Yamaha CS15D modification

[MacroDX]

Hi wigglers,

thought I´d introduce my CS15D modification to you guys.
I´ve always liked its sound and when I eventually grabbed a copy of the service manual I knew I had to make something out of it.
First thing I did was to make the bandpass filter available for channel 2´s manual control. This was simply routing 10V over a switch to the filter selector FET.
The major modification however was to make channel one controllable, too.
Who needs a tuba preset anyway, right?
Yamaha´s design really plays right into your hands regarding this mod.
It´s simply replacing the preset PCB with a copy of the channel 2 manual control circuit and substitude the preset switch panel with a custom control panel.

Got this thing working with a good two days work and can only recommend this to anyone who owns this rare synth .
The good thing is: you do not have to alter the original circuit or the front panel, so you can always go back to the original state.

Here comes the vid
[video][/video]

[monstrinho]

Wow! I had forgotten how good this thing sounded. I had one of these years ago but ended up selling it when I moved. I'm amazed at the ingenious solution you came up with for the mod. Kudos to you. Oh yeah, and the music on the video is great as well!!

[a100user]

Terrific work.

Sounds great too.

[MacroDX]

Wow! I had forgotten how good this thing sounded. I had one of these years ago but ended up selling it when I moved.

Thanks for that feedback guys

[Rigo]

Let's bump this thread, now that I have one to No plans for modding it yet though. It will reside above the SK-30, so I have 3 voices available

[MacroDX]

I so envy you for that SK-30

[Rigo]

I so envy you for that SK-30

Have been lucky with that one ... saw one for sale, but the add was gone quite fast. Turns out that the woman selling it got flooded by offers ... that she found too high A few weeks later she listed it again, and I was fast enough. It was still more expensive than the CS15D though.
I had been looking (sort of) for the bass pedals, but it is probably easier to find a GX-1 Now I can play the synth voice from the SK-30 with the CS15D
Just had some time with the CS15D, even with the simple presets it can sound amazing already

[MacroDX]

Turns out that the woman selling it got flooded by offers ... that she found too high

Nice touch, gotta try that sometime, just offer less

Anyways, not to get off-topic too much, if you plan to mod your 15D and need more input I´ll be glad to help

I already have a PCB layout in the works using Design Spark PCB. I am no expert at that though. Does not have priority for me anyways since my handwired solution works well enough. But maybe one day I´ll take it to the next level...
Also pending is an amplifier for the external CV inputs. wanna make them Eurorack compatible so I can plug in a 5V signal and have it amplified to the 10V level demanded by the CS.

[Rigo]

No modding yet, I will first check how well it plays together with the modular. Which means buying an English Tear or something similar for the CV conversion.

[midnightmarauder]

Turns out that the woman selling it got flooded by offers ... that she found too high

Nice touch, gotta try that sometime, just offer less

Anyways, not to get off-topic too much, if you plan to mod your 15D and need more input I´ll be glad to help

I already have a PCB layout in the works using Design Spark PCB. I am no expert at that though. Does not have priority for me anyways since my handwired solution works well enough. But maybe one day I´ll take it to the next level...
Also pending is an amplifier for the external CV inputs. wanna make them Eurorack compatible so I can plug in a 5V signal and have it amplified to the 10V level demanded by the CS.

This is so cool, your mod really takes the cs15d to the next level! I also have a cs15d and would really like to mod it with ch1 controls. Some of the presets sounds good when layered with ch2 but hey, controllable is way better. Did you get anywhere with the PCB layout?

[drenmc]

MacroDX
hi! saw this post about your cs15d mod...maybe you can help me out? I just got one a month ago, and it was working great, but now I lost a couple of notes...play a G and hear an Ab (Ab key plays an Ab as it should), play a C# and hear a D (D plays a D). Something about the key assignment is fouled up. Would you have any idea what might be causing this? It seems like you know yer way around a CD15D pretty well. I'll try PM as well, or if anyone else has an idea about what's wrong...i absolutely love the sound of this thing and have used it on several projects already. thanks!

[MacroDX]

Hello all,
first of all I apologize to everyone I left hanging with questions on the mod.
I have just prepared an article with an annotated high-res picture of the mainboard as well as some explanations which I hope shed more light on how the mod works. I have also started on a schematic in eagle. I am not a very skilled schematics designer though, so this might take a while. Or maybe someone wants to help...
Happy modding

[butter]

Really interested to see what you did, but seems your link isn't working....

[MacroDX]

Really interested to see what you did, but seems your link isn't working....

Thanks for the hint, I corrected the link.

[MacroDX]

OKay, so I´ve managed to create proper schematics for the mod and, for me personally, passed the prototype stage. Watch this space...

[butter]

Taken a while to get back to commenting after you fixed the link - cool project! Although after some thought, I guess what you end up is still somewhat less than an actual CS15, if I'm not mistaken. Anything else you "get" that you wouldn't on a normal one? Anyway will be keeping an eye out for a (cheap) old junked out one to turn up to give it a go...

Seeing that board of presets though, the thought struck me that there might be a cool way to add presets back in - not "tuba" particularly lol, but something like the music easel or erica pico system 3 with the edge-contact preset cards. Again its not the most practical/vital feature, but combined with your mod, would score a pretty good pimp factor... Haven't looked closely, but guess its just banks of resistors handling CV though, wonder if there's any way to cram in some more "active" circuits too...?

Anyway, cheers for sharing!

[MacroDX]

Taken a while to get back to commenting after you fixed the link - cool project! Although after some thought, I guess what you end up is still somewhat less than an actual CS15, if I'm not mistaken.

I never stated otherwise, did I? The mod is called CS15D channel 1 modification, not How-to-turn-your-CS15D-into-a-CS15 mod.

Anything else you "get" that you wouldn't on a normal one?

-Manual control of channel one
-External modulation inputs for Cutoff, Resonance and PWM
-Filter LP/BP switch

Seeing that board of presets though, the thought struck me that there might be a cool way to add presets back in - not "tuba" particularly lol, but something like the music easel or erica pico system 3 with the edge-contact preset cards. Again its not the most practical/vital feature, but combined with your mod, would score a pretty good pimp factor... Haven't looked closely, but guess its just banks of resistors handling CV though,

If that would float your boat... the presets are really just resistors followed by diodes.

wonder if there's any way to cram in some more "active" circuits too...?

Well, I´ve developed a little daughterboard to add a suboscillator to channel 1. You can always expand the functionality of a true analog synth as long as the PSU can handle it. But I myself am a fan of least-intrusive mods in most cases. My mods can usually be easily reversed.

Anyway, cheers for sharing!

Welcome

[WilDFire]

I happen to think the tuba preset leads to some of the most pant flapping bass any yammy has ever made...

But I digress. Very cool project. Wish I had enough balls and electrical engineering background to try something like this. Such a gem of a synth.