Yamaha DTXpress/DTXplorer/DTXtreme

I have assembled the "cheap DTXpander" circuit that Keith posted to 
this site recently and have had partial success with it.
A mono trigger wired to input J3 plays the "pad" sound fine. 
My problem is with input J1 and it's related circuitry: a mono trigger 
wired to input J1 will only play a "rim" sound on a hard hit, on a soft 
hit it plays the "pad" sound. Naturally, I want J1 to play the rim 
sound all the time, and with at least some dynamic range. Tweaking my 
DTX 2.0 brain did not help.
If anyone out there has tried this neat little circuit with different 
results, or has any ideas on circuitry modifications, please post.
Thanks
Phil
P.S. Many thanks, Keith, for your hard work.

--- In DTXpress@yahoogroups.com, "plhalli" <phalli9966@a...> wrote:
> I have assembled the "cheap DTXpander" circuit that Keith posted to 
> this site recently and have had partial success with it.
> A mono trigger wired to input J3 plays the "pad" sound fine. 
> My problem is with input J1 and it's related circuitry: a mono trigger 
> wired to input J1 will only play a "rim" sound on a hard hit, on a soft 
> hit it plays the "pad" sound. Naturally, I want J1 to play the rim 
> sound all the time, and with at least some dynamic range. Tweaking my 
> DTX 2.0 brain did not help.
> If anyone out there has tried this neat little circuit with different 
> results, or has any ideas on circuitry modifications, please post.
> Thanks
> Phil
> P.S. Many thanks, Keith, for your hard work.

The DTX 2.0 will not adjust your way out of this problem.  Have you
got an output adjustment on the pad itself?  If so, increase the pad
signal as much as pissible using it.  Another possibility is to
reverse the connections from the pad (a bit of a long shot, but you
want the positive going peak first).

If neither of those suggestions don't work then unfortunately you will
need the complicated circuit - with gain on the rim detect.

Keith.

Keith, PFozz, plhalli, et al:

First off, I'm a regular poster on DIYedrums, but maybe I should pay more attention to the DTX groups :)  Keith, fabulous work!  We all knew it was possible...  Thanks for doing what we were too lazy to figure out hehe

Anyway, I tried out your circuit last night (with a Roland TD-7t box and pads), but I had bigger problems...  The main pad (J3 in the pdf) was severely cut down on the sensitivity, and same as plhalli, the rim pad (J1) was sensitive enough, but wouldn't trigger the switch for lighter hits.

My dad, who is much more of an electronics guy than I, first shorted out the diode on the main pad (D2, essentially removing it from the circuit) which cured the sensitivity problem on the main pad.  I might have had the polarity flipped, so the first spike was negative, but removing the diode seemed to bring sensitivity back to normal without adversely effecting the rest of the circuit.  I understand the idea behind this diode (half-wave rectifying), but it's apparently useless, atleast for Roland boxes...  Any idea what the deal is?

To cure the high threshold on the switch, I adjusted the resistance of R1 down.  I brought it all the way down to 1.5k, and now it works GREAT for all hits that can be heard, and I cannot get it to false-trigger the switch on the main pad.  It DOES get confused for VERY light hits, but they're so light that I can't even hear the sound, and the only way I can tell it's messing up is to go into the trigger editting screen, where I can see what's being triggered.  When I build your circuits for use on my kit (instead of on breadboards), I'm going to put pots in there so I can adjust the thresholds.  So, plhalli, since you're having this issue too, try lowering R1's resistance.


Again, thanks Keith!!


--- In DTXpress@yahoogroups.com, "Keith" <keith@k...> wrote:

> --- In DTXpress@yahoogroups.com, "plhalli" <phalli9966@a...> wrote:
> > I have assembled the "cheap DTXpander" circuit that Keith posted to 
> > this site recently and have had partial success with it.
> > A mono trigger wired to input J3 plays the "pad" sound fine. 
> > My problem is with input J1 and it's related circuitry: a mono trigger 
> > wired to input J1 will only play a "rim" sound on a hard hit, on a soft 
> > hit it plays the "pad" sound. Naturally, I want J1 to play the rim 
> > sound all the time, and with at least some dynamic range. Tweaking my 
> > DTX 2.0 brain did not help.
> > If anyone out there has tried this neat little circuit with different 
> > results, or has any ideas on circuitry modifications, please post.
> > Thanks
> > Phil
> > P.S. Many thanks, Keith, for your hard work.
> 
> The DTX 2.0 will not adjust your way out of this problem.  Have you
> got an output adjustment on the pad itself?  If so, increase the pad
> signal as much as pissible using it.  Another possibility is to
> reverse the connections from the pad (a bit of a long shot, but you
> want the positive going peak first).
> 
> If neither of those suggestions don't work then unfortunately you will
> need the complicated circuit - with gain on the rim detect.
> 
> Keith.

--- In DTXpress@yahoogroups.com, "Chris Todesco" <desco911@y...> wrote:
> Keith, PFozz, plhalli, et al:
> 
> My dad, who is much more of an electronics guy than I, first shorted
out the diode on the main pad (D2, essentially removing it from the
circuit) which cured the sensitivity problem on the main pad.  I might
have had the polarity flipped, so the first spike was negative, but
removing the diode seemed to bring sensitivity back to normal without
adversely effecting the rest of the circuit.  I understand the idea
behind this diode (half-wave rectifying), but it's apparently useless,
at least for Roland boxes...  Any idea what the deal is?

I don't know what Rolands expect - only the Yamaha.  I know all the
Yamaha pads I looked at have a positive going pulse first, and that
one is often considerably larger than the negative going half cycle
which is later, so polarity is important.  D2 doesn't do a lot - just
provide some symmetry between the two halves, so no harm in removing
it.  It shouldn't be detrimental if the polarity is correct, unless
the Roland pads are a bit feeble in their output signal where the
volts drop could matter.  D1 is essential otherwise the rim trigger
will trigger from either pad.

> 
> To cure the high threshold on the switch, I adjusted the resistance
of R1 down.  I brought it all the way down to 1.5k, and now it works
GREAT for all hits that can be heard, and I cannot get it to
false-trigger the switch on the main pad.  

Depending on the transistor you have used, you may blow it up with
excess base current with 1.5k - you can get > 20V out of the Yamaha
pads.  Still, transistors are cheap.

> It DOES get confused for VERY light hits, but they're so light that
I can't even hear the sound, and the only way I can tell it's messing
up is to go into the trigger editing screen, where I can see what's
being triggered.  

This will always be a issue, even with more sophisticated circuits.

When I build your circuits for use on my kit (instead of on
breadboards), I'm going to put pots in there so I can adjust the
thresholds.  So, plhalli, since you're having this issue too, try
lowering R1's resistance.

I am pleased someone is finally getting a chance to use the simple
circuit.  When I get chance I will do some more work on it.  I think
that somewhere between the rather simple circuit I have posted, and
the complicated one I have also built, there is probably a good
compromise, with better performance than the simple one but not as
complex and expensive as my other one.

Keith.

--- In DTXpress@yahoogroups.com, "Keith" <keith@k...> wrote:

It was getting late last night and I forgot about the real reason for
D2 - to stop one pad loading the other.  Without it, the signal from
the pad with D1 will be halved due to the load from the other pad.  I
will try to get hold of a Roland pad to test, but I think it sounds
like the polarity is different.  Certainly some of the Yamaha pads
have very little negative going pulse (e.g. the kick pad, from memory)
due to the lack of mechanical resonance and high damping.  If this is
the case with the Roland pads, but negative going, the circuit will
only work well with the pad polarity reversed, but then this will not
drive the Roland module well if it is expecting negative going pulses.

If I can get hold of a Roland pad I will check and may be able to
devise a different cirucit for Rolands.

Keith.

--- In DTXpress@yahoogroups.com, "Chris Todesco" <desco911@y...> wrote:
> Keith, PFozz, plhalli, et al:
> 
> Anyway, I tried out your circuit last night (with a Roland TD-7t box 
> and pads), but I had bigger problems...  The main pad (J3 in the pdf) 
> was severely cut down on the sensitivity, and same as plhalli, the rim 
> pad (J1) was sensitive enough, but wouldn't trigger the switch for 
> lighter hits.

I have managed to get my hands on a Roland tom pad for a quick test. 
While the polarity is negative, there is plenty of positive going
signal as well.  However, if the Roland module only takes notice of
the negative going signal, a diode as I have drawn it would be a bad idea.

Could you try something?  Fit both D1 and D2, but the opposite way
round to my diagram!  This should give the isolation between the two
piezos, still drive the transistor for the rim switch and allow the
negative pulses through for the Roland module.

Keith.

I'll try all combinations, but right now, the breadboard's over at my father's, so I'll have to wait for the weekend to get to it.  Bear in mind, I don't really know which way the polarity of my pads are...  They're old Roland PD-31s, but I assume they always to ceramic-to-the-tip so the first peak is positive-leading.  He has an oscilliscope, so we can hook it up and figure out the polarity.  But like I said, only removing D2 seemed to do the trick, and both pads had the same sensitivity to a "control" pad hooked straight in.



--- In DTXpress@yahoogroups.com, "Keith" <keith@k...> wrote:

> 
> I have managed to get my hands on a Roland tom pad for a quick test. 
> While the polarity is negative, there is plenty of positive going
> signal as well.  However, if the Roland module only takes notice of
> the negative going signal, a diode as I have drawn it would be a bad idea.
> 
> Could you try something?  Fit both D1 and D2, but the opposite way
> round to my diagram!  This should give the isolation between the two
> piezos, still drive the transistor for the rim switch and allow the
> negative pulses through for the Roland module.
> 
> Keith.

I also meant to ask-- I had mentioned that I adjusted R1 to make the rim switch more sensitive, but on edrum.for.free.fr it says to adjust R2 (for the piezo/piezo-to-piezo/switch circuit, not the two-mono-pad citcuit)...  Is there a difference, or is R1 just adjusting one side of the threshold, and R2 is adjusting the other so in effect it's the same thing?




--- In DTXpress@yahoogroups.com, "Keith" <keith@k...> wrote:

> 
> I have managed to get my hands on a Roland tom pad for a quick test. 
> While the polarity is negative, there is plenty of positive going
> signal as well.  However, if the Roland module only takes notice of
> the negative going signal, a diode as I have drawn it would be a bad idea.
> 
> Could you try something?  Fit both D1 and D2, but the opposite way
> round to my diagram!  This should give the isolation between the two
> piezos, still drive the transistor for the rim switch and allow the
> negative pulses through for the Roland module.
> 
> Keith.

--- In DTXpress@yahoogroups.com, "Chris Todesco" <desco@m...> wrote:
> 
> I also meant to ask-- I had mentioned that I adjusted R1 to make the
rim switch more sensitive, but on edrum.for.free.fr it says to adjust
R2 (for the piezo/piezo-to-piezo/switch circuit, not the two-mono-pad
citcuit)...  Is there a difference, or is R1 just adjusting one side
of the threshold, and R2 is adjusting the other so in effect it's the
same thing?
>

You can do either.  Increasing R1 would have a similar effect to
decreasing R2.

Keith.