There are gadgets that turn a computer into a low-frequency scope, but dunno if they are worth the money, especially if you don't need one regularly. For the last few years, my scope rarely escapes from its toolcase, but when you need a scope, hardly anything else will do.brok landers wrote:iirc, it's the 512 ... but again, i don't think that is the problem:JCJR wrote:I can't recall the bucket brigade chip that solina used. Foggily recall maybe the early solina's used a part that was hard to find later on in the USA. Anyway, most of those gadgets used for musical chorus had 1024 delay stages. I saw some 512 stage units but they were rarer in music gadgets. Much larger 4096 stage and bigger chips could be found in some of the later-generation Analog delay stompboxes. SAD1024 and SAD512 were common parts in synths and stomp boxes.
the problem is imo, to know at which speeds the 3 lfo's modulate each delay, and which phase-offsets are used, also if the dry osc is mixed phased inversed with the modulator fx ...
i don't have a hardware-scope ... is there maybe a free plug that you are aware of that can do this? and, how would i do this? i can't isolate the seperate delays, to then be fed into the scope for examination, can i ...?JCJR wrote:If you are not already, then exactly emulating the delays used in the solina might be a good place to start. If the schematic doesn't specify clock rates, it would be easier to poke a scope in the circuit than mathematically try to calculate the frequency range of the clock generators.
well, how would i do that?JCJR wrote:Anyway, if you determine the min-max frequency of the clock generators (I'm guessing they will all be the same approx range except for component tolerances), you can divide the number of stages in the BBD chip by the clock frequency to calculate the maximum and minimum delay range of the circuits.
no, i didn't, i wouldn't know how ...JCJR wrote:Maybe you already did that, but if not, then if you get the delays in the ballpark it might help.
but yes, that might help ...
IF one had a scope, one would poke the probe on the output pin of one of the clock generators (or a clock input pin on the delay chip), and see a chain of square waves getting skinnier and fatter in response to the LFO. Without a memory scope, you would eyeball the wave looking for the skinniest and fattest wave-widths, and compare the widths against the grid-markings on the scope face to estimate the maximum and minimum frequency of the clock generator. Or zoom out a little more, and count how many square waves you can see in the scope screen at the max and min points.
With a memory scope one might estimate a bit more accurately, by pushing the memory button just the right times to get static snapshots of the frequency extremes.
To look at, or listen to, pieces of a circuit, a hardware hacker would place probes or clip leads on select places inside the circuit, and even selectively break connections to isolate pieces of the circuit. But that is pretty extreme unless you are confident that you won't make a mistake and smoke a perfectly nice old keyboard.
Anyway, best I recall, think you are correct that the Solina delay chips were 512 stage.
To avoid clock leakage, the BBD's had to be filtered below nyquist. And with such a small amount of delay, often compromises were made. Nyquist was set pretty low to get the max available delay, traded off against how much high-freqs you could afford to lose. Depending on the budget, the Nyquist lopass filters might only be second- or fourth-order.
So you might ballpark-infer the minimum clock rate by determining the frequency of the Nyquist filters. Looking at the circuit component values and calculating the frequency. Or, if the direct signal isn't mixed with the chorus outputs, you could just play a high note and look at the output on a spectrum analyzer and see where the frequency brickwalls.
But if the Solina mixes the straight sound with the delays, yer back to either clipping wires or attaching clip leads somewhere on the chorus board.
A wild generic guess- Maybe the brickwall could be as low as 5 Khz (maybe even lower). On the high side, it is doubtful that it is any higher than 20 KHz. With 512 stages of delay, and a clock rate 2X the Nyquist filters, that probably equates to a max delay somewhere in the ballpark of 12.5 to 50 ms.
Given a max length of your delay line, the minimum length could be experimentally ear-tuned. If the vibrato sounds too extreme, then your LFO is sweeping the delay too short.
The delays with fast LFO would make bigger vibrato pitch deviation than the delays with slower LFO's. Assuming the basic circuitry is identical on each delay line. So one might ear-tune the delay sweep distance of the fastest LFO for 'the right amount' of vibrato, and then let the other LFO's make whatever pitch-mod-depth they want to have, sweeping the same delay distance, but at a slower rate.
So you could set up a listening experiments with a 12.5 ms max delay, then ear-tune an equivalent experiment at 25 ms or 50 ms, and see if one of them sounds more realistic than another.
Longer delays have less audible flanging effect, because there are more-and-narrower notches and peaks in the flange. So if you don't hear much flanging in the Solina, PERHAPS that implies a longish delay, within the constraints of what is possible with the measured frequency range of the instrument and the 512 stage delay limitation.
Just some ideas to consider, anyway.
The stock Freeman had fairly subtle modulation. Could sound pretty thin, especially after some reverb was applied. Reverb could wash out the subtle modulation, and make it sound more like to a cheezy single-oscillator Farfisa organ than a 3 oscillator string ensemble. That is the main reason I finally added the chorus unit on mine, to fatten it up when reverbed.hmm, i only heard the freeman once, but i didn't like what i've heard back then ...JCJR wrote:I liked the Freeman, >snip<
The 3 independently modulated oscillator banks feeding into a 3-parallel-delay random-modulated chorus, was an unlocked wobbly wash. You could hold a key for a long time and never find a pattern inside the agitation.
but afaik, it was highly configurable, so i maybe just heard an unpleasant setting, who knows ...
on the chaos lfo:
that's exactly what i don't want.
you'd hear a change all the time ...
on those great stringmachines there of course are some repetitive cycles one can hear, but the signal nevertheless was wide, rich and lush, and you wouldn't notice these repetive "vibrato's" as unpleasant or disturbing, also, again, they're really minimal, compared to what you can reach with conventional chorusses, whatever you tweak them ...
like i said, i have my independant lfo sections with independant phase settings, rates and depths .. but still ...
slowly but surely i'm going nuts on this ...
Solina was used on some hit records where it sounded awfully close to a real string line. Pads on some Chicago tunes and whatnot. Must have been awesome studio wizardry of that time, EQ and great reverb, to turn that churning electronic drone into a string that could fool you (I'm joking, not trying to offend). But I never figured out how to make that transformation recording a Solina.