[sdiy] Vacuum Tube Synthesizer Project

[René Schmitz]

Hi Thomas,

Thomas Holley wrote:
> Hello All, I have embarked on a rather ambitious and foolhardy
> adventure. I am building a modular synthesizer using vacuum tubes
> almost exclusively for every module. I have done preliminary design
> work and SPICE simulations to get the parameters narrowed down. I
> have collected up most of what I need to start breadboarding circuits
> and working out the inevitable bugs. I would appreciate any comments
> and suggestions that may help me along and keep me from pitfalls you
> may know about. I have put up a small web page that includes the
> project at: http://users.adelphia.net/~thomasholley/. I will post any
> significant progress on this project as it moves along and keep the
> DIY list informed as I will surely need much advice since I am a
> novice synthesizer person.

Thats quite an agenda! Highly interesting ideas I must say!

I don't want to brake your enthusiasm, but I've seen several circuits 
where you have used AC coupling for the CV signals. That will probably 
not work satisfactorily. A cure for that is to replace those with direct 
coupling, or coupling via a voltage divider. You terminate the divider 
to the negative supply, and choose it so that the following tube sees 
the right grid voltage. Usually you loose some gain in the process, but 
you can also replace the resistors in the dividers by zehner diodes or 
neon stabilizers /lamps to get a DC voltage drop without reducing the gain.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159