Large console DIY??

[NewYorkDave]

It's a popular fallacy that active mixing requires less gain. Take your typical inverting-opamp active summing stage and redraw it as a simple inverter (with the input resistor being made up of all input resistors in parallel) and you'll see what's going on. And note that any noise present on the "+" input terminal is amplified by an equal amount, plus 1.

 

[ijr]

Very large console is not very diyable...but 16 channels
(line pre/eq/aux/switching) using P&G faders, EAO/Elma switches,
input trafos from 3M tapemachine, discrete tr. opamps
in pre/eq sum circuit/fader booster,
604's in eq filters of S@ntec ;-) -based circuit
are allmost ready, 4-layers pcb's...6 of them soldered and
fine tuned...yes, time is main issue...
now working on others and monitor section pcb....
then, I gonna add 8 stereo channels with just el.bal. input/auxes...
this gonna be little but enough large in sound console))
btw, three summing circuits swtchable and commutation (solo/mute/assigns) done on relays....
Now, some TOO-lazy-to-DIY-good-stuff people will call me crazy...
Some jealous people will talk about where can he still enough money
to build it...
This topic will be finished like 2254 topic. BLABLABLA.

:grin:

 

[dale116dot7]

One thing, though, is the gain of the summing amp in a virtual ground mixing arrangement varies as channels are added or taken away from the mix bus, so you have the option of lowering the amount of noise from the mixer's assign switches. With a passive plus makeup you don't have that option, and crosstalk seems to pop in there.

 

[rich]

What is good technique to minimize cross talk in a passive mixer?

 

[bluebird]

Ijr,

Hey its all cool buddy as long as you share those PCB's :green:

 

[rich]

[quote author="ijr"]
This topic will be finished like 2254 topic. BLABLABLA.

:grin:[/quote]

I know when ever I get super involved with things like building mixers I run the serious risk of missing my mortgage payment, for others they probably run certain risks like getting divorces etc...

 

[Linear]

[quote author="rich"]What is good technique to minimize cross talk in a passive mixer?[/quote]

in a word - grounding. check out grounding buss bars on an old Neve. with good grounding you minimise crosstalk and improve your S/N.

Chris

 

[Carl_Huff]

It seems to me ....

That it would make sense for us to come up with a 'standard buss' that could be used to create frames. We then could design up a series of 'API like' modules that would drop into those frames to create the most basic, or most exotic solution.

Just my two cents worth ....

 

[Guest]

I am in my newbieness creating something like a modular mixer
I have had the drop in cases already made in 1 u and 2 u racks - 8.5 inches high
Turn them vertically
I have a large 2 unit rack case that I am filling with modular PSUs
e.g. 48v phantom supply, 18v supply, 24 volt supply

My first drop in is a Calrec EQ (it's becoming a bit of a squeeze to put the 2 pcbs into a half width rack unit - as well as adding a relay board to handle illuminated push buttons instead of the 2 and 4 pole Alps)

Currently I am using 5 pin XLRs to provide power to the Calrec from the modular PSU case
18-0-18 AND a separate 24-0 for the relays and lamps
I have a 48-0 in there as well (for global phantom - but it's not used yet)

I am very worried about grounding but to help matters am using plastic PCB pillars and going to start looking at star grounding and how it will help

The next drop in after this is going to be a 1176 but mounted vertically in a 2 unit rack (similar to the original SSL compressor)

The frame is in my head at the moment but the concept is quite easy
Mount 19inch rack strip horizonatally and these are used to anchor the drop ins
I will be using a wooden desk to house it all

One thing that is worrying me is how to house the mic pres - I think I will mount a half width rack 2U box normally (i.e. horizonatally) and "divy" the channels up on the face plate so they will match the modules mounted vertically beneath them
Otherwise I will be having one channel of mic pre in a 8.5 inch 1U vertically and there is going to be a lot of blank space around.....

 

[jstark]

I keep reading about the grounding buss bars in Neves, as well as the extruded aluminum duct that houses the wiring...

Since the owner of the only Neve I have access to would not appreciate me poking around inside of it, does anyone know of somewhere with images of these sorts of things? Thanks,

 

[NewYorkDave]

One thing, though, is the gain of the summing amp in a virtual ground mixing arrangement varies as channels are added or taken away from the mix bus

That's a strong feature of active mixing. On the other hand, it can also be a liability since the closed-loop gain of the amplifier (and thus the amount/type of distortion products and the "sound") will change as channels are switched on and off the buss. A well-designed active summing stage will have so much open-loop gain that this change shouldn't be noticeable.

What is good technique to minimize cross talk in a passive mixer?

Crosstalk is minimized when the buss impedance is low with respect to the source impedance. In passive mixers, the crosstalk figure improves with the number of channels added (but so does the loss!).

In passive mixing, it's important to avoid disturbing the buss impedance when switching inputs in and out. That's why passive arrangements usually use channel-switching arrangements that are a little fancier than simply disconnecting an input resistor from the buss. The simplest approach (assuming the signal source impedance is low with regard to the value of the input resistor) is simply to ground the input side of the input resistor, either directly or through a small resistor with a value equivalent to the signal source impedance.

The old constant-impedance systems made passive mixing a lot easier. Channel attenuators had a constant output impedance of 600 ohms. A channel "mute" could be implemented by simply switching the mix network input resistor from the attenuator output to a 600-ohm dummy load. In reality, mute buttons were fairly uncommon back then; you turned off a channel by turning the attenuator all the way down!

 

[henk]

Have calculated what the table with 40 mic , 16aux , 16 groups and 2 masters would cost , to high!
So , new plans are to make a 40 mic , 8aux , 8 groups and 2 master.
Plans are a small big table but with the same quality.
No trafo on the input and everything is balanced , input/output/bus so noise on bus will be minimal.
We still need about 1500 opa2604's a lot but not so much as with the big table 2300 opa's would be needed.
So cost come down but not the quality.

 

[Svart]

1k opa2604s will cost you around 2500$usd at digikey.. that's a big chunk of change on opamps..

also,

My Alesis X2 has a grounding bar that all the channels hook up to.. that thing is about 1/2" thick and 3" wide and as long as the whole console.

 

[amorris]

i declare myself crazy. I have been working on a neve 5104 frame for a while now.
got my 7amp llambdas up and solid.+/-24 adjust able.
I have a preamp that I have de-populated and have traced both sides of the pcb in the cad software of pcbexpress.
I have a VR EQ de-populated and waiting for pre ampp success to procede.
the frame has motherboards and some faders and such. all test clean with contiuity.
Im moving it to a garage 1 mile from work Sunday night to start firing it up. at least the meter bridge and what have you.
I want to work on the control room monitoring first so i can do my channel testing throught the board properly.
it has been 3 years now but I am going to do it.
$4200 gets me 40 pcbs with pre and eq.
+ cost of compnoents(in software i have moved the switch traces to a standard footprint so i can put any schadow switch in!)
wish me luck!

 

[Svart]

:shock: goooood luck.

 

[pucho812]

AM I remember when that frame was on it's side in storage. It's good hear it is comming along. :thumb:

 

[pucho812]

Amorris,
why don't you indulge us about how you got the console and it's condition. I remember a band saw. :green:

 

[ijr]

i declare myself crazy

Hi brother! ))))

 

[verbos]

[quote author="amorris"]i declare myself crazy. I have been working on a neve 5104 frame for a while now.
got my 7amp llambdas up and solid.+/-24 adjust able.
I have a preamp that I have de-populated and have traced both sides of the pcb in the cad software of pcbexpress.
I have a VR EQ de-populated and waiting for pre ampp success to procede.
the frame has motherboards and some faders and such. all test clean with contiuity.
Im moving it to a garage 1 mile from work Sunday night to start firing it up. at least the meter bridge and what have you.
I want to work on the control room monitoring first so i can do my channel testing throught the board properly.
it has been 3 years now but I am going to do it.
$4200 gets me 40 pcbs with pre and eq.
+ cost of compnoents(in software i have moved the switch traces to a standard footprint so i can put any schadow switch in!)
wish me luck![/quote]

So you have the Schematics for this board...

I sure would love to see them, if you please.

Thanks,

Mark

 

[amorris]

verbos
i have the preamp schematic and maybe a few more. john musgrave in la gave me them.

pucho knows the nefarious origins of my board too well!

well, i came across the 5104 frame outside a place in LA. they wanted to sell some modules so i looked. the board looked great-36 frame with maybe 12 modules loaded. the rest blank panels. that's actually what i wanted- larger frame that i could load with custom modules. but if you pulled a module. the pcbs as well, as the module metal work, was cut out 2 inches below the surface. all knobs in place and some meter lights working. the console looked complete to the naked eye, but had huge internal smuggling cavities inside. almost hollow. so we thought, why?
maybe ship across a borger with a high insurance capacity and you have a mule!!! what is worth more per pound than an analog cnosole? none was left inside(i looked!!!) so they wanted rid of it fast and i had a truck!
rock and roll.
also in the deal- an atr 101(mono) but hey it was free!!!!!
another man's junk is another man's treasure for shiz.....