16-01-2023, 07:10 AM
It's an interesting subject Lucien, I was researching this recently whilst looking for valve oscillator circuits for an idea I had. The idea was basically a one octave LF keyboard, a bit like a sub Fender Rhodes bass keyboard but lower frequency, eg 16.35hz & up. I tried a phase shift oscillator but that wasn't a success, it was too hard to adjust & the sine wave was distorted. I couldn't find a simple valve oscillator so experimented with a op-amp wein bridge oscillator adjusted using 10 turn presets. With that I could dial in the frequency so it was bang on.
I saw how Hammond did it, IE with notched disks and pickup's, this would be hard to do DIY as there's to much engineering brackets etc. I saw some Lowry organs that looked like they were using individual oscillators and also at the Thrytone that used thryratrons, I've yet to try those oscillators but the thryratron idea looks interesting.
The other tricky bit as regards organs is the keyboard, the action of the keys themselves. I think Hammond used a "waterfall" key & each key had multiple contacts that engaged with bus bars. Hammond keys are clever in that the spring contact slides as it makes contact, the idea being that this action cleans itself ridding itself of any potential oxidation or carbon.
I could be wrong on some of this, my research was brief, so this thread is very timely, i look forward to more. Andy.
I saw how Hammond did it, IE with notched disks and pickup's, this would be hard to do DIY as there's to much engineering brackets etc. I saw some Lowry organs that looked like they were using individual oscillators and also at the Thrytone that used thryratrons, I've yet to try those oscillators but the thryratron idea looks interesting.
The other tricky bit as regards organs is the keyboard, the action of the keys themselves. I think Hammond used a "waterfall" key & each key had multiple contacts that engaged with bus bars. Hammond keys are clever in that the spring contact slides as it makes contact, the idea being that this action cleans itself ridding itself of any potential oxidation or carbon.
I could be wrong on some of this, my research was brief, so this thread is very timely, i look forward to more. Andy.
