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?
+4dBu to -10dBv Switching
- Thread starter RSRecords
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Help Support GroupDIY Audio Forum:
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
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
ruffrecords
Well-known member
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
Cheers
Ian
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.
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.
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.
Both actually. It a send and a return.
OK and what's the local nominal 0VU?
if +4dBu the input must support up to 12 dB of gain selectively. The output needs a pad (could be passive.
if -10dBV the input needs a pad selectively, the output need boost selectively.
JR
Scope is also an issue. How many I/O of externals, I/O of console? Is this a mod of existing console or a new design? There is no "one size fits all" for bumping.
Would I mod all the aux sends/returns on a mixer to deal with one Alesis Microverb? No, I would address the Alesis not the console, and it will work with any output and input.
If designing a mixer, look for the sescom or any active bump box circuitry, it's opamp 101. A toggle switches between two different resistances in the feedback. I also calculate agg factor of building, and opt for modified ART CLEAN Boxes for connecting phones and laptops to the studio rather than build from scratch.
For -10 synths, old 'verbs, and stereo equipment I use the Ebtech Line Level Shifter. It is a passive device and 8 channels bi-directional -10:+4 so you use the channels as you wish. They have transformers inside, but I never was interested in making my own. The transformer also eliminates all the interface mess with cheesy semi-pro equipment and synths from the 80's 90's. Do you get tons of gain and headroom from a transformer? No, but man, that BOSS reverb sounds sweet. And quiet.
I'm 100% transformer'd with older synths these days, either DI or simple "ground loop eliminators".
Mike
Would I mod all the aux sends/returns on a mixer to deal with one Alesis Microverb? No, I would address the Alesis not the console, and it will work with any output and input.
If designing a mixer, look for the sescom or any active bump box circuitry, it's opamp 101. A toggle switches between two different resistances in the feedback. I also calculate agg factor of building, and opt for modified ART CLEAN Boxes for connecting phones and laptops to the studio rather than build from scratch.
For -10 synths, old 'verbs, and stereo equipment I use the Ebtech Line Level Shifter. It is a passive device and 8 channels bi-directional -10:+4 so you use the channels as you wish. They have transformers inside, but I never was interested in making my own. The transformer also eliminates all the interface mess with cheesy semi-pro equipment and synths from the 80's 90's. Do you get tons of gain and headroom from a transformer? No, but man, that BOSS reverb sounds sweet. And quiet.
I'm 100% transformer'd with older synths these days, either DI or simple "ground loop eliminators".
Mike
