Pearl DRX-1 Programmable Electronic Drums  

The Pearl DRX-1 has 5 Instruments which could be triggered by drumpads. Of course you can also feed some trigger-signals into it. All intruments have the same parameters and are therefore sounding identical, although the pitchranges are little different. Beside Bassdrum there is the Snare and 3 Toms. Each has its own trigger-in and an individual out jack, 6.3mm. If you dont use the individual jacks, all sounds are summed together to a stereo-out.

Very solid, professional and expensive hardware, 2x13900 (dual channel-OTAs) per channel.

You have 8 kits to save your parametersets. the kit-selectionbuttons recall the kits immediately, you can switch them live in the song to change ths sounds. you can hear that in the soundclip at the pagebottom.

To edit the sounds you select a pad (=sound), with two buttons (+/-) you select the parameter and with two other buttons you can increase/decrease the value. The range is from 1-19 for all parameter.

The Parameters:

1. Pitch = the basic tune of the sound

2. Bend = the amount of pitchmodulation, the pitch is also velocity-dependant. heavy hit=more bend. Only positive (piuuuu).

3. Mix OSC/Noise = here you can blend from OSC-only to Noise-Only

4. Overtone = WOW, i love this parameter! It makes this thing MUCH better than the simmons-crap. This adds some ringmodulation sound to simulate the second drumhead of a tom.

5. Attack = Volume of Attack-Sound, makes the drumsound more defined and aggressive.

6. Filter = lowpass for the Noise, also dampens the Attack-sound and even the Oscillator.

7. Decay = with high settings, the sound is very long, 808-like. With the shortest value, the decay is still quite long. It's because this unit doesnt work with t-briges like the 808/cr78/er-0/dr55 a.s.o. machines but with oscillators that get modulated by enveloped VCAs like on the 909.

8. Level = well ..

Here is the soundclip - first half BD,SD and 2 Toms, second half without the toms. The pattern comes from my modified fricke MFB-502 with trigger-outputs. Each two measures, i switched to the next kit so you will get a really good overview of what this thing is capable of.

Update May, 2008:

Making the parameters Pot-tweakable and even voltage controlled

After selling my unit, i luckily re-grabbed a broken one on the bay for 30 EUR. I had to replace a PSU-voltageregulator (7808, ~1 EUR) for geting it work again. I always wanted this thing to have pots instead of ++++/---- tapping-editing. After measuring a bit on the PCB (see on the right) i found the solderingpoints for tweaking the parameters with pots. The PCB is VERY clean and professional, Pearl did an excellent job on this drumsynth. The 5 instuments are nealy identical, As far as i recognized it on the fly, only the bassdrum can be tuned lower than the other 4 (SD+3xTOM).

Each of the 8 parameters goes from 0-4.75 Volt on the 4 outputs of the 4046 PhaseLockedLoop, there are 2 of these 4046 for each voice.. On the pic to the right, you find them in the first and third chip-row from above, i drawd red circled around them. They just needed to be replaced with standard chipsockets (dont know yet how to get them out without expensive ic-desoldering-tip?). In the sockets there should go a jack with 14 pin-multicable to the pots - ready. To put an IC-socket on the pcb allows you to put back a 4046 if you want to reput it in the original state.

Update 02/2010

Front

Back

And a look inside

HA! The first voice is successfully potted. Just a test yet, other 4 voices will follow.

Update 05/2010

The housing

i decided to replace the metal housing of the 19"-unit with a wood-U, well not really wood, it's somewhat between wood and paper called MDF here in germany. Its easy to drill and stable enough - and cheap, just 2 EUR. I glued it together, drilled the 40 holes, painted it with some paint i had left over - of course water-based and therefore environement-friendly.

The cabling

The pot-plate needed to be detachable from the unit for easier assembling, painting a.s.o. The unit itself got two 20-pin jacks on a holematrix-pcb.

The hotspots

click image to the right for a detailed view on the points where the cables need to be attached. I lifted of the resistors and soldered the cables directly to the open pin of the resistor. Just pitch is a bit different, to enlarge the pitchrange i replaced the lifted resistor (68k) completely with 10k before going to the pot. This enhances the range of the pot, if you keep 68k your pitch doenst go as high as i could. If you remove the 68k the range of your pot is to big and some turningway wont make the pitch any higher, 10k workes well.

The 8 cables of each channel then go to the middlepin of a standard resistor/slider. I grabbed about 200 from the bay quite cheap, they are 100k-Ohm, take linear ones, not logarythmic. Linear Pots have an 'A' beside the value - 100k A means linear, 100k B means logyrythmic.

All the resistors have mass on one pin and -5 Volt on the remaining pin. Thats it. If you like you can also tweak the parameters with external voltages. Although i would NOT exceed 8 Volt, thats the voltage this unit is running on, Some modular systems work with even 15 volt, that might burn some chips.

the hotspots for one channel, the other 5 are similar.

The 7808

40 resistors in parallel cause an increase in currentflow. As a result the 7808-voltage regulator of the PSU gets quite hot. There is an unwritten rule which sais 'as long as you can hold your finger on it, the regulator doesn't get too hot'. Well, this was quite on the edge. I desoldered it and put it directly on the metal-housing, now it can get rid of its heat quite better.

Finished

Ready! 40 pots for direct twaeking. Didn't turn out as a beauty but it works well. The backside is now the frontside, all individual outs still work.

Modding

Enlargement of pitch-range

The 68k-resistor at the poitch-tweakpoint can be replaced by 15k. This enlargend the range from lowpitch to highpitch.

Shortening of decay

The decay of the sounds is very long, even the shortest possible time is quite long, compared to the typical double-t-filter-sounds (cr8000 e.g.). But that can easily be changed: just

put a 10k-15k-resistor in parallel to the 62k-resistor near the decay-tweakpoint and the decay gets very short. I added a switch to the each of the 3 toms to change between long and short decay. the decay pot works in both  modes as before, just the timerange is changed by the switch.

Pushing pitchrange higher

The normal highest archivable pitch is even quite low. To simulate claves or congas i want to pitch to be much higher. Just put ~ 25k-resistor in parallel to the resistor above the 4016-ic at the bottom of the pcb (opposite to the printed labels 'Snare', 'Bassdrum' ...), see pic to the right. Making this switchable lets choose you from normal pitchrange to a pitchrange much higher. As with the decay-pot, the pitchpot works perfect as before, you just have another pitchrange.

The resistor BELOW the 4016 is responsible for the overtone-oscillator. Change for your needs.

moddingpoint for pitchrange