[sdiy] Tube signal conditioner ?

[Matt Jones]

--- Michael Buchstaller <buchi at takeonetech.de> wrote:
> Hello friends,
> 
> i am on the quest for some kind of Schmitt-Trigger
> or
> Comparator that allows me to clean up a possibly
> noisy
> signal to an exact 0/1 level.
> 
> Purpose of this is for my tube DAC. At this moment,
> i am using
> tubes to amplify the TTL output from my digityl
> circuitry to drive
> a R/2R ladder. But, TTL seems not to have very exact
> signal
> lexels (H is anywhere between 3.9 and 4.4 V, L
> between 0.4 and
> 0.9 V) between outputs of different chips.
> 
> So, i want to make some kind of "hard switching", by
> means of a tube.
> How can i achieve this ? OK, i have the schematics
> of that old philbrick
> tube opamp, and could use it as a comparator, but i
> feel there must be
> a more simple solution for that.
> 

Your best bet is to switch the tube drivers to CMOS
devices - if you keep the load small, they will 
swing much closer than the TTL gates will.

One problem comes to mind - I don't recall tubes
having
a very predictable "saturation" (transistor term) 
voltage. This may cause problems with driving the 
ladder.. just a thought.

  --mdj


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