My Bus/Buffered/Send Thingie where i need help

[JanJuno]

Hey guys,

happy to be here and happy to find this board and i learned something already in terms of electronics and eurorack. Close to 20 years ago i was on a school for basic electronics but down the road i switched to graphic design and now UX Design. I am on eurorack since 3 years now and now i want to tackle my first DIY Module. And i need a litte help. A lot of what i have learned is gone. And i hope you guys are able to help me. So tips on youtube clips and sort of are relly helpful.

I currently working on a 1U, 126hp module for my suitcase. It will be a bus/buffered mult module kinda inspired by the make noise cv bus case. My concept will also include a sort of patchbay for my external gear which will be just a “connection” to my external gear and is centered within the modules frontplate. So therefore i don’t need any help here.

I have watched several post on this board and copy out some concepts and put them together for buffered mults and LED to indicate what is currently running. What i have created might be working but it can also be total idiotic crap. Like i mentioned i have no clue what i am doing and my knowledge is 20 years old, never used and was also just basic of the basic knowledge.

Check Frontpanel Layout on Screenshot

In the center you see my external gear patchings. On the left and right side you see my concept of the Bus / Buffered Mult. I will be 4 times my bus and mult solution. We will discuss just one since they will work the same.

Check the basic schamtic section of the screenshot.

There are three different conditions that the Bus/Mult will offern:

1.Just a Buffered Mult

In The First configuration everything is acting like a 1X3 buffered Mult on each side.

2. A Bus to Right
A input on the left will be bussed to the right, everything else will be a buffered mult

3. A Bus to the Right to Mult

A input on the left will be bussed to the right and mult.

One thing to note. Several Inputs will later act as output or via versa. So above you see the behaviour i have in mind. Check the inputs “CV in” vs. “CV out”. Also on the left you will see LED indicator which indicating the current setup of the module.

So based on that concept and my 20 year old knowledge and the diving through this board i came up with this electronic schematic. I have several questions and i guess you have the answers. So it would be great if you can pin point me to certain erros or give me a better schematic. Check the schamtics on the screenshot.

A little explaination on that schmatic since i use no curcuit app or something. The red dotted lines are relais route to switches. You will see if they are on or off. I have no clue which type of diodes i need to use. All other parts are based on this post i found here

Can Someone Look at My Buffered Mult Schematic Please?

Sorry I did not take into account the history of the panel , so if I understand correctly maybe your solution is to add another connector for the switch connection on panel [e46e3e7387f4c4956c2b5bd591e9ef94cb9f76cf]

So here are some question:

1. Do i understand the concept of diodes correctly and do you have any reccomondations what type to use?
2. What to do with open switches? Do they need an resistor or something? To ground? (Check Screenshot)
3. Is there a better way for using relais. Are they practical for usage? Is there something better?
4. If you check the post above where i get a lot of my concept there is this and i have no idea what this is but i see it is realated to power supply?(Check Screenshot)
5. What about those oben jack inputs? Check input 2. (Check Screenshot)

[antoine.pasde2]

My first bit of advice: make smaller posts, there is too much to unpack in this one.
You scare off people who might be able to answer.

@JanJuno

1. Do i understand the concept of diodes correctly

It’s a bit hard to interpret what you are trying to do with your not quite standard schematics, but it looks like you have diodes in the signal path, that is quite unorthodox (unless the signals are only gates and not audio).
What are you trying to do with the diode? Why did you put the diodes where you put them? Start with a small section of the circuit, like the diodes near the jack in the top right corner of your image.

@JanJuno

2. What to do with open switches? Do they need an resistor or something?

Yeah, you don’t want to leave opamp inputs floating. If the switching is to mute/unmute, you could ground the opamp input through a resistor when it is to be muted. Not sure why only the LED buffers are switched though.

@JanJuno

3. Is there a better way for using relais. Are they practical for usage? Is there something better?

Mechanical relays are noisy both acoustically and electrically and they are bulky. Depending on what you are switching analog switches might be more appropriate. (But design choices are personal, LMNC makes excellent uses of all sorts of electro-mechanical devices.

@JanJuno

4. i have no idea what this is but i see it is realated to power supply?

Yes that is the Eurorack power connector with some protection circuit, filtering capacitors and connections to the power pins of the various devices in the circuit.

@JanJuno

5. What about those oben jack inputs?

What about them, hey.

[JanJuno]

Hey Antoine,

yes i was seeing that i might be overwhelming with my concept. But to be fair i wanted the post a more structured post with several screenshots but when i was uploading it i wasn’t able to upload several images, only one so…

But thank you very much for your help. The first take away i will have is to split the signal path and create another circuit for switches to setup those different behaviors. This is related to the 1. Question regarding the diods.

Regarding Question 5 of those inoput jacks. Pin 2 is open? This is why i am confused.

The other answer will help down the road. I will come back to you if it is ok.

In general i will come back next with an proper schematic also done in an software suited for electrical circuits. I will then have definitly help on all those used parts and values of those resistores diods n stuff.

Thank you very much Antoine!

[konthaar043]

On this type of input jack, pin 2 is the switched pin that connects to pin 1 when no cable is inserted. You can connect it to ground if it’s on one of the op amp inputs in order to not leave them floating.
If it’s on one of the outputs make sure there is a current limiting resistor at the output in order to not short the output to ground.
(They are in the schematic so that should be ok)

If you use diodes in the signal path there are some things to consider:
Your control voltages will be lowered by the forward voltage of the diodes. For normal silicon diodes this will be about 0,6 to 0,7 volt, but will drop for every diode in it’s path.
Probably not a problem for gates, but your volt/octave cv will be out of tune.

When using the multiple for ac, like audio and lfo, only the positive half of the wave will pass, signals will be distorted (soft clipping) and also one diode drop lower in amplitude.

[JanJuno]

Thanks Konthaar,

i come to the conclusion that diods aren’t suited. I need an extra signal path to controll routings of my signal path. I am hoping to achive that, if it is the right way to do it?! I will see

[JanJuno]

Hey,
i got some spare time today and i was able to get into EasyEDA. So i hope you guys get an better understandig in my idea. And now i am aware that the used parts are important. So i tried to find the correct ones. There is a main component still missing. I guess i need an multiplexer? Or some sort of an simple IC? Dunno.

I put some infos into my schematic and also circles (in pink) with my main problem connections (Orange dashed lines). i let out all diods and relais since i come to the conclusion that i was wrong, thx to @konthaar043 konthaar and @antoine.pasde2 antoine for further explanations.

I try to be short and explain my idea again:
I want to build an 1U, 126hp Module with 3 modes. The main idea is to bus signals from left to right or/and multiple. It will be used for CV an pitch CV signals only. So no audio is involved. One of the difficult parts for me at least is that i will need sockets to be IN and OUT depending on the modes.

Here a basic frontpanel design to visualise my idea better:

Check the schematic and detailed mode description below.
The PIN (2-4) are referring to the main switch in the schematic.

PIN 2 = The module will provide two 1x3 multiples (Left 1x3, Right 1x3)
PIN 3 = The module will bus signal from left to right (1x1) and provide also two 1x2 multiples (Left 1x2, Right 1x2)
PIN 4 = The module will bus a signal from left to right and multiple to 1 (left) x 4 (right). The rest on the left side will function as an 1x2 multiple.
PIN 2-4 = Depending on the mode selected there should be an LED indicating the selected mode.

Here the new schematic:

I hope you guys will understand my idea better now? Like i mentioned above i think i need an multiplexer? Or some sort of an IC? I need a solution to turning an input into an output and also change the signal flow. I tried to achive this with relais and diods. I also was thinking about having some sort of an 12 pol main switch the provides me more signal routings to switch the CV signal path via an multiplexer? But it might be just an noob idea.

[antoine.pasde2]

It’s much clearer now.

Starting by the easy mistakes:

• You have connected the tip of the jack sockets to ground and the sleeve to the signal, it should be the other way around.
• Feedback around the opamps should connect the output to the - input.
• The 100k pull-down resistors should probably go after the switch so that the opamp inputs are never left floating.

For switching signals you can look into the 4016, 4052 and 4053 CMOS analog switches/multiplexers, they are often used for that type of applications.

[JanJuno]

Hey @antoine.pasde2 thx for the fast reply. i will dive in today and try to figure out those multiplexers and will have another shot on the schematic.

Thank you so much!

[JanJuno]

Hey,

@antoine.pasde2 thx for your advice, yes i got those jacks wrong but i didn’t care since i got confused on those assets provided my easyEDA. I corrected also all the other points you mentioned. I hope it was a better idea to setup 3 resistors for each mode signal path?

I also did a little more diving into 4053 and i hope i choose the right one? So i got a new schematic and i am stuck now. Since i have no clue about how to control the at least four 4053 i used. i guess there is a way more clever way the get that logic controlling the path of the three modes. but i am blind for those things. Fun Fact i am an UX Designer and a heavily visual guy.

Attached you will find a new version of my project. A little note on whats going on. You see those grey connections, they are connected to an resistor, just ignore them they will help me drawing those lines i need to attach them to something if not they are gone. I need them to control those 4053s. I wrote donw conditions they need to switch on.

Several Questions again:

1. How do i controll those 4053 units? I have no clue. my first thought was to hook up the main switch somehow but i don’t know how.
2. What about open ports on those 4053 units (check those LED circuits on the bottom or U25.3. Not sure if they need to be grounded or put an resistor in? I forgot everything. (See pink circles)
3. What about those other conncetions on the 4053 (See left side, hanging around)
4. I am not happy with that circuit (see big blue circle)

Any advice, like always, is very welcome.

[analogoutput]

I still am not sure I understand what you’re trying to do, not sure what you mean by “bus signal from left to right”. But I’d say you’ve set yourself a fairly complicated design goal and maybe you should first attempt something simpler. In particular the idea of having some jacks be inputs in one mode and outputs in another presents some major difficulties and potential for problems in practice.

My suggestion is to consider just building a dual 1->3 buffered multiple (your pin 2 functionality) and maybe add eight more separate jacks to do either your pin 3 or pin 4 functionality. Doing these as two separate circuits would be a lot easier than trying to make one set of jacks handle both jobs. You’d have only two and not all 3 modes, but it’d give you a firmer footing to attempt the more elaborate idea later.

[JanJuno]

Thx for your advice @analogoutput i get your point and i was there, but i wanted to learn and tackle myself to go further. Iam not that type of a guy just be happy. I see those dual buffered multiple solution an thought i can do a little more on that. But you guys are the pros and i will take your advices seriously.

In my job i handle/create a lot of creative ideas on software and mobile app products. I can create them visually and in deep concepts. But sad as it is i can’t build them since i am no back or frontend programer. But i had the basic of the basic education on electronics. This is where i see myself going on creating nice solutions for my hobby. i don’t want to sit around and consume

Regarding the “bus from left to right” just imagine sending a signal from the left of your synth to the right. is just kinda routing the signal and get less mess on cables. In this case with a twist and nice features like the different multiple modes.

[antoine.pasde2]

I’m not sure I’ll be able to analyze everything, just writing thoughts down as they occur, not necessarily in order of importance.

• What @analogoutput said!
• Switching inputs to outputs is a bit risky, you risk shorting two outputs together, unless you unplug the cable first. If you are going to unplug and plug back in anyways, why not use separate input and output jacks? You seem to have plenty of room on the original front panel which, by the way, also didn’t show the combined input/output jack. Separate in/out jacks could greatly simplify the design.
• The resistors on every input path is good.
• You have red dots at various places that are not consistent. See e.g. connections near R1 vs R16, or the output of U22.1 vs U1.1 They may be a symptom of things not connected as you expect. If you intend to make a PCB from this schematic (highly recommended if you end up with many chips in your design), you will have to clean that up before transferring the netlist to the PCB part of the software package.
• I’m wondering why the bi-color led buffers inputs are switch, why not just always monitor the main inputs?
• If you use these analog switches, you will have to make sure that the signals they are switching stay between their supply voltages. You mention the signals will be CV and pitch CV, if the CV can go negative, that means you need a negative supply to the analog switches. (Mechanical relays might not have been such a bad idea after all…)
• For better precision with pitch CV it is better to have the 100r protection resistor inside the opamp feedback loop so that any drop across that resistor is compensated.
• Re. Q2, control ports should be tied to logic low, signal inputs are less important but could be tied to signal ground to avoid any risk of injecting noise into adjacent switches.
• Re. Q3, those are the power supply pins they will have to be connected to appropriate power supply voltages as determined by my other comment above. (I’d have to read up on that myself before I can be more precise I recommend the TI datasheet ).
• Re. Q1, the control inputs must be driven to logic high or low based on the position of the switch, this could be done with pull down resistors on the control inputs forced high through wire-or diodes controlled by the switch. See rough drawing below. The main switch controls the analog switches instead of switching the signal directly. A similar diode based circuit can control mechanical relays, if you chose to go that route.
  
  

[JanJuno]

Wow thank you so much @antoine.pasde2 i will dive into that tomorow. And i will think about what @analogoutput had adviced

[JaggedNZ]

Lots of good advice already, but it’s suggest making it many smaller modules that connect internally (if they need too) rather than one single monolith. It will make it much cheaper to build and easier to debug. This is not uncommon approach, eg many modules have expansion module and there is a whole ecosystem of modules that talk i2c to each other via internal connections.

[JanJuno]

Thank you so much guys a lot of feedback . I will take my time on the weekend and will think about the whole concept. i already got some ideas to make things way more easy. I will show some concepts without schematics. Of course you guys are invited to discuss then.