128 step volume controled by relays

[roger-k]

Have a look at:

An alternative attenuator/pot?

[MarekM]

Hi Roger,

What is the adventage of using so many relays for this task?
using 8 relays you are able to build 256 step attenuator.

Regards,

Marek

[roger-k]

Hi Marek

What do you actually mean by that?
I am using 7 relays and have 128 step.
But offcourse I could add one more relay and get 256 step.

[MarekM]

Roger,

Sorry I was not precise. You use 7 double-contact relays, and 14 resistors, which have to be high accuracy ones. The idea I had in my maint was to use one serial resisstor and 8 resistors switchable to ground with following values:
N*2^0, N*2^1, N*2^2... N*2^7. This allows to reduce twice the number of relay contacts and resistors. Nothing special, but it simplifies the circuit :)

Regards,

[roger-k]

Thats right, but I want to use 14 resistors, becorse if I use 8 resistors the circuit is not so flexible.
With 14 resistors the circuit have only two connections.

With 16 resistors the circuit have three connections and it is very easy to replace a conventional pot with the circuit.

I will use relays with two normally closed contacts and two normally open contacts and control both left and right channel with seven relays.