I’ve decided to start selling these on ebay to raise some money for parts. Here’s a link to the current auction… and here’s a photo of the current model:
Here’s a revised schematic showing additions/changes, as well as a parts list:
I recently ordered a couple of CD2024 dividers from Jameco, but got Motorola MC2024’s instead. Last time they sent me Motorola substitutions, it didn’t matter- but this time, the chip is entirely different: a dual VCO, as opposed to a divider. Turns out these might be useful, so I won’t bother sending them back, but I do plan to point it out to them.
This chip is designed to operate at radio frequencies (MHz), and a chart in the datasheet shows that the noise performance gets worse as you go lower in frequency. However, I didn’t let that stop me from having a go at it on the breadboard. Although it’s not perfect (the noise/distortion gets noticeably worse as you go into low frequencies), it is fun to play with.
Below is the circuit I came up with for using it as an audio-frequency oscillator. Note that the datasheet recommends +5V operation, so I also put that in the schematic- however, the version I built on breadboard uses +9V, and it seems to work. That is to say, it doesn’t seem to overheat or anything like that. Also note that the function of SW1 is to switch between CV modulation of the 2nd osc along with the first one (thus making it like a unison osc if using a dual-ganged pot, which I represented in the schenatic as VR2a & VR2b), or modulation of the 2nd osc from the first (thus making it a pseudo-FM osc).
Here are some recordings of my tests- the first one shows the oscs in “unison” mode, with CV modulation from a Schmitt trigger LFO:
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The next one shows the oscs in “FM” mode, with osc 1 being modulated from the same LFO:
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The third and last one is a combination of both modes, with the modulation source’s rate also being tweaked, often going into audio rates:
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After trying unsuccessfully to sell my Yamaha Electone 315u-i electronic organ for a good long time now, I finally decided to take it apart and see what might be useful elsewhere.
The following view from the back shows some of the more interesting parts: a Leslie hookup, a wannabe-Leslie rotating speaker setup (in the boxed-off area in the bottom right), a spring reverb tank, and the main speakers. My initial thoughts are to use all this to make a combo amp.
The next photo shows the power board:
This one shows the microcontroller board, which contains the arpeggiator and auto-accompaniment components- I think at least the sequencer portion of the drum machine resides here too:
So far I’ve also found a couple other interesting things, including an IG02610, which is the same filter chip used in the CS-01; and several MN3006 chips, which are digital BBD IC’s designed for use in modulated-delay-based effects such as chorus. None of the IC’s are socketed though, so it could be tough to remove them from the board(s) without damaging them.
The stops and other lever controls all use Alps pots, though all the stops are stepped, which will make them less useful. Plenty of wire in there though! The keys and associated circuitry could also be useful.
After posting the PBBPF schematic to the Deathlehem forum, RichardC64 posted an improved schematic which adds small (1k works) resistors to keep the whole signal from being sent to ground, and also adds quick & dirty voltage control using diodes as variable resistors:
From his forum post:
Note that as VR1is reduced, HPCV has less and less effect. On the low pass side, As LPCV increases, there’s less resistance in series with C3, increasing the total capacitance to ground, and thus lowering the LP roll-off. The overall effect of both CVs would be a BP with variable width. Suggested values are R1 & R3 1k-10k, R2 & R4 100k or more, and C3 maybe another 1uF. Trial and Error.
Neither of these circuits has been built on perfboard yet, but I have two more additions to go into Loid tested: a simple passive, buffered band pass filter; and an equally simple patchable buffer/glide circuit which was originally posted at Deathlehem by Rich: here’s the thread with the schematic. The following two recordings demonstrate what it sounds like driving the Phoenix 566 VCO- in the first one, it’s just being used on a simple squarewave oscillator from Loid to make the VCO pitch rise and fall, starting with a slow setting (more glide), and going to a faster one (less glide):
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The next one is the same VCO being modulated, but this time the glide circuit is being fed a more interesting signal from the R/2R:
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The band pass filter I mentioned is really two simple passive filters in series (high pass, then low pass) with a buffer between them to keep them from interfering with each other. For the buffer, I’m using the other half of the LM358 which I used for the R/2R buffer. Here’s a schematic:
…and here’s what it sounds like on one of Loid’s oscillators:
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The high pass portion can actually sweep high enough to make the signal disappear, but the low pass filter is less effective. You could try experimenting with different capacitor values and types in the LPF section to get a better response. I used a 1uF film cap because it was the biggest I had of that type. I also tried a 4.7uF electrolytic, and although it did a better job of cutting the highs, I thought it removed too many highs even “fully open”. I considered adding a SPDT to switch between the two, and may still do so. I do also plan to build an active filter though, so then again, I may not.
The same dead guitar amp from which I had recently harvested a number of pots and dual op amps also contained two CD4053’s (well, one was an equivalent with a different part number, but still…). After getting Loid transferred to the new container, I had stuck one of these on the breadboard for playing around with, and finally got around to putting it on perfboard to become a permanent addition. This is another module which is just wires going right to the pins, and fit perfectly on one end with 4 rows of 3 screws (control inputs A, B, and C, which switch the X, Y, and Z in/outs between two other sets of X, Y, and Z in/outs- I chose to ground the inhibit pin).
Here are a trio of recordings made with the 4053 in various combinations with Loid’s other modules:
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So, the coffee cans-with wires thing turned out to be less than ergonomical. I’ve gone with a new approach, involving plastic Wal-Mart containers and metal screws for a “bolt-bay” patching system:
The mixer & R/2R remain uncased, and the 4019/Switchgate combo remains in the old modem case. I’m finding this much more fun to work with.
Here’s the first video of Loid in action:
My friend Kris recently gave me a couple of old joysticks, the first of which I’ve modified to be used as a CV controller.
The photo below shows the inside of the joystick, before any modification:
As you can see, the X and Y controls are actually slide pots (150k linear, to be precise). Using the bottom pot in the photo as a reference, the far left pin is the wiper. The first thing I did was remove the PCB and the PC connector cable. Then I drilled holes for the jacks, and wired it so 9V comes in via a 1/8″ switched jack, and goes to the far right pin, and it’s equivalent on the other pot, with the middle pin going to ground to form a voltage divider. Since I used a switched jack, I could also make it capable of running off a battery for portable control of stuff like the Modutronic Messmaker.
Here’s a video of the joystick in action with Phoenix:
I have plans to also add some internal LFOs which could be switched in with the buttons, but this is definitely a fun start!
An R/2R ladder is a simple circuit, often used as a Digital to Analog Converter (DAC). There is a good introduction and how-to guide here.
Here’s the circuit on perfboard (the op amp is an LM358):
It may not be immediately obvious how such a thing might be useful in a noisemaking device- I know it wasn’t to me. They say a picture is worth 1,000 words, so here are some screenshots from s(M)exoscope… the first one is a shot of 4 of Loid’s oscs, roughly tuned with two at one frequency and two at twice the frequency:
…and here’s a couple with them completely detuned:
Here’s the obligatory audio example- this is just those same four oscs being fed into the R/2R, whilst I twist knobs:
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After posting about the Switchgate at Deathlehem, the always-helpful Rich suggested a method for extracting a short pulse from an incoming signal- see the thread here. Though that original suggestion didn’t work, it got me headed down the path of breadboard experimentation that led me to this:
I added two of these to the same board as the R/2R:
Switchgate is a simple dual gate based on a 556 in monostable mode (with trigger input), with the monostables triggering two switches. The monostable outputs are also accessible via their own outputs.
Here’s what half of it (a single monostable/switch circuit) looked like on the breadboard:
I put a 4019 quad AND/OR select gate (wires straight to pins) on the same perfboard with the dual gate VCA, and put them in an old external modem case:
I’ve also added a 4051 multiplexer wired straight to the pins to the Melody Generator/ring mod can.
Here’s a recording of the Switchgate/4019 in action with the other modules- the Melody Gen and 4051 were left out:
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