+4dBu to -10dBv Switching

[RSRecords]

Looking for a circuit to switch between the 2 ref levels. Balanced +4 and unbalanced -10dBv. I hoped to find a simple circuit to to be able to switch between the two I haven't found anything yet. Would it just be a 12db attenuator for the -10dBv?

 

[RSRecords]

found this from a mackie 1402vlz input. Pretty simple with the 2kOhm resistor to ground. going to steal it! Still looking for an a simple output though.

 

[JohnRoberts]

Since you didn't say, can I ASSUme you are talking about modifying an input to accommodate both +4 dBu balanced inputs and unbalanced -10 dBV (note the capital letter V denoting a 1V 0VU reference).

If you can accommodate balanced/differential inputs, the level difference is the obvious issue.

First, what is the nominal 0VU after this stage? that will determine if you need to add gain, or pad down too much level.

JR

 

[merlin]

+4dBu = 1.22V rms
-10dBV = 0.31 Vrms

So yes, you could use a simple pad with a loss of 0.25 or -11.9dB.
Unbalancing should be taken care of at the input connector, nothing to do with the pad surely?

 

[ruffrecords]

Here is the schematic of a small PCB I designed to fit on nominal +4dBu balanced outputs that allow the level to be switched from +4dBu to -8dBu (-10dBV). Assuming to final load is a 10K line input then the balanced output needs to be able to drive a 2K4 load.


Cheers

Ian

 

[Newmarket]

All good - but is it not preferable to simply accept the nominal balanced +4dBu signal then attenuate to the required line level? Assuming voltage rails are good for this.

 

[RSRecords]

Ok I was over complicating per usual. Current design operates at +4 but I wanted to allow for connections to -10 unbalanced equipment.

Outputs are impedanced balanced, so I'm not sure how that will affect things.

I'll draw up the schematic and see where I eventually get lost.