+4dBu to -10dBV line attenuation?

[Cableaddict]

I need to make a simple U-Pad, to convert a 600 ohm balanced signal from +4dBu to -10dBV

I can't for the life of me figure out the calculation.

Can someone help a brother out?


- THANKS.

 

[CharlieLaub]

Helpful web page for you:
Convert between dBu dBV and RMS Volts

 

[Cableaddict]

Thanks, Charlie.

Good info there. However I already knew that I need 11.78 db attenuation. I should have included that in my first post.

What I need is the correct resistor values, again for a simple balanced 600 ohm line.

 

[rayma]

I need 11.78 db attenuation.

T-Pad / H-Pad Calculator - Resistor Values for Attenuation

 

[Cableaddict]

Thanks Rayma, but I'm not making a T or H pad.
I don't need to convert impedance and I need to do this inside an XLR plug.

Again, I want to make a U-Pad. There may be a way to interpolate from the H-Pad numbers, but I don't know how.

 

[rayma]

Again, I want to make a U-Pad.

http://3.bp.blogspot.com/-NH_cxciYf...T4IBGMLdKnQ/s1600/balanced_pad_attenuator.png
Uneeda Audio - Build your own attenuator pads

 

[rayma]

Similar to an L pad calculation, but split the input resistor into two equal parts,
each half the value calculated.

 

[PRR]

12dB is 4:1. This is approximately a voltage divider made with two resistors of 3:1 ratio. (1.5+1.5:1 for balanced.) You can do it on a very large matchbook.

 

[AndrewT]

I need to make a simple U-Pad, to convert a 600 ohm balanced signal from +4dBu to -10dBV

I can't for the life of me figure out the calculation.

Can someone help a brother out?


- THANKS.

Helpful web page for you:
Convert between dBu dBV and RMS Volts

A Jensen app note has the resistor network for this conversion.
I don't remember which one. There are over a dozen, so it will take some searching.

 

[Cableaddict]

SO.....


No one can just calculate the values?


I'm totally stuck here.

 

[rayma]

No one can just calculate the values?

For a matched 600R source, with the output -12dB (with a light load),
the series resistors are each 150R, and the shunt resistor is 300R.

 

[AndrewT]

A Jensen app note has the resistor network for this conversion.
I don't remember which one. There are over a dozen, so it will take some searching.

I had a look through my Jensen AN last night and did not see the resistor network.
Maybe it was another of the balanced retailers that published it.

I do remember having to work through it because intuitively it did not make sense. Took a little while to understand why they placed the resistors in the arrangement they showed.

 

[Cableaddict]

Thanks, Rayma !


- And thanks to all for the help.

 

[rayma]

Thanks, Rayma ! And thanks to all for the help.

Remember this calculation relies on the source impedance being 600R,
and also the load being >>300R (say at least 3k or more).

 

[PRR]

..... No one can just calculate the values?

I just did. The "true 600r" case and a more real-world case around 2,400r.

Is my image not showing for you?

 

[Blues]

Two L-pads connected in Balanced mode. Try 2250R for the 2 series resistors and 750R for the 2 shunts with their midpoint connected to audio ground. Input/output impedances are 6000R and 1125R Balanced respectively.

SO.....


No one can just calculate the values?


I'm totally stuck here.

 

[jvhb]

I just did. The "true 600r" case and a more real-world case around 2,400r.

Is my image not showing for you?

Nice walkthrough/example. Textbook quality stuff

 

[PRR]

Textbook quality stuff

It's a matchbook size problem. Dunno why it needed so much thread space.

 

[Blues]

Design decisions!

If you want to keep the 600R output Z of your source (to keep its character, allegedly into your preamp) use 1200R for series resistors and 400R for shunts. It's still a healthy 3200R balanced load...5.33x.

 

[Cableaddict]

It's a matchbook size problem. Dunno why it needed so much thread space.

Well, I have a matchbook-sized understanding of such things.

But actually, given the somewhat wide swing in the responses, maybe it's not really so simple?