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SYSTEM MODIFICATIONS
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| BE AWARE; MODIFICATIONS TO MOST PRODUCTS WILL VOID THE MANUFACTURERS WARRANTY. | |
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| ANALOGUE SYSTEMS ADSR | |
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RANGE SWITCH: The Analogue Systems ADSR is very close to what I would consider a fully-functional ADSR, as it has a lot of the features I prefer in such a device. It self oscillates in A/D mode, it will ignore the on-time of the input pulse (gate), it has some VC parameters and a level pot which affords both an inverted and non-inverted output. The unit itself stock behaves, IMHO, more in the interests of keyboard performers however in that it's overall envelope time is on the short side (at about 35 seconds for the A/D mode). I added a modification to change all that with the simple addition of a RANGE ON-OFF-ON single pole switch which fits neatly on it's faceplate above the location of the HOLD/ONE SHOT switch (go here to see a picture) This mod is very easily accomplished by connecting the wiper of that added switch directly to the + side of C8, a 4.7 mf tantilum capacitor which governs the overall timing of the envelope cycle. To one side of this new switch I connected the + side a 15mf tantilum and to the other side I added the + side of a 50 mf tant. The negative side of both of these caps should go to ground. The net effect is a range switch whiich in it's center position has no effect, but will also allow overall envelopes of 4x over it's normal maximum length and 10x over its maximum length (3 minutes, 50 seconds for 1 A/D cycle). click here for a Range Switch Modification diagram
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END-OF-CYCLE PULSE OUT: A second mod was a bit more complicated, but still quite easy which allowed me to bring the ADSR's internal end-of-cycle pulse to the faceplate. This was done be adding a simple NPN inverter (w/ a 10k current limit to the base and a 10K pull-up to the emitter, with the output of the emitter also fed through a 1k to the jack). The stock Analogue Systems ADSR will allow a user to self-oscillate the ASDR so it behaves like an LFO. It does this internally by routing the output of the ADSR before the inversion circuitry through a comparitor, whose negative-true output is fed back to the retrigger input via a switch. It will also fire this negative true when the ADSR is not self oscillating, but this signal at that point it shunted at the switch (which is obviously not passing that signal when in that mode). The addition of this jack (which can be seen in the photo directly above the added RANGE switch) fixes all that. My ADSR now fires a positive-true pulse at the conclusion of all envelopes, which affords me several enhancements: 1) A sync pulse when the ADSR is operating as an LFO 2) The ability to sequentually fire two ADSRs together for complex envelopes. 3) One hell of a gate delay (just under four minute maximum delay and anything in-between).
click here for an End-of-Cycle Pulse output Modification diagram
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| ANALOGUE SYSTEMS GATE DELAY | |
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VOLTAGE CONTROLLABLE DELAY The Analogue Systems Gate Delay is not voltage controllable. There are two manual pots for setting the amount of delay and the pulse width of the delayed signal once it is active. While this circuit is not what I would consider a true VC of this R/C time constant dialed up in the one-shot, I have added another circuit which uses the timing signal coming from the one shot at IC1 to achieve (basically) the same effect. To do this, an new input had to be added which will allow a positive exrernal voltage to shorten the delay currently dialed up on the DELAY pot. A new output was also required which supplies the output of that modified delay. (go here to see a picture). Admittedly, this is not the best way to handle this. I would prefer a single VC iwhich would effect the delay output jack alreay provided on the module stock. In any event, this does work and will effect a delay approx 40% less than what is dialed up. This is perhaps the most difficult modiofication to install in that it will require a small PCBA to be added within the Analogue Systems Gate Delay unit, which is already a bit cramped in that it's only a 6 unit wide mdule to begin with. A wire must be taken from pin 2 of IC1 which is fed through two TL062 op amps' positve inputs, with the negative sideof the first connected to th VC input and the second becoming the feedback loop of the final output.
click here for the Gate Delay VC delay input modification diagram |
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| DOEPFER A-147 LFO | |
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PULSE OUTPUT This is an extremely simple modification which consists of nothing more than adding an R/C to the square wave output of the Doepfer VC LFO and running the output of that to it's own jack. It acts as a differentiator and returns a very short spike which is timed to the period as the square wave, which is ideal for triggering non-pulse dependant envelopes. (go here to see a picture).
click here for the Doepfer pulse wave output modification diagram
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| DOEPFER A-151 SEQUENTIAL SWITCH | |
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2, 3 or 4 STEP RESET SWITCH This modification will allow the outputs of the internal clock in the A-151 to reset itself before it reaches it's last step at either step 3 or step 4. This is an extremely simple modification which consists the addition of a ON-OFF-ON switch, two 1 K resistors and a 1N4148 diode which allows for an internal reset of the A-151 Sequential Switch with three options: a 2 step sequence (reset on 3) when the switch is in the UP position; 4 step sequence (no reset) when the switch is in the middle position; and a 3 step sequence (reset on 4) when the switch is in the down position. I did not allow for a one step operation (reset on 2), as this defeats the purpose of the device altogether. This switch is diode protected into the reset jack, so external resets may still be applied to the jack even if the switch is active (in either the up or down position). Use of this internal reset will allow the A-151 to be used as a 2,3 or 4 step sequencer, if use in conjunction with an A-176 CV Source (one channel plugged into each of the I/O (1-4) of the A-151) -or- four channels of an A-129/3 vocorder slew limiter. A hole must be drilled in the faceplate directly below the I/O 4 jack in which to mount this additional switch. Look for a photo in the near future. click here for the Doepfer A-151 internal reset diagram
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| BLACET ENVELOPE GENERATOR | |
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The first is an end-of-cycle (EOC) trigger output, which when installed, can be used to trigger any number of things after the completion of the EGs cycle, including itself. Yes, by running this output into the GATE input and pressing the manual start button once, the EG will go into self oscillation without the need of the external constant high signal usually required. In the configuration shown, C1 and R1 form an R/C that dictates the length of the end of cycle pulse, in this example about 15MS. You can play with different values depending your system's ability to respond to such a short pulse. The second mod produces a constant high (EG ON) as long as an envelope is active. It rises immediately at the onset of the attack, and stays high until the envelope has reached its end. I find this helpful for enabling pulses to pass only when an envelope is firing - especially when creating short retard or accelerando phrases. I believe the Serge EGs also provide such an output. The activation level in the circuit documented is about .05 volts. So, technically, this signal does not track the envelope perfectly, but pretty damn close. You should be careful bringing it too much lower than shown as you are about to enter into the noise floor as is, which a comparator circuit will respond to. I have installed this mod into my two Blacet EGs, it works great - and will actually for any AR type envelope generator. I have not tested this on an ADSR as yet. While the EG ON should work fine, I would be curious to see how an ADSR responds to a short trigger pulse. |
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| BLACET MINIWAVE 1 | |
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The following modification is as yet untested, but should provide a high signal at it's output each time and only when either the bank or wave pots or VC are changed enough to effect a change of state. The changes to the current bank number or wave number in the Miniwave is provided by an analog voltage that is converted to 4 bit digital (in use) that comes from either a pot or an external voltage. This is done via an ADC 0804 analog to digital converter. This mod takes the output of the ADC through a four bit latched register and passes a high at it's output ONLY WHEN the current 4 bit binary number changes states. This mod will provide you a sync pulse when changes occur. In this way you could, for example, trigger an envelope when a change of state occurs.
For any of you considering the nifty modification listed above, there is a MUCH easier way of doing it which is tested. The Milton ACB board will do the very same thing using a PIC. You can built the circuit yourself, but reuqires the purchase of a Milton ACB PIc for $`0 USD. See decription here |
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