External Summing of Lexicon MX400XL Outputs - Please Help

[Darclinc]

Hello All,

Firstly, this is not another ‘should I be summing externally’ or ‘in the box’ thread.

I recently rebuilt my studio PC and I’ve decided to ditch 32 bit. As a result I have had to also ditch my VST plugins for my external Lexicon MX400XL unit as well. This was used as an effect in Cubase and doesn't work in C64.

Now, since I’d like to use both channels of the Lexicon ( both hooked up to 2 stereo channels of my Nord Lead ), I am short 2 inputs on my new sound card. As a result I need to somehow sum the Lexicons 4 XLR outputs into 2 so that I can use both channels simultaneously.

I don’t need something fancy, and from what I’ve seen online most external passive / active summing boxes are overkill for me, as are any basic mixers. They’re also mostly hideously expensive and I just can’t justify the cost tbh.

I’ve looked into cheap-ish passive summing boxes, like this one : http://www.unitaudio.com/milli-unit.html and also looked at summing cables. My brother in law is an electrical engineer and reckons it is possible to make some 4xXLR to 2xTRS cables that would work, assuming I can figure out the input impedance of my Access Virus. Could it?

I don’t know much about balanced / unbalanced / resistors / impedance and all that, so please be gentle.

Any advice or guidance would be greatly appreciated.

Thanks,

D

[Hugh Robjohns]

I agree some kind of passive mixing arrangement would make sense, and if you have someone to hand who can solder a few resistors into connectors that would be the way to go.

I would use miniature 1% metal film or metal oxide resistors -- you'll need eight -- and the value should be 470 or 560 Ohms. Then exact value isn't critical but they do all need to be the same.

The resistors need to be soldered into the output XLRs, from pins 2 and 3 in series with the respective hot and cold wires of the output cables.

At the TRS input plug, the two hot wires go to the tip, and the two cold wires go to the ring. The sleeve goes to both cable screens and then connect to pin 1 in the two XLRs.

The idea is that the resistors effectively buffer the outputs of the lexicon and allow the output signals to be passively mixed into the interface input. They'll be a small reduction in the signal level, but since you're combining two lots of signal anyway, that's not going to be an issue. And by mixing the hot sides together seperately from the cold sides you still have balanced signals into the interface.

I'll draw you a diagram tomorrow... If I remember.

[Moroccomoose]

No need to ditch the 32 bit vsts to control the MX400.

I use jbridge which is 64 bit a wrapper for 32bit vsts. It works perfectly.

There is a 'gotchya' though. When I first tried it, only one vst would work at a time. As soon ad you opened the second one it said the device was un-available.

However with a little digging, there is a behind-the-scenes tweak you need to make so you can have both vsts operational in dual stereo mode.

It was a while back when I sussed it, but if you want to try that, let me know and I'll try and see what I did. ( basically jbridge has a txt file that accompanies each vst which has all the options. One setting needs tweaking)

Stu.

[Darclinc]

I agree some kind of passive mixing arrangement would make sense, and if you have someone to hand who can solder a few resistors into connectors that would be the way to go.

My brother in law kindly offered to make them for me. I haven’t soldered anything before in my life so that’s a plus. He just wanted to know whether the various ins and outs are balanced / unbalanced and what the input impedance of the virus is, as this is where the Nord to Lexicon is currently routed to, i.e. Nord into Lexicon input, Lexicon outputs to Virus input. From the Virus it then goes to the soundcard.

I haven’t been able to find this impedance information online though and have mailed access to find out.

I'll draw you a diagram tomorrow... If I remember.

If you could that would be very nice indeed ! The rest of your post is almost Greek to me, but I’m sure my brother in law will understand it perfectly.

Thanks for the advice, as always.

D

[Darclinc]

No need to ditch the 32 bit vsts to control the MX400.

I use jbridge which is 64 bit a wrapper for 32bit vsts. It works perfectly.
Stu.

Hmmm .. interesting. I have and have used Jbridge for years, but to port 64bit plugs to 32 bit Cubase. So I can do this the other way round?

Do you also have this multi FX unit then?

There is a 'gotchya' though. When I first tried it, only one vst would work at a time. As soon ad you opened the second one it said the device was un-available.

However with a little digging, there is a behind-the-scenes tweak you need to make so you can have both vsts operational in dual stereo mode.

I’ve found this already with Cubase 32 bit, i.e. one plugin being ‘unavailable. Weird, as it never used to do this. If you can tell me how you did it that would be great. It would still be useful to have these plugins available in Cubase 64, purely for recall purposes.

Thanks !

D

[Hugh Robjohns]

I haven’t been able to find this impedance information online though and have mailed access to find out.

In this situation it really doesn't matter. As long as the input impedance is around 5 to 10 times higher than the source impedance, all is good in a voltage-matched system like this. In this case, the source impedance is the output impedance of your sources (probably 100 Ohms or less) plus the 470 Ohm mix resistors -- so definitely less than 1K ohms. The input impedance of most line level gear is at least 5K, and usually 10, 22, or 47K (or more)

So here's the diagram. This is for two channels mixed into one. Obviously, you'll need to make a second set for the second channel. If you wanted to mix more channels, just add more input XLRs and resistors... although you would probably need to increase the resistor values a bit...

Hope that helps.

H

[Darclinc]

Thanks Hugh !

Your help is greatly appreciated.

D

[Moroccomoose]

Hi Darclinc,

I have the non XL version which has TRS I/O instead of XLR.

To get the jBridge to work with both the 'A' and 'B' vst plugins, obviously first you need to created appropriately bridged versions.. i.e. 32 bit to 64bit.

Create an instance of the bridged 'Lexicon A' vst in a DAW, open the GUI and click the 'Settings' button in the jbridge border.

Click on the Edit settings button and a notepad file will open. You will see each setting named in text with a 1 or 0 at the end. Change the following line to read:

RUN_IN_EXISTING_AUXHOST 1

ensuring there is a 1, not a 0 at the end.

Save the notepad and repeat the same procedure for the 'Lexicon B' vst.

You may need to reload the vst into the DAW or even restart the DAW.

This is a one time fix, so you shouldn't have to do it again.

Remember to make sure that you have the Lexicon Mx400 control midi channel set to inactive.

Hope this helps

Stu.

[Darclinc]

Tx for the detailed information, Stu!

I will try this once all the rest of my software is up and running and summing cables installed.

Regards,

D