Wiring Uraltone Rotary Switches

[Bonsaimaster]

Can someone help me with the wiring of the uraltone switch for a volume attenuator. I have a 4 wafer switch with two wafers for  resistors and two wafers with two tabs. No sure how to wire them I have using a balanced signal so do I need to use 4 sets of resistors?

Thanks
Bonsaimaster

 

[abbey road d enfer]

There are several types of "Uraltone" switches. Point us to the relevant webpage.

 

[Bonsaimaster]

Here is the first and second wafer

 

[Bonsaimaster]

Second wafer

 

[Bonsaimaster]

Entire switch

 

[druu]

try this:

http://analogmetric.com/download/24%20Step%20Ladder%20Type%20Attenuator%20User%20Manual.pdf

 

[abbey road d enfer]

What you have is a 2P24T type, i.e. 2 pole-24 way
With that you may build the equivalent of a dual potentiometer. You can control two balanced signals with it but it won't be a dual balanced attenuator.
You can wire it as a double-L attenuator, which would be balanced.

What is it you want to do? How many signals do you want to control? Does it really need to be balanced (or just usable with balanced signals)? What is the signal source? Where does it go?

 

[rainton]

Yes some more info would be important.
If you want to build a ladder step attenuator as in the link above it would be an "equivalent" to a mono pot.
If you want to build an "equivalent" to a stereo pot it'll have to be a series step attenuator or you'll need to buy a different switch with more wafers...

 

[abbey road d enfer]

If you want to build a ladder step attenuator as in the link above it would be an "equivalent" to a mono pot.
If you want to build an "equivalent" to a stereo pot it'll have to be a series step attenuator or you'll need to buy a different switch with more wafers...

No. With an SPxT one can build an L-pad. The shown rotary switch can be wired as a stereo pot.

 

[s2udio]

No. With an SPxT one can build an L-pad. The shown rotary switch can be wired as a stereo pot.

Absolutely
Just done 4 stepped stereo ones with exactly those switches...

Used this calculator to get all the values...windows only though
"program to design stepped volume controls", go to bottom of page
http://tonnesoftware.com/miscellany.html

 

[Bonsaimaster]

I got the resistor values for the required impedance. I am using it to control the output of a summing mixer. It will control two balanced signals that will then be routed to XLR connectors. So which is better 4 wafers (sections) or 2?

Thanks
Daniel

 

[abbey road d enfer]

I got the resistor values for the required impedance. I am using it to control the output of a summing mixer. It will control two balanced signals that will then be routed to XLR connectors. So which is better 4 wafers (sections) or 2?

Thanks
Daniel

Can you post a schemo? I'm not sure you realize that placing a variable attenuator at the summing node is not really good practice. Traditionally (and with good reason) the summing node goes to a controlled-impedance active device and any final level control is done after this active stage.

 

[Bonsaimaster]

Here is the idea

 

[abbey road d enfer]

Here is the idea

What is connected at the primary of the transformer?

 

[Bonsaimaster]

A twin line amp

 

[abbey road d enfer]

A twin line amp

??? I don't see how this integrates in a summing box...

 

[Bonsaimaster]

DB25 ----> Twin Line Amp ----> VTB2291 ----> Attenuator ----> XLR output

 

[abbey road d enfer]

DB25 ----> Twin Line Amp ----> VTB2291 ----> Attenuator ----> XLR output

OK, so now I got it (almost). DB25, is it the mix nodes of the summing box?
What is the expected level at the output of the "twin line amp" ? What is the structure of this "twin line amp"? Tube or SS? What is its output impedance?
Supposing the level is comfortable (>-20dBu) with a low output impedance, the attenuator can be a twin L-pad, so two wafers.
If it was not the case and you need to make the input impedance of the attenuator constant, you would need one more wafer per channel so 4 in total.