24 channel mixer the "Stereotype"

[Brotastic]

can't wait for this to become available!!

 

[Ninuz]

Thanks,
Ill try and go for the APP992 then. Only heard good things about them

Can't see any reason why APP992 shouldn't work in this, I've compared them against GAR1731
and GAR2520 and I like them all. The 992 has a very open naturall sound to them with a solid bass.
1731 has a nice soft coloration and 2520 has a cool presence lift but the 992 has this " elegant expensive" sound.

Good luck!
//M

 

[jpertusi]

Hey gang,

Anyone know if the stereotype boards are available?  I might be interested in 2 or 4 of them.

I'm in brooklyn so I could pick them up...

 

[hakanai]

They have been on the back burner for a few months now. I don't want to say "soon" because I feel I have said it too many times already. I will say this project is still actively being developed. Getting the standard summing boards back for sale is my top priority at the moment. The channel boards and more extensive mixer options are getting overhauled as I realized I wanted a more scalable eco-system then I had designed (and the channel boards needed some tweaking).

I will re-list the white market thread when they are ready.

thanks for the interest
Don

 

[Mellowroni]

Hello!

I am building a stereotype based on 2  rev 3 summing boards in this thread.  will also use the 2 Channel ACA & Booster from capi.com

It wil be 20 gar2520 DOA's in this build.

My question is regarding the PS for this build:

Will this PS be a good choice:

http://www.fivefishstudios.com/diy-kits/psu-2448mk2-kit

(As far as I can see, it delivers 1.5 amp on the Positive side, and 1.5 amp on the negative side.)

 

[kante1603]

Hello,welcome to the forum,

yes,should do,but you might have to use a bigger heatsink (C/W around 10 or less,the lower the better).....depends on how much wattage the regs have to handle.
Given a GAR2520 will need 30mAs/piece you will end up around 30VA total,so a say 30VA transformer or higher will be good to go.
I"m in the very same process atm,using 3 boards (mk4),same DOAs and one ACA/BO,so 28 pieces to "feed".
Because of the protection diodes you will loose 0,7vdc per board,therefore best to trim the psu rails to +/-16,7vdc.

Hope to have helped,

Udo.

Edit:Have set up mine for measuring some minutes ago and can confirm the above statements.
Torn 1 Board from the psu is the same than yours,so under load and feeding a sine at +19dBm (that's where my generator ends) showed roughly 600mAs per rail,so 30mAs per DOA.
Still a good heatsink with a C/W of 7-10 or lower seems very useful!
As a hint the transformer vac matters quite a bit since a lot of power might be wasted in the regulators when the vac is to high.You can fool around with Joe Malone's AC/DC-calculator to get an idea.

 

[Mellowroni]

Hey!
Thank you very much, this was very helpful. I am pretty new in this game, so any help i can get is good as gold

Ronny

 

[kante1603]

Have fun!

Udo.

 

[hakanai]

Hey guys. I really love when I come to the thread and find things happening. it always gets me motivated. Anyway, here is what I have for you today. The latest prototype of the basic mixing board. This is all tested and is in good working order. I just need to move one or two parts for a little better clearance and maybe tweak some labeling. I'll be ordering a batch this week. Once that order is in, I will re-list the white market thread and start taking orders.

So what's this version like? It is back to the basic summing mixer like the mark4. This will, in fact, be the mark5 and the larger more complex mixer will be the next version. From the mark4 to this you get two big changes. First, each channel gets it's own set of decoupling caps and diodes for better channel separation. The second new feature is the more interesting (if you ask me) the fader and pan pick off points have been arranged so that they can be wired as they have been in the past with terminals connecting to wired off controls, OR you can mount the controls directly to the board for LCR pan and a fader per channel. Now using both on every channel in the board mounted setup will make for a cozy fit on the controls, but my thinking was that many of these summing mixers are built with only some sort of LCR pan so this will simplify that greatly. Then I also thought that these are summing mixers not consoles. If the controls are a little snug it's not the end of the world because most people won't actually riding the faders or doing "moves" they just need a variable attenuator so they dial in there outboard. So extending that logic even further made me think a good build for many studios would be to do 4 channels fixed center fade only, four channel LCR and fade, and as many channels of LCR only as you need.
This brings me to the other difference from the mark4, the mark5 is 4 channels. Probably not shocking if you have been following the progression of this project. With the board sized as they are you should be able to get 3 across a standard 19" box. So 24 channels in 2RU with the controls mounted directly to the board will be possible.

test channel with hard wired controls

showing the wiring options for controls

I'll post again once the white market thread is open again.
Don

p.s. oh yeah, the boards will be blue, as always. I was trying out a new fab house for the prototypes, so no purple (even though I do like them)

 

[kante1603]

Hello Don,

very very nice indeed!
Can you tell us the pcb size please?
And can you shine a light on the "...diodes for channel seperation....."?On the pic I can see the protection diodes.....
Isn't it the same schematic as the MK4 boards?
4 channels is really cool,I might extend my project with some FX returns now.....

Best regards from germany,

Udo.

 

[hakanai]

And can you shine a light on the "...diodes for channel seperation....."?On the pic I can see the protection diodes.....
Isn't it the same schematic as the MK4 boards?

Well those diodes on the supply rails are implemented the same way as the mark4 if you only look at a single channel schematic. However if you look at a schematic of the entire board (I have never drawn one) you will see that the mark4 has one set of diodes and one set of supply decoupling caps for all 8 amps. The mark5 has a set of diodes and caps for each amp. Those diodes are providing protection from wiring the supply backwards, but that is more a symptom of the circuit design than a primary feature. The diodes are there to complete the decoupling filter and isolate the supplied circuitry. It does this by making the connection from one amp's supply pin to another amp's supply pins NOT zero ohms. In many modern circuits you will find 10-100 ohm resistors in this position rather than diodes. You could in fact stuff these boards that way and it work just fine, some would say better, but in keeping with the API style I put diodes. And honestly since it is a DIY kit, I really don't mind having the wiring protection as default, if a guy knows that they could be resistors then he is probably also the type who wouldn't think twice about deviating from the BOM. The decoupling caps act as filters AND reservoirs, so rather than 8 channels sharing a reservoir and filter set, they each get their own. These are subtle differences, but real ones.

The board is 5.17"x3.95"

Don

 

[kante1603]

Thank you Don,

Udo.

(...and I like them blue btw...... )

 

[hakanai]

white market thread re-opened:
http://groupdiy.com/index.php?topic=49242.msg622887#msg622887

 

[kante1603]

Hello all,

Don asked me to post this after we had contact some days ago.

Close to 2 years ago I bought some boards from him with the intention to build a summing device for doing my mixes OTB.
I have built 3 boards (the 8-channel version) and all the DOAs and Jeff´s ACA/BO then,but due to my real busines the project went to the shelf.....until now.

Rethinking all the previous led me to slighly "extend" the project to have some more features.Not to build a full mixer but having some of it´s main functionality.Will still do my mixing stuff in PT with a bunch of motorfader boards (Avid Mix) attached,so far so good.
But on my OTB summing/mixing thing I decided to go on as follows:

*Frontpanel will now be 4 or 5 ru.

*Still 24 input channels going to the ACA/BO stage.

*Inputs will now have the attenuator pot(Bourns),this will allow me to drive the input DOAs (GAR2520) harder from my interface outputs (3 x FF800=24 out-channels) if I want.

*Don´s panboards for Grayhill switches.I managed to tweak the resistors so their values are more or less "correct" after old german broadcast recommendations for panning.I used the recommendations from Ebehard Sengpiel,excellent stuff to read (and learn).So 11 positions.Here´s a link for those who might be interested:

http://www.sengpielaudio.com/RegelunterschiedeBeiPanpots.pdf

It´s german,I´ll happily translate it or summ up what it is about.

*Simple Mute and Solo functionality.I decided to add some C&K pushbuttons driving relais for that.LED indicators will show the current state.Solo is very simple and destructive,but it will exactly fullfill my needs:I can now bounce down some tracks by just hitting the corresponding solo switches instead of muting all others and record back to PT,as said OTB (with all my beloved analogue toys attached),not bad.
Mute is done on the panboards,I extended them a bit to carry the relais.
Btw.,all relais as well as all C&K switches are mounted on ic sockets,very usefull for super-easy service/swap them out in case of something will ever fail or break.

*It will have Joe´s PPMVU-Meters on the main o/ps,maybe his Amphead (headphone amp) too.

*Master level pot will be an ALPS Blue for now....who knows.

*PSU will be external to keep things clean,it will be one of Joe´s (JLM) AC/DC so.It will also have a second single 12vdc rail (maybe just a swiched mode "wallwart-style") without gnd reference to audio as the dirty rail to supply the relais and leds.

I´ve already bought  a bunch of nice knobs and some other stuff from Jeff to make it look nice.Frontpanel is still to be designed as well as the PSU,but I´m looking forward to it,I love doing things like that.

All in all a very nice project for my summer holidays I think.

Don asked me to show pics of the current state of build,so here´s what it looks like atm.

Best,

Udo.

 

[kante1603]

Pan and switch board (for 6 channels each) from top....

 

[kante1603]

..and bottom...

 

[gar381]

Nicely done Udo!!

GARY

 

[hakanai]

Udo, that looks great! I can't wait to see the finished build.

little update - the new boards have shipped from the fab house. should be shipping to people next week.

Don

 

[hakanai]

Ok new BOM for the mark V is available:

https://drive.google.com/file/d/0B1tn6X6wXoplRlVtTGRTeHI2QWM/edit?usp=sharing

 

[kante1603]

Hi all,

holiday time now,and time to work a bit my little project.
So here´s my first test and the solo stuff I wanted to have implemented.
Current draw was 103mAs for a block of six channels with all LEDs and relais switched on.....not bad.
All boards do interact as I wanted,great!

Here a pic of one block: