Recommendations for a complete DIY rack

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, luketeaford, Joe.

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 04, 2021 1:24 pm

Yes DMMT3904 I think? It replaces LM394 and MAT something. Can't remember. Not as good as MAT or LM394. Someone told me it is not really valuable so I stopped trying to sell them. They are collecting dust in a drawer.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 04, 2021 1:55 pm

Yay! Just got my Turing machine kit, and a bunch of smd parts from mouser. Got a lot of soldering to do this weekend.

Anyone have a recommendation for a diy clock source and maybe a simple sequencer? I was wanting the music thing startup because it had tap temp, simple clock division, a mixer and headphone out and line in all in a tiny package, but nobody seems to have one in stock. Not even as just pcb and panel.

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 04, 2021 2:48 pm

use an LFO for a clock. square wave LFO works best.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Ayab
Wiggling with Experience
Posts: 338
Joined: Wed Dec 18, 2013 7:19 am
Location: London, UK

Re: Recommendations for a complete DIY rack

Post by Ayab » Fri Jun 04, 2021 3:01 pm

KSS your bar analogy is excellent and clearly explained, plus entertaining and original! I didn't mean to be anything but friendly and respectful. You are a font of knowledge and very kind to impart it to others. It would be excellent if you could post the Ohms Law explanation you referred to! I mainly don't understand how these things actually apply to the circuits we use. Have a good weekend. I am hoping for a bit of sun tomorrow, am going to a bbq but must not have any :guinness: because I am getting my 2nd vaccine next week. At least should help me remembering to do social distancing!

I am going to solder up some utility patch cables. I suppose they are like an advanced version of the VCS 3 matrix pins (which have resistors in them, I think)! Will try the overhead soldering iron trick, a great tip.

So a capacitor utility patch cable with (say 2.2uf) decoupling cap will work as a dc to ac CV to audio cable.

ProfBio I recommend the M185 sequencer by Ryk. It is the business - Intellijel licensed Ryk's for their Metropolis and his new version has even more features but is still very immediate to use. Get in touch with him on here or electro music and he may have some in stock. A square wave lfo is the standard for a clock source (edit - EatyrGuitar beat me to it but glad I was right).
Last edited by Ayab on Fri Jun 04, 2021 6:11 pm, edited 1 time in total.

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Fri Jun 04, 2021 3:50 pm

here is a schematic for a clock divider I made. 100pF caps are optional. if you want to use it as a sub oscillator the 100pF caps should not be there. any input that crosses +2.5v will be logic HIGH. there is no hysteresis because the comparator is a TL074 instead of a comparator IC. outputs are +/-6V so you can use them as a sub oscillator.

this is the old thread you can see pictures of the finished build on strip board. you will need to make your own strip board layout or etch your own PCB.
viewtopic.php?f=17&t=161243
Attachments
4024schem.gif
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Fri Jun 04, 2021 4:01 pm

EATyourGUITAR wrote:
Fri Jun 04, 2021 2:48 pm
use an LFO for a clock. square wave LFO works best.
Nice, I'll probably grab a small lfo module for that purpose.
Ayab wrote:
Fri Jun 04, 2021 3:01 pm

ProfBio I recommend the M185 sequencer by Ryk. It is the business - Intellijel copied Ryk for their Metropolis and his new version has even more features but is still very immediate to use. Get in touch with him on here or electro music and he may have some in stock. A square wave lfo is the standard for a clock source.
I saw that one on Molton modular and was interested in it. It looks like a great sequencer to stumble upon happy accidents with.

I was also eyeballing the Per|former sequencer, but the build looks a bit crazy and it almost seems like I would be better off using my computer if I got something that complex.
httpss://westlicht.github.io/performer/

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Tue Jun 08, 2021 8:25 pm

Well a few things have progressed.
PXL_20210609_001736405.jpg
Built my Turing machine bad it seems to work as it should. I did have to turn the trim pot ALL the way counter clockwise, but it seems to function just like the. Videos I've seen.

And then feeling I needed more modulation I picked up a rampage kit. Man that kit had a lot of parts. Got it all built and I only messed up one solder joint on one of the sliders.

Although I think I messed up somewhere. Nothing comes out of the min out ever and the mix knob doesn't work as I would expect it. envelopes, I'm going to have to go over the schematic and see if I accidentally swapped a resistor or two.

I also fixed my case. Filled the wholes with dowls. And redrilled. Now I only have a gap in the middle.bwhich is better because the way I had it the screws from each row were trying to take up the same space because I had the rows at too much of an angle.

The next kit coming is the Penrose quantizer to tame the Turing machine when I want to use it musically..

I'm really starting to feel the need for a second voice. Was thinking something digital, I was thinking plaits but apparently stm32 chips are impossible to source.

I also did some research into wave table oscillators but I didn't really find any diy ones. Any recommendations for another voice to contrast the analog vco I have?

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Tue Jun 08, 2021 9:51 pm

STM32 are available for $27 + shipping from china.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Wed Jun 09, 2021 2:15 pm

That was rough. My rampage kit came with the ic sockets with bent metal tabs. Out of frustration of not being able to find the problem I just decided to reseat all 8 tl074 chips. And now it works...

Now days when you have to directly solder on ICs on smd circuits, why do we still socket through hole ICs?

I was only able to find the stm32f373cct6 chip on ebay from china. Maybe I'll risk it I show one up now for less than $20

User avatar
KSS
Super Deluxe Wiggler
Posts: 5824
Joined: Mon Jan 25, 2016 7:28 am

Re: Recommendations for a complete DIY rack

Post by KSS » Wed Jun 09, 2021 2:51 pm

Pr0fBi0 wrote:
Wed Jun 09, 2021 2:15 pm
Now days when you have to directly solder on ICs on smd circuits, why do we still socket through hole ICs?
Mostly it's cargo cult practice. Putting expensive chips in sockets makes sense. But for most others, it's kinda dumb.

However there is one good reason to do so nowadays. Fake chips. These are seen in all types and even from well known and trusted dealers.

The biggest reason you see so many chips in sockets is lack of knowledge or trust in the design and build. Also lack of skill or tools to properly unsolder when necessary without it being a big hassle or wrecking a PCB. If you're selling kits you had better include sockets for these reasons.

You are quite right to point out the obvious flaws in the thinking by comparing SMD to TH. But there are still good reasons to use sockets too.
Treat utility modules as stars instead of backup singers.
Treat power supplies like Rockstars instead of roadies!
Chase magic sound, not magic parts.

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Wed Jun 09, 2021 3:36 pm

In all the instructions I've read people claim it's because ics can be damaged by heat, but certainly a through hole ic can take more heat than an smd one.

I also find it funny that in the guitar pedal world everyone also sockets transistors, but in all of the module builds I've done nobody has said anything about sockets for transistors. And as far as I've seen I haven't killed one with heat yet.

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Wed Jun 09, 2021 3:38 pm

I never use sockets for transistors but I do use sockets for DIP. I have burned SMD IC hand soldering before.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

imrae
Learning to Wiggle
Posts: 28
Joined: Fri May 11, 2018 12:22 pm
Location: United Kingdom

Re: Recommendations for a complete DIY rack

Post by imrae » Thu Jun 10, 2021 7:33 am

Maybe I missed something but in this rack I don't see a way to generate/scale offset voltages. This is something Maths has and Rampage doesn't; I complemented my Rampage with a Fonitronik Cascade, which is a nice compact DIY attenuverter/mixer/offset module. This is particularly useful for shifting/scaling CV going into Penrose, as it provides a way to transpose patterns before they are locked into scale.

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 8:49 am

imrae wrote:
Thu Jun 10, 2021 7:33 am
Maybe I missed something but in this rack I don't see a way to generate/scale offset voltages. This is something Maths has and Rampage doesn't; I complemented my Rampage with a Fonitronik Cascade, which is a nice compact DIY attenuverter/mixer/offset module. This is particularly useful for shifting/scaling CV going into Penrose, as it provides a way to transpose patterns before they are locked into scale.
Thanks, I've been looking for something like that. I did order a cheap attenuverter, but I was looking for offset as well.

imrae
Learning to Wiggle
Posts: 28
Joined: Fri May 11, 2018 12:22 pm
Location: United Kingdom

Re: Recommendations for a complete DIY rack

Post by imrae » Thu Jun 10, 2021 2:05 pm

Pr0fBi0 wrote:
Thu Jun 10, 2021 8:49 am
Thanks, I've been looking for something like that. I did order a cheap attenuverter, but I was looking for offset as well.
Another DIY option is https://github.com/mxmxmx/3HP_dual_OA ; basically ALM O/Ax2 with one less hp and different ergonomics. Pusherman sell the PCB https://pushermanproductions.com/produc ... l-pcb-set/.

(FWIW I have O/Ax2 and Cascade and reach for Cascade more quickly.)

You could also DIY a Shades, which is a little wider than Cascade and has unipolar/bipolar switches, but I think you're ok for unipolar attenuators/mixing anyway!

User avatar
KSS
Super Deluxe Wiggler
Posts: 5824
Joined: Mon Jan 25, 2016 7:28 am

Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 2:35 pm

If you have enough mixers you don't need offset specific modules.
Any plain mixer module can do offset. Simply put a DC voltage into one of its inputs. AC volts works too!
Get the DC from an EG whose output is fed back into its gate. Manually trigger and then adjust sustain level for a DC bias source.

Since this is DIY, you can instead just add DC to your first mixer input via the normal of the jack. Simple. Effective. Important. Cheap!

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 4:33 pm

KSS wrote:
Thu Jun 10, 2021 2:35 pm
If you have enough mixers you don't need offset specific modules.
Any plain mixer module can do offset. Simply put a DC voltage into one of its inputs. AC volts works too!
Get the DC from an EG whose output is fed back into its gate. Manually trigger and then adjust sustain level for a DC bias source.

Since this is DIY, you can instead just add DC to your first mixer input via the normal of the jack. Simple. Effective. Important. Cheap!
This explains why you were suggestion mixers earlier. I didn't know you could get DC voltage by patching the envelope output into the gate. Assuming that's by looping the envelope. And do you have to split the output to send it to it's gate and also send it to the mixer?

I think I'm starting to see the usefulness of the AI Synthesis matrix mixer.

I would kinda like to get into the whole perfboard diy circuit design, but designing a circuit seems like an unachievable goal...I have no idea where to start

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Thu Jun 10, 2021 5:06 pm

You need a mixer or a unity gain mixer or a precision adder before the gate input if you want the envelope out and the manual trigger to be mixed. You could maybe do it with a mult but that depends on output impedances, input impedance, gate detection threshold etc... So you end up using two mixers and an envelope to get a DC offset. No use if you need a negative offset. This is why you should build a DIY mixer with the jack normals connected to +5v on input 1. -5v on input 2. Or you can build an attenuverter with +5v connected to the input jack normal.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

User avatar
KSS
Super Deluxe Wiggler
Posts: 5824
Joined: Mon Jan 25, 2016 7:28 am

Re: Recommendations for a complete DIY rack

Post by KSS » Thu Jun 10, 2021 5:53 pm

Pr0fBi0 wrote:
Thu Jun 10, 2021 4:33 pm
This explains why you were suggestion mixers earlier. I didn't know you could get DC voltage by patching the envelope output into the gate. Assuming that's by looping the envelope.
Yes, there are reasons behind my posts. ;)
Looping EG is a different tihing. You just want it stuck in sustain mode so you can use that knob to set DC levels. If the EG has a negative output you can also set negative DC levels. <--Which is why a good EG has this output and why you want inverters in yor system somewhere.
And do you have to split the output to send it to it's gate and also send it to the mixer?
Again, this will depend on the system architecture and the module* itself. Which is why I didn't specifically say. Since you are sending the output two places it will need to be multed at least. I'm not sure why EYG wants it to be more complicated than that. I may have missed his point or reason.

*Many older designs have more than one jack per function. Buchla, E-Mu and ARIES are good examples. Banana systems can stack cables to mult directly. Even the old PAIA 2720-4 EG had both an attenuated and full strength output.

When you press manual start -or gate by multed patchcord, which can be removed once the S stage is present- the EG will go through its AD phases to sustain. As long as the sustain level is set high enough to be considered a gate by the EG -usually about 2V- it will stay there. In this case we want a high level DC because we have the mixer channel level knob to reduce it. So keeping the EG sustain high enough shouldn't be a problem.
I think I'm starting to see the usefulness of the AI Synthesis matrix mixer.
Matrix mixers can be very useful and fun. But don't forget the immense value of plain old simple 3to1 or 4to1 mixers -ideally, with the added features I wrote about before.
I would kinda like to get into the whole perfboard diy circuit design, but designing a circuit seems like an unachievable goal...I have no idea where to start
It's a path many before you have managed. Start with the Doepfer DIY pages. Or the simple circuits with stripboard layouts by Nicolan Woolaston over on Electro-music.com in the DIY section. They're a sticky there. I suggest you start with his EG as it will cross over directly to Euro rack. EM threads about the NicolasW builds will be very useful. You'll see you are not alone.

When you build kits don't just make a finished working module the only goal! Try to see how the parts on the board relate to the schematic drawing. Choose kits for modules which do show you the schematic so yo can do this. AI is a good example of a maker trying to help you learn and not just sell you a paint-by-numbers result. Support those kinds of makers!

The first thing you're wanting to learn is how the schematic drawing relates to the actual parts and PCB tracesand his simple projects will begin teaching this immediately. You don't have to figure the whole thing out or necessarily understnd how the whole thing works at first. But you can see how the Circuit and the actual parts used to make the circuit relate to each other. Once you have that basic relationship in your head, the rest of the path will be clear. Not always easy. But as many here will attest, well worth the effort!
Last edited by KSS on Thu Jun 10, 2021 6:06 pm, edited 3 times in total.
Treat utility modules as stars instead of backup singers.
Treat power supplies like Rockstars instead of roadies!
Chase magic sound, not magic parts.

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Thu Jun 10, 2021 5:59 pm

My point was that you might want to use a mixer before the gate input. You are suggesting a mult before the gate input. That is not always going to work but it probably will work. This gets into the mult is not a mixer debate which is muddy waters. I will leave it there.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 7:01 pm

first off, i really appreciate you two helping me out and pushing me towards building modules from scratch. I really liked the clock divider module posted earlier, but i saw the schematic and picture of it and instantly said....nope....that's way above my skill level
KSS wrote:
Thu Jun 10, 2021 5:53 pm
The first thing you're wanting to learn is how the schematic drawing relates to the actual parts and PCB tracesand his simple projects will begin teaching this immediately. You don't have to figure the whole thing out or necessarily understnd how the whole thing works at first. But you can see how the Circuit and the actual parts used to make the circuit relate to each other. Once you have that basic relationship in your head, the rest of the path will be clear. Not always easy. But as many here will attest, well worth the effort!
I can sort of do this now. When something isn't working i do have to dig into the schematic to find the part that isn't working (usually outputs or pots) and trace back in the signal flow and check those parts. I should probably do it more while I'm building it and not just when I need to trouble shoot things. LIke on the rampage the min light wasn't coming on or outputting anything so searched the schematic till i found the min out jack. found the pin that the signal uses to go from the main board to the control board. and found out its signal was related to IC 4 and 1. that led me to know where to check solder joints, make sure the component values were correct. where my knowledge stops is understanding what each thing in the signal flow does and why.

i did build the AI synthesis 002 mixer which does both cv and audio. i could try to use that as a basis to make my own design, but i wouldn't know where to begin to make changes to add the features id want. the complicated thing about modular is it seems like you don't know what you really want/need out of a module until you get further in and can use some things and start to understand how it all works. i'm still trying to understand how mixing cv works. because when i've tried it with the modules i have it did not produce anything like what i was expecting. but i have only messed around with it a little. i've mostly been using the mixer to do boring things like plug my volca sample in and use it for drums.

It's a path many before you have managed. Start with the Doepfer DIY pages. Or the simple circuits with stripboard layouts by Nicolan Woolaston over on Electro-music.com in the DIY section. They're a sticky there. I suggest you start with his EG as it will cross over directly to Euro rack. EM threads about the NicolasW builds will be very useful. You'll see you are not alone.
which pages were you referring to? the only ones i could find were these two:
http://www.doepfer.de/DIY/a100_diy.htm
http://www.doepfer.de/DIY_Synth_e.htm

were those the ones you mean?

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Thu Jun 10, 2021 7:37 pm

I made this to amplify a +/-5v signal to a +/-10v signal. I was in a hurry. I did the design on the computer but I could have used a pen and paper %100. This is a TL072. Connections are +12v, 0v, -12v. Two pins are shorted together. There is a 100K input resistor. 200K negative feedback resistor. 1K output resistor. I used black wires to connect the sleeves of the jacks to ground. There are some traces on the strip board that were cut with a drill bit by hand with a pin vise. This took less than an hour. Total cost $2. By the way, I built this as a tool to debug another module that requires a +/-10V LFO for testing.
IMG_20210603_142109_804_2.jpg
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 8:47 pm

I just had to look up negative feedback. The article that explained it was very math heavy, but I think I sort of got the concept.

Is that what's happening in this schematic where the output if the ic is going back into pin 6?
Screenshot_20210610-180605~2.png

User avatar
EATyourGUITAR
has no life
Posts: 6840
Joined: Tue Aug 31, 2010 12:24 am
Location: Providence, RI, USA

Re: Recommendations for a complete DIY rack

Post by EATyourGUITAR » Thu Jun 10, 2021 9:07 pm

Yes exactly. It is easier to think about this circuit without the 47pF and without the 330R resistor there. Those are optional. We can simplify this circuit to 100K input resistor from input jack tip to pin 6. 100k negative feedback resistor from 7 to 6. 5 to 0v. Jack sleeve to 0v. Bipolar power supply could be +12v, 0v, -12v. Whatever signal goes to the input jack comes out at pin 7 buffered and inverted. For audio it doesn't matter if the signal is inverted. For a control voltage from an envelope you might not want it to be inverted so you would not use this circuit. Or you could use two inverting buffers in series to flip it twice to get it back going the right way.

What I did was I put 200K from 7 to 6. The gain of the amplifier is 200K/100K = 2.

See the math is super easy. Hard math is much later. Wait till you start doing parallel resistors. It gets harder. Every day you learn something small. You try it. There will be many failures. This is important. Everyone learns through failure. If you keep going you can do anything.
WWW.EATYOURGUITAR.COM <---- MY DIY STUFF

Pr0fBi0
Learning to Wiggle
Posts: 43
Joined: Thu May 20, 2021 3:43 pm

Re: Recommendations for a complete DIY rack

Post by Pr0fBi0 » Thu Jun 10, 2021 10:35 pm

KSS wrote:
Thu May 20, 2021 11:46 pm
Go with 6U,104HP.

Build the AI, and add a couple of their mixers too. <--Or somebody else's but have some mixers on hand.

Make sure you've got some sort of bias-offset utilities, or wire DC into the normal of at least one mixer channel per mixer. Wiring -5V into one channel and 5V+ into a second lets you covera lot of territory a mixer and system without these will miss..
I was going back and re-reading the early posts and I can see now I had no idea what this meant at the time. It's like you were telling me I needed to know how to play arpeggios but I didn't know what a chord was yet.

I can see how useful it would be now. How would you know how much you are offsetting by? Do you have to have an oscilloscope to be precise? I'm going to have to research how to normalize something but have it change when a cable is plugged in. And also how to get the +5v and -5v wired into the channels.

Post Reply

Return to “Music Tech DIY”