Hammond clone anyone?

[HughBanton]

Nothing much to show yet, apart from a visual clue :

16 drawbars.png (17.67 KiB) Viewed 25266 times

Red drawbars will be played by the 'Unison' generator set, green by the '5th-tuned' generator, and blue by the '7th-tuned' gen. Just 16 at this stage, to try and prove the principle. (Many more greens and blues higher up).

And so far I've successfully managed to decipher MV's ingeneous masking process and made the 9th harmonic drawbar work correctly. Hey, it's a start

Now that I've realised the complexity of this (to me anyway ..) I fear I'm going to be rather short of time in the coming weeks to get much done, so might have to leave it for now and come back to it.

And there's an added dimension which is worrying me. A major failing of Hammond (partly addressed by Compton, and 'nearly perfected' by Makin during the 80's) is that for a proper organ voice the harmonic levels need to substantially change up the keyboard; in general lower harmonics get louder and high harmonics get quieter, indeed inaudible in some cases. And then I want to add stops together.

I know exactly how to do this, I've already perfected it in HB3, but the best I can visualise for this particular format is a 61_note x 64_harmonics array - presumably a mem array - which would need to be read by the keying in place of the simple set of drawbar floats. Yikes...

So why ?? Need to remember the massive advantage with this method is total polyphony and, in principle, a limitless stop list.

Hoping for that Eureka moment at some point ...

H

[lalalandsynth]

This is pretty sweet , sounds very nice indeed.

[sha664817]

Electrostatic Compton organs utilized pulleys and belts so were sensibly near equivalent personality. Later they (or all the more especially Makin) included second and third off-tuned sets of wheels to get the pitches of the maverick sounds nearer. On the off chance that I can get the new task working I'll attempt and re-present that.

A debt of gratitude is in order for those connections Spogg, fascinating to see every one of the subtleties spread out that way. It's constantly stunned me that Laurens Hammond couldn't play a note, did you know? He was a splendid innovator (synchronous electric clock, 3-D film glasses and so on.) and his organ configuration is so off the divider - very not at all like the instrument it should duplicate. But then it remains, on account of shake and jazz, the main electric instrument of old that is as yet held in such high respect.

[MrFuls]

Hugh pointed me here (Hope Johnburtell doesn't mind my somewhat unsolicited banter in his thread ), so I think the following post will be more at home in this thread.

I've been tinkering with tonewheel hammonds (Porta-B and E-112) for about a decade, so I'll be patiently monitoring, and possibly in the future contributing to this thread.

I've briefly peeked behind the curtain of Martin V's tonewheel generator schematic, and was blown away by how much was done in code. I'm clueless to understand all of how it works (clearly put together with a much better understanding of DSP than I can muster), but regardless it will be of great help to not have to re invent the (tone)wheel

I've got a host of project ideas, some grandiose and ridiculous, some modest and doable. You'll all hopefully hear of some in due time (Don't want to hype up what doesn't exist yet). In any event, I hope to have some really fun discussions here. Gigging with an original tonewheel organ (all ~300 pounds of it) is a unique experience that tends to create its own funny short stories

[deraudrl]

Gigging with an original tonewheel organ (all ~300 pounds of it) is a unique experience that tends to create its own funny short stories

Or, as in the case of Keith Emerson, legends.

[MrFuls]

Or, as in the case of Keith Emerson, legends.

Indeed! I don't think I would have the gumpton to lie an L-100 on myself and play it (Knowing the voltages that zip around those things, yikes!)

My Porta B was a somewhat steamlined L-100 series that would separate from its base, a factory hammond "chop", if you will. Still shared a lot of L components, like that wimpy saturable reactor phase shift vibrato.

Had to do a whole Bob Marley tribute concert in high school performing arts band with only that vibrato (a leslie couldn't be sorted out in time and the organ kept 'messing up' any amp we plugged it into)

Tons of shenanigans with that thing now that I think about it. There was the one time it just up and went flat and started smoking during practice (It's become common advice to "HOLY DEAR GOD REPLACE YOUR SELF-START MOTOR RUN CAPACITORS NOW" on hammond forums and webgroups these days)

Later on, the bottom base unit with the pedals started to split apart, and had to be hastily screwed back together with some screws from the shop. After the shows came and went, I finally took the thing home, where it collapsed in a sorry heap of wood and hammond parts.

Said parts now line the walls of my workbench...waiting...although the synch motor is in the other organ now because I'm an idiot hack and broke the original one that belonged to it (to ebay!)

Addendum: I might've been quick to dismiss my ability to understand Martin's tonewheel organ. My trigonometry is rusty (it was awful when new), but I start to see how it relates to sine production, the role of the dispatcher module in setting amplitudes, etc. Still have that ''way over my pay grade' feeling (Self taught in electronics, no formal qualifiacations), but a lot of this stuff somehow starts make sense and "look like what it is" under scrutiny. Martin's Quadrature oscillator writeup PDF also helped a great deal.

I really can't wait to get into this stuff at a greater level, but it's the busy season, and time is short. Up way too late myself!

[Spogg]

I’m currently experimenting with my own version of a clonewheel organ using more “conventional” methods. So, I’ve been reading and re-reading everything I could find on the subject and watching a lot of YouTubes. I’ve listened to various sampled instruments and noticed something that doesn’t seem to have been mentioned anywhere. Each note can have a slightly different timbre. I’m not talking about the effect of ageing capacitors on the wheel filters, but the makeup or balance of the partials.

In the Hammond Tone Generator (TG), the wheels are mounted on their shafts with slipping clutches. That means that if a wheel gets mechanically stalled the others continue to spin. A guy on YouTube showed this. I concluded that Hammond didn’t have any type of wheel detent or fixed rotational orientation, which in turn means the relative phases of the sines are fixed but not defined, and can vary between individual instruments.

We know that human hearing is said to be insensitive to partial’s phases but is sensitive to the balance of harmonics. I know from my experience with my Quilcom Wavemaker that when you define partial ratios, but randomly scramble the phases, it has an effect on the timbre due to mathematical summation/cancellation effects.

To check this out I added phase knobs for my 9 oscillators, together with a randomise button. The results of randomising relative phases are clearly audible and I’ve attached a zipped MP3 file to demo it. Each click in the file (I removed the de-zipper) is when I randomise the phases.

In a real TG, each and every wheel will have its own relative phase, so I would expect this would lead to any note, with more than 1 harmonic drawbar pulled out, to have a slightly different timbre to the other notes. It also has an effect on the signal peaks, so some notes should be a little louder than others. I think this may be a desirable, if unintended, effect on the “organic” aspect of Hammonds!

[martinvicanek]

Thanks, Spogg, for this interesting demonstration. Some time ago I noticed that the phase of partials does matter, but that was for integer ratios. Now I was surprised to see an influence on timbre also for non-integer ratios, where the relative phases constantly change. Therefore, I would have expected the initial phases to quickly randomize, so in the end it would not make any difference. However, your demo clearly proved me wrong!

[Spogg]

I just found some new information from YouTube where a guy examines a tonewheel in great detail.

In fact, the tone wheels are mounted in pairs and their relative rotational positions are fixed solid during manufacture. There is a Bakelite drive wheel for the pairs and the coupling between the Bakelite drive gear and the pair of wheels is on a slipping clutch and so not defined. But pairs of wheels are n octaves apart, so any cross-talk between the pickups will always be phase-locked. Of course, these pairs will be at any random phase between other pairs, so the issue/feature I talked about remains.

All this is pretty irrelevant, especially when playing actual music, but this thread seems to be about the details so I thought I’d mention the new info.

[tulamide]

I just found some new information from YouTube where a guy examines a tonewheel in great detail.

In fact, the tone wheels are mounted in pairs and their relative rotational positions are fixed solid during manufacture. There is a Bakelite drive wheel for the pairs and the coupling between the Bakelite drive gear and the pair of wheels is on a slipping clutch and so not defined. But pairs of wheels are n octaves apart, so any cross-talk between the pickups will always be phase-locked. Of course, these pairs will be at any random phase between other pairs, so the issue/feature I talked about remains.

All this is pretty irrelevant, especially when playing actual music, but this thread seems to be about the details so I thought I’d mention the new info.

My info may also be irrelevant, but i thought, if you look at such detail into it, you might want to look at the mother of Hammonds. The tonewheels were not their invention. They are based on the "Telharmonium" (or "Dynamophon"), created over 20 years by Thaddeus Cahill in the late 19th century. Mr. Cahill also was the first to use the word "synthesize" to describe the sound creation process.
https://120years.net/the-telharmonium-thaddeus-cahill-usa-1897/