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tinfoilcat
Joined: Apr 16, 2019 Posts: 8 Location: Stockholm, Sweden
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Posted: Tue Apr 16, 2019 3:45 pm Post subject:
New frontpanel design for Soundlab (and buildlog) |
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Hi all!
I usually end up here on EM searching for information, and was thinking that I should give something back. Also, a MFOS sub forum is awesome.
My winter/spring project has been a Noise toaster (done) and a Soundlab Mk 1. I wanted to add some of Rays mods to it and do a few myself, but I try to keep close to the original.
The octave selectors are Rays design, but I added a voltage divider (1M trimpot between V+ and V-) to feed the fine tune pot with -1 V insted of ground which gives it a range from -1 to +1 V which seems more logical than the original design which just grounded the pot and provided 0-1 V. Schematics (on MFOS) are here, I am talking about R13, pin 3: http://musicfromouterspace.com/analogsynth_new/HOT_TIPS/PDF/FiveOctaveSwitchAndOctaveAdjust_schem.pdf
I added a switch to modulate the pulsewidth with the envelope generator.
I made the EG switch in the VCA section send the gate signal if you turn off the EG (seems common enough for a single envelope synth)
The trig/gate selector switch in the EG section is upside down compared to Rays design. Be aware when following his wiring diagram.
I am using Rays scales for most knobs. A 21-22 mm knob is maximum if you print at 600 dpi. I made my own for the tuning knob since I couldn't stand having a fine tune pot normalled in the middle between 5 and 6.
I also made scales for 0-10 (making 5 sit nicely in the middle) and -5 to +5. I ended up keeping Rays since mine would have been a tight fit and I was tired. I will upload these later though, I need to clean up the GIMP files.
Anyways, pictures!!
The panel is 3 mm MDF with spray glue holding tinfoil on one side and the laminated print on the other side.
The attached GIF should print nicely at 600 dpi (I use A4 paper). Gimp and mspaint gets the scaling right, windows photo printer does not. My fine tuning scale measures 25 mm across on the printout.
Use it however you like! More posts coming as the build progresses and I get the GIMP xcf files in order.
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tinfoilcat
Joined: Apr 16, 2019 Posts: 8 Location: Stockholm, Sweden
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Posted: Sat Apr 20, 2019 3:36 pm Post subject:
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I am not a woodworking guy but I wanted to try and make something for the Soundlab. Pretty happy with this considering that I only used a handsaw. A dining chair is my workbench.
It is some kind of oak. I plan on treating it with linseed oil since I already have that laying around (oil painting..). But still some work left before that.
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Sat Apr 20, 2019 5:02 pm Post subject:
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That's very impressive for just a handsaw. Good work! |
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gabbagabi
Joined: Nov 29, 2008 Posts: 651 Location: Berlin by n8
Audio files: 23
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Posted: Sun Apr 21, 2019 12:52 am Post subject:
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good hand-work!
be carefull with the linseed-oil, somethimes it will do spontaneous combustion under certain circumstances
and of course to the forum |
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tinfoilcat
Joined: Apr 16, 2019 Posts: 8 Location: Stockholm, Sweden
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Posted: Sat May 04, 2019 4:16 am Post subject:
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I did all intra-panel wiring a while ago, so this week I started wiring up everything else. I did run into a few bumps and spent a few hours thinking about how to impement my mods. Learned about the LM13700 in the process. I've found this to be the best part with these projects - you solve problems or add mods and suddenly you realize that you are learning! Sneaky! I bet Ray would like that.
However, this took me a couple of days (maybe 15-20 hours of work/thinking/fixing small problems). I am slow, but it's a nice process. Why rush it?
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tinfoilcat
Joined: Apr 16, 2019 Posts: 8 Location: Stockholm, Sweden
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Posted: Sat May 04, 2019 4:44 am Post subject:
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All that work did pay off. Yesterday was power on-day and everything* worked!
* Naah, OK. The saw/ramp selector switch for the LFO is upside down. And a few tweaks needed as you'll see. But those are design changes.
Since I chose to replace the regular coarse/fine tuning potentiometers with Rays octave selectors there was an issue: 0 volts in on all CV imputs is a high pitch on these oscillators. I needed to add a 150K resistor between -9 V and pin 6 on the LF444:s in the VCO:s to pull it down. Now it sits perfectly at 32' and goes just into the clicks with the fine tune all the way down (-1 V). This might be bushcraft but it works.
I did follow the older wiring diagrams at MFOS and not the ones for the PLUS model. I did change it to the PLUS model when I realized that the EG and LFO are terrible for the VCO.. So the level pots are now tied to ground instead of -9 V. RTFM and this would not have happened. The filter cutoff pot is also connected straight to -9 V eliminating the 4.7 K resistor.
For some reason the VCA did not close fully. I was using the new resistor values Ray recommended, but once again I should have read the PLUS schematic. I solved it by soldering another 27 K resistor in parallel with R17 (which was 27 K), effectively making R17 15 K.
I still need to tinker with the EG in relation to the filter. At low levels it raises the cutoff point (since the level pot is now GND at one end). And the noise sounds wierd at times. I think VCO 2 is disturbing it (not the other way around thankfully).
And a final mod will be to connect the VCA:s EG switch directly to EG out instead of the level pot. This will allow me to use a lower level for modulating something while retaining the maximum output of the VCA.
Oh, apart from these minor issues it sounds fantastic. I had a blast playing it yesterday. Still need to calibrate the VCO:s and finish the case. No more playing until that is done!
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