Search found 106 matches

by bagoly
Thu Jun 18, 2020 8:51 am
Forum: Music Tech DIY
Topic: Fixing a Korg Poly-61
Replies: 15
Views: 435

Re: Fixing a Korg Poly-61

I don't have any experience with Caikote, but I fixed dead keys by gently brushing on some very fine graphite powder (the stuff that's sold in a spray can as a "lubricant") onto the rubber pads with a q-tip before. The rubber is usually sticky enough so that the fine powder adheres. I didn't think e...
by bagoly
Wed Jun 17, 2020 7:15 pm
Forum: Music Tech DIY
Topic: Fixing a Korg Poly-61
Replies: 15
Views: 435

Re: Fixing a Korg Poly-61

Perhaps another thing you could try is to set Parameter 51 to 1 and read the voltage at pin 13 of IC12. It should read 5V when voice 2 is active, i.e. the small LED lights up. If it stays low then you'll know that there's something wrong with IC12. You could also try to temporarily break the connect...
by bagoly
Wed Jun 17, 2020 3:18 pm
Forum: Music Tech DIY
Topic: Fixing a Korg Poly-61
Replies: 15
Views: 435

Re: Fixing a Korg Poly-61

I repaired a few of those over the years and they all had similar issues to what you describe. The Poly 61 is famous for it's leaking battery, so I'd first inspect all components and traces in close proximity of the battery. Especially connector CN12 and the logic buffers that are connected to it. I...
by bagoly
Wed Apr 22, 2020 9:10 am
Forum: Music Tech DIY
Topic: lm4040 function ?
Replies: 13
Views: 535

Re: lm4040 function ?

So either precision absolute voltage or additional trimmers with cheaper references. To come back to my example of the sawcore VCO: What's the point of using a 0.1% reference when the integrator cap has a tolerance of 1% or worse? I don't think I ever came across 0.1% capacitors. I'm sure there are...
by bagoly
Tue Apr 21, 2020 12:31 pm
Forum: Music Tech DIY
Topic: lm4040 function ?
Replies: 13
Views: 535

Re: lm4040 function ?

LM4040 price depends on output voltage precision. LM4040A (best precision) cost is three times more than LM4040D (1 piece, TO92), for example. But indeed, it is quite handy. True, but then the precision refers mostly to the absolute voltage, not stability. In practise, it does not matter much if a ...
by bagoly
Sat Mar 28, 2020 5:59 am
Forum: Music Tech DIY
Topic: Channel Strip/Compressor/2164 Circuit Advice
Replies: 2
Views: 207

Re: Channel Strip/Compressor/2164 Circuit Advice

You could try to adapt the SSL Bus Compressor to work with the 2164, shouldn’t be too hard I think. For schematics and a short explanation of the circuit look here: http://www.gyraf.dk/gy_pd/ssl/ssl.htm Perhaps you’ll also want to have a look at the THAT4305 Analog Engine IC, which combines a VCA ce...
by bagoly
Tue Jan 28, 2020 6:58 am
Forum: Modular Synth General Discussion
Topic: VCA with offset uses
Replies: 5
Views: 497

Re: VCA with offset uses

I wish more VCAs came with both offset (or manual gain) controls AND attenuators for the CV, I think it's a very handy to have both! Here's some ideas: Amplitude modulation, either tremolo effects or audiorate AM without having to offset the LFO/VCO first. Set the offset to around half unity gain an...
by bagoly
Sat Jan 25, 2020 4:51 am
Forum: Music Tech DIY
Topic: New Sound Semi parts
Replies: 52
Views: 3855

Re: New Sound Semi parts

SSI2130 looks pretty interesting, thanks for sharing!
I'm all for SMT, but QFN32 4x4mm sounds like a bit of a challenge.
by bagoly
Fri Jan 17, 2020 3:34 pm
Forum: General Gear
Topic: Behringer: practices, ethics, morals and legitimacy.
Replies: 1384
Views: 67648

Re: Behringer System 55

I've also never seen the owner of Roland or other big companies in the forums, talking the the customers, asking them what they want, changing stuff when people arent glad about something.. that's how you do it. I've also never seen the owner of Roland or other big companies in the forums, filing l...
by bagoly
Fri Jan 17, 2020 7:22 am
Forum: General Gear
Topic: New gear from Behringer, what would you like to see happen.?
Replies: 225
Views: 16709

Re: New gear from Behringer, what would you like to see happen.?

Kattefjaes wrote:
Fri Jan 17, 2020 6:43 am

The horrible inevitability of Blouds is something we need to brace ourselves for.
Bings into Blouds?
by bagoly
Fri Jan 17, 2020 6:35 am
Forum: General Gear
Topic: New gear from Behringer, what would you like to see happen.?
Replies: 225
Views: 16709

Re: New gear from Behringer, what would you like to see happen.?

Not what I’d like to happen, but it will be interesting to see what the general consensus will be, once they decide to go after some of the more „likeable“ manufacturers, i.e. companies with roots in the modular community. Their eurorack entry is most likely going to be a success, so it’s naive to ...
by bagoly
Fri Jan 17, 2020 6:09 am
Forum: General Gear
Topic: New gear from Behringer, what would you like to see happen.?
Replies: 225
Views: 16709

Re: New gear from Behringer, what would you like to see happen.?

Not what I’d like to happen, but it will be interesting to see what the general consensus will be, once they decide to go after some of the more „likeable“ manufacturers, i.e. companies with roots in the modular community. Their eurorack entry is most likely going to be a success, so it’s naive to a...
by bagoly
Sun Jan 12, 2020 6:30 am
Forum: Music Tech DIY
Topic: DIY TouchKeys surface mount touch sensors
Replies: 8
Views: 550

Re: DIY TouchKeys surface mount touch sensors

How many keys do you need? One possible solution would be to use a microcontroller and a couple of MPR121 touch sensors. Plenty of dirt cheap breakout boards on eBay or aliexpress. It's pretty easy to setup and very reliable due to it's self-calibration routine. You can hook up four devices on a sin...
by bagoly
Mon Oct 28, 2019 1:15 pm
Forum: Music Tech DIY
Topic: [IC] 4U Single Function 'Sergesque' panels
Replies: 440
Views: 53530

Yes, the Intellijel-sized cheeks from ModularSynthLab work with LW-panels, I ordered some a couple of weeks ago!
by bagoly
Sun Jul 14, 2019 2:12 pm
Forum: Modular Synth General Discussion
Topic: new module hate ( my first one ) ... now what?
Replies: 25
Views: 3161

If you patch both the original sawtooth and the sub-square to the inputs of a balanced multiplier ("ring modulator") you should be able to get a sub-triangle.

Mixing the sawtooth with the sub-square at the right ratio will give you a sub sawtooth.
by bagoly
Thu Jun 20, 2019 2:04 am
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

No doubt, an analog harmonic oscillator is crazy and challenging, no matter how you go about it. I have two or three AD633 DIP-8s in my parts drawer and I had to talk myself out of buying a couple more when I placed a mouser order yesterday. I’d love to give it a try and see how far up we can get be...
by bagoly
Thu Jun 20, 2019 1:23 am
Forum: Music Tech DIY
Topic: 2164 Linear Control Circuit Differences
Replies: 2
Views: 448

Here's a link to the original article by Mike Irwin, which all of the above circuits are based on: http://www.sdiy.org/philgallo/EDN-072402.pdf This should explain how to adjust the operating range of the VCA. The normalled +10 in veils ensures that the module can be used as a simple mixer with a ga...
by bagoly
Tue Jun 18, 2019 3:31 am
Forum: Music Tech DIY
Topic: A "through zero" VC flanger that tracks?
Replies: 41
Views: 2194

I do think the delay CV input in the VCV Rack module is slew limited. Any decent-sized step change at this input produces a rounded-off FM pulse to the signal at the delay output that is proportional to the size of the step, both in size and duration (and polarity). This FM pulse is always relative...
by bagoly
Mon Jun 17, 2019 5:17 am
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

each term is based on other calculation , each with their own noise and gain ... and so on. I guess we're not on the same page here. The whole idea of the approach I was suggesting (and that clorax hurd is talking about as well) is to not use your final outputs (dressed up, sidebands and offset rem...
by bagoly
Sat Jun 15, 2019 2:48 am
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

the AD633 is around 8$ at reasonable quantities, and one is required per harmonic produced. so for 8 harmonics that 64$ for just the multiplier ICs. Arrow appears to sell the SOIC version of the AD633 for 6.10$, but you’re right, the accuracy and convenience of the AD633 comes with a hefty price ta...
by bagoly
Fri Jun 14, 2019 3:26 pm
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

It’s a simple recurrence relation really, in order to get the 7f you multiply 2*6f by 1f and subtract the lower sideband, which happens to be 5f. The same is true for the second harmonic, because you multiply 2*1f by 1f and subtract 0f (which is 1, a DC offset). Following that scheme, you can work y...
by bagoly
Fri Jun 14, 2019 1:23 pm
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

Ah, now I understand what you're getting at! Turns out it's not an issue though, everything just magically falls into place: Let’s say you derive your 2f as 2*sin(x)^2-1 and your 4f as 2*(2*sin(x)^2-1)^2 - 1 respectively, multiply both terms by each other and and 2, then substract your 2f from the ...
by bagoly
Fri Jun 14, 2019 9:32 am
Forum: Music Tech DIY
Topic: diy harmonic oscillator?
Replies: 75
Views: 7451

Analog Devices AD633JN analog multipliers, which are available as an 8 pin DIP, or in smaller packages, and can be bought quite cheaply (e.g. ebay). Unfortunately most, probably all of those 2$ AD633s on ebay are fakes. Maybe somebody got lucky, but people usually report them to be fake and I've ex...
by bagoly
Mon May 20, 2019 6:45 am
Forum: Music Tech DIY
Topic: How did you go from knowing nothing to designing circuits?
Replies: 53
Views: 3106

I think one of the most important things when starting out is being able to dissect a circuit into its "building blocks". Looking at a large and complex circuit suddenly becomes a lot less intimidating once you’re able to spot the "boring stuff" right away. Things like summing stages, inverters, com...
by bagoly
Sat Dec 29, 2018 1:44 pm
Forum: Music Tech DIY
Topic: DEADLY CA3280 chips. Watch out!
Replies: 30
Views: 3873

Well, I like the small footprint and the fact that the CV Input expects a 0-5V signal (on the 3381 at least). I imagine it would be very straight forward and space efficient to throw in an auxiliary VCA or two on original designs. I like the idea of having voltage control over the modulation index o...

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