you know how on the cp 251 you can break the connections and use other things than square waves oor noise, what are some other things you can do with the module other than the normal random stepping that comes on normal synths?
I once heard that BBDs are a kind of sample and hold circuit and after seeing ikaziar’s post
I am not sure if keyboard voltages (from analog keyboards that is…) are DC. In some synthesizers pressing a key means that a voltage is produced, then passed through a S&H for a short period of time, then passed thorugh an AD converter so it can modulate the oscillators or whatever. I am not sure though, maybe MC knows more.
in the CV theory thread i started to wonder what these things can be pushed to do.
is the S/H on the cp 251 more customisable than the one on the voyager?
Are there any more advanced S/H units available?
One of my favourite S&H-applications is to get a softly chnaging CV - which is quite the opposite of the typical “stepping”-mod most S&H’s are used for.
What I do for example is use the LFO in the CP-251 to trigger the S&H and feed into the S&H the noise source so that I get a true random S&H signal. However, I then process it through the lag processor in the CP-251 which gives a very nice and very variable smoothing of the signal and produces a softly changing but truly random CV. I feed this e.g. into the filter CV-input of the MF101 and channel the noise into the audio input - this results in great wind/storm-type sounds with a random character which is very natural. Another application would be slowly changing detune-effects of oscillators or changes on LFO-frequencies.
The point here is that it’s not only the pure S&H-circuit but also the processing of the output of the S&H which makes a big difference.
BTW: indeed, BBD’s are by nature S&H-type circuits, as are all analog-to-digital converters. The difference to “our” applications is that the sampling period (and even more the actual sampling time) is always much shorter than the period of the signal to be processed while in “our” area the associated frequencies and time periods are much more similar or even inverse in their relationships.
By clocking the S&H at audio rates, you can get an effect similar to lowering the sample rate on a digital sample. It sounds especially cool with drums or vocals, but really anything works.
Sampling a waveform at a clock rate rate similar to the S&H’s clock rate gets some interesting semi-regular output. Check out the “Phaser Rhythm” patch in the CP-251 manual for an example of this. Try a sawtooth for a “staircase” pattern.
This might be a more typical application for sample+hold, but I like to use it to vary ocsillator sync and filter freq at the same time time while the sample rate is controled by Keyboard gate. This can be done on an Arp Odyssey by internal patching, but could also be done with the CP251 and a Moog Prodigy with Sync and Filter input and gate output. Each time a key is pressed, the voltage changes randomly, giving each note a varing amount of timber and tone. It makes a really good synth electric piano sound. It has the character and richness of a fender-rhodes but still sounds like a synthesizer.
For my experiences, the most useful application of S+H is when you want to introduce subtle random elements into you sound. It makes the synth sound more like a real instrument, and not just a programmed computer patch. It’s still a synth, but more unpredictable.
Of course, this is probably a fairly common use, I know you were fishing for more experimental type uses. But I’ve found that only certain signals work well as inputs (Osc.s, Noise). Probably anything else would need to be amplified (and/or compressed?) before patching it to S+H input.
i always feel like i can never have enough sample and hold circuits. anyway, since you asked, i mentioned in an earlier thread how useful having two cp251s is. i can’t remember if i wrote about exactly what i do with them.
one thing i like to do is to patch the smooth out of each to an attenuator and then to the lfo in of the other. then then the voltages coming out of the two stepped outs follow eachother in an interesting way. if you patch each smooth out to the multiple before the attenuator, you can direct these elsewhere as well. you’ll get interesting results patching one of the smoothed outs to the vca, and the stepped out from the other cp251 to vco pitch, and either the other stepped or the other smoothed to filter.
you can also get interesting patterns patching the triangle lfo out of one cp251 to the s/h in of the other, and then by varying the speed of the lfo you’re sampling you’ll get a lot of interesting sequencer-like patterns. i think this may be described in the cp251 manual, but i’m not sure. i kind of prefer this to having a sequencer because it forces me to discover interesting patterns by “tuning in” to them as opposed to inventing a pattern and explicitly instructing the sequencer to reproduce it again and again.
another thing to try if you have a modular with several oscillators is to sample the pulse waveform of three or four mixed together. (don’t sync them). this will give you some interesting melodic sequences with 6 - 8 distinct voltages. of course you’ll need at least one more oscillator to hear what you’re sampling. vary the sampling rate or the oscillator pitch ever so gradually and the tune changes. if you don’t have as many oscillators, you can always tape record your oscillators mixed together, then feed the playback into the s/h in and use the s/h out to control the pitch of the same oscillators. for a variation on this, when you’re taping the oscillators, plug a very slow sample/hold out to the cv in of one or more of them. when you’re sampling the taped voltages later you’ll get a change in the melody every time their pitch changed.
the possibilities are endless and what you can do is far greater than than the sum of sample and hold circuits you have available. you can probably approximate all the above effects with midi, but there’s no substitute for what you discover by accident listening sample/hold patterns in real time.
but no, not really, since the circuit can only really sample at frequencies in the sub-audio range, you won’t hear much if you do this.
of course you may hear more if you tape the output and then speed it up to the audio range. you might get very interesting results this way if you run stuff through the lag processor before taping, and twiddling with the knobs very slowly. but you won’t hear what you’ve done until you’ve sped things up. (kind of the opposite of how the barrons created the forbidden planet soundtrack by taping electronic circuits and slowing them down)
Some tape delays have voltage control, and I have read of people modifing their Roland Space Echos to accept voltage control for tape speed; but I’ve never seen a tape delay that does flanging. I think this may be because the original studio technique for flanging required more than one tape deck.
There are a bunch of electronic delays (Roland, Korg) that accept voltage control of various parameters. I have two rack delays/flangers with voltage control. One is a very rare Bel Line Delay, and I think it’s actually analog. The other is a Delta Lab Time Line, it’s probably digital; But they both are from the 70s and sound very cool, and totally unlike a typical digital delay. The voltage control is very cool for creating freaky modulated delays from an LFO or synth control signal.
I wouldn’t think Moog would be interested in producing a tape delay, especially since they already have an analog delay effect.
I tried sampling things in the audio range and it didn’t work for me. I was using the 101 with the resonance cranked and an lfo modulating the cutoff, that was fed into the “in”, and I connected the “out 1” to my amp. Through the range (.2-50 hz?) of the 251’s lfo all I would get was a audible click when a new sample was taken. I assumed that there’s some kind of filter so only subaudio range samples are taken, especially because the noise source is audible white noise and not pink or whatever.
I had thought that I would’ve been able to get an effect similar to cranking the resonance on the 101 and sending the s/h out 1 to the 101’s cutoff, but it didn’t work.
I might have misunderstood your first post though. Did you mean that the sampling rate has to be really high (well above the 50 hz possible with the 251’s lfo)? I didn’t try increasing the 251’s lfo rate above that…
Right, you won’t get into the audio range with just the cp-251 LFO. I used the square out from a VCO as the clock, any audio source (drum machine, whatever) plugged into the input, and the output (you might want to attenuate) to the mixer or amp.
I went back and tried this again and got it to work, although it was a lot different than what I expected. Here was my setup:
101-
resonance:10
cutoff:a little above 1k
audio out to 251 s/h “in” (Obviously this could be any sound source)
102-
frequency:a little above 1k
carrier out to 251 mixer 1 in
251-
mixer 1 “in” from 102 carrier out
mixer offset: about +2.5 volts (so sampling happens)
mixer “+ out” to s/h “trig”
(all other mixer knobs at 10)
s/h “out 1” to amp
Then I patched the triangle wave lfo’s from the 102 and 251 through the attenuators to control the 102’s frequency and 101’s cutoff for some variation.
I don’t really understand how or why it works, but it does.
nevermind i’m a goof. i just saw it. but i still don’t understand how you can control the 102’s frequency and 101’s cutoff by going into the attenuators. or do you mean the attenuators on the mixer?
i wonder if the sampling freq has to be above the freq of what your putting into it for it to work eg:
if you want to hear how it effect a VCO at 200 hz, then you’d need another VCO of at least 200 hz so that it can sample each period of the waveform?
just a thought, as i don’t have a CP 251 yet, all i can do is think about it. Can’t wait till i get one, i was just about to think about getting round to order one, when the little phatty came out (or until we knew they were up to something, depending on what they would eventually release after all the clues i would get a cp 251 or get the new thing)
by april next year i want my main rig to include
little phatty (on order)
midi-cv (probably one of the frostwave ones)
cp 251
Mf104sd (already have)
at the moment i don’t really have a main rig, just a huge (probably more like.. small but i like to call it huge) pile of keyboards and a four-track MD recorder. sigh, i yern for some CV interaction between my gear
yes, the cp251 s/h circuit actually can sample at audio frequencies, its just that the built-in lfo won’t go faster than the low audio range on its own. i haven’t really experimented with doing things this way much. i recall the last time i tried, of not being able to sample faster than 100hz or so. how fast have others successfully sampled voltages? and have you noticed a difference between how fast the moog circuit can sample compared to other sample and hold modules?
