Help me make a stepped attenuator

[fragletrollet]

Hello!

So i got four of these:

https://www.don-audio.com/Elma-Rotary-switch-Type-06

And i want to make them into 1k log switches. They are only 12pos and are going to be used in a summing mixer, so i was thinking to have 2db attenuation pr step ? Seems reasonable? What resistor values should be used? And is this what youd call a series attenuator?

Over to the building process; ive been trying to read up on the theory, but i get confused. Resistors are soldered between the discrete and common terminal? Where is the input and output of the switch, and where do i connect ground?

Also, i once got some resistors that were really small in size, but i believe still 1/4w. What are these called, what search criteria do i input to find them in mousers inventory?

Thanks for any help,

Magnus

 

[bluebird]

What part of the summing mixer is this for? The main stereo output? is it passive?

Look at the picture below showing a pot next to a stepped switch. See how the resistors are mimicking the carbon strip on the pot.

The top of the pot/switch will be connected the output of the summing resistors. The wiper will be going to the output XLR pin 2 with pin three and one to ground for an unbalanced output.  This is just a basic description, I don't really know exactly what you are trying to do. You should post a schematic of the summing circuit.

[edit] I reread your post and you got four switches so are these input switches? More info please.

 

[fragletrollet]

The switches are to be used for volume control for the stereo channels in my dr-2402.

https://postimg.org/image/aakqizvsn/

 

[seva]

I use elma calculator, maybe you can modify the exel table for your application.

search for XLSX:
dB Calculator for A47 Shunt Type Attenuators

 

[rackmonkey]

Hello!

So i got four of these:

https://www.don-audio.com/Elma-Rotary-switch-Type-06

And i want to make them into 1k log switches. They are only 12pos and are going to be used in a summing mixer, so i was thinking to have 2db attenuation pr step ? Seems reasonable? What resistor values should be used? And is this what youd call a series attenuator?

2dB per step is reasonable. The old Daven ladder attenuators which were often used as individual channel controls in high level mixers usually had 1.5 or 2dB steps.  Ladders are just a series of pi networks, so in that sense, yes, they are series attenuators. API used plain old pots for the purpose IIRC but after the output transformer, so not sure if the variable impedance you get with a ladder will be a big deal here or not. But my sense says it isn't.

BT

 

[ruffrecords]

I am not sue you have enough steps to make a sensible fader for this design if you want to create a mix from several sources. If you just want to trim the gain of different channels then it should be OK but a true fader will need a lot more steps and finer ones.

Cheers

Ian

 

[rackmonkey]

From the schematic I assumed it was for a channel.  Agree with Ian if I missed that this is for multiple channels.

BT

 

[fragletrollet]

I am not sue you have enough steps to make a sensible fader for this design if you want to create a mix from several sources. If you just want to trim the gain of different channels then it should be OK but a true fader will need a lot more steps and finer ones.

Cheers

Ian

I understand that 12 steps is pretty rough for a volume control;  however, 12 steps would mean up to 22 db attenuation if in 2db step increments (am I right?), which will be enough for rough volume matching. Reason to use switches is for accurate L/R tracking, I can do more detailed volume adjustments at the source.

 

[fragletrollet]

I use elma calculator, maybe you can modify the exel table for your application.

search for XLSX:
dB Calculator for A47 Shunt Type Attenuators

But a shunt attenuator is different to a series attenuator, no?

 

[ruffrecords]

I understand that 12 steps is pretty rough for a volume control;  however, 12 steps would mean up to 22 db attenuation if in 2db step increments (am I right?), which will be enough for rough volume matching. Reason to use switches is for accurate L/R tracking, I can do more detailed volume adjustments at the source.

Ok, as long as it is for rough volume matching that it will be OK. Just don't try to use it to fade a track!!

Looks like you need a 10K pot version for your application. Don't worry about shunt and series types - these are just buzz words invented by the audiophool community to make themselves sound knowledgeable. You need a regular potential divider. Plenty of on line calculators for those. This one seems to work OK:

http://rssconsultancy.co.uk/atten.html

Just change the pot value to 10000 ohms and the steps to12. Fill in the 2dB steps and press calculate.

Cheers

Ian