what is a bobble (old analog synths?)

Anything about hardware musical instruments.
Cruba
KVRist
253 posts since 13 Dec, 2015

Post Thu Oct 11, 2018 7:44 am

Hi people...

I've searched all over the inet, but I didn't find an answer.

In both videos, they speak about a bobble that should be caused by banks hardware. Could you explain me, what a bobble exactly is? I wanna simulate the effect/fail/error with vst, so I've to understand, what it is:

https://www.youtube.com/watch?v=m52-FvE7nVs
https://www.youtube.com/watch?v=lYLNDHL6RKo

JCJR
KVRAF
2337 posts since 17 Apr, 2005 from S.E. TN

Re: what is a bobble (old analog synths?)

Post Thu Oct 11, 2018 9:10 am

From "artistic" point of view seems about as fruitless as Charlie Parker wanting to go back to digitally fix 1940's sax klinkers that millions of folks think sound just great, or Hendrix trying to go back and digitally remove hum from his most-famous solos. :) But whatever floats the boat.

If the bobbles in question are not musical performance mistakes then it could be dirty keyboard contacts or an intermittent cable/connection inside or outside of the synth. A common early synth keyboard was Pratt & Read keyboards with gold-plated busbars and thin springy gold-plated "j-wires" which could wear and lose their springiness, and get dirty/corroded in spite of the gold plate, especially when the gold starts wearing off. So if you hit a note and its making intermittent contact with the busbar, the VCO control voltage could wander around making a burbling sound. But the same could happen with intermittent connections other places maybe triggered by stage vibration or phases of the moon. Or dirt or a "bad spot" in a potentiometer or whatever.

Some of those keyboards used two sets of j-wires and two busbars per note, one for the control voltage and the other for gate/trigger. When the trigger or gate fires on some of the synths (depending on design) it "freezes" the acquired voltage from the CV bus in a Sample-hold circuit, so that the pitch will hold the same for at least a minute or two before drifting off, after the key has been released. Allowing the pitch to remain steady for sounds with long key-release times. If the gate/trigger bus contact is acting up, it can make stuttering re-triggers of the envelope or maybe odd stuff like re-trigger the CV S/H right as the key is being released, causing the S/H to remember the wrong voltage.

Some contact designs back then were pretty durable and some were not.

Cruba
KVRist
253 posts since 13 Dec, 2015

Re: what is a bobble (old analog synths?)

Post Thu Oct 11, 2018 9:42 am

Well, that's why I've posted the question.

For me it sounds, that Banks hyperspeed overstrained (translated, if the term is wrong, sorry lol) the synth. The synth Banks used for this solo seems to be an Arp Pro Soloist.

Banks never made capital errors, the more he would not repeat them in one solo. So what you hear should be a technical thing.

I definately agree with you, that fixing such things is kinda murder "as is music". ;)

JCJR
KVRAF
2337 posts since 17 Apr, 2005 from S.E. TN

Re: what is a bobble (old analog synths?)

Post Thu Oct 11, 2018 10:21 am

Many if not all the Arp mono analog synths of that era used the Pratt & Read keyboards with the j-wires.

There was another design that was also good until it started wearing off the plating, which used little tight-coiled springs. Like a tight-coiled slightly longer version of the return springs built into clicky-button ballpoint pens. Pressing the key would bend the little straight length of coiled spring around the busbar. Making a "self-cleaning wiping motion" on each keypress.

Other designs were built like a tank with big flat pieces of stainless steel relay reed for contacts.

The j-wires were a bit fiddly and fragile but it was a pretty fast keyboard.

Most of the early analog keyboards were pretty fast because the voltage was direct hot-wired to the oscillators. Maybe sometimes delayed for a few microseconds gating the sample/hold to avoid initial "splat" voltage instability when the contact first meets the busbar.

Don't take this as authoritative, but I seem to recall some folks thought the minimoog was faster/more immediate for lead playing than arp because it didn't have any s/h gate delay to allow switch closure voltage to stabilize. Wheras Arp tried to make a cleaner but slower note-start by giving the contact a few microseconds to settle before triggering the S/H.

OTOH any modern system which uses a multiplexed scanned keyboard ain't gonna be anywhere near as fast unless the scanning is real fast.

Its a question "how fast does it need to get" before you can't tell the difference between slightly delayed vs instant? Some of those old blistering players, the Chick Coreas, Keith Emersons, etc. Man were they fast. I guess there are blistering fast modern players too but am too ignorant to know.

Then there is the tradeoff of taste and attention span. Most listeners, myself included, zone out and lose interest after the first minute or two hailstorm of 64th notes. :)

Jim Y
KVRist
382 posts since 29 Jun, 2008 from Mid Wales, UK.

Re: what is a bobble (old analog synths?)

Post Fri Oct 12, 2018 1:32 am

To an Englishman, a "bobble" is a pulled thread in a woollen garment. So yes, it's a defect.

1970's Italian organs / string machines etc. Perhaps there wasn't one made that didn't have a little keying bug, like one key that always plays 2 footages when only one is selected. Those kind of faults can take ages to track down. Someone who plays with everything on would never notice.

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