KORG MS10 VCO PCB BOM
Here is the BOM.
I'd match RS1 through RS8 for better octave switching
Match d12 and d13 for voltage drop
I'd also match r84,r85, and r86. For C1 I used a polystyrene cap.
I used burrbrown op-amps opa604 for the cv and an opa2134 for the wave shaping
(all in sockets).
PARTS LIST
C1 6200p
C2 100p
C21 0.1uf
C22 100uf/16v electro
C23 10uf/16v electro
D1 1N4148
D2 1N4148
D3 1N4148
D4 1N4148
D12 1N4148
D13 1N4148
F1 2SK30A (O)
F3 2SK30AGR
IC1 TL081
IC4 TL081
IC6 LM4558
R 22M
R8 100R
R9 10M
R10 5.11K
R11 10K
R12 10K
R13 2.2K
R15 100K
R16 100K
R18 110K
R19 33K
R20 1.5M
R21 10M
R70 100K
R73 427R
R75 427R
R76 56K
R77 10K
R78 4.7K
R79 6.8k
R80 43K
R81 330K
R82 4.7K
R83 100K
R84 100K
R85 100K
R86 100K
RS1 100K
RS2 100K
RS3 100K
RS4 100K
RS5 100K
RS6 100K
RS7 100K
RS8 100K
SW1 SCALE
SW2 WAVEFORM
TR1 2SA733
TR2 2SC1685
TR3 2SC1685
TR4 2SC1583 or nte42
VR2 100KB TRIM
VR4 100kb TRIM
VR6 100KB
VR9 100KA
VR10 100KA
VR11 1M
I'd match RS1 through RS8 for better octave switching
Match d12 and d13 for voltage drop
I'd also match r84,r85, and r86. For C1 I used a polystyrene cap.
I used burrbrown op-amps opa604 for the cv and an opa2134 for the wave shaping
(all in sockets).
PARTS LIST
C1 6200p
C2 100p
C21 0.1uf
C22 100uf/16v electro
C23 10uf/16v electro
D1 1N4148
D2 1N4148
D3 1N4148
D4 1N4148
D12 1N4148
D13 1N4148
F1 2SK30A (O)
F3 2SK30AGR
IC1 TL081
IC4 TL081
IC6 LM4558
R 22M
R8 100R
R9 10M
R10 5.11K
R11 10K
R12 10K
R13 2.2K
R15 100K
R16 100K
R18 110K
R19 33K
R20 1.5M
R21 10M
R70 100K
R73 427R
R75 427R
R76 56K
R77 10K
R78 4.7K
R79 6.8k
R80 43K
R81 330K
R82 4.7K
R83 100K
R84 100K
R85 100K
R86 100K
RS1 100K
RS2 100K
RS3 100K
RS4 100K
RS5 100K
RS6 100K
RS7 100K
RS8 100K
SW1 SCALE
SW2 WAVEFORM
TR1 2SA733
TR2 2SC1685
TR3 2SC1685
TR4 2SC1583 or nte42
VR2 100KB TRIM
VR4 100kb TRIM
VR6 100KB
VR9 100KA
VR10 100KA
VR11 1M
MS10/20/50 Components by Peake
This entry consists of thinking out loud about the MS series circuits and components thanks to the great PCB projects from EAS, available in the muffwiggler.com DIY forum. Thanks EAS! And thanks to Tim Stinchcombe for his amazing MS series pages and his thoughts. The majority of this is thanks to Tim. Thanks for putting up with my selfish musings, both of you.
The suffix on Japanese transistors seems to refer to specific behavioural ranges, so that you may select a FET with the proper Idss range and regular trannies with specific gain characteristics. Your circuit will function with components which operate in the specified behavioural ranges.
The Oscillator.
2SK30A (GR)
This FET is still easy to find on eBay and other places, and was used in everything from oscillators to effects pedals.
Vgs range: -0.4 to -5.
Idss range: 2.6 to 6.5.
The BF245A covers the same VGS and Idss ranges but goes slightly outside of them as well, so it is a good idea to test and select ones in the desired range(s).
Vgs range: -0.25 to -8.
Idss range: 2.0 to 6.5.
www.smallbearelec.com $1.00 each
2SK30A (O)
Got a batch from Dalbani.co.uk / Nikko Electronics. Good people, I recommend them. Thanks!
Vgs is between -0.4 and -5, same as the GR.
Idss range between 0.6 and 1.4.
Difficult to find! Didn't get a reply from XOX box parts suppliers. The Idss of this component is also evidently directly responsible for the square wave purity/duty cycle of the TB303 oscillator. I haven't seen a specific Idss measurement posted representing the purest square… I note that it appears in the first revision of the MS series noise generator as well.
The 2N4339 of Buchla fame (oscillators, frequency shifter, etc.) is similar. Vgs range: -0.6 and 1.8. Idss range: 0.5 and 1.5. These are very difficult to find, and even then, you'd need one with max Idss. Vgs could also be a little low…I've found some of these online for between $3.53 and $6.70 each.
I note that for some short time, Fairchild produced their own version of these FETs, with a KSK30 prefix. I have not been able to find these components anywhere. If you do, know that
2SK30A GR = KSK30 G (Idss of between 2.6 and 6.50 for both).
2SK30A Y = KSK30 Y (Idss of between 1.20 and 3.0 for both).
2SK30A O = KSK30 O (Idss of between 0.6 and 1.40 for both).
2SK30A R = KSK30 R (Idss of between 0.3 and 0.75 for both).
Check the datasheets to see if pinout is the same.
2SK and KSK are =not= available at Mouser, etc.
TR1 2SA564A (S) or 2SA733 (K)
The 564A is a better component than the 564.
"S" version Hfe: 260-520.
Pinout ECB
www.goldmine-elec.com Item A10402 2SA564A , has "S" suffix. Ten quantity averaged 350 hfe, right in the correct range. They have a mininum $10.00 order, so check out their ICs and such. They have 3046s hidden in the transistor section, for about $0.49 each.
http://www.goldmine-elec-products.com/prodinfo.asp?number=G32158
EAS post that the 733 can be used here per the change to it in the MS50 oscillator. But it's a "K" version, high Hfe, between 300 and 600.
I note that higher gain 733P can easily be in the 400 range as well. I got a bunch of high-gain 733P from Polida on ebay for $2.00.
2SC1685 (S), matched pair(?)
The MS10 Service Manual does not state if these components are special selected / matched. The "S" version of this component has a rated Hfe range of between 290 and 460.
Found some 2SC1685 on eBay and in looking closely at the item photo, noted an "S" on them…they are selling in batches of five; I bought fifty and from that, pulled several pairs matching both Hfe and Vbe, although the Hfes were on the low side of things, averaging around 320. Too bad if Hfe matching isn't important in the oscillator, I'm working on the side of "thorough" because I can.
http://tinyurl.com/42cdyd6
That sale now shows a pic of a "Q" version, not applicable to this build.
2SC1583 (F) or (G).
The difference is in the gain charcteristic(s). F: Between 250 and 500 G: Above 400. Many of these on eBay show an F or G if you enlarge the item photographs, even though the sales listing does not specify "F" or "G".
This component is also used in the original TB303, so you know that the XOX box crowd have them stashed, if you can find anyone willing to part with some. I note that there is a warning in the XOX box crowds against 1583s with a "52G" on them; they may be re-labeled 798s. Check the Hfe to confirm or deny 1583 pinouts…and I see that one seller on eBay does indeed show the 52G, so take care as they may have gotten some from the same source.
andrewselectronics.com lists it for $4.11, but say that they no longer have it, despite their internet posting.
You can match a pair of transistors for this section if you have to, but in my experience, depending upon the circuit, you can end up with much lower performance results than if they are on a single silicon strata as with the 1583.
Two TL081?
I'm not using two TL081 as specified because the MS10 Service Manual shows that there is indeed an 081, IC4 just after the matched resistors, but half of a 4588 is used for the modulation summing, and a 4558 is basically a dual 741. So, a 741 will go there…DIY means each person can choose what they like. I've owned a few MS20s in my day and never found a problem with their tracking or stability so a 741 will be closer to this than other options.
C23
The 10uF electrolytic directly following the main FET might have audible importance, even if its purpose is a slight highpass function (1.4Hz according to EAS..Thanks!). I'm going to try Elna Silmic II caps here because I have some. Sorry, no Mundorfs :D
Worth considering as in this design, the sawtooth waveform is very nearly right out of the FET, only interrupted by the capacitor and a single level-compensating resistor, if that's its function. Nice, clean, gotta have it. No opamps there. The word "discrete" comes to mind, even though the rest of the circuit uses opamps. This part is just fine.
C21
Is a 0.1uf non-polarized; there is only one .1uF listed in the MS10 service manual, a ceramic 25V. It is clearly visible in the following pic.
Mouser, 0.1uf 50V disc, 5mm pitch.
140-50U5-104M-RC
They have small multilayer as well.
6200uF Polystyrene
6800pF Mouser 23PS268 $0.37
(EAS say just play with init Fc trimpot a touch)
or
6220pf polystyrene capacitors, US distributor, $10.00 minimum:
http://www.surplussales.com/Capacitors/Poly-Unelco.html
(CPF) 006220R0AFAV 6220 pF 33v 1% $1.25
C22
10uF / 16V? Listed as such in the 10, 20, and 50 schematics.
1S1555 Diodes.
4) 1S1555 (D12 and D13 in the triangle wave circuit appear desirous of matching)
Tubeshunter on eBay have 1S1555 in large batches, but they are actually 1S1588, which are electrically compatable. These are also used in the DS1 distortion pedal.
Diode matching is said to best be accomplished with your VOM at DC voltage, ground to power supply ground, and +15V to a 100K resistor, to the diode to the positive VOM input. I haven't tried this yet.
These do indeed have a different rating than the 4148. Anyhoo, D3 and D4 in the modulation inputs / summing might be worth matching as well, if that sort of thing is very important to you.
Matched pair, 427R
The MS50 oscillator schemo does indeed indicate that these need to be matched. Grabbing 200 quantity 430R 5% as 430R 1% probably won't dip low enough…will select with VOM.
8 100K point 1% (999,950K to 100,050K only).
Mouser 71-CMF55100K00BHEK
24 for three oscillators is $8.64.
http://tinyurl.com/3n8w8ho
It may be possible to use appropriate value trimpots jumpered across the resistor pads, if you don't have a VOM that can display five or six digits, or if you don't want to order .1% components. In that case, set the trimpots for the appropriate total K for each batch of resistors they are superceding. Turn the hopefully multiturn screw so the VOM jumps between 100,0 and 9999. This is theory, it is untried, so caveat emptor. Of course, you can use your ears against a digital synth for tuning reference.
Linear FM?
The jack at the base of the resistor chain/Scale switch is a hz/volt control voltage input. It would be interesting to use it as an FM input from another oscillator's audio out to see if it makes available some form or amount of linear FM. You could use these oscillators with a MIDI/CV converter capable of producing a hz/volt output.