I was just testing out a new power supply. I use a very low cost method so this means that I just plugged a new wallwart into my rack Aaaanyway, I like to use a simple sample and hold ( Moritz Kleinâs circuit, opamps, no sandh chip) with a simple opamp triangle for the cv source and a simple analog square for my clocking (in this case it is a 555 ic). I managed to get a very interesting result from the first sounds I got after the initial plug in of the new wallwart and patching the inputs. The demo doesnât start with tones for about 30 secs. It starts on the low end of an apparently long scale. I show the sample and hold then I tried to show the input source activity LEDs. The bottom blue led on the 555 module and the top LFO on the module with the opposite polarity leds and switches.
Iâm not sure if itâs an ne555 or which other model, but itâs definitely a 555 of some sort for the clock. I wanna say itâs not ne555, because I bought like 50 super cheap from Bojack (Amazon brand generic Chinese).
Yeah, and you would expect the cv source to be a very low frequency, but as you can see itâs blinking quite rapidly. The trigger is just hitting it at an interval that allows for the source wave to be sampled at points in the voltage that are musically proportional and in a respectively ascending or descending orderâŚI guess?
I did not use that schematic, but I am definitely going to put that circuit on breadboard. I like it. Never seen it before, so thanks! I used this one
I just put a 1uf polarized cap on the output and I think I used an emitter follower transistor setup for the led. I just put 4 point to point deadbug style circuits on the back of a panel. No circuit board. And I wired an input into pin 5 to of each circuit which enables you to sync them with the other ones on the panel or other square waves.
Hit and miss with the opamps and 555s. Opamps (lm358, tlo72âŚ) may burn out on you quite soon from overloading and Iâve noticed better filtering circuits with the brand name (Texas instruments). I have had circuits fail with Bojack but work with TI. The 555s seem to work great in any application. Like the opamps some of them will take relatively little experimenting type abuses that I am prone to put them all through. Iâm teaching myself almost entirely with the exception of the fine coaching and tons of advice I get from this forum. So I try to buy the cheap bulk stuff for my experimenting and when I really want to build something I really like I invest in some brand name opamps at least. DO NOT BUY LM13700 FROM BOJACK.
Does the Atari punk console circuit use pin 5 on the 555 for cv input?
If yes, it probably wonât be a conventional scale as the 555s have a weird relationship between pin 5 voltage and the output frequency, also its upside down, more voltage = lower frequency and lower voltage = higher frequency.
If a low frequency triangle wave (or ramp) is sampled at regular intervals â substantially shorter than the wave period â then youâll get voltages at equal differences from each other. How big those difference are depends on the amplitude of the LFO wave and the relative frequencies of it and the clock signal.
If you control a 1 V/oct oscillator with it youâll get equal musical intervals, and if those voltage differences happen to be an exact multiple of 1/12 V youâll get: A chromatic scale if theyâre 1/12 V, a whole tone scale if theyâre 1/6 V, a diminished or augmented arpeggio if theyâre 1/4 or 1/3 V, and so on. More likely, though, they will not be an even division of an octave and youâll just get something resembling a scale but a xenharmonic one, not one in standard tuning.
And the note sequence you get on one LFO cycle will probably be displaced relative to what you get on the next.
I must say, Iâve only gotten passives from Bojack. It really is the best general policy to stick with brand names for ICs at least. Transistors and diodes and whatnot are a maybe.
So, Iâm embarrassed a little because I titled the video wrong. I did not use the Apc for the video. The APC was the last thing I had hooked up before I went to bed though. LOL. I will try to change the title. this is actually my first post with video for this forum as well as my very first you tube post. I rushed through the title. It is an exponential opamp vco.
I do love my APC though. I almost always use it with my sandh. I have a modified APC. Itâs like my own mingling of Samâs aaappoccc and juanito Mooreâs Apc1.5. Tons of noise with a nice lowpass resonant filter. The Mimms APC was my first circuit, as taught by Sam on youtube.
I actually owned (still have it somewhere) That Mims book from a young age, but somehow managed to overlook the stepped tone generator circuit that later became the APC. Since rediscovering it as the APC I have experimented with various adaptations. One thing I tried was having 2 monostables triggered by the same oscillator and can get some harmonies and also total discord!
That is what Juanito Moore (modular for the Masses on YouTube) uses. He calls it Apc1.5. Mine has one complete APC circuit (oscillator controlling monostable multivibrator) controlling another monostable multivibrator. Sounds dope on the sample and hold.
LFO of some configurations, if not all, take forever to start simply from the inital âfilling-upâ of the capacitor that determines the frequency.
Iâd say, âSet it 0 output highest Hz, then set it low,â but it still takes as long to fill said cap to point of oscillation, so basically one would be doing something else during that cap-charging process, then itâs ready by the time youâre done âworking-aroundâ the issue, ay?
Aaaanyway, I like to use a simple sample and hold ( Moritz Kleinâs circuit, opamps, no sandh chip) with a simple opamp triangle for the cv source and a simple analog square for my clocking (in this case it is a 555 ic). I managed to get a very interesting result from the first sounds I got after the initial plug in of the new wallwart and patching the inputs. The demo doesnât start with tones for about 30 secs. It starts on the low end of an apparently long scale. I show the sample and hold then I tried to show the input source activity LEDs. The bottom blue led on the 555 module and the top LFO on the module with the opposite polarity leds and switches.
So I try to buy the cheap bulk stuff for my experimenting and when I really want to build something I really like I invest in some brand name opamps at least. DO NOT BUY LM13700 FROM BOJACK. 
