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

  • 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? :)

  • 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

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  • 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).

  • Hallo

    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

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  • 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

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  • @ 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.

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  • Good job! I think if you ever distribute/sell your synth, people will be thankful for that.

  • Thanks. It’s a long way until the end of my development :) The Sounds on my synth have now more “click”.

    The next step on my work is: Loading wave-files and sound-parameter from SD-CARD and USB-Stick with ALFAT board.

    Greetings from germany

  • Wow. I just listened to the youtube video and it sounds rather nice !


  • Hallo

    Here pic from my enveloop. I have change the longest time for attack, decay and release a little bit more time (see pic).

    All ENV-Parameters can adjust with midi-controller value 0-127.

    Geetings from germany

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  • I just wanted to say: great work so far (sounds quite interesting!) and I’m really enjoying your live work in progress report here!

  • Thanks. The next: I work now for SDCARD- and USB-Interface (see above).

  • Hallo. There is new information in my webblog about shruthi and wave1:

  • The touchscreen is a nice idea. But I can imagine that drawing the display takes some CPU time.

  • No. The Touch-Screen have a cpu (ATMega) on board. I send short commands for touchbuttons and drawing lines and text.
    The ALFAT-Board for SDCARD and USB-Stick have a Soc-Prozessor on board and i send short commands for reading and writing datas to SDCARD or USB-Stick.

  • Will it be possible to draw waveforms or manipulate envelopes with the touchscreen?

  • Hallo fcd72

    That’s a good idea. This option comes in the future. I work now for the ALFAT-Board on my synth.
    The data transfer is verry fast.

    My idea is: My synth have a fast 8MByte SDRAM onBoard and you can loading a lot of Sample-Files from
    SDCARD ore USB-Stick in my synth and play.

    But there is still a lot of work so far. I’m only and i work a little bit every day on my synth.

    My synth is my hobby and my love :)

    Greetings from Germany

  • Hallo

    I have the “ALFAT OEM board” connected to the AVR-Synthesizer (see pic) and programming first funktion as for example init SDCARD and USB-Stick, Format, read rtc-clock.

    I have change the cap in the power supply circuit. The +5 Voltage was too little when I contact alfat on my synth. ALFAT Board need 5Volts for USB. For the sdcard there is an internal 3.3 volt regulator on ALFAT Board.

    The next step is funktion for save and loding files to sdcard and usb.

    Best greetings from germany

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  • Hallo shruthi users

    I have change the power supply circuit for my synth. The old version has an 7805 Chip equipped with heat sink module and this was very hot. The new version has two DC/DC Converters for VCC +5 V and VCC +3.3V. The DC/DC Converters work fine without heat sink modul and the temperature is verry low.

    Greetings Rolf

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  • I don’t think D6 and D8 are no longer needed ; but a protection diode like D4 would be indeed useful for the switching regulators, as they don’t like sinking currents (this will happen when the synth is powered down and your downstream capacitors discharge).

    Do these switching regulators add extra noise on the DAC outputs?

  • Hallo pichenettes

    Thanks for your tips :)
    The dac outputs have no extra-nois because the MCU (32MHz Xmega with two dac’s) has a separate 3.3V power supply on ATMEL Xplained-Board. It is powered by the +5 V power supply with TSR 1-2450 chip. I think that the protection with diode of the DC/DC converter is not necessary, because data sheet says maximum capacity for output is 470uF. The cap in my circuit are not so high.

  • > The dac outputs have no extra-nois because the MCU (32MHz Xmega with two dac’s) has a separate 3.3V power supply on ATMEL Xplained-Board.

    Ah OK… so there’s still a linear regulator in the loop to clean things up!

    > I think that the protection with diode of the DC/DC converter is not necessary, because data sheet says maximum capacity for output is 470uF.

    I am not sure this spec is related to the problem I am pointing – and that this capacitance constraint is related to start-up / initial conditions issues. But in your board you don’t have much bypass capacitors anyway…

  • Ok. I have test the ripple and noise of power supply.

    VCC +5 V = 12mV, Nois 500KHz
    VEE – 5 V = 5mV, Nois is not measurable
    VCC +3.3 V = max 80mV (Touch-Display make high ripple when dimming backlight) 500KHz Nois

  • So.. my next step is a new concept for the panel in my synth “WAVE 1”. When i have work with my old panel (Touch-Display and one encoder), a lot of touch-function for adjust a sound. My new panel concept see the picture.

    The new panel has five encoders. Four for datas (example: ADSR) and one for funktion. I think it’s better if I adjust a sound.

    Greetings Rolf

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  • Is mode a button or encoder? If it’s an encoder you must be lefthanded ;)

  • It’s a Shruthi in a mirror ! :)

  • I like shruthi-Synth and the big brother (or sister) ambika. Its my inspiration for building a synth in the last year. In 1986 i build my 1st 8Bit soundsampler with a Comodore C64 homecomputer. Afther than i build a 8Bit soundsampler from doepfer in germany.

    The “Mode” button is an encoder. All Encoders with switch. When you play keyboard with righ hand, the left hand can operate the panel. When you play with left hand, you have a little problem. A lot of synth’s have panel on left site (example: Moog Little Phatty).

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  • @rolfdegen
    A fine example is the MicroKorg XL by Korg. All the tweakable knobs are on the right hand side. IMHO, this is wrong for so many reasons.

  • Yes. I have not a case for my synth. The panel position is not shure. The case from Moog Littel Phatti is nice.

  • Hallo

    This is the final power supply for my synth:

    Greettings Rolf

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  • Hallo again..

    Its time for thinking a case for my synth “WAVE 1”. First I considered my little midi-keyboard rebuild for my synth (see pic 1 photo montage). But it is not easy for the replica and i have no free choice for the front panel.

    I looked on the internet many self-built synthesizers. Some very “interesting” designs. See pics :-)

    The last pic is the case for my synth. I found it on mouser electronics (

    Its verry nice looking. The front panel for my synth make the company schaeffer in germany (

    Greetings Rolf

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  • @Rolf: Ooh – where did that amazing pyramid synth pic come from?


  • Google image and it’s ability to upload files is always your friend for that kind of stuff :D

  • @Mdashdotdashn: thanks for the link. I almost wish I hadn’t bothered though – it looks so gorgeous, but all it does is make silly noises

    Makes my Shruthi sound like a huge modular by comparison though!


  • Hallo again

    This is the first design idee for my synth “WAVE 1”.
    Thanks Wolfgang from cc2-forum (

    The original case is the 2nd picture (;ACTION=3;LA=446;ARTICLE=126237;GROUPID=5194;artnr=ATPH+1865-200).

    I change the housing on both sides with wood and yellow frontpanel from company schaeffer (

    The cost of case are 40,- € and yellow front panel are 70,- €.

    The Idee is some controllers for live working example cutoff, resonance and 3 controllers (Edit) for free programming funktion.

    Greetings Rolf

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  • Hi shruth-freaks :)

    Here is a small preview on Youtube of my new ADSR function from my AVR-Synth “WAVE 1”. The idea is a little copy of waldorf blofeld ( :)


    Greetings from germany. Rolf

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  • Have you ever thought of leaving the old worn ADSR Path to something more sophisticated as Multistage Time/Level Envelops like on the ESQ-1 ?

  • Or loopable/repeating envelopes like some of the modulars?

  • or the 256 stages that Kurzweil felt was necessary?

  • Kurzweil has 256 Stages Envelopes????

    OK, which one?

  • Hallo “shrutis” :)

    I have work a little bit to my synth “WAVE 1”. At the pictures you can see my new menu pages of grafic display. Some menu pages are still missing. I’m still working for that. All menu functions are controlling to rotery encoders and switchs. The encoders have a dynamic move funktion for high counts. The old touch functions for the display is deleted. This makes it possible to use other (low cost) graphic displays without touch function.

    Greetings Rolf

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  • This is looking very nice, just like the blofeld display. Do you have just this display unit or an synth engine/an idea for this?

  • Hallo tmk009

    I have studied the youtube videos from woldorf blofeld and all good ideas programmed myself in C (ATMEL Studio 6.1) for my synth with ATMEL Xmega chip (8Bit Unit). My source-code is not finish and a little confused. I’m not a professional programmer :) If you’re interested, i can send you the source-code.

    This is the latest Filter-Page on my Synth. I programming now to the graphical representation for the filter resonance.

    Greetings from germany

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  • Hallo shruthis :)

    I have worked a little bit to filter section on my Synth “WAVE 1”. The following filter function available at the moment: ADSR, Cutoff, Resonance and Env Amount. Keytracking “KTrack” is not yet imlementiert the time. The change in the resonance parameter is now displayed graphically in the filter curve. Best thanks to Wolfgang from CC2-Forum for the midi sequence that plays my synth in the YouTube video.

    Link Yotube:

    Gruß Rolf

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  • My 2cts on this – I think this graphic could be improved!

    Let’s talk about graphics in general…

    • Showing a drawing of an oscillator waveform is a useful piece of information: it’s faster to parse the graphic than reading the letters. Of course, we are unable to “hear” a waveform seeing its curve, but we recognize the sawtooth, square shapes etc. and know how they sound. They work like signs rather than data visualizations.
    • Showing an ADSR envelope curve is super useful I think. Anything that unfolds in time, at low frequencies (< 10 Hz) is perceived by our brain “in the time domain”, so curves/plots work well. This includes envelopes curves, LFO shapes, histograms of step-sequences, piano rolls of sequences…
    • But this filter curve… I am not sure how helpful it is. That’s a lot of pixels for basically showing just two bits of information – cutoff and resonance value. It would have been a different affair if your filter was something like the 4PM, for which the shape of the curve would be more readable than “LP3”, “BP2” or “NOTCH”.

    Here’s an idea: first, maybe you could try animating the curve in realtime to reflect keyboard tracking and modulations applied to cutoff ; and show a basic representation of the spectrum of the oscillators signals – without doing an FFT of course! (start with two spikes showing the oscillators frequency, maybe some harmonics if you know their waveshape… and a rectangle if the noise is on). This could help people use the filter to “lock” on certain harmonics, get an idea of what’s to filter/enhance, or immediately see why they don’t get any sound at all from the filter (the cutoff is way below the first harmonic).

    A second idea is to make this curve much smaller and less detailed – given that the slope and shape of your filter cannot be changed these details do not matter and do not belong to the visualization, and the same amount of information can be provided by a horizontal slider for cutoff and a small vertical slider for resonance. This would free up some display space for something more useful… One thing I have experimented with in the UI of a product I am working on is mini-oscilloscopes showing the actual value of a parameter (say cutoff) with all modulations applied to it. It reminds you that even if the screen shows “cutoff = 57”, there can actually be LFO, step sequences, and keytracking altering the actual value! If your synth has a modulation matrix, devoting some screen space to show source and destination mini-scopes is super useful!

  • Hallo pichenettes,

    thank’s for your great interest and good ideas. For drawing audio curve in realtime the display is not fast enough. I’m still thinking about what I’m doing, comes time comes idea :)

    The modulation matrix comes..

    Greetings from Germany. Rolf

  • Hallo

    This is my new idea and video for the filter-page in my avr-synth. The display-controller (EDIP160W7LW) is not so fast, the screen refresh is 500msec. For this reason, i think for a new low cost graphic display (EA DOGXL160W-7) with led-backlight.

    My Youtube-Video:

    Greetings Rolf

  • you should rethink one thing: this display is large. its not really necessary to have a HUGE lfo wave, but you might need more info on the lcd or some shortcuts to different pages. e.g.: you are programming a lfo-speed and want to switch to the filter section – then you have to dial, to dial and to dial, and oops, too far so dial back – this is not very useful for playing with it. have a look at the well crafted emu os with a really nice usability (always function buttons on the bottom of the display with further functions). if you need help with this: maybe yo have a structure/overview of all “pages” of the wave1?

  • Hallo

    My new scope-funktion. Its not finish. I think a little window in the Osc-Page for scope outsignals and a new menu-page for big scope-funktion.


    Greetings from germany

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  • Hallo lovely shruthis :)

    Here is my new “miniscope” function in my DIY Synth “WAVE 1”.


    Greetings from germany

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  • looks cool ! (Oktave is so much cool than Octave :D )

  • Oh.. thanks. Its a little bug from my german language. :)

    My next step is some scope-funktion for example: timebase, sync, enveloop-screen and a little bit more. But i think, my diy-synth is a synthesizer and not a digi-scope. For this reason, I will not implement so many functions.

    Greetings Rolf

  • yes, is the digi-scope only for the Synth, or there is input to check analog signal for an modular for exemple ?

  • Hallo Lamouette/rck

    In time the scope-funktion its only work for the synth. The audio output of synth is coupled to the adc-input from the cpu (8Bit CPU: Atmel Xmega128 32MHz). A lot of Interrupt-Funktion is work in the background for synth-funktion and a good scope function needed too much processor power. In the future my next DIY-Synth works with a faster 32Bit CPU.

    Greetings Rolf

  • > A lot of Interrupt-Funktion is work in the background for synth-funktion

    Which ones? Don’t you have DMA on the XMega to make interrupts almost useless?

  • Hallo pichenettes

    Sorry.. i’m not a good programmer. Honestly.. DMA is to complicated for me. In my synth works a little timemachine with interrupts for DCA-Out, ADC-IN, GLCD-Screen, Encoders and Enveloop-Generators. I’m not sure if DMA it’s easier and faster.

    Here is my new Youtube-Video for scope-funktion:

    Thanks for your interest and helbs. Greetings Rolf

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  • There’s a learning obstacle to overcome the first time you use DMA, but then it’s easier, cleaner (less code!) and faster.

    If you have any computation/rendering going on in the interrupt handlers, you’re probably doing things the wrong way.

  • I’ll try it later when I’ve finished all the program-modules. The first software-version is not so fast and good. The next is better :)

  • Second Olivier. As any Interrupt Handler shoud be processes as fast as possible (if not, whats the meaning of having an interrupt, you could then poll for the event…) you wont do any serious computation within.
    Although its sometimes hard if you only have one Interrupt to resist…...

  • Hallo..

    I worked a little bit on the scope function in my avr-synth. Now there is also an automatic trigger function and a single sweep to individual transactions (see video).

    Greetings from germany :) Rolf

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  • Hi ..

    I have completed the development work on the graphics routines for the display. Now I’m sitting and programming the routine for LFO’s and modulation-matrix. In my synth, there will be three LFOs. LFO 1 for the DCO, LFO 2 for VCF and LFO3 for VCA. Later in the modulation-matrix its free connecting.
    I have uploaded a small demo sound on soundcloud. In the demo sound of the LP filter is modulated in the AVR-Synth from a slowly oscillating LFO with sine shape. The filter is set to a medium value of resonance. The two oscillators operate with a SAW waveform and a difference of one octave each other. In addition, a slight detune of +3 is set.

    My Demo:

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  • Hello

    Here the whole LFO program the AVR-synth. I admit, sounds are not necessarily to everyone’s taste but hopefully you can see in the video the whole modulation possibilities. Of course it still lacks a good modulation matrix in which one can link the modulation sources and targets flexible. But that will come ..
    The modulation matrix almost replaced the typical patch cable from an analog modular synthesizer. At the moment the three LFO’s are firmly linked to the DCO, VCF and VCA.

    But now have fun listen ..

    Greetings to all musician :)

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  • sounding nice Rolf!

  • Good work!

  • Thanks :)

  • Hallo

    Here is my new Modulation-Matrix of AVR-Synth “WAVE 1”

    You can select a modulation-source with encoder on left site and see the depth-values of destinations on the right site. The depth-value can modify with anather encoder. It still lacks some destination, for examble Pan, FM and noise generator.

    Geetings Rolf

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  • Hello there ..

    I am now reached “Digital Signal Processing” on topic. In the modulation matrix, the digital signals of the LFO’s and Enveloop generators are associated with the control signals for VCF, VCA and the output signal of the DAC’s and calculated.

    With an 8bit MCU, example an Xmega128A1 in my synthesizer, you can not expect great performance for digital signal processing. The calculations for digital signal processing need too much processor resources of Xmega MCU and they can not do other things at the same time. Floating point calculations or fast Fourier analysis, as they often occur in digital signal processing, can be realized only with powerful processors example digital signal processors (DSP) in real time. A XMega it has other advantages: a lot of peripheral modules 12 bit AD / DA converter, timer, and a lot of IO ports.

    In my AVR-Synth no floating point ore filter calculations are made. All calculations are simple 8-bit and 16-bit multiplication, division, addition and shift operation.

    In the Attach file is an example for stereo panning-mixing in my avr-synth

    I have upload Demosound to soundcloud from my AVR-Synth with Panning-Funktion

    Greetings Rolf

  • Hallo

    I programming currently the modulation matrix on my synth and have constructed new sounds :)
    You can listen here :

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  • Hallo

    This is first sequenz with my DIY-Synth “WAVE 1”.

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  • Hallo lovely shruti community

    The internal 32MHz oscillator in my Xmega is not as yet been the right thing, if goes to exact sound frequencies and temperature stability. I did a temperature test with a normal hairdryer and found that the sound frequencies to run away a few heart. If the AVR synth sits in a later case, thereby increasing the CPU temperature, then no longer tune the sound frequencies to the midi notes and the musician turns sour wink :)

    The solution is an external crystal. This is more accurate and less sensitive to temperature as the oscillator in XMega. Looking for a way to solder an external crystal Xmega Xplained on the board, I have still found a way. At the post header J3 on the board Xplained the two terminals are connected to pin 7 +8 + XTAL1 XTAL2 led out for an external crystal on Xmega. To these two port connections I had connected a total of five encoders. This has now been connected to a different port to make room for the crystal. Crawling in my box I had laying around for a 16MHz crystal. Thanks to the adjustable PLL register in Xmega I was able to increase the clock frequency of 16MHz to 32MHz, the Xmega the works at its full clock speed. How to enable the external crystal can be seen in the Attach-example. The Midi-Note in my synth are now stable. I can play in a desert :)

    I don’t have a frequency meter, but ebueb a high-performance computer with a good sound card I’ve googled a bit on the internet and a program called “Instrument Tuner” found to measure the exact sound frequencies of the AVR synthesizer.

    Link for “Instrument Tuner”:

    Greetings. Rolf

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  • Hello again..

    Soon I’m going to shop around for Dusseldorf in germany. Like women, we men also likes to go shopping. But say something different, to our way of example. in the Conrad store. Actually, I ordered my electronic components on the internet as always. Reichelt, but I have to get out into the fresh air and Dusseldorf is not far away from my location in Wuppertal. Dusseldorf is also known as the Rhine and it makes sense to combine the useful with the pleasant.

    Unfortunately, as an electronics shop has not ordered everything on the spot and so I had a part for my AVR Synthesizer on the Internet. It is a so-called breakout board ATxmega128A1 it with a chip (see pic). Such Breakout Boards served for all the chips as possible here: List of Breakout Boards. Because the ATxmega128A1 chip can be soldered by hand hardly sits this already prefabricated on a board (called a breakout board). All the IO ports are led out of the XMEGAs on the breakout board to solder. About the soldered pin headers breakout board can be integrated into a circuit.

    Compared to Xplained board from Atmel XMega100 the breakout board has some advantages: it is cheaper, smaller, and provides all 78 programmable I / O pin connections. The breakout board has all VCC pins are connected. The same applies to GND and AVCC pins. In addition, decoupling capacitors are included and a red power LED.


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  • “I don’t have a frequency meter, but ebueb a high-performance computer with a good sound card I’ve googled a bit on the internet and a program called “Instrument Tuner” found to measure the exact sound frequencies of the AVR synthesizer.

    Link for “Instrument Tuner”:”

    Hi Rolf: I suspect that utility is a bit ‘over the top’ for tuning a synthesiser, and while the evalulation version is a free download, the full product is also $89.

    However, there are various freeware frequency meters available, either as standalone utilities or VST plug-ins that should be perfectly accurate enough.

    For a VST plug-in example, I’m now using the one that comes free with Reaper, but before that I used C-Tuner

    Or of course then Andre’s (tubeohm) filter calibration tool for the Shruthi discussed in THIS thread


  • Hello there ..

    On the board from Atmel Xplained there was many things that I did not need for my synthesizer project. In addition, some port lines were not accessible. I do not have this disadvantage, because I ds ATXMega all 78 port lines are the Xmega breakout board available. Additionally, I’ve decided on a budget SDCARD BREAKOUT MODULE. Previously had an expensive SDCARD module of ALFAT planned with USB. But that is about 59 – but very expensive euro. The expensive touch screen was also replaced with an inexpensive DOGXL160 display. Thus, the AVR-Synthesizer for the replica is much cheaper. I’m still used because the filter IC SSM2044, if I do not want this to replace a cheap filter circuit with OTAS type LM13700. But for now I stick to the SSM2044.

    Pic 1: Atmel Xplained Board
    Pic 2: SDCARD Breakout Modul

    Pic 3: AVR-Synthesizer Prototyp mit SDCARD und Xmega-Breakout Board.
    This picture shows the current hardware configuration of the AVR synthesizer. On Frontpanal time is still being worked on. The Frontpanal consisting of display, encoders and buttons is connected by a wide ribbon cable to the controller board.

    Pic 4: free bytes from SDCARD

    Greetings Rolf

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  • @ yewtreemagic
    “Instrument Tuner” is very accurate measurement (+- 0,01 cent). The trial version has small restriction, but you can frquency measurement at any time.

    I have free cubase LE6. How can installed the C-Tuner ?

  • Just drop the C_Tuner.dll file into your existing vstplugins folder, and when you next launch Cubase LE6 it should be discovered and added to the list of your available plug-ins.

    If you click on its ‘i’ button (bottom right in the screenshot) you can set the Accuracy from the default ‘economy’ setting (one decimal place) to ‘Normal’ with two decimal places. There’s even a ‘Super’ setting with three decimal places, but I’ve never felt the need to use that ;)


  • Hallo yewtreemagic

    Thanks for your help. I have test “C-Tuner” in cubase le6, but the frequency measurement is incorrect. Test frequency 440Hz is right. Test frequency 880Hz is show 883,24 (+6 Cent). Test with “Instrument Tuner” is very accurate (see pic). I compare the result with my multimeter (is not so exactly) and “Audacity”. My frequency is 880Hz. Frequencies above 2500 Hz can not be measured with C-Tuner.

    Greetings Rolf

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  • Hi Rolf,

    Thanks for the feedback – I wonder why it’s not performing as well for you as it does for me?

    I’ve just done some more testing with C-Tuner, and in my system it measures accurately to three decimal places.

    It does so all the way from:

    MIDI Note 0 = 8.257 Hz

    up to

    MIDI Note 106 = 3729.310 Hz

    Admittedly it’s annoying that C-Tuner won’t measure fundamentals above 3.7kHz, but I haven’t personally got many instruments that go higher than this anyway


  • Hallo Martin

    I have test once more. The incorrect values ​​were in my wrong settings in cubase (ASIO driver problems). Now the frequency measures is correct.

    Thanks :)

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  • Hallo Martin

    Can you test frequency 440Hz, 880Hz, and 1760Hz from shruthi. I dont have a shruthi and I want to know how accurate it is.

    Thanks a lot.

  • @Rolf:

    The ‘A’s on my Shruthi with C_Tuner measure an incredibly accurate:

    13.75, 27.50, 55.00, 109.99, 219.97, 439.95, 879.89, 1759.78, 3519.57 Hz

    I’ve also confirmed these readings exactly using another standalone PC-based frequency meter/scope/analyzer, which also manages to measure the next higher A at 7039.14 Hz.

    The highest note from the Shruthi I can measure with this 2nd frequency meter is MIDI Note 127 (G5) at 12541.81 Hz (official frequency for equal tempered scale is 12543.85 Hz, so once again the Shruthi is incredibly close to the theoretical frequencies across a 10-octave range).

    I continue to be mighty impressed with this little synth


  • Thanks. My synth i have similar frequencies. The basis for my DDS calculation was 440Hz :) The max. difference was + 0.5 Cent.

  • You might see a slight transposition/offset from the right tuning due to the crystal inaccuracy and its temperature coefficient, but the frequency ratios, created digitally, should be exact (in particular, the software equivalent of the “exponential converter” rounds things in such a way that true octaves are generated).

    Hence the 3519.57 / 1759.78 = 2.00000

  • was mentioned in the beginning of the thread, but it has to be said – relying on midi interface control really doesn’t provide the same thing that on-board pots/encoders will (at least the option for). just my opinon and i’m sure there are plenty of others who don’t mind, but i wouldn’t ever want a synth without at least the amount of control the shruthi has (by default).

  • Hallo wavehead

    I am glad that there is the shruthi :) Otherwise I could not build a good synthesizer. In shruthi are many good ideas and i have copy for my synth-project. I’m not a professional, but i learn every day new things for my synth-project and change this.

    Here are some pics of my synth-case (not yet finished):

    Greetings from germany. Rolf

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  • Hallo friends :)

    This is a information for my case building: The case is from the company Bobla and costs Reichelt about 36, – € (Size: 181x68x200). That gives it in other sizes. We’ll see who can mill the special cover me now. Since the GLCD display with LED backlight (EA DOGXL160-7) has a total height of only 6.4mm and the other components are smaller, the board can be screwed later just under the top cover (see pic).

    Link Case:;ACTION=3;LA=446;ARTICLE=126237;GROUPID=5194;artnr=ATPH+1865-200

    Other supplier:

    Greetings. Rolf

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