Posted: Mon Nov 26, 2012 9:04 am Post subject:
Oh no! Another Hi-Hat!
My goal was to duplicate the sound of the DR-110 HiHat and Cymbal. I simplified the already (fairly) simple design by using four schmitt oscillators mixed for "metal" and a reverse-biased transistor for white noise. The first time around, I didn't quite get the sound I wanted, but it was "close enough" on breadboard that I committed it to perf -- where it failed, convincing me once and for all to never tear down the protoboard before the finished project worked.
Unable to determine what I'd done wrong, the prospect of breadboarding four schmitt oscillators -- and tuning them -- and a white noise source ALL OVER AGAIN was unappealing, so I put the whole idea on the back burner. Then I found The LDB-1 Analog Drum Machine, a pretty cool -- and compact! -- little drum sequencer that uses analog percussion circuits. (Check it out!) In it, Mickey Delp had streamlined the '110 metal-noise generating circuitry by programming an 8-pin PIC to do all that. I persuaded Mickey to sell me one. They cost $4 each plus $2 shipping to the US. If you want to buy one, just contact Delptronics (http://delptronics.com/contact.php). The top portion of the attached schematic shows how I set it up. NOTE the power pins. Pin 1 is +5V and pin 8 is Gnd.
I separated noise from the mix so I could independently set its level for any voice that uses it. In the Roland 606, 808 (which don't use white noise,) and DR-110 (which does,) the mix goes to two bridged-T filters that separate the signal into two bands. I reasoned that starting with the mix at a higher amplitude than in the '110 (four 100k into 560 ohms, as opposed to my 100ks into 4.7k,) passive filters would do the job and their inherent losses would reduce the signal to levels that wouldn't overdrive the simple 1-transistor VCAs. Active filters at the output of each voice would further refine the frequency spectra.
The basic HiHat circuit is simple and by now should be familiar: Two diode-cap-resistor envelope generators; one with short decay for Closed and another with longer decay for Open. I've made the Open Decay adjustable, but not Closed, since by definition Closed is short. The two E.G. voltages supply the collector voltage for a transistor acting as VCA. The metal mix reaches the transistor base through a hpf with a corner freq. rolling off at 6dB/oct. anything below 15.9kHz. (Which means my old ears shouldn't be able to hear anything!) The 470pF cap at the transistor collector shunts the highest of the highs to ground.
The signal from the transistor gets filtered by an Infinite Gain Multiple Feedback filter as hi-pass. The values I used allow tuning from high and thin to low enough to satisfy the most passionate Lovers of Clank -- especially when no white noise is present.
A foot switch paralleling the Decay pot provides a simple mechanism for Open/Closed decay when triggered by OH. The triggering and enveloping could be replaced by something similar to the front end of Thomas Henry's Clangora or Dan Lavin's adaptation. http://electro-music.com/forum/viewtopic.php?highlight=monkey&t=52556 On my breadboard triggers were 5V positive @ 1mS.
The #s in parentheses are the frequencies of the metal oscillators.
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_________________ Revenge is a dish best served with a fork... to the eye Last edited by richardc64 on Mon Nov 26, 2012 3:57 pm; edited 1 time in total
I want to play this HiHat by hitting a pad with sticks, so I added an amplifier and a piezo pad to provide triggering.
I want more control over decay than fully Open or completely Closed, so I replaced the foot switch with a transistor to do that via voltage from a continuous pedal. As a refinement, the pedal voltage is also routed to the amp input by a resistor and capacitor. The effect of this is that if the pedal is pressed smoothly it just affects the decay caused by striking the pad. If, however, it's pressed rapidly the resulting voltage change briefly "jumps" across the cap, creating a low level trigger, which in turn produces the sound of closing the 'Hat without striking it. (Called "Chiff" in drummer's jargon.) The faster (more vigorously,) the pedal is pressed, the louder the Chiff produced, as can be heard in the sample. You will also hear what's called Pedal Splash, the act of rapidly closing the 'Hat then quickly opening it to let the top and bottom cymbals freely vibrate. I'm not skilled enough to achieve that effect consistently, but I've been practicing.
Note that with changes/additions described above, +5V Open triggers had to be routed to the piezo amp input to make pad hits or trigger pulses produce equal output levels. No change to CH was needed.
Again, the metal/noise IC is available from Delptronics (link) While you're there, check out the Little Drummer Boy. http://delptronics.com/ldb1.php The analog portion looks mod-able.
Note that when the output filter is tuned low, the result doesn't sound much like a HiHat, but omit the CH envelope, foot switch or pedal control, and Chiff stuff and you'll have a rather nasty sounding Crash Cymbal. I hope to design a Cymbal circuit that can be adjusted for Ride or Crash, but I probably won't get to that until after the holidays. I have other ideas for the Delptronics metal/noise generator IC.
pad_pedal2.mp3
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Hitting the pad and operating the pedal
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chiff_splash.mp3
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Operating the pedal alone
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hh_111412.gif
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Corrected T-S-R jack & plug
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_________________ Revenge is a dish best served with a fork... to the eye Last edited by richardc64 on Mon Nov 26, 2012 3:42 pm; edited 1 time in total
Joined: Nov 09, 2006 Posts: 649 Location: Spring Lake, Mi, USA
Audio files: 21
Posted: Mon Nov 26, 2012 6:34 pm Post subject:
Thanks Richard for your usual thoroughness and frugal use of components. My circuit would have been 2-3X+ and probably not sound as well! I'm sure the readers here appreciate the full project description which seems to be lacking a bit around here with others projects lately. _________________ Synth DIY since 1977!
Joined: Nov 10, 2011 Posts: 878 Location: Lancashire, England
Audio files: 14
Posted: Fri Nov 30, 2012 11:01 am Post subject:
are you sure you didn't just record a real hi hat there? that sounds great, totally realistic! better than a lot I hear in popular songs. _________________ As a mad scientist I am ruled by the dictum of science: "I could be wrong about this but lets find out"
Hi exagonal. Thanks to you -- and others -- for the positive comments.
Quote:
Can you tell me how i can program this microcontroller for have the source of the sound?
No can do. I am PIC-ignorant. I obtained the micro from http://delptronics.com/contact.php email Mickey Delp. He is also a member here at e-m. _________________ Revenge is a dish best served with a fork... to the eye
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