hello world, or forum. this is about tubes

galactic plane · Joined: Dec 05, 2009 Posts: 3 Location: hemma bl a

Hi i´m new, I want to make a synth and I have questions.

This is not gonna be a breif post.

Ok a few months ago I started getting tired of softsynths, sure its very convenient and so but for those really kickass non perfect sounds I feel I need something more. I have found some hardware that i think sounds really fat, the SEM for instance, I wish I could buy one of these.

But then i heard something seriously much fatter, tube synths, and like 12 hours ago I wanted to build a 6voice 12osc 12lfo tubesynth with separate hp and lp filters 1v/oct (running at the same time so i get 2 q) and more

But then i found out that tubesynths doesnt exist, at least not with vacuum tubes, cos the osc-tube is actually a gas discharge tube.

as far as I know you can make a "tube"-osc of a thyratron or a neonbulb.

But then i started thinking; why cant you make an osc of any kind of gas disharge lamp? you probably can I'd say.

There are many types of gas discharge lamps, and one of them is the flourecent light, well not really a "gas discharge lamp" but still there is gas in there that does something, or maybe its lack of gas. somehow this type of tube emits light, and it probably has some kind of theshold voltagevise when it starts to glow and conducts electricity.

Well i found vid http://www.youtube.com/watch?v=s_6xyMU-uV8

Thyratrons dont respond very well outside 2,5 octaves i read, neither does neon bulbs, too bad for me, and thyratrons behave different from speciemen to specimen, it would probably be very difficult for me to get these working over 5-6 octaves in a kinda linear/predictable fashion.

I have a feeling new flouros are made to pretty good tolerances,
still I havent figuerd out exactly how this would work, I guess the tube would be connected parallell to a cap and a resistor, there are both variable caps (up to like 500nF) and pots available, maybe i should get some?

The difference between a thyratron and a flouro would be that the thyratron has like 1-3 controlgrids and a flouro only has 2 connections, but then again a neon lamp has only 2 connections too (but its a negative resistance device), now i started to think a bit more, I dont really know how flouros work but I guess electrons go from one side to the other and they change direction fast heating something in these tubes eventually turning it to plasma that i guess conducts electricity quite well.

Electrons have a negative charge and maybe you could regulate/modulate this flow somehow, maybe put an ironpowder toroid which you have made into a an inductor by threading some copper wire around it and apply voltage while you inserted the torois halfway across the tube?

I dont know really i guess i have to try, do you guys have any suggestions or ideas/knowledge about this?

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I also have a question about multimeters, i measured the +and - poles of my stereo amp today and it reads 6v, it was quite loud, and I read my multimeter has a bandwidth of 45hz-1khz, does this mean my multimeter detects a voltage of 5v between 45hz and 1khz and ignores the rest?

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Seems like a nice forums this, I guess these are stupid questions but still I would like to know.

EdisonRex · Posted: Sat Dec 05, 2009 11:52 am Post subject:

hi, and

You're right about the thyratrons. I have a Wretch Machine and 2 octaves in any particular range is about right. I don't think that's really a bad thing, it's more to me that it is the limitation of the physics of the thyratron. Once upon a time I had an old Lowrey organ that used scads of neons for its oscillators, Range wasn't a problem since each oscillator was fixed pitch.

I don't know much about using modern fluorescents, but the better ones have some fairly constraining design points. I've seen some neon oscillators that have a lot of range, but linearity/tracking can be an issue there. Packaging would be interesting for a start.

thermionicjunky · Joined: Dec 07, 2006 Posts: 90 Location: san francisco

There are some options beyond thyratrons. You could try a wide-range self-oscillating filter controlled by a vactrol. Metasonix has a prototype based on an old design for a "tunable amplifier," which was just a resonant bandpass filter. The output could be distorted for some waveform options. The thyratron oscillators in the Wretch Machine cover nearly six octaves using a gas regulator tube, but it is arranged in three groups of two. Metasonix is working on a self-tuning MIDI to CV converter, so anything can be played in tune if it is reasonably stable. Aside from that, there is a Metasonix schematic on Ken Stone's website for a keyboard or MIDI programmer with trimpots for each note.

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

lot's of good info here:
http://www.cgs.synth.net/tube/index.html

but heed the caveat:
A note to readers: this circuitry is intended for the more advanced builder. Because high voltages are used, a shock hazard exists. We do NOT recommend that the novice DIY musician try to construct this synthesizer. Some experience with tube electronics is highly recommended.

better to start w/ some simpler semiconductor circuits that are less likely to kill you, IMHO...
b

j.dilisio · Joined: May 19, 2009 Posts: 200 Location: baltimore

Check out the samples of Ken Stone's Tube VCA at Metalbox.. http://www.metalbox.com/
You can get a lot of great tubular sounds out of just the one tube module in conjunction with whatever you want to run through it.
Lots of options there.

galactic plane · Joined: Dec 05, 2009 Posts: 3 Location: hemma bl a

There seems to be a wide range of "oscillators" http://en.wikipedia.org/wiki/Electronic_oscillator

I have read most things now at http://www.cgs.synth.net/ the tube section,
plus a few other sites. The thing I would like is a no IC, no transistor, no OPAMP synth, at least not in the oscillator and lfo circuits. I felt I needed to read up on different circuits so I opened a few
electronics books. I haven't gotten very far reading since its much information to digest and eventually understand. The more I read the less I understand.

Making a "RC oscillator"?
"Timeconstant" for a(an?) RC circuit = R*C, I guess its in ohms and farads, not quite sure what this means yet.

does it mean R (10ohms) * C (0,001F) = 0,01 seconds to charge the capacitor = 1/0,01= 100hz oscillation? (if I discharge the cap into a flouro tube for example)

And to make things worse I read this also a simple lp-filter and if I change the position of the components it becomes a hp-filter.

I feel It may be better for me to just get some components and something that can measure frequencies and try out some ideas and see what comes out of it.