adding direct outs

[Disjointed]

is it possible to add direct outs (post eq, post fader) to a console..

instead of routing them to a master buss, route them to the back?

would i need some kind of transformer, or output mini board?


thx in advance

[Disjointed]

come on ... someone has 2 seconds for a quick answer to the uninformed

[stellar]

I am sure you could easily do this, depending on the console. you would only need the transformer or output mini board if you are trying to get balanced direct outs. at what point in the signal chain are you trying to pull the direct out from?

[Phil Cibley]

Originally Posted by Disjointed

is it possible to add direct outs (post eq, post fader) to a console..

Absolutely. I just added 6 to a Soundcraft GP-1 portable mixer for one of our
faculty members. You just have to be careful to maintain the console ground
scheme when you do it. Just find the spot to pick off the signal, use a piece of
2 conductor shielded cable and either use an unused jack on the back, or do a
bit of drilling and you're there. Transformers are the best insurance against
RF and hum, but if you're careful, and the associated equipment doesn't
mind, it should work. The hardest part will be the drilling.

[Disjointed]

sweet, those were the answers i was looking for!..

i would probably put the out... post eq, and maybe post fader...


on a similiar idea... could i wire in meters just as easily?



thx for the replies

[Matt Syson]

Hi
Yes.
If they are VU meters (wiggly ones) it may be best to use a 'buffer' amplifier (unity gain) so that the distortion caused by the diodes in the meter don't go on your audio.
Matt S

[Cpl. Fatty]

i know this is an old thread but i thought i would post here instead of starting a new one. i want to add direct outputs to my old console and can't find the points on the pcb and need help. i'm trying to take the signal post preamp. any help would be appreciated.
thanks

[Matt Syson]

Hi
If you want the signal 'prefade' it is easy to find the wires that go to the 'top' of the fader.
A buffer amplifier is recommended as the circuitry feeding the fader may not like a few metres of wire attached to it.
Matt S

[Cpl. Fatty]

thanks i found them no problems. would the circuitry of the eq 'flavour' the sound a bit? is it possible to do it pre-eq?

[Matt Syson]

Hi
Yes, One of the contacts of the EQ in/out switch will have a pre EQ signal on it.
Use a resistor of say 100 Ohms in series to reduce chances of 'killing' any circuitry or encouraging oscillation.
I am wasting my time on GS this morning whereas I SHOULD be doing this very mod to a Midas desk.
Matt S

[Cpl. Fatty]

sounds easy but i just don't have an eq switch for this desk. is there any other point easily spotted?

[Cpl. Fatty]

sorry there not great pre's anyway so i'l just do it post eq. but i looked around and found nothin on how to add a buffer amp. can you guide me in the right direction?

[Matt Syson]

Hi
Which desk are you modding and does it have single or 'bipolar' supplies (plus and minus 17 or so)?
A simple buffer can be made using a NE5532 with a handful of resistors and could give a balanced output. Made easier if you have bipolar supplies but not too tricky with a single supply.
Look on google or wherever for simple op amp circuits, You want a non inverting buffer and an inverting amplifier (gain of 1). The inputs of these come from your postfade (or prefade) point.
Matt S

[Cpl. Fatty]

hey,
thanks for all the help and i'm really sorry to say that i need more help as i'm pretty new to this but really need this done so i can input these channels into my interface.

its an old crappy alto amx-220 console thats just gonna be used for drum replacement with an old speaker i've turned into a mic for the kicks. so i need 2 of these pres into my interface, do i need to build 2 of these buffer amps?

i don't know if its a uni or bipolar power supply, how can you tell?
again thanks for your help and patience with this simple mind haha.......

[Cpl. Fatty]

can anyone help me anymore with this whole buffer amp deal......parts list, diagrams etc?

[Matt Syson]

Hi
Yes you would need a buffer amp per channel.
I would suggest buying a kit like those available from Velleman. They make a 'dual line amplifier' card which if wired slightly unconventionally would do the trick.
You need to get some info on your desk (schematics and put up some internal pictures) before anyone can make any concrete suggestions.
Matt S

[JohnRoberts]

+1 You need to study the schematic and to a somewhat lesser extent the physical layout. Console design is a constant struggle to minimize active stages. You are not helping sound quality by running a signal through 20 opamps, and that current times tens of channels causes heat and power supply concerns.

One thing to be looking for is the polarity of where you grab the signal relative to input. If you add a buffer you can perform an inversion in that buffer to get back right. Also be alert to where the signal you grab is ground referenced, you can't just pluck a signal from the middle of a PC board and reference it to the chassis. Also be careful to do no harm, many internal paths do not have the drive capability, or decoupling to interface with external loads. So adding buffers is probably useful. The internal reference ground may not be robust enough to sink shield grounds so any unbuffered interfacing with SE gear could corrupt the entire audio path.

So I would use active differential buffer from the internal signal and ground pickoff, to the robust rear chassis ground, and from there balanced to the outside world.

First do no harm. Adding direct outs or inserts to a console is more than just a few jacks.

JR

[Matt Syson]

Hi
As a general note, simply 'adding a transformer' is rarely a good option as there is more to driving a transformer than is apparent. Internal paths of desks often use ICs like the TLO72 where, in the design they are not required to drive an arduous load. Adding several metres of cable, a transformer and of course the original circuitry is well beyond the capability of a TLO72.
Matt S

[Lee Cardan]

personally, I would be making something like this:



Use a TL072 for the and 10K resistors would work fine for R1 and R2, and a link should be used for R3. Use something like a 0.68uF (or higher) MKT capacitor in series with the input, and both output stages

That'll do it

Keep in mind the TL072's nominal supply voltage is +/- 18V, so check out what voltages you have in your board and go from there. there are a few LM series opamps that will run off higher supply voltages, something like +/- 36V are available

You also put a little switch in there that would select whether the feed is pre EQ or post EQ, or post fader too if you like

[Cpl. Fatty]

ok thanks for the reply but i just have a couple of questions. how come no-one has given me a straight answer like this and how do you know that it will work for me in my particular case?

sorry if i sound ungrateful but i'm just making sure haha.

also my desk has an adapter which is 18v. thats ok isn't it.

[Lee Cardan]

just farken do it ay!

everyone else sucks, that's why nah they're good. I just did a quick search and came up with this

There are many many many different ways to do this, such as transformer, buffered into transformer, tube!, op amp, op amp with filter tweaking (to add sonic character), etc.. etc... etc.. BJT, FET, freaken... more, there's more, PASSIVE!

I chose this because it's a no brainer to build: one chip, 4 resistors, 3 caps. It's buffered meaning it won't adversely affect the channel strip, and it has enough guts to drive a long balanced cable run, and typically it doesn't really care what it's connected to (buffering!). The resistor values simply set gain. As you want unity gain, you can use basically anything you want. 10 ohm or 10 megaohm would probably work, personally i stick around the 10k region for this kind of thing, most kind of things. If you had bypass caps in the feedback loop then the resistor choice is more critical because you're forming a filter and controlling the frequencies to which the opamp will work on which comes into 'character building' of the circuit.

basically, it'll work

[Cpl. Fatty]

ok i will just farcken do it lol.

but before i do i have to understand more of what i'm doing......as in that diagram looks ok but i still don't understand fully where things go. i know its a small circuit but i've only just got into this sorta thing a couple of days ago when i wanted to do this. i have hired out a book on understanding circuits and i will read it eventually.

just a quickie, why is there 2 opamps in this picture?

[Lee Cardan]

There's two opamps because there's one to drive the +ve signal, and another to drive the -ve signal.

So, you've got +18 in your desk, do you have -18 as well?

Essentially a TL072 wants to see 36 volts, but really it doesn't care too much. Most opamps will work fine below their rated voltage, but operating them at a lower voltage will reduce their potential output. In this case though, it really doesn't matter

This may help put things into perspective:

[Cpl. Fatty]

Originally Posted by Lee Cardan

There's two opamps because there's one to drive the +ve signal, and another to drive the -ve signal.

So, you've got +18 in your desk, do you have -18 as well?

Essentially a TL072 wants to see 36 volts, but really it doesn't care too much. Most opamps will work fine below their rated voltage, but operating them at a lower voltage will reduce their potential output. In this case though, it really doesn't matter

ok i'm still a bit confused. is that 18v ac your talking about? if so then it is.
do i have to grab a point off the power supply and put - into pin 4 and + into pin 8?

and do i put the positive part of the signal into either pins 2 or 3 depending on if i want to invert the signal or not and it will come out pin 1....same with i/p b and negative signal?

and then put caps on the outputs and bridge between pins 2 & 6?

i've prolly got this completely wrong so i thank you for your patience.

[Matt Syson]

Hi
Go away and read your book a couple of times.
THEN:
Establish exactly what power rails are available in your desk.
Get a cheap multimeter so you can make basic tests.
A TLO72 is NOT the chip to be using for driving cables they will work but pretty badly in this application. A NE5532 is cheap and powerful enough. Using 10K resistors is fine but if you are using a TLO72 about a fifth of it's load driving capability is used to feed the(10K) resistors in it's own circuit.
Input capacitor can be a 0.68uF as suggested but output capacitors should be 100uF MINIMUM.
Matt S

[Lee Cardan]

This should help

10uF should be fine on output, but 100uF won't hurt either
I've personally never used the NE5532, but if dude says it's better then use that

but yeah, definitely confirm what power you have in there

by the way, the diagram attached, your output will have to be in the form of fly leads coming from the desk, or an XLR socket in which the shell casing (pin 1, ground) is isolated from the mounting holes! Reasons is the ground in the circuit is not the ground of your desk (the chassis), so the two can't touch otherwise problems

[Matt Syson]

Hi
The above circuit would work.
Could do with power rail capacitors and (say) 47 Ohm resistors in series with the outputs.
One possibility is the Velleman K2572 Stereo amplifier board which with a small amount of thought would accomodate this circuit, linking out component positions as necesssary. The Velleman board assumes a single supply rail but of you have a 'split' rail desk it can be reconfigured with a little thought. The kit has a TLO72. Change it for a 5532 or other type. MC33078 is quite a favourite of mine as they are quite tame and in most instances as good as the 5532 but less power drain. The 'super fast' chips available now should not be used as they require considerable experience and test eqipment to ensure they are 'happy' in their environment.
Matt S

[JohnRoberts]

Originally Posted by Cpl. Fatty

ok thanks for the reply but i just have a couple of questions. how come no-one has given me a straight answer like this and how do you know that it will work for me in my particular case?

sorry if i sound ungrateful but i'm just making sure haha.

also my desk has an adapter which is 18v. thats ok isn't it.

I would have to study your schematics and maybe layout to give you a professional answer, and what i would charge for such specific advice with implicit guarantee that it would work, is beyond what you want to spend, and I'm not looking for work.

OTOH it's easy to criticize other suggestions. Specifically the TL07x is precisely the kind of opamp I would use inside console designs for the light lifting. They only have a nominal 2k drive capability. The circuit offered looks OK by itself, but like I already suggested, you need to first differential between the local ground where you are tapping into you signal, and the rear chassis outside world ground. If you don't properly differential, you will get crosstalk and who knows what between arbitrary grounds. Adding a second opamp to create another polarity output while common in professional gear, may not be needed for your application, or worth the extra cost, complexity, and PS loading. Another +1 to 553x for an inexpensive opamp with outside world drive capability (nominal 600 ohm IIRC). Note: while the proposed circuit does not cancel out ground errors, if it uses the correct ground close to the signal being tapped the ground errors will be sent out common mode and presumably cancel in a following balanced/differential input.

By all means try it on one channel and see what happens. You might get lucky. If not you will get smarter.

JR

[Matt Syson]

Hi
Having just looked at the user manual it 's supply is 18 Volts AC so I suspect it may well be a split rail design (+ and - 17 Volts or thereabouts).
It will not have a lot of 'spare' supply current capacity so only do a couple of channels.
I would also suspect it will be a 'single board' design with surface mount components to get it all in a small space so getting anything else in there will be fun.
Talk to the Taiwanese manufacturers about getting the manual.

Matt S

[Cpl. Fatty]

Originally Posted by Matt Syson

Hi
Having just looked at the user manual it 's supply is 18 Volts AC so I suspect it may well be a split rail design (+ and - 17 Volts or thereabouts).
It will not have a lot of 'spare' supply current capacity so only do a couple of channels.
I would also suspect it will be a 'single board' design with surface mount components to get it all in a small space so getting anything else in there will be fun.
Talk to the Taiwanese manufacturers about getting the manual.

Matt S

upon first inspection of inside the board i thought to myself it is a bit tight in there but then again i didn't think i had to build anything either. but what if i just add the jacks to the desk and then add a link to an external box with the buffer amps and maybe a different power supply, then into my interface? it would only go maybe 1foot or so, would that do anything to the signal chain inside the desk?