24 channel mixer the "Stereotype"

[kante1603]

Yes,p&g,does same as neumanns and many others,thank you very much indeed!
Btw,are you working on this little mixer too?If so,did you build panpots to it?I'm asking because I will do so,have grayhills here and Don's panboards.Thinking of a good way how to set up the resistors now concerning pan law,just thinking........

Udo

 

[funkmuffin]

Hi all -- thought I'd stop by and show off the last part of my Stereotype build -- the control section.  Since I replaced an actual mixer with my Stereotype, I needed a couple functions that were all of a sudden missing -- namely, monitor volume, monitor mute and monitor source select, plus needed to do something with the 2ACABO fader.

So, I built this:

Its got the ACABO fader mounted, that's a Tc Electronic level pilot for monitor level control.  The buttons are connected to a set of Classic API relay boards on a breadboard/p2p rig I hacked together.  Used a DB15/VGA cable to move the signals back and forth to eh Stereotype box in the rack.

 

[kante1603]

Very nice,congrats!
Good idea with the level pilot,I know it for it's "heavy feeling" and has a Bourns pot inside.
I built such a thing later with an Alps blue pot.Cool because it is passive,and as long one doesn't run heavy cable length it works excellent.
May I ask some questions?
The switches,are they momentary or latching?
What are the sources you monitor,is it stereotype output and an external device?
I'm about to build a mixer based on stereotypes (have finished 30 pieces of gar2520 yesterday) and I'm working on some design and features stuff now.

Thanks in advance,

Udo.

 

[funkmuffin]

Udo -- The switches are latching, light-up jobs.  They were ebay specials.  One lesson learned: these are 16mm, which are almost too small for my fingers to comfortably push.  The 20mm would be a better choice.

I didn't have a lot of switching needs.  I basically have two sources: 1. the computer, which runs 24 channels of DA out to the Stereotype, and, 2. My 2 channel reel-to-reel.  The way things are wired up, I can either monitor directly from the mixer output, or when the switch is engaged, I'm monitoring through the tape deck's electronics, which is very helpful to make sure I'm hearing what I print.

Ryan

 

[kante1603]

Thank you very much Ryan

Udo.

 

[Aniol1349]

Hey guys!

I'm thinking to build this great summing mixer, but I'm quite concern of the grayhill's price..

anyone know good source in europe for those?

Thanks!

 

[kante1603]

Hey guys!

I'm thinking to build this great summing mixer, but I'm quite concern of the grayhill's price..

anyone know good source in europe for those?

Thanks!

Hi,

sadly I had the same trouble to source them here in europe.
I ended up buying them from Jeff at Classic API,he had the best price by far!

Hope to have helped,

Udo.

 

[Aniol1349]

Thanks Udo!

have you already finished your unit?
could you comment on difficulty of this build?
I'm fairly new in diy world but I'm really keen to learn.

Thanks!

 

[kante1603]

Hello,

no,not finished yet,I'm still designing it,depends on the money too ;D.
Also my real job doesn't allow to spend much time on this at the moment.
Is it difficult to build?I'd say no,but it depends on how complex you want to do it,e.g. Just a say 16 in 2 mixer or adding on more subgroups,maybe mute switches or even solo functionality etc.
Both the aca bo and the stereotype pcbs are layed out very well and give a lot of possibilities to easy modifications.
What is a bit more difficult is to build all the DOAs on your own.It takes a certain amount of time as well as pretty good soldering skills,these guys are very small!
Have done 30 pieces some weeks ago so I know what I'm talking about,hahaha......but it's doable.
Next step on my side is measuring them,and then......who knows?

Cheers,

Udo.

 

[Aniol1349]

can you easily add stuff to the design(like the mute or solo), or you rather have to plan it before and then do it?

 

[kante1603]

can you easily add stuff to the design(like the mute or solo), or you rather have to plan it before and then do it?

It's up to you of course.Planing it helps a lot,hahaha..... ;D
But a thing like a mute button should be easy to do since it is nothing like the volume fader or pot fully down.
The aca bo already has a (master-) mute option,just put a fet switch in and apply control voltage,done.
Look at the schematics for a while and you'll get a lot of ideas.

Udo

 

[muffy1975]

hey there,

i am in the process of building a mixer using an active discrete transformerless input for each channel.

Is this essentially what's going on here?

However, is there a virtual earth for the summing?

Could all these GAR opamps be plugged straight into two of Igors Ba283 for example? and Have the BA283 as the make up gain? Will the BA283 need an  input transformer for summing say 16 channels?

Michael

 

[kante1603]

Hello Michael,

hey there,

i am in the process of building a mixer using an active discrete transformerless input for each channel.

Is this essentially what's going on here?

Yes,meant as a line mixer with balanced inputs.You can see the schematics on page 4 of this thread

http://www.hakanairecording.com/mixerpics/Stereotype%20mark%202.pdf

So for mic input,eqs and dynamics simply add on to your needs.

Could all these GAR opamps be plugged straight into two of Igors Ba283 for example? and Have the BA283 as the make up gain? Will the BA283 need an  input transformer for summing say 16 channels?

Michael

As you can see all the Doas go to a stereo bus system via 47k bus resistors.So the next step should be a summing stage.Sadly I'm not familiar with Igor's circuit,but I guess it will work.Maybe someone can chime in here?
Don's stereotype was designed to work with Jeff's ACA-BO,you can get it from him at classic api.
This piece consists of 2 parts on one pcb.First there's the ACA which is the summing amplifier,it is an Active Combining Amplifier.There's a transformer on it's output that provides a balanced output signal.
If you want you can go to a master fader from there.In this case you'll get a signal loss which is made up again by the second stage on the pcb,the BO or Booster stage.There's another transformer on it's output to give you a balanced signal.
BTW, the aca bo is dual so gives a complete stereo build.

Hope to have helped,

Udo.

 

[muffy1975]

thankyou.

yes that has helped. The unit I am re working seems to demand 68k summing resistors. Quite high!

michael

 

[kante1603]

Hi Michael,

May I (or better we) ask what you're working on?

Cheers,

Udo.

 

[Humner]

I'm new to the forums and have much interest in this mixer. Please excuse the following stupid questions 

Has anyone tried with faders(or a pot) on the input channels? What are the results?

Would you recommend a fader buffer? What about using another stereotype board as a fader buffer? Or is this overkill?

 

[Winetree]

Got the 24 channel kit. Great Job on the beefy boards.

 

[Aniol1349]

Hey guys!

I just ordered my Pcb's today and I can't wait to build this beauty!

I was just wondering if there will be a chance to insert a width control like in Neve 8816 for example. I'm quite new in DIY so for now I'll probably stay with the original design but is good to know the possibilities for the future!
Also, will there be a chance to have separate faders for each channel?

and btw. Don thanks for this great project!

 

[kante1603]

Also, will there be a chance to have separate faders for each channel?

and btw. Don thanks for this great project!

Hello,

Please have a look at the schematics:

http://www.hakanairecording.com/mixerpics/Stereotype%20mark%202.pdf

After c2 (before the pan) you can easily put in a fader or pot,should be 1k.

Hope to have helped,

Udo

 

[gar381]

Just a thought guys..

The BOM has for R1-4      71-CMF5520K000FHEB  which is a 1% part.
why not use                    71-CMF5520K000BHEB  which is a .1% part

This should help CMRR.

Best

GARY