buffer or not buffer on vu meter after passive DI

[ratrace]

Hello all,

I'm asking myself if when i use a little mic preamp (preamp) for driving some VU meter (wf1029x) after a passive DI (lunhall 1935), do i need fome kind of buffer between the vu mic preamp and the ll1935 out ?

In other words : does the vu mic preamp will induce some sound and/or impedance changes to the mic preamp that i will use for recording the DI out ?

Just for being more clear the vu mic preamp is only here for driving the vu meter, not for recording audio.

Thank's!

Bests regards to all!

 

[JohnRoberts]

It depends on the VU meter. Old school true VU meters have rectifiers inside that can present non linear loads that could express as distortion with other than low impedance sources.

the wf 1029x link says "The VU meter reads 0db at 1.228V +/- 10% trough an external 3.6k resistor" this sounds like it does have rectification inside.

The distortion caused by this rectification is not likely to be very audible but could be measurable.

JR

 

[emrr]

....and a DI will likely not make a signal large enough to register significantly on a VU meter.....

 

[ratrace]

i think i wasn't clear enough, i want to implemant un simple mic level preamp ONLY for driving vu meter in parallel with the DI XLR output that goes to a mic preamp for recording.

 

[ruffrecords]

Unfortunately the schematic you posted will not work. A balanced signal only exists between the hot and the cold pins. The third pin is for cable screening only and is not a signal connector. You need to make your VU mic pre have a balanced input.

The VU mic pre itself will buffer the input from the VU meter. You just need to be sure your DI box output can drive two balanced inputs in parallel.

Cheers

Ian

 

[ratrace]

this preamp is unbalanced, so do yo said it will "broke" the balacing that is provided by the ll1935 for the record mic pre ?

 

[ruffrecords]

this preamp is unbalanced, so do yo said it will "broke" the balacing that is provided by the ll1935 for the record mic pre ?

What I am saying is there is no signal between the two wires the VU preamp is connected to so you will not get a reading. What mic preamp are you using? Why not connect the VU meter to its output?

Cheers

ian

 

[ratrace]

it's for a live situation where the VU meter is in the same box as the DI and the preamp is the built in one from a sound card that is far away from the DI and VU enclosur.

 

[sodderboy]

You are better using your ears, gain stage it during sound check, set it and forget it. Trying to VU an instrument pre compression will either show little, or be bangin’ the needle.
Make something more useful with the saved time/¥.

Mike

 

[ratrace]

thank you for your advice but it is for the musician and for esthetique purpose.

the gain staging is allready done and all good don't worry, we are out from 2 weeks residence.

 

[ratrace]

if you want all the story, the DI are in a midi controler custom made for an electronic artiste.
the DI are for the 3 synth on stage (boog, prophet 8 and ms10) the signal goes into RME sound interface wich is in backstage.

 

[ruffrecords]

OK, what you need to do is change the VU meter preamp to have a balanced input. What power supplies voltage(s) do you have available?

Cheers

Ian

 

[ratrace]

i got 5V, but i plan to uplift this to 9V (with the positiv half from this design) for a brighter light on the VU.

 

[ratrace]

OK, what you need to do is change the VU meter preamp to have a balanced input. What power supplies voltage(s) do you have available?

Cheers

Ian

maybe i could add a neutrik nte1 between LL1935 out and VU pre ?

 

[ruffrecords]

maybe i could add a neutrik nte1 between LL1935 out and VU pre ?

That would certainly address the balanced input problem. You might as well get some free gain by choosing the NTE4 version and because the signal level is low I would recommend you use the NTM4 version which is screened.

Cheers

Ian

 

[ratrace]

Thank you Ian!
i give you feedback when it's done!