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add direct out on Sony MXP 29
Old 25th February 2013
  #1
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add direct out on Sony MXP 29

hello
I have a sony mxp 29 mixer and I would like to add a direct out on each channel!

Could you help me to pick the signal post eq and pre /post fader at the right place?

I've indicated 3 different points but as I'm not a tech ... I'm not sure!

Here is the schematic of the channel in:
http://www.migroz.com/gabtemp/mxp.zip

thanks a lot for your help
Old 26th February 2013
  #2
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mjrippe's Avatar
 

Use the wiper of the aux send pot and you can switch the pre/post switch as needed. For lots of details on a similar mod, read this thread: Mod for Direct Outs on a Yamaha M-508 vintage mixer?
Old 26th February 2013
  #3
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Thanks for help!
Just one more question:
If I follow the indicated procedure I will have a direct out but I will disconnect the fb out of the channel or could I have both?
please have a look on the schematic:
http://www.migroz.com/gabtemp/mxp.zip

thanks a lot
Old 26th February 2013
  #4
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mjrippe's Avatar
 

You are correct that the FB will be disconnected. You could add a switch to select direct out/FB. If you take the direct from the pre/post positions you have marked, you will have to choose one. Also you won't have that pot as a level control for the output.
Old 27th February 2013
  #5
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last question:
aux1 and aux2 catch the signal at the same place... one more output (direct out) will cause trouble if I send fully aux1 + aux2 and direct out?
Any possibility to have aux2 signal + direct out at the same time?
schematic:
http://www.migroz.com/gabtemp/mxp.zip
Old 27th February 2013
  #6
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Richard Crowley's Avatar
You have not revealed what you want to do with these Direct Outputs? There are "proper" and "conventional" and "safe" ways of providing this kind of feature, but there are also shortcuts that have hazards and/or limitations. You can "cheat" the rules if you know what you are doing and/or can live with the consequences.

A big question is what kind of load from the Direct Outs are you trying to drive? And what is the chance that they might be accidentally shorted? And what is the consequence of drop or loss of signal if the output is shorted? There are scenarios (such as casual fooling around in a home studio) where these potential issues are of no consequence at all. But there are other scenarios where it is very undesirable, embarrassing, or worse for something like this to happen.

You have several questions that come down to the "drive capability" of the buffer op-amp stages. Depending on your (undisclosed) situation, I wouldn't particularly worry about that. You should be able to add several of your typical (high-impedance) loads without significant consequence.

IMHO, you have identified the proper pre- and post-fader signal points:
Pre-fader output node is the -- end of C236
Post-fader output node is the -- end of C238

A quick-n-dirty way of adding an output to one of these places would be to connect a 5K~10K resistor between the output node (the -- side of the capacitor) and an output connector. That provides a rather high-impedance output while protecting the other outputs from accidental shorts. But it may be too high-impedance for some loads. We just don't know what you are doing with the signals.

A more proper way to do it would be to use a buffer amplifier which could be as simple as a single op-amp stage connected as a unity-gain amplifier. This is practically the most simple and basic kind of circuit you could make.
Old 28th February 2013
  #7
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My goal it's to have 8 direct out to feed the 8 in of a digital converter (unbalanced -10db )

I'll be happy to have the 2 aux and a direct out working and not to have direct out or aux!

is it possible?
Old 28th February 2013
  #8
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Richard Crowley's Avatar
Yes, is possible and even easy.
Since you didn't answer any of the other questions, can we presume that you don't care?
Old 28th February 2013
  #9
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Hi Richard,
thanks for helping.

As my english is really poor and yours is for me almost like scientific poetry I'm not sure to understand everything…
So I apologize and I will try to answer to your questions.

----"what you want to do with these Direct Outputs?"

My goal it's to have 8 direct out to feed the 8 in of a digital converter (unbalanced -10db ) for recordings in a studio. I have some unbalanced to balanced converter units that I eventually could use (-10db to +4db). My digital converter are -10db or +4db balanced.

---"what is the chance that they might be accidentally shorted?"

I will be very careful to don't short these direct outs.

---"what is the consequence of drop or loss of signal if the output is shorted?"

I would be sad!!!

I'm looking for a simple solution to have the 2 aux working and a direct out on every channel. 2 years ago I have added direct out on a altec 1678c and it's fine. As I'm not a tech I've just followed carefully the procedure I found on the web. Today, it's a mxp 29 mixer and I've no other infos that your precious advices....
Old 1st March 2013
  #10
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Richard Crowley's Avatar
I would simply use a connector (1/4-inch phone, or RCA or whatever) for each direct out, and connect a 5K ohm resistor between the source and the direct out connector. The source can be C236 for pre-fader, or C238 for post-fader as you wish.

We don't know what levels to expect at these points inside the circuit, so we don't know whether they will be adequate for your converter (which you did not identify). And we don't know whether the input levels are adjustable on your converter.

It sounds like this is a non-critical application, so accidentally shorting a signal is of almost no consequence. So we don't need to concern ourselves with that potential problem.
Old 1st March 2013
  #11
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You didn't say if I could still have the 2 aux full working...

my converter are:
apogee ensemble
kronauer genio x1
could be digi02

thanks a lot!
Old 1st March 2013
  #12
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Richard Crowley's Avatar
Adding direct outs as I described will have NO effect on the existing functionality of the unit.

We don't know what the levels will be on your direct outs, so we don't know whether they will be compatible with the inputs of any of those converters. Simple buffer amplifier circuits would solve that problem, providing a good isolated, low output impedance, with adjustable signal level.
Old 1st March 2013
  #13
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It would be fantastic if you yould you let me know the schematic of a buffer amp,
how to power it and what components ar needed.
You're THE MASTER!
Old 2nd March 2013
  #14
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Richard Crowley's Avatar
A perfect example of a buffer amp is right there in your circuit diagram. IC205a (pin 2/3 in, and pin 1 out) is the buffer amplifier for the channel. It uses a NJM4560 dual op-amp in an 8-pin socket and costs only around 50 cents. It would operate on the same +15V and -15V power busses as everything else.

Recommended to use all the same circuit around it, including R259, R260, R261, R262, C238, and RV205 if you want the direct out to have independent level control. R263 is the "build-out", isolation resistor to protect the output against shorting.

Since the NJM4560 has two op-amps in each package, you could use one chip for each two channels

I think I would actually try just the simple one-resistor solution before assuming that you need buffer amplifiers. Simpler is always better.
Old 2nd May 2014
  #15
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thought i'd share my experiences of doing this(albeit on an MXP-290). it's possible to remove the dsub connectors/wiring from the back without affecting the desks functionality, so that's what i did! then knocked up an impedance balanced d25 connector and installed it, the PCB tap points are the same as on the MXP-29. works great!

you can see photos and a slightly(only slightly) more in depth description of the whole process over here if you like - Sony MXP 290 direct outs mod.
Old 10th July 2014
  #16
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anyone have full schematics&manual?

I got a US model(Im in Ireland) so removed the bulky internal transformer(1.5kg), does the alternative 12v dc supply work just as well?
Old 11th July 2014
  #17
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nazaroo2's Avatar
From the bottom, it looks to me like the best physical option
might be to add line out RCA jacks along the bottom of the back of unit.




The issue of buffering the line-out to prevent effects inside the mixer,
seems could just be solved in a stand-alone, 8 RCA cables in,
8 RCA/1/4" jacks out (unbalanced), with 8 op amps in a box.

There is probably something out there that simply does this, like an active "DI" 8 in / 8out , 19" maybe Behringer.


Old 11th July 2014
  #18
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nazaroo2's Avatar
Quote:
Originally Posted by colm View Post
anyone have full schematics&manual?

I got a US model(Im in Ireland) so removed the bulky internal transformer(1.5kg), does the alternative 12v dc supply work just as well?
two words, "clean power".


If you have a 12 volt supply, it should be low-noise and able to
deliver the wattage marked on the back of the mixer unit.
Old 11th September 2014
  #19
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does anyone know the vca editor signal voltage range?
Old 11th September 2014
  #20
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ok I hope this is correct/close, the 4560 op amp buffer between db15 connector and channel vca input(dbx2150 pin 3) seems to convert 10v at input to 861mV at output, which equals 143 x 6mV steps, dbx2150 has a 140bB range, 6mV/dB
Old 15th May 2016
  #21
Help find post fade output node

Hi there

Just hoping someone with technical knowledge can help me with an issue I am having finding a Post-fader output node to add a direct output to my Sony MXP 290 Mixer

After studying & reading the thread i followed Richard Crowley’s advice for the “quick n dirty” solution of connecting to one of these places
[please see attached pics in links]

Simple File Sharing and Storage.
Simple File Sharing and Storage.
Simple File Sharing and Storage.
Simple File Sharing and Storage.

I find I have a nice clean signal present with levels adequate to drive my convertors [Line inputs Focusrite Clarett 8Pre] from C236 which is “pre-fade”
When i connect the same wire [with or without the 5k resistor] to the — Negative node of C238 which is supposedly “post-fade” I am getting no signal present @ my line input whatsoever.

If someone could reference the pics & point me towards another solution or Cap node to take a signal [post-fade] I would be extremely grateful
Old 18th May 2016
  #22
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Richard Crowley's Avatar
The - side of C238 is clearly the primary post-fader output from the channel strip.

Are you measuring with the fader pot UP?
Do the internal functions all work properly? Main mix bus, L/R pan and mix buses, Aux1 and Aux2 buses, etc.
Do ALL the channels have the same symptoms?
Can you trace through the circuit "upstream" (towards the input) to find where the signal is re-appears?
Old 18th May 2016
  #23
Thanks for the reply Richard,

All the functions of the mixer are functioning as they should and I tested various channels with faders up /aux sends/ pre/post switching etc.

I was able to source a [post - fade] signal from the —negative side of C240 and all seems to be well.

Then it occurred to me that I have been cross-referencing with the schematic posted earlier in this thread which is for a Sony MXP 29 & mine’s a MXP 290 so perhaps they’ve modified the design and features between models.
I would say that’s thrown me off track..

http://i66.tinypic.com/v8339d.jpg
Old 29th May 2020
  #24
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Hi All.

I know that this is a quite old subject but I thought I would give it a go..

Just a quick clarification, if anyone can help, in an MXP-290 for direct out (pre-fader) I connect the minus pole of C236 which goes to a Hot connection (with an additional resistor) in an DB25 socket? what about Cold and Ground in Db25?

Noob question, I know..

Thanks in advance!
Old 3 weeks ago
  #25
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Answering my own question - to anyone that might find this info useful.

I've tried inlieu's (Facebook page link) mod of adding direct outs but unfortunately I had a strong buzzing noise coming up from both pre or post fader points.

After some experimentation I found that ground point was the issue so getting the ground from PFL (S205 on the the board) worked flawlessly without any noise at all.

So in my case (Sony Mxp290) c236 (hot) and S205 (ground) did the job for pre-fader direct outs.
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