the nessursary skills to acheive this with Eagle Light.

Also i note that my strong points may lie in the realms of Graphics & Interface Design , Some Hardware Design ....aaand Developing ideas & Concepts ?

I really do wish i could be the 'one man band' affair & have the skill to see the entire processes through from start to finish by myself.. but i may not acheive that..

DrBunsen:

Best mixer proposal yet!  But not the only one.  Have you read some of the others?

This thread suggests using serial controlled audio mixer chips rather than AOUTs and VCAs. Could work out a lot cheaper, and simpler to build.

I managed to miss those posts; theres alot of stuff on these boards :) ...will look them up...

DrBunsen:

Quote from: moebius

Pilo has already modified AOUT driver to work with PGA2311 volume control chip.

There's also this one which sources a 16x16 audio matrix chip, with any input to any or all outputs (but no gain control).

With regards to realising a audio mixer, the pga2311 would definately be a simpler & better solution. i like that idea :)

However two points may counter this.

Firstly the VCA soloution may provide faster volume/envelope control without articfacts compared to the 2311; Which would make it useable as a fast signal modulator as well as a mixer - will have to find out how the 2311 handles from a current user..

Also Secondly each chip is £10-6 (rs & Farnell) each for two channels of control. whereas the VCA is £4.70 for 4 channels - however the additional hardware required for the VCA puts the price up overall..

So the remaining deciding factors are Overall price, complexity & flexability...

My vote currently favours the 2311 :)

The matrix chip is a really interesting idea. It would be a useful consideration for this concept. in allowing the ability to re-route signals internally. Possibly useful for selecting from many devices to mix togeather ..or where to send the signal to..

or even as a even more basic MIDI controlled 'audio patching bay'.

Though ultmately in the end, MicroMixer should probably be developed to accept a number of suitable 'standard' modules Ie: Mixer (main mix / send), Matrix & Eqaliser, Etc..

For Which the hardware configuration could be setup quickly - through changing afew settings in the code; or ideally through a remote configuration sent via a firmware MIDI SYSEX dump maybe..

DrBunsen:

Both threads then go on to discuss quite a few other chips.

I'm not dissing your design at all!  Personally, I'd love your front end attached to a simple to build and control mixer-on-a-chip, but I have no idea how the sound quality might be.  It looks like you are designing for quality.

Then again ... I found this external link which said

Quote

the PGA2311 from TI has a 120db sn ratio and 0.0004%thd

... and said many other interesting things

One more thought ... DCAs?

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With audio processing, quality should always be the highest priority - where possible & where project costs do not make it unreasonably expensive.

True. I was thinking though that for small mono and submix-type things, a lot of the time it may not be fully appreciated. A MIDI controlled headphone cue network for tracking bands would be great. I'm usually running mono signals for that, and in a loud environment with "average" quality headphones on, I doubt people could tell within a reasonable range (not sure what range you're actually talking about ;)). PA stuff might be the same way. I use controllable cuemixing from the DAW for that, but I'm pleased to say, I would probably trust any of you guy's creations far more than I do my MOTU hardware.

Go cheap, go many. ;D 

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yes good point, had half thought about headphone section... but forgot about it...

No need for that to be midi controlled ;) ..so a small (op)-amp circuit piggybacked onto output rail; with a no thrills resistor pot for direct volume control should suffice.

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a small (op)-amp circuit piggybacked onto output rail; with a no thrills resistor pot for direct volume control should suffice.

Yeah, I'm fine with a basic analog mixer if it's me tracking, or somebody doing vocals with one main mix to the phones. The problem is, I occasionally track bands and need several different phone mixes. It's a bunch of lines (and hassle), plus now I'm running a "minimalist" rig to the audio interface with nothing but a pre-amp/AtoD combo putting out lightpipe to the other room, so I don't even have the individual aux. sends to feed them. If you've ever had to get drummers or some guitarists to 'explain' to you what their cuemix sounds like from the next room while you make the adjustments for them, you probably can imagine the benefits of giving them their own knobs. ;D

Take Care! (and thanks for the work)

George

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As mentioned above; the design shifted over to 'pot in a chip' ...namely the pga2311.

Has already been coded up to work with mios & tested by Pilo :)

There is also a 4311 ..which is a 4 channel version in surface mount form - im keeping this in mind for heavily condensed channel control. Theres no reason why upto 32 (or more) channels couldnt be stuffed onto one DOUT size board ! ..only thing is how much space all the connectors would take up..  ;) ...would be good when mixing to alot of side chains & effects sends though.

Have got the chips now.. when ive got a moment i will be making up the pcb traces for a standard size module.

Will build the unit, Get it working under exhisting firmware - then spend some evenings digesting all the documentation on MIOS... and try from there to Develop the GUI. The most awkward bit will be coding the Graphical bars. which will require the creation of custom characters not available within the display rom. From what i can tell this has already been done with mbseq. some of the graphing stuff done on there is not from the standard character set.

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Hello!

Why not using a AD Mixer and a DSP or FPGA?

Source:

http://www.beis.de/Elektronik/ADDA2496/AD2496.html

Pricelist for a very good AD and DA Converter from Cirrus.com

Type                        PiecesPerPackage      PricePerPiece in Euro

CS5381-KZZ              62,00                        16,20

CS4398-CZZ              50,00                        7,10

Jack

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welll.. firstly that would be a entirely different project alltogeather...

Not only would it require lots and lots more programming.. but it would also probably would not work with the existing 18f chipset.. and before you know it ..it becomes a case of writing all the code from scratch for a completely different chip inferstructure ..if someone else wishes to start a project to allow open ended tinkering with AD DSP DA tinkering ..they are welcome to do so :)

..Frankly i am more of  a designer than a programmer.. i am neither experienced enough, nor patient enough to take that route.

Please understand the intention of this box of tricks is to quickly enable the possiblity of mixing audio signals in the analog domain by MIOS. Converting them to digital & then back again just to do abit of mixing seems abit overly complicated & will more noticebly degrade the sound than streight forward analog mixing. also isn't it just a tad of a diversion from the original intention ?

With regards to DAC and ADC conversion... i have the stuff kicking around here to protype some really high quality, affordable modules capable of 24bit 192khz conversion with noise floors exceeding -120db (Burr Brown DSD1796 & PCM4202) ..which may prove useful to people here. However, currently the concept is being held back by ready availability of chips (namely Cirrus CS8412) that convert from SPDIF to the plain PCM used by almost all DAC's..

Maybe this could be implimented simply with a PIC ...however thats beyond me right now. ...maybe someone could help ? :)

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Have a look at the new MOTU UltraLite - $US 550 and very very close to your concept.

/edit/ except of course it's all digital internally.  If your all analogue version progresses, I look forward to beta-testing it

motu_ultralite.png

ultralite_rear.png

And the software mixer map is just begging for cloning as a MIDIBox:

ultraliteconsole.jpg

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yes, very, very cool widget from MOTU :)

Defenitely a marked similarity in concept there; did half notice this when i recently visited the MOTU site when pricing up possible firewire multichannel soundcard solutions... wondered if anyone would make note of this.. and indeed you did :)

im currently eyeing up a 828.. matter of funds tho.. (hmm... motorbike - or soundcard ? ..hmm all of a sudden it all seems expensive!)

Hopefully this modularly scalable solution, will be abit cheaper ;) ..admittely it wont nessursarily do all the cool things the MOTU's capable of.

organisation is not a strong point here.. i will get this project seen to shortly; i hope. most of the nessursary groundwork has already been done by other people previously.. as noted in this post.. so this just leaves making a pcb design for the module.. and then getting to grips with customising a front end, for ease of use.

Having said that, essentially it should be possible to have the concept actually working with everything thats already available here... if anyones in a rush for a quick solution...

*****UPDATE*****

I've been informed of some serious problems with MOTU hardware; customer support & design policys. Which i was entirely un-aware of. Shame.. I shall myself be considering some other options first..

*****************

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Just read this thread and its pretty similar to the idea I have in mind.  Have you made any progress on the mirmixer?

Jason

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Progress has stalled currently...

I have all the bits sitting here for the project, summer has been overly fun here.. and iv'e not spent an awful lot of time in the house.

Building the project around  exhisting firmware is possible & the item will be fullly  useable via midi control... however i currently lack the patience to figure out how to program the LCD gui.. maybe someone else is highly proficient at that here ? ..probably take them afew evenings to sort (when the hardware spec is nailed down) ..whereas itd take me several months of getting my head round it all...

Will try to make something happen soon.. Time management & appropriate distrobution of enthusiasm has never been a strong point of mine...

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to figure out how to program the LCD gui.. maybe someone else is highly proficient at that here ?

I wish! It seems like TK is the only one around here who has made CS menu routines from scratch.... To the rest of us, it's voodoo science  :-\ Maybe that's a topic for a thread in the development forums?

Did you end up using the PGA2311 IC's? I'm toying with those at the moment too....

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Hi Everyone.

New user, first posting, please let me know if I've got something wrong. :-)

I've just built my first Core (and it works!) and I have been planning to build

a line mixer backend. 8 stereo pairs to 1 stereo pair out. No local controls

or display, just the analog end of a simple line mixer. I have been looking at the

PGA 2311/4311 to get the job done.

Now I'm wondering what the most flexible way to configure the PC board would be.

I know exactly what _I_ want, but how can I design this to be modular and easy to reuse for other applications? If I build it all in one PCB, then it'll be a line mixer and not much else for anyone that wants to use it. What variations would be useful to everyone else?

Also.. the 4311 is cheaper per pair, but the 2311 is available in DIP, which really helps hobbyist level builders.

Don't expect big progress really fast here, I'm a married man, so I have a very tight budget, especially when it comes to PCB proto orders.

Looking for peoples opinions here, I can detail some of my own ideas too if y'all are interested.

LyleHaze

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Hi Everyone.

New user, first posting, please let me know if I've got something wrong. :-)

All good mate :) Welcome aboard!

I've just built my first Core (and it works!) and I have been planning to build

a line mixer backend. 8 stereo pairs to 1 stereo pair out. No local controls

or display, just the analog end of a simple line mixer. I have been looking at the

PGA 2311/4311 to get the job done.

Well never let it be said, that you aren't ambitious ;)

I assume you have some circuit design and programming skills? It sounds like you might...

Now I'm wondering what the most flexible way to configure the PC board would be.

I know exactly what _I_ want, but how can I design this to be modular and easy to reuse for other applications? If I build it all in one PCB, then it'll be a line mixer and not much else for anyone that wants to use it. What variations would be useful to everyone else?

Also.. the 4311 is cheaper per pair, but the 2311 is available in DIP, which really helps hobbyist level builders.

I think that a very small PCB could be built around this IC which would support a single pair of audio channels (It can be stereo or dual mono). As for flexibility, the important part is to make it simple to cascade the serial I/O and power. The rest can be handled by the core. This leaves the audio summing to a separate circuit which would be specific to each users requirements (if they require summing at all).

Don't expect big progress really fast here, I'm a married man, so I have a very tight budget, especially when it comes to PCB proto orders.

Looking for peoples opinions here, I can detail some of my own ideas too if y'all are interested.

Please do :) There is a storm of interest growing around these IC's at the moment. Don't worry about how long it takes, it's your adventure :) Plus, I get the impression you'll be working as part of a growing team on this one ;)

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hi,

the project is probably going to be prototyped around pga2311 ..with the 4311 as a smaller condensed design later on. I'll try to take the time next week, to test one chip; then come up with the pcb design for a modular pga2311 board, which should comfortably hold 2-4 pga2311 chips.. and would allow cascading for additional channels.

With concerns to board layouts, the configuration for chips and opamps shoulld leave the audio signal connections configurable via jumper wires. This leaves configuring the nature of the signal mixing down to the end user ..and should be a streight forward process.

Also with small additions, it would be possible to modify the control of the opamps used to turn one of these boards into a midi controlled filter of sorts..

...there you go tho.

From thereon.. if someone would be so kind to provide a small batch of the boards.. people can tinker on with these things, using exhisting firmware to control em'..

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Hi,

I'm also working on a mixer based on 4 PGA2311 and one Core.

Do you know if a preamp part is needed is I want to send the same signal to several PGA input ?

Regards,

ludo

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Can't wait to hear about the results using the PGA2311.  Being able to control audio volumes with MIDI would solve so many mixing problems for me.

A total noob question for those experimenting with the chip...what MB modules and MIOS drivers are needed to make this chip work?  For some reason I have it in my head that only the core module is needed.

Jason

 

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The PGA2311 provides a serial interface with Chip Select, SDI and SCLK line - so it's very similar to the MAX525, which means, that there are assembly and C based drivers available which you could use as a template.

From the MB side you only need a core module...

Best Regards, Thorsten.

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I'm also designing a board to host 4 PGA2311. I will post the PCB as soon as tested and validated. But I'm facing to the audio routing system (with TL072). If you have some source of schematics...

ludo

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