[sdiy] Tubes in Synths [ was : Harry's Nightmare! ]

[jhaible at t-online.de]

> Has anyone ever built a tube based phaser? 

It's not easy.

At first glance, just build a phase splitter with one tube
to drive a LDR / Capacitor combination per stage.
On second glance, this passive load will vary in a wide
impedance range, and this will interact with the tube's
output resistance @ anode and @ cathode. It's difficult
to build an all pass network with truely constant amplitude
gain this way. So I guess it's quite easy to build a
resonant phaser (with one dominating peak), but difficult
to build a notch phaser with deep notches.

I'm not a tube expert at all. This is just where I stopped to
follow the tube path when I built a univibe-style
(transistor phase splitter) phaser some years ago.
(That was the Neptune Phaser, and it's all transistor in the
end.)

JH.