Shruthi-Synthesizer and my "WAVE 1"

Hallo Mutable Instruments and User

I would like to formally express my thanks to the Olivier Gillert and his Shruthi-Team.

One year ago I started to develop my Stereo Synthesizer “Wave 1”. At the beginning of the 90s i want building a digital synthesizer.
My first project was a 8Bit soundsampler from DOEPFER Musikelektronik GmbH in germany. My next step was a digital
synthesizer on the basis of a digital sound chip SAM9203 from dream company. But I could not finish the project, because
my development tools was not not professional enough.

Now I have found many good ideas and tools for the construction of a synthesizer on the internet. Great help was the hardware
of opichenettes shruthi-synthesizers. My “WAVE 1” Synth is a Stereo-Version of an Hybrid-Synthesizer and have two analog Filtes (SSM2044) and
VCA-Chips (SSM2164). For sound editing is a small built-in touch-scree.

On yotube you can watch and listen to my first sound test. Youtube:

My Synthi-Pic’s:

Project-Site in german:

My Projekt-Site has a lot of information for musicelectronics and DIY synthesizers.

Geetings from old germany Rolf

PS: The new forum is very nice :slight_smile: But in my old posts are no more pictures. For this reason I have saved my old mutable posts from 4 years on my google cloud. Its free for everyone. Here is the link:

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I’m guessing that you will be moving away from the devboard?
I would personally add 4 potentiometers or encoders for editing of on-screen parameters, since tactile feedback is nice, and more precise… Then again, that might just be me? :slight_smile:

Hallo V’cent

I have one encode on my synth for change parameters. My idea is later, the sound of editing via midi controller.

Geetings Rolf

Hallo shruthi-fans

I have make a Musikvideo for my AVR-Synth “WAVE 1”. Its new Stereo-Sound. The sound is only from synth stereo out without effect units.



Greetings Rolf

Hallo shruthi users

I forgot the pictures of my synth in the post. Here they are…

In the next time i’m working on an sd-card interface for my synth.

Greetings from germany

I have just one question : why wouldn’t you use 2nd order filters for PWM filtering?

Hallo MicMicMan

The PWM-Frequency is verry high and you can’t listening on the audioout of my synth. In the new Software-Update for my Synth, i have change the pwm-Signal to 8Bit and 125KHz.

Sounding good!

As it has been discussed here before the Problem with high frequency PWM carriers may occur when redigitizin the signal. Try running your signal thru a (decent - not a Behringer…) compressor and you will see what i mean, it will compress even if theres no audible signal. On my old MX-8000 console i can just see those signals on the VU-Meter. Maybe you take a measurement and eventually think about filtering a bit more…

The most sensitive point is the VCA CV (you’re already using a DAC for the oscillators, good!).

Here, you have a generous amount of filtering in place: 100k / 33n (cutoff at 48 Hz) ; vs a 125kHz carrier, so about 60dB of attenuation. However, I am unsure about the 100k / 33n combination for the RC filter - to me it looks like this would lead to excessive smoothing of the VCA modulation (and hence a lack of punch in the envelopes).


Thanks for your tips. I’ll think about it and make a few tests. I make scope pics from envelopesignal here.

See you and geeetings from germany

Hallo shruthi-fans

I have test the envelope-time from my synth “WAVE-1” withe my scope (see pics).

Bild 1: Attack-Level = 0 / Attack-Level = 20
Bild 2: Attack-Level = 64

The shortest time for attack-phase is 4msec and for release-phase is 2msec.
The longest attack-time is 20sec with attack-level 127.
The interrupt-timer in my Xmega-Prozessor for ADSR-Signals is 1msec.

I think is good ?

Best greetings from germany

Some people prefer snappier attacks for bass and percussive sounds.

Hallo shruthi-users

I have looking for a simple and practical storage solution for the wave files and
Sound parameters in my AVR-Synth. I found the “ALFAT OEM Board” from
GHI Electronics (see pic 1).


By ALFAT board you can transfer datas on the XMEGA spi interface to SD & MMC cards and USB flash drives.
The maximum data transfer rate is up to 4 Mbytes per second specified.

A FAT file system for an SD card or USB stick requires a lot of resources on the microcontroller
in my synth. The SoC processor on the ALFAT module allows a fast and easy access storage via
UART, SPI or I2C interface.

Some features

  • Built-in 2-port USB Host controller.
  • FAT16 and FAT32 File system.
  • No limits on media size, file size or file/folder count.
  • LFN (Long File Name), licensed by Microsoft.
  • Friendly user interface through UART,SPI or I2C.
  • Programmable UART baud-rate.
  • Up to 8 simultaneous file access.
  • SD/SDHC card support, no 2GB limit. GHI electronics is an SD association member.
  • High speed 4-bit SD card interface.
  • Up to 4000 KBytes/sec file access speed SD cards/USB.
  • Single 3.3V power source.

Bild 1: ALFAT OEM Board
Bild 2: ALFAT concept

Greetings from germany

@ pichenettes

Hallo pichenettes. Do you mean attack-time even shorter ?

On Ambika I use ChaN’s FatFS code (I rolled my own FAT reader for the bootloader, though, because it has to fit in 4k) - it was very easy to adapt it to my project.

Yes, shorter attacks, lower than 1ms ideally.

Attack-Time: Thanks for your information. I think i can do that in my programmcode. How long is your longest Attack- and Release-Time.

a synth should have envelopes so fast the click - if you are unshure take a google trip with the waldorf click

Hallo shruthi users

I have change the adsr-circuit in my synth “WAVE 1”. My shortest attack-time is now < 1msec.