24 channel mixer the "Stereotype"

[AUDIO-ON]

Thanks Udo! Soon I will start my project, too...
Gruss, Rafael

 

[kante1603]

Hello,


I'm trying to find the schematics and/or bom for the 4-channel input board (MK5).
The link to the wm seems broken or dead,and from what I remember all the info was there.
I have these boards here finally but can't go on without having any infos.I want to finish my mixer project,now I'm stuck.


I did not get any answers so far,Don seems to have "disapppeared".I also pm'ed a few members,so I'm still waiting.


If anybody has downloaded some of those files and could give me any infos I'd be really gratefull.


Thank you in advance,


Udo.

 

[Charles Turkmen]

Hi Udo,

I think I might have the docs you are after    Send me a PM with your email address and I'll send them to you right away.

Charles

 

[Charles Turkmen]

I see that the PM feature of the forum is down..

Seeing Don had made the files publicly available recently, I don't think he'd mind me re-posting them now ...

 

[Charles Turkmen]

I'm not 100% sure these are the very final versions but they are the last ones I had downloaded from the links that Don had put up..

Cheers

 

[hakanai]

Sorry for the documentation issues. I have just reinstated the white market thread, so it should be back up in a few hours. Just another symptom of my current situation. Sorry for the lack of attention here, I have been completely bogged down with work and personal things for the last few months. Unfortunately Udo has gotten the worst of it and I'd like to say publicly, thanks for your patience. His boards took ages to get to him (through various lapses on my part) and now I see when they finally did I had just let the white market fees lapse causing the documentation to disappear.

Don

 

[audiomixer]

Standing up for your own mistakes is the only way to deal with them, to bad this is not common practice (the cat ate the homework syndrome)... good on you, Don, cool!

 

[hakanai]

Higher will work but lower is better (generally). Basically those are the feedback caps that help stabilize the amps. My understanding of them is that in an ideal amp, they aren't needed. In the real world you usually need something, maybe only 10pf for a schmancy IC. Too high a value and you lower your bandwidth and high frequency distortion increases. Too low and you get instability (oscillation). What value is right for your amp? That technically needs to be tested for square wave response, or just ask what is recommended by whoever makes your amps. I'm pretty sure that is what I recommend in the opamp compatibility link i have in the white market. There is also The Eisen Audio list here:
http://www.eisenaudio.com/diy500/tables/opamps/

The C8 column is the one to look at. Jens has had a ton of stuff across his bench and has been nice enough to compile what he has seen. You can see things mostly range from 33pf to 120pf, with older amps tending to be higher.

So where do the 3 values you have seen in my info come from? and why even put a value if it is case by case? Well 82pf is what Jeff Steiger mentioned to me ages ago as what he uses, and when you look at that chart and actually do some bench testing for yourself you see that 82pf is a pretty safe top value. For the type of amps most guys are using with this project, everything should work with 82pf. Once I actually got to go to a friends bench with a proper AP, oscilloscope, function generator, and all the other toys, I found that my gar2520's actually liked a lower value. 68pf and 47pf were tested and worked wonderfully. So I wrote the BOM as you see because these amps are what I see most guys using. With the sl2520 red dot 33pf worked well and one value lower could have been even better but I didn't have it handy. I use the higher value as the general recommend because, while Gary's amps are great and his kit thorough, he isn't the one building them. DIY is an inconsistent affair and 68pf should cover most things using modern transistors without much penalty. Most of my stuff is written/laid out this way, if you don't ask any questions then things will work. If you do ask questions and/or can see the options built in then you can potentially get things optimized for your particular build.

When I say "better" or "worse", what I am primarily referring to is high frequency distortion. That's what this cap is all about. Some may say bandwidth, but who gives a crap about bandwidth? If the circuit could make 12k perfectly clean and not make 13k at all, I would be satisfied. But the reality is, in order to make 12k cleanly, the circuit wants a couple octaves more bandwidth as headroom and that quickly gets you in the 100k region. So bandwidth becomes a by product of distortion performance (in my book).

Don

 

[hakanai]

Oh yes the schematic. not a whole lot has changed since the mark 4 other than the decoupling. Here is a link to the prototype mark V schematic. Ignore the optional channel header output and add diodes between the supply and amp/filter caps on every channel. Does the labeling system make sense? So Rx01 is R101 on channel 1 and R201 on channel 2, R301 on channel 3 and so on.

http://hakanairecording.com/mixerpics/markVpics/Stereotype-2.pdf

Don

 

[kante1603]

Lesson learned about C1 & C7.


To sum up changes in the schematics (see link in previous post):


Yes,labeling system us easy enough to understand,even for me.
Omit header to channel part (not existing on board).
Decoupling,C5 & C6 are now 47uf,schemo shows 560uF(each channel has its' own filter caps now),add protection diodes.
Schematic,there's no R10 on the actual board,it was 0r anyway.
C1 (220 or 330uF,bp) should be C2,seems to be a typo.


This all refers to te actual 4-channel input board MK5,V2.21.


Is that correct so far?


Udo.

 

[hakanai]

Yes,labeling system us easy enough to understand,even for me.
Omit header to channel part (not existing on board).
Decoupling,C5 & C6 are now 47uf,schemo shows 560uF(each channel has its' own filter caps now),add protection diodes.
Schematic,there's no R10 on the actual board,it was 0r anyway.
C1 (220 or 330uF,bp) should be C2,seems to be a typo.


This all refers to te actual 4-channel input board MK5,V2.21.

correct on all counts

 

[kante1603]

May I ask for the pitch(es) between the centres of the switches and pots?
Just have a cheap caliper here,not sure if it is imperial or metric.
Should be easy to read from your program I guess.


Thanks,


Udo.

 

[hakanai]

fader to associated pan = 0.65
fader to fader = 1.35

in inches

hope that helps

don

 

[kante1603]

fader to associated pan = 0.65
fader to fader = 1.35

in inches

hope that helps

don

Yes,thanks Don.


Udo.

 

[Mellowroni]

Hello!

Is it possible to use a power supply (from a TAC  Scorpion console) that delivers  +-18 volt on my 16 ch stereotype?

Ronny

 

[hakanai]

Is it possible to use a power supply (from a TAC  Scorpion console) that delivers  +-18 volt on my 16 ch stereotype?

That depends on 2 things. First is the amps you used for the project. If they are happy seeing 18v then great. Second is the decoupling caps used on the power rails. I am almost certain I have never specified lower than 20v caps but you should make sure that they are at least 20v. Probably they are 25v. I think they are C5 and C6, off the top of my head.

Those are the voltage limiting factors of the boards. I guess technically you may want to have the coupling cap at the output of the amp be rated above 18v. I know that a lot of boards have a 16v ELNA in this position, but if you used another part (like the Nichicon HE or VP I have spec'd at times) then it will be rated at 20v or higher. All the other parts on the board are rated for voltages so high that they don't really factor into this issue.

hope that helps
Don

 

[Mellowroni]

Hey, thanks for your fast response!

The DOAs are GAR2520s, and the caps I used are rated 25v or higher as far as I can remember!

I guess It should be safe to try then

Ronny

 

[Mellowroni]

Hello again! Sorry for all the questions!

I also have a PSU for a A&H GL4 Console, which gives +-16 v .

Is it better to use this psu?

Ronny

 

[hakanai]

Is it better to use this psu?

This may sound circular, but the better PSU to use is the better PSU. Meaning those 2 volts aren't going to make nearly as much of a difference as basic PSU performance issues like ripple, noise, and all the normal PSU metrics. For the extra nth of a db headroom the 18v will give you, I would forget about the voltages and just try both and see which one performs better in terms of noise. You are far more likely to see a performance gain on that end, then the other. Going to 18v from 16v might get you something like .5db (I'm not doing the math right now) in output swing, but the right PSU could give tens of db better noise floor. While there may be some subjective "color" to be looked at from the different supplies, we can't really discuss that because your setup is incredibly particular to you. I somehow doubt anyone on this board has built this kit with everything the same as you and tried both of these PSU's, and that is what is required to give a sensible response on those more abstract aspects. What we can easily discuss in the more traditional spec sheet type performance, and that is what I am getting at with the mention of noise figures. What we are talking about is dynamic range, the distance from the noise floor to clipping.  It can be improved by increasing output level capabilities or by reducing the noise floor.

So, short answer? With everything hooked up (inputs and outputs) power it up, then try the other supply and see which one is quieter (and free from any weird low-level noises). Use that one. If they are equal, then use the newer one.

did that help at all?
Don

 

[Mellowroni]

Oh man, thank you  for a great response!

This was VERY helpful!

Ronny