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diy passive multiple with buffered leds : advice needed
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author diy passive multiple with buffered leds : advice needed
big job head
Hi everybody.

I plan to build my 1U utility row, nothing too fancy but i want to be sure i made no mistake before testing.

just draw this simple schematic of a passive multiple. It is obviously inspired by make noise cv bus. i'm going passive because most of my modules have buffered outputs and i want to be able to input signal in any place.

Does it seems ok to you?



thanks!
julian
Im not 100% on what you are trying to do, but i always thought "passive" meant no power? Certainly no opamps.

Also the diagram is problematic - all the inputs are connected. This is probably just a mistake on the diagram, but it makes it more confusing.

But then ive never looked at the module you reference to, so i may be missing the point entirely!
big job head
the left part of the schematic is based on a passive multiple, which explains why all the inputs are connected : any connector can be an input and the others becomes outputs (which i don't think i can achieve with buffered multiple and switching jacks, but i may be wrong)

the right part of the schematic is buffered leds for each in/out to reflect the signal passing thru the bus. Even if my modules have buffered outputs i'm afraid that without buffered leds i'll have some voltage drops on some critical cv.
julian
OK.

As is, all the LEDs will see identical input. Ie they will all behave simultaneously.
tojpeters
This is overly complicated and won't do what you think it will. A signal to any jack will go to all of those buffer/led circuits.
What are you trying to accomplish?
Do you want the original signal to be indicated by a led?
Or do you want any jack that has something plugged into it to light?
big job head
julian wrote:
OK.

As is, all the LEDs will see identical input. Ie they will all behave simultaneously.


that's exactly what i want to achieve.
want the original signal to be indicated by a led

i think i have not been very clear with what i want to do so here is the explanation.
i want to built a large 1u tile with 4 1:4 passive multiple to distribute cv around my case. My starting point is the make noise cv bus

the multiples are passive so any jack could be an input, the others becoming the outputs.
each jack have 2 leds showing positive and negative voltage of the signal at the input AND the outputs (so if a cv is plugged in one input, the leds also lights on the corresponding outputs)
each bus have different color leds so you can easily indentify which cv/clock/gate.

hope it helps, sorry if it's a bit confusing.
tojpeters
Maybe just 1 opamp and multiple high brightness LEDs with a larger current limiting resistor.
JohnLRice
At a quick glance I think you'd only need one LED circuit, unless you want to draw 5 times the power to see multiple LEDs all flash the same? cool

big job head
maybe one opamp is a better solution.

Quote:
At a quick glance I think you'd only need one LED circuit, unless you want to draw 5 times the power to see multiple LEDs all flash the same?

yes i want to see all the leds all flash the same Mr. Green
With 4 different busses i need instant visual feedback on each output accross the whole rack.
i'll try to wire the thing on a proto board as soon as i have time.
thanks for helping thumbs up
kristian
did it went well? did u build a faceplate for it?
soundshaper
big job head wrote:
Hi everybody.

I plan to build my 1U utility row, nothing too fancy but i want to be sure i made no mistake before testing.

just draw this simple schematic of a passive multiple. It is obviously inspired by make noise cv bus. i'm going passive because most of my modules have buffered outputs and i want to be able to input signal in any place.

Does it seems ok to you?

thanks!


Yeah so how did your build go? I’m wanting to building something similar as well.
Spivkurl
I would think of this as a waste of opamps, even with one per bus.

I would use a single transistor driver for a single LED, especially since as people have mentioned, multiple LEDs would just show exactly the same information. The input and output would be the same in a passive multiple as well, since that is the point.

Might be worth just making some LED display plug to plug into an unused multiple jack instead of requiring power for an inherently passive module. Maybe that's just me?
NANO-Jorge
I stand with this.

Spivkurl wrote:
I would think of this as a waste of opamps, even with one per bus.

I would use a single transistor driver for a single LED, especially since as people have mentioned, multiple LEDs would just show exactly the same information. The input and output would be the same in a passive multiple as well, since that is the point.

Might be worth just making some LED display plug to plug into an unused multiple jack instead of requiring power for an inherently passive module. Maybe that's just me?
euromorcego
soundshaper wrote:

Yeah so how did your build go? I’m wanting to building something similar as well.

don't know about the OP but i for sure built something like it.

The panel looks like this:

it is two passive mults with an (active) led indicator in the middle, using a TL072 and bi-color 5mm leds (also very useful as a poor mans oscilloscope).

I always wanted to make a version that consists of two panels so that the mults are distributed across two panels ... similar to the MakeNoise bus.
Jay F.
FWIW, I did this recently : two passive mult with bicolor LED indicator :

https://growyoursynth.blogspot.be/2018/04/the-next-diy-modules.html

mmagin
Spivkurl wrote:
I would think of this as a waste of opamps, even with one per bus.

I would use a single transistor driver for a single LED, especially since as people have mentioned, multiple LEDs would just show exactly the same information. The input and output would be the same in a passive multiple as well, since that is the point.


The genius of OP's opamp configuration (same as in Mutable Links, I think) is that you get a linear LED current in both polarities across the whole input voltage range (possibly limited by how close to the rails the opamp can output.)

I think with a transistor this gets tricky if you want a bipolar indication and if you want the LED current to remain linear with the input voltage (and not off before you reach Vf of the LED or Vbe of the transistor).

I think you could do a unipolar indication like:

This would keep the emitter of the transistor sufficiently negative that it can respond to small input voltages. But then you have R2 either too large and you can't light the LED brightly or too small and ridiculous idle current flows through the biasing diode.

But opamps are cheap.
Spivkurl
Yes that looks like a familiar configuration. I thought there was another way to achieve it, but can't seem to find the data right now.

I suppose in the case of a multiple, I have chosen to omit any LED indication. I generally prefer to display in active modules, but not always displaying the control voltage.
fuzzbass
extra credit to mmagin for presenting on an actual napkin. My guess mmagin was having a pint, and responded from the pub. Guinness ftw!

I guess everyone figured out now that a passive mult and an an active mixer are two different things. With a simple mixer, there is a load resistor in series with every source. This somewhat isolates each input so it does not get yanked around by the input with the lowest impedance. Typical values are 25K to 100K.

Extending this idea back towards its inspiration (the MakeNoise bus), its probably only useful to have indication on timing (gate/trig) signals, and these should only have one source, not a mixer. LED indication on the other busses is something I could live without.
euromorcego
fuzzbass wrote:

I guess everyone figured out now that a passive mult and an an active mixer are two different things. ...

i think the thread was always about passive mults, never about a passive mixer (even though Makenoise has suggested mixing gates in their bus is ok).

fuzzbass wrote:

Extending this idea back towards its inspiration (the MakeNoise bus), its probably only useful to have indication on timing (gate/trig) signals, and these should only have one source, not a mixer. LED indication on the other busses is something I could live without.

no one ever mentioned "mixer". And I disagree that leds are only useful on timing signals (gates and triggers). All my passive mults have a (buffered) bi-color indicator leds and I find these very useful to e.g. monitor lfos and other modulation signals.

The multiple leds (as seen in the first post) only come into play when the jacks of the mult are spread out on different locations (like the MN bus). Then it is indeed useful to have several leds, one for each jack (to identify the signals, etc ...). Whether separate Opamps are needed is another question ...
fuzzbass
euromorcego wrote:
All my passive mults have a (buffered) bi-color indicator leds and I find these very useful to e.g. monitor lfos and other modulation signals.


You're not wrong. Fun thing about DIY is that everyone can have it exactly as they prefer. I just use one of those little Division6 LED plug thingies to inspect, when needed. When not needed, the LED is not consuming power. Not that I am averse to twinkly lights or anything...
Navs
fuzzbass wrote:
...Fun thing about DIY is that everyone can have it exactly as they prefer...


Absolutely, but to the OP, why go to the bother of making the visual indicators active while leaving the CV - the signal - unbuffered?

IIRC Daverj posted a good schematic for a buffered mult that was turned into a PCB by a Wiggler. The mixer configuration mentioned above can also be useful, viz the Analogue Solutions MX224 Inverter, Buffer, Mixer.

If I understand it right, the reason you can mix triggers in a Makenoise bus - and originally Serge (and others?), is that their trigger outputs are isolated by diodes. This means that sticking several triggers into a mult effectively 'builds' a passive OR-gate: http://www.doepfer.de/a186.htm
ersatzplanet
Navs wrote:

Absolutely, but to the OP, why go to the bother of making the visual indicators active while leaving the CV - the signal - unbuffered?


The main advantage of an unbuffered multiple is that it is bi-directional. a 4 jack passive must can be used as a 3>1 or a 1>3. Of course this affects the loading etc, but it still can be used that way for non-pitch CV.
tojpeters
Or you could use banana jacks and stack them
Spivkurl
tojpeters wrote:
Or you could use banana jacks and stack them


This is why when grabbing a frac setup, one of the first things I did was make a mult with both 3.5 and banana to fit with my earlier banana rack. It's either 2x6 or 4x3 (with two of four having a banana). Only two switches of jacks are needed.
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