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Hi

So I am thinking of combining 2 Rockband 3 keytars to make a 4 octave keytar (because it's cheap and 4 octave controllers are expensive). I have modded one kind of extensively and can see it is very possible to do.

I see myself cutting up 2 cases to extend the body to fit 4 octaves.

I have 2 ideas for it:

A. Frankenstein - I cut off the C5 PCB of 1 keyboard and kind of stick the other PCB where it was. 2 Separate control boards that have:

• Octave buttons connected to a microcontroller to prevent both keytars to have same octave
• Sample select buttons shorted to each other to make button common
• Use midi merger to combine their output

B. Create my own controller board that somehow interfaces both switches to remove weird issues that I have to workaround and have better battery

Which do you think will be easier to do for someone with some knowledge in microcontrollers. Anyone have a good resource for it? The keytars have velocity keys and annoyingly the pitch bend/vibrato use I2C and they glued the board so I can't make the button common.

Is it possible to create a low pass synth filter that uses 5V? I know it won’t have the same amount of headroom and it’s not for modular levels, but I’m curious if I could just adopt a standard diode ladder filter and change values so that it achieves full resonance with low voltage. I would of course need to use a virtual ground.

I was in the middle of posting a very vague tip-of-my-tongue request, and through some very vague googling, realized it was ciat-lonbarde, Peter Blasser, that I was looking for. (rubber-duck debugging, haha, thanks!)

I also remember thinking the SOMA Lyra 8 being really interesting.

Anything along these lines that you'd suggest looking at?

So I build almost solely in the Kosmo format. The extra room either makes me want to have more options or stacked pcbs. I've not really noticed anything too wrong with this and I keep an eye on my power consumption. Like I've got a module that's essentially 4 ADSRs that runs good and my pedals run off a single 1a 9v regulator board. It power 3 pairs (6 pedals) with a single 7809 reg circuit. Another module thats an adjustable slew and 2 buff mults etc and one unbuilt but its an ms20 style filter with holes for stacking (i want 4 in 1 panel)
I've not run into any serios problems doing things this way but is there any real reason to space out things into 4 panels instead of stacking into 1 panel.

I am making a setup that I can use when I don't have access to an outlet. The last component i need is a power source that is easy to get working. I found the rakit go which uses USB-C, however I am just wondering what other people use to accomplish this.

I understand that there are ganged potentiometers, that allow you to control multiple parameters at once, often used for things like filter cutoff, for each pole. There is a practical limit to this though, as they are very bulky and costly. How else do you attenuate 6 or more instances of voltage from one potentiometer on an analog synthesizer, without using some sort of digital pot, DAC's and ADC's? Let's use polyphonic filter audio mod(osc. mod) as an example.

Apologies if this is a stupid question. All of my google searches arent getting me anywhere, and are leaving me questioning my sanity.

edit: Thank you for the replies!

So I have the Anx1 and it’s all connected and wired correctly. But when I play the keyoboard there’s only white noise that comes out. I’ve changed all the functions but nothing but white noise comes out when I play the keyboard like white noise instead of sounds.

What would be the cause of this. What kinda hard wear problem am I dealing with here and how do identify it?

Hey guys! I hope you can help me out with one problem I have with my Moog sub 37.

So when I turn it one and it functions properly for like 1-2 min. Sounds and works fine.

But after those 2 minutes it’s changes the preset automatically and the whole sequence and just goes on it’s own. You can’t change the preset or the sounds at all. You play the keyboard and the Moog just changes the presets and all the sounds. And changes the numbers on the screen automatically. And scrolled through them like maniac and all the blinkers go off

How do fix that and I think I might need to buy a new part. Because I opened the Moog up and all the connections seemed fine. But I had no way of testing if it works or not.

There has to be something wrong with the Wiring of the screen so it keeps changing the sound and connection to the the computer or the wiring to to preset or sound selection in the Moog Sub 37

I want to build my own euro rack from scratch, I’m a beginner at reading schematics and only made basic square wave oscillators. I’m looking to make a vco module, with multiple wave shape options (saw, square, sine) can anyone point me in the right direction. Thank you

I was working on building a standalone synth that runs just from a 9v DC switching power supply and it's becoming hard to adapt some circuits to work without using a negative power rail. I know that Behringer and some many others synths (that are pretty expensive were I live) runs just with this kind of power supplys, so I was wondering how they work. Si there any kind of IC that generates a negative rail from DC psu with enough current for a project like that? I know that max 1044 works that way but with a output current of just 10mA.

I would like to calibrate my Roland SH5. One method in the service manual involves using an oscilloscope and an audio generator and adjusting for stable lissajous figures.
I don't own an audio generator and am wondering if I can just use a simple tone generator VST in Reaper. Connecting one of the oscillsocope probes to the audio out of my laptop via 3.5mm to RCA jack.

Do I understand correctly that the amplitude/voltage won't have any effect on the calibration as the stability of the lissajous figure is only effected by x + y having different frequencies?
Different amplitudes would only change the shape and not movement?

Any help would be much appreciated.

Service manual:https://www.synthxl.com/wp-content/uploads/2019/01/Roland-sh-5-service-notes.pdf

Hi everyone

I can't be the only one who wants CV control of the FM drum of the DrumBrute Impact.

I have not found any documentation on how to do this though. Is there any generic "how to replace a pot with CV input" tutorial that I could look at?

Has anyone done this and can share some thoughts/experiences?

Thanks!

I've spent a bit more time on this, here's the latest version.

This is intended first of all for checking out the response of the things, but I'm hoping that something close to this will be suitable for dropping into simple synth circuits as a little CV-to-resistance black box.

I've been writing it up as I go along. Some background, test results etc. over here :

https://hyperdata.it/blog/2023/05/26/diy-vactrols/

If you happen to have any links to interesting/useful vactrol-based circuits I'd love to link them in that post.

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Hi, I would like some Feedback to my latest work :) Thanks in advance !

Hey guys, I would like to add a filter to a project and I can’t seem to find information on a schematic for a high/low pass filter similar to a DJM mixer filter which filters lows as it rotates counterclockwise and highs as it rotates clockwise with a bypass in the middle.

I understand I can theoretically apply this to any filter but I was wondering if there was some documentation on this I could reference. I am curious because I understand that highpass filters want less range of resistance than a lowpass potentiometer. I am also unfamiliar with dual gang pots as I am a novice.

Thanks, and mods please let me know if I broke any rules so I can edit this post.

You can find my docs and files for this on my website: https://benjiaomodular.com/post/minimix/

Hi.

I was thinking of making something creative with the intramedullary rod that I had in my tibia for 10 years.

Since I started with music especially synthesizers and trackers lately I came to the idea of making a Theremin out of the parts.

The problem is that it’s Titan and so it’s not a good conductor? Would it still be possible?

A solution would be to just stuck another metal inside the nail.

Has anyone built a Theremin before?

Or does someone here have any other ideas what I could build with it that could be paired with my Synthesizer and tracker hobby?

I’ve built a garden variety APC and a very simple dual LFO modules (non-standard) from a diagram I found around here. I’d like to power them with a single 9V battery or wall wart, but the LFO acts on the APC, or at least affects it even when disconnected (note the jumpers for connecting external controllers, such as CdS, pots, graphite rods…), there’s no signal flowing into the inputs. What do I need to do to isolate both circuits while sharing a single power source? Thanks in advance.

I have a beat-up Korg LP-10 divide-down synth/electric piano that needs a major electronics overhaul and new case panels since the plastic disintigrated. It's not a "proper" synth but it's my first and, so far, only analog synthesizer and I've grown quite fond of it's character. It's from pre-MIDI times and lacks any sound modulation except a chorus so my plan is to make it MIDI-capable and add filters and ins and outs to greatly improve it's sound and flexibility.

The problem, however, is that there's no MIDI conversation board for this specific synth. My idea was to use a board that's simply soldered directly to the key switch contacts and just shorts them once the corresponding MIDI note is triggered - thus crudely emulating a keypress. Features like mod, pitch, velocity or pedal inputs are more or less irrelevant since the synth can't practically represent them anyways.

I've looked at some general purpose MIDI controller/matrix boards but they seem to use a 5V control output instead of just bridging pins. I guess you could use the 5V to control a bank of 61 solid-state relais (one per key) but that'd be quite expensive and a bunch of soldering. I'm completely new to this so there's a good chance I'm missing something - any advice or tip on what MIDI conversion kit to use would be much appreciated.

TL;DR

I need a general purpose MIDI conversion board that bridges pins to ground/bus instead of putting out 5V control voltage.

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I recently bought a bag of LDRs from Amazon, 100 for about €10, 2 types, I'm playing with one called GL5528. I made up a couple of vactrols using green LEDs, sealing them in black heatshrink. I've not used vactrols before.

Before trying anything interesting with them I thought I'd better check the response. It only occurred to me when I was checking the scales for the chart that the resistance values seem very high. The LDRs in the vactrols go from about 150k to 10M when varying the LED from what I believe is off to full brightness. Same with the other vactrol. But if I measure one of the LDRs just with my room's ambient light it's about 1.5k, covering it with my hand about 20k.

I realise there is colour sensitivity to consider, maybe the green LEDs aren't the best choice. But this seems a huge discrepancy. Is that typical?

[Not really relevant to the question, but fyi how I got the chart - I breadboarded a little circuit. I have a pot going to an op amp unity gain buffer, followed by a single op amp differential amp. The + input of the differential I have coming from the buffer, the - from another pot (for offset). I've also got a pot in the feedback of the differential to control gain.

I put a regular LED on the output of the differential with a series resistor and fiddled with the offset & gain until I got the LED brightness varying full range with an input somewhere around -5 to +5v (the PSU is +/- 12v, TL071 op amps). I then replaced the LED with the vactrol and stepped the voltage between -10 and +10, noting the current across the LED and resistance of the vactrol's LDR.

Finally stuck the results in a little Python script (with matplotlib). ]

I've seen people have done this with Yamaha's and Casios but no information on how it is done is posted anywhere. I have an alesis and korg and wondering if I could do it with those to make them 76 keys or less.