Calrec advanced gain issues teaser

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Dr nEon

Well-known member
Joined
Jan 11, 2006
Messages
232
Location
Grate Britain
Hi all!

Could someone very kindly explain/confirm what is going on here!:

Last year i built a dual calrec . In itself it works fine, I love it .

I originally had it hooked up to my soundcraft 2400 unbalanced patchbay , using some high quality xlr to bantham flying leads .

The input resitors r1 and r2 were 10K , but I wasn't experiencing the higher gain issue that most people were reporting.

Until now!

i have just finished wiring my new rack bays to the fx edacs on the 2400 , and been very careful to observe the correct procedures re screening . i.e attaching screen to the correct end , going from bal to unbal etc..

And now I get the 6db or so gain boost!

I am aware that 22k resistors are the solution , but my question is why did i not experience it when using flying leads?

The only thing i can think of is that the flying leads have the screen attache d at each end , and my permanant installation wiring doesn't .

That is truly the only thing different , but if it is that , then could someone explain how it works , please!?


Cheers

nEon.
 
That depends on how you connect balanced output to unbalanced input.

See for reference :
http://www.rane.com/note110.html

Look at 9b connection, this is what you get when you connect a balanced output to an unbalanced output with a TRS/TRS balanced cable, the - pin is not connected on the TS unbalanced input (because this connector has not contact to mate the ring of the TRS connector), in this case you loose 6dB.
 
Thanks for that info ,Keefaz .

It has slightly confused me though , because it goes against what the original soundcraft manual says , which i've followed in my wiring.

Basically , the fx return edacs have a single pin for each patch point , and a whole bunch of pins which are commons . Its an unbalanced bantham bay.

From the balanced end , xlr pin 2(+) goes to the edac signal pin , and pin 3 (-) goes to one of the common pins ...and the shield goes to either xlr pin 1 ,or ties with the common at the edac , dependng on which way the signal is going.


The info you gave me has made me start to wonder if I should be doing it differently .


I replaced the input resistors on the calrec last night , and it cures the gain boost (infact I'm now 0.8 dB down on output) , but this has done something serious to the sound of the calrec.

I have been using it for a year , I hand matched every component to try to build two identical channels ,hoping to use it over the mix bus sometimes . It has been sounding stunning , all the time sitting near the patchbay on short leads . But now that I've racked it in properly , and done the 22k resistor mod , when I a/b it over a reference cd , it seems to be choking the sound , reverb tails go , width goes , whereas before it was transparent.This is just switching it in and out with the eq flat.

It actually sounds like something to do with impedance .

What do you think?

This one has got me real foxed , because I love the unit , and was just about to start mixing with it ,and didn't expect that I was gonna encounter any of this , just by properly installing it into my rack.


Thanks again!

nEon.
 
When going from balanced to unbalanced and vise versa. I usually will wire up all 3 pins on the balanced and on the unbalanced side do not connect pin 3 at all. so unbalanced would be pin 2 as hot or tip and pin 1 as sleve,shield.
 
Ok, thanks pucho!

Well it does seem my wiring isn't correct !

The weird sound I described is nothing to do with impedance . What I'm suffering from is Severe crosstalk between the L&R outputs on the calrec . But the calrec itself is fine.

I spent all day yesterday reading up on bal/unbal connections, from various sources including the rane diagrams...and I realize now what an absolute can of worms this subject is !!!

BTW since I found the crosstalk problem , and knowing that I've wired all of my racks bal xlr connections to the unbalanced patchbay in the same manner , I set about checking if this problem existed on other units as well , and it does....
:cry:

In the two suggestions you guys have made , the idea is basically to leave pin 3 disconnected , and connect the screen at both ends..

Unfortunately , seeing as I have already wired everything with the screen only connected at one end , I am stuck with having to use the cold conductor as part of the signal path.

So...I can either move the cold conductor from pin 3 to pin 1 and basically have what you guys are suggesting,

..or I found that if I leave my wiring as it is , but link pin 3 to pin 1 on the xlr end (therefore grounding the cold) , then this cures the crosstalk problem.

BUT... having read a lot more about it , I'm learning that I need to know what kind of balanced outputs I'm dealing with !

So , on the calrec eq , and GSSL , are these "quasi floating balanced " out puts , and is that the same thing as a differential output ?


Cheers


nEon
 

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