# Can Someone Look at My Buffered Mult Schematic Please? **URL:** \ **Category:** DIY STUFF\ **Created:** [February 25, 2021, 8:58pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035 "2021-02-25T20:58:12Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [February 25, 2021, 8:58pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/1 "2021-02-25T20:58:12Z")
Hi…I am trying in KiCad to create a schematic for a buffered mult. The original schematic that I am taking this from is by Morrocco Dave [here](https://moroccodave.com/2017/06/02/diy-modular-synth-buffered-multiples/) who based it off of a MFOS design. There are 2 changes I was trying to make to his schematic: 1. I wanted to add an LED to the input so I visually knew if the input was receiving a signal. 2. I changed the power section to add in diodes, caps, etc… because isn’t is supposed to have this protection? I saw this particular schematic on another buffered multiple [here](https://syntherjack.net/wp-content/uploads/2017/03/yato-active-multiple-schematics-syntherjack.png). Below is my schematic. Pretty sure there are errors here. Can someone look it over and tell me please any changes I need to make to this? ![Screenshot 2021-02-25 13.29.51](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/7/7037f9bafe18c183b4c8a8bbfb003b8e9b172c7b.png) ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [February 25, 2021, 9:08pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/2 "2021-02-25T21:08:58Z")
The LED shouldn’t be in series with the output. It should go from the opamp’s output to ground thru a limiting resistor (value depends on the LED and the brightness you want, usually somewhere between 1K and 10K) ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [February 25, 2021, 9:12pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/3 "2021-02-25T21:12:04Z")
And you power connector seems backwards (that’s today’s bug) > [@Envelope Generator 555 Timer Overheating](https://lookmumnocomputer.discourse.group/t/envelope-generator-555-timer-overheating/3034/3): > > The eurorack power connector seems to be connected the wrong way. 1-2 should be -12V 9-10 should be +12V ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [February 25, 2021, 9:15pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/4 "2021-02-25T21:15:20Z")
Okay. I just rotated the power connector. Does the rest of the power section look correct? ![Screenshot 2021-02-25 14.14.22](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/7/7dde6a5df0942aca03b27cd2c0d342d5d6db4aee.png) ---
**Author:** ![ChristianBloch](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/christianbloch/32/56_2.png) [@ChristianBloch](https://lookmumnocomputer.discourse.group/u/ChristianBloch)\ **Post date:** [February 25, 2021, 10:51pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/5 "2021-02-25T22:51:17Z")
The diodes appear to be backwards, actually. ---
**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\ **Post date:** [February 25, 2021, 11:04pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/6 "2021-02-25T23:04:20Z")
I’ve buid this module 2 or 3 time and i just add a switch , for 2 x (1 in with 3 out) or 1 x (1 in with 6 out) ![buffered multiple - sound bender (1)](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/c/c4f841d3be71cd78efed34fdf13955dc69297d35.jpeg) you can also do this with switch jack ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [February 25, 2021, 11:12pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/7 "2021-02-25T23:12:28Z")
thanks @ChristianBloch . @Dud do you have a schematic for this? I really like that switch option. ---
**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\ **Post date:** [February 25, 2021, 11:27pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/8 "2021-02-25T23:27:29Z")
i search , but i don’t think, if not i ll did a quick draw it’s simple 😉 wait … ---
**Author:** ![ChristianBloch](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/christianbloch/32/56_2.png) [@ChristianBloch](https://lookmumnocomputer.discourse.group/u/ChristianBloch)\ **Post date:** [February 25, 2021, 11:38pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/9 "2021-02-25T23:38:24Z")
You may also want to switch the out resistors to 1K in stead of 100. The original schematic also has a 220K resistor from input to ground. ---
**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\ **Post date:** [February 25, 2021, 11:48pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/10 "2021-02-25T23:48:17Z")
![buffered-multiple-](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/c/cb8a43a706833a749a74ada8b60ccdd88bd4c534.png) ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [February 26, 2021, 12:04am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/11 "2021-02-26T00:04:17Z")
They’re for power reversal protection. If +12 V is really +12 V then the top diode won’t conduct, but if it’s actually -12 V the rail will get shorted to ground, hopefully blowing out the 10R resistor before any other damage is done. That’s one approach, not my favorite but not terrible; see [Typical module power circuit](https://lookmumnocomputer.discourse.group/t/typical-module-power-circuit/1134) for discussion of different options. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [February 26, 2021, 12:07am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/12 "2021-02-26T00:07:20Z")
100R output resistors and no resistor to ground on input is better for preserving 1V/oct CVs. Another option is to put the output resistors before the feedback connection; that gives you no voltage drop even with 1k resistors. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [February 26, 2021, 12:10am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/13 "2021-02-26T00:10:33Z")
If this is for a PCB design, you’ll want to use different labels on the left and right. E.g. IN1\_B for the op amp input and the one on the left pin header and IN1\_P for the jack and the right pin header. Otherwise the software will want to connect all of them together. If it’s for a stripboard or other non-silicon-idiot-designed option, presumably you’ll know better than to do that. ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [February 26, 2021, 7:24am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/14 "2021-02-26T07:24:04Z")
Okay, I am hoping that I listened to everyone. @eric is option #1 or option #2 how I should do the LED on the input? Or are neither correct? @analogoutput is that what you meant by putting the resistors before the feedback connection? I guess technically it’s in the middle of the connection. Can you guys take another look at this and tell me if this looks correct please? @Dud thanks for the drawing. I plan to implement that switch you drew. I just haven’t drawn up the other outputs yet in kiCad so that’s why it’s not on this version of the schematic. ![Screenshot 2021-02-26 00.17.33](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/debd1f7b399068ab80b46b28c66c07eeff0fc1fe.png) ---
**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\ **Post date:** [February 26, 2021, 10:01am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/15 "2021-02-26T10:01:24Z")
I think you can keep the 100ohm resistor like in the first schem (the @analogoutput proposal was if you changed with a 1K that you had to move it) and for the led, not in serie, #2 is better 🙂 ---
**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\ **Post date:** [February 26, 2021, 12:53pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/16 "2021-02-26T12:53:59Z")
Did you know, and this is just a Kicad Schematic thing. You can set your labels as INPUT or OUTPUT which helps to visualise the path the signal should be taking. Not overly necessary in this instance but as you progress it will aid you. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [February 26, 2021, 1:35pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/17 "2021-02-26T13:35:01Z")
> [@popflier](#): > > @analogoutput is that what you meant by putting the resistors before the feedback connection? I guess technically it’s in the middle of the connection. No… Like this: ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/2/2891720db3249282587084b195916781acf039dd.png) Then output = input voltage regardless of what load you connect. (There can be drawbacks to doing it this way so some like to use it only when preserving V/oct CV is needed.) ---
**Author:** ![ChristianBloch](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/christianbloch/32/56_2.png) [@ChristianBloch](https://lookmumnocomputer.discourse.group/u/ChristianBloch)\ **Post date:** [February 26, 2021, 5:01pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/18 "2021-02-26T17:01:40Z")
Duh, never mind me, then… 🤣 ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [February 26, 2021, 5:27pm UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/19 "2021-02-26T17:27:55Z")
> [@popflier](#): > > @eric is option #1 or option #2 how I should do the LED on the input? #3 🙂 ![Screenshot 2021-02-26 00.17.33](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/2/24a617e22f52a6f27ea0c4548d14d7f5a27a4154.png) But now the first output may be slightly different… Depending if you want “the bestest” or the simplest multiple, you may want to do it this way : > [@Witches Brew stick CV Joystick Module V.1'ish](https://lookmumnocomputer.discourse.group/t/witches-brew-stick-cv-joystick-module-v-1ish/1239/23): > > I was Finally able too get past this Design Error. After A lot of reading Books and Trial and error I was able to linearly Display the Voltage output on a Red and Blue LED By Converting the Voltage too a Current Source For the LED Thanks for Pointing me in the Right Direction. I know it was a small problem, But I really liked Working on fixing this error. Which needs an opamp just for the LED. Or just look up one of the hundreds tested eurorack-ish multiple out there… Something like this : > **[Building the Signal Clone | SYINSI](https://syinsi.com/projects/building-the-signalclone/)** > > The Signal Clone is a 5×1 buffered mult for CV, gate/trigger/clock, or audio signals. One of the outputs is inverted. The circuit is built around six Opamp buffers, with one used to drive a bipolar… ---
**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\ **Post date:** [February 27, 2021, 8:35am UTC](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035/20 "2021-02-27T08:35:04Z")
Or look closer to home > **[STUFF - LOOK MUM NO COMPUTER](https://www.lookmumnocomputer.com/projects#/1161-buffered-multiple)** > > Click on the images for more info on the projects, this is a work in progress and will build on the pages as i go. [Next page](https://lookmumnocomputer.discourse.group/t/can-someone-look-at-my-buffered-mult-schematic-please/3035.md?page=2)