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msi

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  1. I have a line6 footswitch that I would like to use to send midi out using the midibox. I'm having an issue though because I don't understand how they are handling the 74hc595 chips. It appears to me that the serial data, latch and clock are all coming in on the same pin. The footboard is designed to connect to a Pod amp simulator using an RJ45 cable. Two pins are used for power, two for ground. One pin is used for switches, and two for foot pedals. The last pin is for the leds and 74hc595's. Here is the schematic of the part.
  2. A while ago I posted some inquires into making an analog synth along the lines of a Juno 106. I hit a barrier when the design started getting more complicated and required more parts than I was willing to utilize. I set it on the back burner to think on other ways to achieve my goals. I've started contemplating using a pic as a standalone DCO. The limitations I can predict are the output would only be a square wave and possibly problems depending on the speed of the pic. The pic would run completely independent. Once power is applied the pic would enter a program loop and start scanning the CV input for voltage. The only requirement is a voltage present at the CV input. I've come up with a preliminary hardware plan. The pic would be a 16F1825. RC3 is the AIN for the CV voltage. This is connected to a CD4051 which is reading the voltage at the pins of it's input. It is being controlled by the pic via RA3, RC4, and RC5. Additionally two inputs for pulse wave modulation are included. RA0, RA1, RA2, RC0, RC1 and RC2 are then available for six square wave DCO's. The program code as far as I can tell once the main loop is entered would be, - Entry point - Set CD4051 to first input - Read CV at RC3 - Adjust frequency of DCO1 at RA0 to match - Repeat for DCO2 through 6 - Read PWM from CD4051 - Return to first step Concerns I have due to my inexperience with micro-controllers is just how much overhead will the pic need to achieve this. I know a single DCO is possible as it was done as shown here, PicSynth Homepage. I am unsure if more than a single DCO is possible. Does anyone have any suggestions or advice?
  3. I've been looking at schematics for a couple of synths namely the Juno 106 and the Wildcat modular synth. The Wildcat synth schematic can be found at http://synthdiy.com/files/2008/efm-wildcat.pdf. The Juno service manual can be found at http://www.hinzen.de/midi/juno-106/manual/juno-serv.pdf. On page 6 of the Wildcat schematic and on page 8 of the Juno schematic are the areas I'm speaking of. The wildcat and Juno both use a CD4051 to multiplex the CV signal into multiple control voltages. My understanding is the capacitor attached to the opamp immediately following the CD4051 maintains the voltage. Does the CD4051 have to continuously switch back to each of the seven outputs to maintain the CV voltage or is there something else I'm unaware of going on? Following that, is there a way to implement this with the Midibox in conjunction with the AOUT_LC. How fast does the switching need to be to have it be seamless?
  4. http://www.analoguerenaissance.com/D5534A/ claims to carry replacements. I knew they had replacements for the filter chips but while doing research happened upon the vco replacements as well. I just noticed your own edit......
  5. So after thinking about it I think I've decided going with the replacement chips that are available for the juno for the time being is a viable choice. With that decision here is what I've come up with. The timing is handled by an 82C53 connected to a pair of 74HC595 chips connected to J10 of the core. I'm sure a DOUT could handle the 74HC595 chips but this seems like a better way to start at the moment. Currently I have the output of the 82C53 going into a MC5534 VCO chip. The chips are only 25 euros plus shipping I believe so there is no reason not to utilize them. The CD4052 handles the saw amplitude like in the juno. There is the transistor connected to the Vee pin of the CD4052 that I am unsure what it's purpose is. Questions I now need answered is can this be extended to multiple modules on a single core? I don't see why not but I could be wrong. Also can a core handle both the DCO and an AOUT module.
  6. I don't believe it can be but can a 74HC595 be used to provide an oscillator if it is modulated at the correct speed. If not can J10 off a core module provide a base oscillator and control an AOUT module? The data lines of the 82C53 can be controlled by a 74HC595 but there are a few pins that cannot, and looking at the way the SID attaches to the core (via J10) it would appear we'd need two cores. One to control the DCOs, and another for CV. I suppose we could hook the 82C53 to the 74HC595 exactly like the SID module, and provide a base oscillator for each 82C53. This means that every group of three DCOs (each 82C53 provides three outputs) would then have it's own dedicated oscillator and using an RC oscillator would be out of sync with other groups of DCOs. Also, I have not read of the SID having any frequency errors on high notes like the Juno. I am unsure why that would be. My studies show the SID runs off a 1Mgz clock where as the Juno an 8Mhz clock. It seems to me that the Juno should have higher accuracy at higher frequencies than the SID. If the SID is more accurate how so?
  7. I think going with the juno's basic design is a safe bet. Adding multiple timers to avoid the timing sync of the juno is an improvement that can be made. Also we should look at consolidating as much logic and timing functions into the PIC as possible. The juno is nearly 30 years old and computer technology has advanced since then. We should be able to do more with the pic than Roland could do with the CPU's it had available at the time. Also we should figure out a way to avoid pitch issues as notes get higher.
  8. If the design uses the Aout_NG we could use a sample and hold circuit for each CV needed. That is basically what the older synths did as well. It would require once CV per voice for the VCA envelope, and two per voice for Cutoff frequency and resonance at a minimum I believe. Again, I'm not sure what the latency would running multiple voices off one CV would be as the voices started increasing.
  9. Here's the thing that is not making sense as far as using multiple master clocks, if the timing source is the same between the multiple clocks, say a crystal on a pic, and the pic is outputting multiple master clocks can't we just vary the output of the pic how ever we decide. If we decide to have an 8Mhz frequency on one master clock and 7.98 on a second, we can do that can we not? Maybe not to that drastic a degree but it's still an option? Or am I still running behind the curve?
  10. Yea, Starting simple is always a good idea when starting a project. I guess the minimum would be to get a tuned raw square wave out of a pic. Care should be taken so that it can be expanded and will not load the PIC down. I do think the idea of using a DOUT to control something like a 82C54 is a decent design choice. The issue I see with that is there is still the problem of higher pitched notes being inaccurate due to timing issues and the only supplier I've found is Jameco and they cost 5 dollars a pop.
  11. Right, the base 8Mhz of the base Oscillator is divided by the range switch, then goes to the 82C54. I was thinking it might be more efficient to maintain that method because once the timers are set the main CPU doesn't have to worry about the timing until a new pitch is needed. I had considered the possibility of using master clocks to avoid the oscillators being in exact sync. Also I had considered using a higher frequency base frequency to avoid pitch errors at higher notes. My main concern is my lack of knowledge concerning the digital side of things. I can program C++ badly and understand analog theories poorly. But it seems like a worthwhile project that hasn't been done yet and a good place to firm up on these subjects. The design goals I'd like to achieve for the digital domain are, -Multiple polyphony (I'd like ten.....ten fingers=ten notes) -Stable tuning -Midi control -Low part count (already moving away from this unfortunately) -Low overhead on the CPU (MBHP Core) -Avoid feature creep Worth attempting -Save patches -MBHP Sid type control surface Unknown hurdles -Exact needs hardware wise -Best methods
  12. Yes, I am aware of the tuning issues with the Juno as the notes get higher. My main thought on using external timing IC's was to free up processor cycles in the PIC and allow for the polyphony to be changed by the builder. At a minimum I'd hope to achieve something similar in ability like a juno, meaning six voices and an LFO. Also it'd be nice if it could support the abilities of a SID with three voices with independent wave forms and VCA's with a shared VFC. Not saying I would want it to sound like a clone, but have similar abilities. So by using external timing IC's all the PIC would have to do is send the square wave cycle to the Timing IC until the pitch had to change. I was thinking that managing the timing on a minimum of six square waves plus the CV's for the VCA and VCF might be asking a bit much of the PIC, but honestly I'm not sure. I've been mulling this over for about a month now and have been looking into how older synths managed to accomplish this. I've begun to look into what options were available but until a few days ago I didn't find much. Also I've been looking into how the Juno used 4051 IC's to generate the CV but that part is still a mystery to me. I understand how those chips are selecting which ports to have open, and understand the idea that the square wave gets smoothed to create the voltage control but the exact process is above my current understanding.
  13. I've been doing a lot of research recently on analog synths with the purpose of actually building one. While looking at the technology of the Juno 106 I noticed that the juno sends timing information from the CPU to an intel chip that outputs a square wave which is then modified to other waveforms using a waveshaper. Likewise the CV is generated by using square waves and smoothed to produce the voltage required. How plausible is a setup like this using a midibox core and external timing chips to produce the DCO signal? Some information on the Juno's DCO's can be found at Roland Juno Series DCOs
  14. There was a lot of talk about how to convert the aout into variable resistors. Why would it not be possible to hard code ldr values into the mbhp core? So what if I were to test the ldr to see how much voltage is requred to get a value. So lets assume I have a LDR that has a on resistance of 200 ohm, and an off resistance of 300meg. After testing I find the ldr gives me a value of 1meg at a voltage of 2v. I can then divide 2v by what ever resolution I have. Again assuming a resolution of 128 steps. If I'm trying to replace a 1meg pot thats wired as a variable resistor I can predict what the voltage will be at any given point in theory. So given 128 steps, at mid point, we can estimate 1 volt would give a resistance of 500k. The way to verify this is to have two ldrs set up. One that is attached to an aout and in the circuit to be controlled. The other is attached to the same aout and is used to verify the voltages and attached to an ain of the core. The core would then sample the ain to ensure a proper voltage is kept. This assumes that the two ldrs are of a high quality and don't differ to much. This wouldn't be great for a box where the core has lots of things to do such as a sequencer, but as a dedicated box that is used to store and retreive settings it should work decent. The other concern I have is I don't know what accuracy the ain modual has. Assuming the scenario I described before, the voltage change between steps would only be 0.02 volts. I know some people would want a higher resolution, but for a box where you set a value then forget it, I think it should be fine. Similar devices such as the mesa boogie triaxis and the ada mp-1 have a resolution of about 16, maybe. Further more a dout could be used to control relays and switch, and encoders could be used to manipulate the knob values. So am I just blowing wind into the air? I've ordered a set of H11F3's for another project and plan to test them to see how sensitive they are and how accurate two diffrent ldr's are between the two. Thanks.
  15. I tried it on another pc with two differnt usb interfaces and got the same results. Also Midi Studio doesn't do anything more than MidiOX. This is really fustrating. I'm thinking I might want to have someone double check my work and PIC to see if I did everything correctly.
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