Korg 35 Clone MS20 HP & LP VCF (1 of 2 MS20 filters) - DIY Modular in a Week 7.3
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- เผยแพร่เมื่อ 4 ส.ค. 2024
- One of the most DIY made Voltage Controlled Filters must be the MS20 filter. But did you know there are two different kinds of filters that was put in the MS20, depending on how old it is. In this episode I go through the first MS20 filter, which was built around the mystical Korg35 chip.
Changes to the original schematics accoriding to the following should/could be done:
- For +/-12V R17 should be changed to 17K (instead of 22k), and R6 to 240K (instead of 300K)
- Change C4 to a 10uF instead of a 10nF for better stability If an electrolytic cap is used then the negative lead should be towards the opamp.
- More resonance could be accomplished by exchanging R16 with just a lead (skip the R16) and change the 100k Trimpot to a 500k. This trimpot should be set depending on transistor used.
- HP input: Connect a 2k2 and an input jack between C3 and R18 to get HP functionality. HP and LP "should" not be used at the same time...
Day 7: Filters
Part 3: Korg35 HP/LP Voltage Controlled Filter (Early MS20 filter)
Difficulty: Intermediate
Price: ~9$
MiaW playlist: • Modular In A Week (MIAW)
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Link to the schematics:
www.synthdiy.com/show/?id=2176
Link to Jürgen Haibles schematics:
jhaible.com/legacy/jh_720_vcf.gif
Link to the frontpanel design:
www.dropbox.com/s/isudwmjx6m5...
Link to oscilloscope:
rover.ebay.com/rover/1/711-53...
Tim Stinchcombes extensive write up on the MS10 and MS20 filters:
www.timstinchcombe.co.uk/index... - แนวปฏิบัติและการใช้ชีวิต
Great job! Thanks for posting this!
Hopefully you will achieve some super resonance with the ota filter. I think that is using the 13700. I built the lmnc layout and it is harmonically rich and musical but can still be tamed. Bravo for your tireless work 👏
Kristian, keep doing this, its awesome.
I know Im kinda off topic but does anybody know a good site to watch new movies online?
@Fernando Chase Flixportal :)
@Thomas Damian thanks, signed up and it seems like a nice service =) Appreciate it !!
@Fernando Chase glad I could help :)
The Korg 35 information was leaked by the Korg employees responsible for the design and engineering of the MS-20. Somebody requested the information and because of the age of the product (this is before the re-issue), Korg determined the information was suitable for limited release but not distribution. Mr. Hiroaki Nishijima / KORG INC. Chief engineer who now works for Behringer released the Korg 35 schematic with notes that the circuit was designed by Mr. Fumio Mieda / KORG INC. Auditor and original engineer on MS-20.
Thanks for sharing!
Dope filter ! Any way to have the veroboard layout, please ?
Actually no, I usually just follow the schematics and build on veroboard/protoboard directly from the schematics. It is quite easy once you get used to it, no veroboard layout needed ;)
Sounds good! What transistors (and diode) do you use? You matched transistor pair?
No I didnt match transistors, and I used regular 1N4148, and I had the correct npn and pnp the 2SA970 PNP and 2SC2240 NPN, but bc550 and vc560 should work according to an old document by Jürgen Haible.
@ Thanks a lot! What level signal was in input? (I think for good sound need signal from vco certain minimum level)
im very new to synth and moduler synths and i wonder if i made a silier system how can i control it using a midi keyboard to play it ?
I will make a midi to cv interface in a later video. So that is how you control it with midi. You convert from midi to cv and gate signals.
The component spreadsheet has a 33uF capacitor, should that be 33nF?
I don’t have it in front of me. But it should be whatever the schematics say. The bom might be a bit off.
@ good to know. wasn't sure if you strayed much off the schematic or not
I'm sorry but what I can hear is not an MS20 mkI filter.
The resonance (peak) network seems to be wrong calculated because it starts to oscillate only in the higher part of the spectrum.
Ms20 lpf is prone to loose oscillation in the low end but especially in hp mode it can start oscillating in the sub very powerful.
Nevertheless the sweep seems to be incomplete.
The filter would be able to cut off totally the signal at full counterclockwise.
Is the CV properly offset?
The series capacitor to the peak potentiometer must be 33uF and the capacitor bypassing the 5k6 feedback resistor has a large influence on peak response.
I fucked up and bought the BOM as it was in the Excel without looking at the corrections in the description :_(
nope, you've built that wrong, it sounds broken.
Lol. Ok. Could you elaborate please? It does happen that i solder wrong so I’m not saying you are wrong. But it would be nice to know what you mean.
Constructive critizism /s lmao
@ The clean unfiltered signal (when Q is at 0 and freq is at 100) to me sound distorted and on an MS20 there isn't that much distortion. When you sweep the cutoff knob is dosn't sound like your actuality removing harmonics just kinda changing them. I think you should check your layout for errors.. Also I wouldn't trust every schematic that's out there on the web as (imho) about 30/40% of them have significant errors in them.