Yamaha DTXpress/DTXplorer/DTXtreme

--- In DTXpress@yahoogroups.com, "jdamph" <jdamp@...> wrote:
>
> --- In DTXpress@yahoogroups.com, "Keith" <keith@> wrote:
> >
> > Jeff,
> > 
> > I have put a new circuit in the files section to make it clear where
> > the capacitor goes.  If you use a polarised capacitor then the
> > positive side should go to the collector.
> > 
> > Keith.
> >
> 
> Ah I didn't see your post until just now.  I figured out where it 
> needed to go, I was just going to post what I did.  Since the KP65 
> already has a 1k resistor and a trimpot, the circuit is more 
> responsive without R1 and VR1.  If you are building your own trigger 
> you would want to have at least a 1k resistor and trim in the 
> circuit.  I experimented with different caps and 1uf to 4uf seems to 
> be a pretty good range.  No missed hits and the sensitivity is 
> excellent.  I also found that the 2N3904 transistor felt a little 
> better than the 2N4401 but both work well.  Light taps will now 
> consistently be recognized by RB.  I have the trim all the way up on 
> the KP65 without double hitting but still plenty sensitive.  I also 
> created a Darlington pair circuit with caps and it felt about the 
> same as the single transistor circuit with cap. 
> 
> Keith thank you very much for taking the time to draw up the circuits 
> on what is pretty much an off topic subject.
>

I am glad it is now working.  The 2N3904 has higher current gain at
low currents, so that may be why it is a little better.  I guess there
is some debounce on the switch inputs which was making it miss short
pulses.

The subject is not too far off topic - it has part of a DTXpress kit
in it!

Keith.