Digitally controlled Baxandall?

[Steven]

What I meant by question 1, however, was if the signal to the top-most attenuator would be different from what the filter tries to output (yes I was thinking active filters). You might have answered that already, but I'm not quite sure

Hmmmm, now I am wondering about what you meant.

Anyway, about the simpler method:
What I mean is that if you intend to use relays for control of the volume and tone (different from your initial question about integrated digital potmeters, at least that was what I understood), then you might end up with less relays if you just use an ordinary Baxandall tone control with a few relays to make the required steps. A volume control is something else; it needs maybe 30-60 steps and then it makes sense to use a binary control in dB. The number of tone control steps is probably far smaller, a few steps up, a few down. Then, if you use three separate volume controls for low/mid/high you will use more relays than would have been required for one volume conrol and some additional for the tone controls.

Steven

 

[BoGoMiPz]

Originally posted by Steven
What I mean is that if you intend to use relays for control of the volume and tone (different from your initial question about integrated digital potmeters, at least that was what I understood), then you might end up with less relays if you just use an ordinary Baxandall tone control with a few relays to make the required steps. A volume control is something else; it needs maybe 30-60 steps and then it makes sense to use a binary control in dB. The number of tone control steps is probably far smaller, a few steps up, a few down. Then, if you use three separate volume controls for low/mid/high you will use more relays than would have been required for one volume conrol and some additional for the tone controls.

Aha, that's actually a thought I've been thinking myself. A volume control would need 6-8 relays, while each 'pot' in a tone control could use 3 or 4. I think it would be great to have 16 positions, 8 boost and 7 cut settings. But how can one get 16 positions using 4 relays?

Looking at the earlier mentioned baxandall circuit, the pot at the bass side could be implemented as shown below. This, however, would only give 4 positions with 4 relays! (and it won't have a center position unless one uses an odd number of relays)

It is of course possible to improve this by using DPDT relays, but that's still not ideal, because dual relays could be used to control left and right channel simultaneously.

Is there a better way to make use of the 4 relays, anyone?

-truls