[sdiy] tonal tilt

[JH.]

>You are mixing R and C values, there,

Mixing?

>The bass circuit does look interesting, too.

Absolutely. You cannot just connect a potentiometer there, though.
I didn't find a value for the bass pot (for the tilt it's 20k linear), but 
with _any_ value, you'd short out the signal on the ccw end.
But then again, the front panel shows less than the usual 270deg of 
rotation, so maybe they just used an ordinary pot and limited the rotation 
mechanically? (You could do the same thing with two fixed resistors on 
either end of the pot, of course.)
But then again (again), the Tilt knob also shows less than 270deg rotation 
on the front panel, but for the printed courves you need the while range of 
the 20k pot given in the schematics.
Whatever. It would be easy to adapt this to a circuit with different 
potentiometer values and full 270deg rotation.
Or to a set of rotary switches.

Thinking of it: Didn't Quad offer Tube preamplifiers with "odd" (and maybe 
clever) filter courves instead of the usal treble/bass stuff, too?
I thought I've seen something like that.

My biggest surprise was
>seeing all those TL071s in the Quad!

My biggest surprise was seeing the 4016 switches.
They do it right, at least: mostly switching against high impedances on the 
"output" side, to avoid distortion from the R(V) or the switches.

JH.