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Jonte Knif

    Finland
Tube synth teaser
« on: July 20, 2012, 06:39:58 PM »
Hello folks,

I've spent several months with this project, and now I'm beginning to believe, that I will actually finish it. Missing from the photos are of course front panels, keys, power supply, all semiconductor stuff etc. Photos and early CAD drawings here:

https://picasaweb.google.com/jonte.knif/July212012?authkey=Gv1sRgCL_bpafW-Mz8bg#slideshow/5767379317611939218

https://picasaweb.google.com/jonte.knif/Syna?authkey=Gv1sRgCPCst9b0gcDuOg#slideshow/5723577193748053346

Shortly: Oscillators, ring modulator, mixer, moog type filter, noise source, Vari Mu type VCA and output amp are tube units. Everything else is IC and some discrete. Don't ask for schematics, I spent full three months on the circuits alone.

Tuning systems can be changed with small plug in boards. Oscillators have saw, triangle, pulse and very crude sine. There is sync and FM modulation. Keyboard will have after touch but not dynamics. Three octaves of keys, in imitation ivory and imitation tortoise shell. 

-Jonte



kevinkace

    Seattle, WA
Re: Tube synth teaser
« Reply #1 on: July 20, 2012, 07:07:15 PM »
That's bonkers! Looks like extremely clean assembly/woodwork.
Good luck!
« Last Edit: July 23, 2012, 02:49:16 PM by kevinkace »

jackies

    DC
Re: Tube synth teaser
« Reply #2 on: July 20, 2012, 10:33:12 PM »
Amazing stuff, very neatly built too!
Did you base it on the Eric Barbour's modules or it's mostly your own ideas?
Dream build either ways - I can't even bring myself to finish the synth I started building with no tubes...

sodderboy

    Long Island
Re: Tube synth teaser
« Reply #3 on: July 20, 2012, 11:13:25 PM »
Wow. It is sparkling already. Your pics really capture the moment.
Go for it!
Mike

Jonte Knif

    Finland
Re: Tube synth teaser
« Reply #4 on: July 21, 2012, 02:38:53 AM »
Ideas are mostly my own, nothing from Barbour, his designs are not refined enough to perform anything else than "hey, this makes cool noises", whereas I like to see this synth as a musical instrument in a very classical way. VCA for example is true symmetrical Vari Mu, with pentodes, and provides clean 40dB range. Output amp is in fact simplified version of my "therapy pre" which I published here a couple of years ago.

Noise source is pretty much based on this funny thing:

http://www.jptronics.org/radios/GR/GR1390.pdf

Filter is true Moog ladder filter, which is pretty straightforward to do with tubes. It requires variable mu - type tubes.

Mixer is a simple virtual earth unit with 12AX7 and ECC88.

Ring modulation is done with vacuum diodes and transformers, with SE-drivers. Behavior is far from ideal ring modulation, but provides a lot of different timbres depending on drive volume.

Power supply is external and includes small speakers and amp. There are +200V, +120V, -100V, +/- 18V, two 12V and two 6,3VAC supplies, one of which is floated to 100 volts.

I hope I have time and energy to put together a web page for this beast some day, complete with sound examples, a lot of pictures, text etc. But first I have to finish the synth.

rob_gould

    Netherlands
Re: Tube synth teaser
« Reply #5 on: July 21, 2012, 03:29:50 AM »
What can I say - wow!

zebra50

    York, UK
Re: Tube synth teaser
« Reply #6 on: July 21, 2012, 04:51:32 AM »
jaw drops.... that is stunning! Do keep us up to date with progress!
Ribbon microphone services
http://www.xaudia.com
Microphone blog

Spiritworks

    Stamford, CT USA
Re: Tube synth teaser
« Reply #7 on: July 21, 2012, 06:01:31 AM »
Very, very nice. I'm sure it will sound as beautiful as it looks.

letterbeacon

    London, UK
Re: Tube synth teaser
« Reply #8 on: July 21, 2012, 06:40:55 AM »
This is fantastic!

Is there much difference in timbre between a tube based synth and a solid state one?

Jonte Knif

    Finland
Re: Tube synth teaser
« Reply #9 on: July 21, 2012, 08:17:13 AM »

That remains to be heard. I am not really a synth freak, (Well...perhaps I am, but I don't own other synths actually), so I will have to quote other peoples opinions then. Luckily my friend has a Mini Moog in a very good condition and it sounds better than the new ones in some way.

I have so far listened to the filter and ring modulator, and I do like what I hear. They both have very wide ranges of increasing nonlinearities, and so has the VCA, but that I only looked from the scope. It does *look* good though, and I think I know when I see a potent distortion waveform.

There is a lot of "iron" in the signal path, but I am not quite sure which of the transformers actually will have a lot of impact on the sound and in which ways. Three transformers are in very central roles in the oscillators and resulting waveforms are not "perfect", nor is the starting point, a sawtooth from thyratron oscillator quite perfect either. I personally believe that it usually requires quite complex waveforms and/or transient phenomena to make a transformer heard in all its glory, so probably the output transformer is quite central in the timbre, and as you can see from the photos, it is the only "high end" trannnie in the synth, a Lundahl 1671, which is not terribly colored.  Other trannies are smaller, and will certainly create color in the bass at least, where they start to saturate. Overall the signal levels inside the synth are very high, starting with ca. 40V p-p waveforms.

So, I would say that at least this particular tube synth has all the possibilities to sound quite different from the discrete semiconductor classics and most certainly beats all the IC stuff, which is just too "perfect". A lot of lossy and saturating iron + tube nonlinearities should make a difference. I wouldn't be building this if I didn't expect something extraordinary. Too much work and expenses for "for the sake of it" -project.

-Jonte


Timothytitus88

    Perth
Re: Tube synth teaser
« Reply #10 on: July 21, 2012, 11:13:38 AM »
Congratulations, That is awesome design and execution!

tubologic

Re: Tube synth teaser
« Reply #11 on: July 22, 2012, 12:58:23 PM »
WOW !!! This looks fantastic ! Nice to see some new refreshing tube-based projects and not the endless boring reverse-engineered vari-schmutz fairclones. I'm just wondering: did you actually used the Sylvania 6D4 noise tube (with the surrounding magnets) as a noise source ? And are the VCO's solid-state, thyratron , or triode based ? Did you considered using beam switching tubes (like the 6AR8) as ring modulator ?
In comparison with yours, E.B's tube (?) synth looks like a joke.
Please keep us posted about the progress of your project with more pictures and some sound samples. This truly desserves a dedicated website.
« Last Edit: July 22, 2012, 01:06:41 PM by tubologic »

Autophase

    UK - Manchester
Re: Tube synth teaser
« Reply #12 on: July 23, 2012, 02:38:44 PM »
This really does look beautiful, the most awe inspiring piece of DIY I have ever seen.
I want to hear samples and I want to know how much it weighs.

Jonte Knif

    Finland
Re: Tube synth teaser
« Reply #13 on: July 23, 2012, 04:19:56 PM »
I'm just wondering: did you actually used the Sylvania 6D4 noise tube (with the surrounding magnets) as a noise source ? And are the VCO's solid-state, thyratron , or triode based ? Did you considered using beam switching tubes (like the 6AR8) as ring modulator ?



Actually I used another thyratron instead, and it works just fine. It is fun to see how the magnet affects electron flow in the tube. Magnet placement is fairly critical but easy to find, and with todays neodymium magnets the structure remains quite small.
I built some filtering options for the noise, pink and red are also available.

I have built a 6AR8 based modulator before, but this time I wanted to try something different. No particular reason for it,  just out of curiosity.

Oscillators are thyratron based, current driven, nothing new here, and the resulting saw tooth wave is also fed into pulse and triangle modifiers. Sine is from a crude silicon based waveshaper using the triangle as starting point, otherwise everyting is hollow state. Pulse modifier (an adjustable tube diode clipper) includes a proper "DC" removing stage, so that pulse width modulating stuff gets canceled and thus audio freq modulator is possible without problems.

Oscilltor sync uses one of the thyratron grids, but since the thyratron "floats above" the current feeding parts, the sync signal has to be fed through a transformer, referenced to thyratron cathode. I hope this works properly, I didn't care to test it yet. Since there probably are quite serious capacitive couplings in the trannie, there is also a relay to completely remove the transformer when sync is not used. This should be enough.

I have tested that the oscillators work fine from 10Hz to 5kHz. How ever, a complicated compensation system is needed to make them work in tune. This is due to the deionization time in thyratrons, *and* some mysterious effect that affect oscillation at very slow frequencies. Probably something to do with electrode temperatures.

It is one thing to make a "funny noises" tube synth and another thing a to make a "real musical intrument" tube synth. We'll see how this one succeeds, I should know it in a week or so.

-Jonte

Ptownkid

    Ajax, Ontario, Canada
Re: Tube synth teaser
« Reply #14 on: July 24, 2012, 08:48:18 AM »
Could not care less about synths as i don't play them, but WOW that is a work of art so far!!! Congrats.

grubbyliver

    UK
Re: Tube synth teaser
« Reply #15 on: July 24, 2012, 10:37:41 AM »
Knockout! That's some classy work there Jonte and I bet it's going to sound killer too..
In spirit, your synth build reminds me of this ridiculously cool bit of DIY I tripped over here the other day:
http://www.groupdiy.com/index.php?topic=49167.0
These freestyle type builds are really inspiring to see, thinking outside the square, great stuff.
Love this place!

Cheers
Ben



« Last Edit: July 24, 2012, 10:46:30 AM by grubbyliver »

Jonte Knif

    Finland
Re: Tube synth teaser
« Reply #16 on: July 27, 2012, 06:42:52 PM »
 Hello again

Three more pictures from this week, starting here:

https://picasaweb.google.com/jonte.knif/July212012?authkey=Gv1sRgCL_bpafW-Mz8bg#slideshow/5769982686215555714

There is still a lot to do.

-Jonte

RATMNL

    Arnhem, NL
Re: Tube synth teaser
« Reply #17 on: July 28, 2012, 05:50:51 AM »
:O

wow, that looks nice! and indeed like there's a lot of work left :)

Nice going Man!

I KNOW what I'm doing, which does not necessarily mean I UNDERSTAND what I'm doing. Subtle Differences.

mulletchuck

    Midwood, Brooklyn, NYC
Re: Tube synth teaser
« Reply #18 on: August 03, 2012, 12:27:36 AM »
that is unreal, man.  My hat's off to you, and I don't even wear hats!
www.youtube.com/mulletchuck for all my recordings

CarlT

Re: Tube synth teaser
« Reply #19 on: August 04, 2012, 07:02:59 AM »
beatiful,

how long has it taken you to get this far?

Congratulations she really does look wonderful


 

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