Shruthi-1 FAQ
I have never soldered anything but am willing to learn, is this kit difficult to assemble?
The Shruthi-1 is not difficult to assemble. The assembly instructions are very detailed, part values are printed on the PCB, and there are no surface mount parts. However there are more than 200 parts to solder, increasing the risks of doing something wrong if you are not 100% sure of your soldering skills.
Our advice? If you never have soldered anything in your life, go grab a kit at Sparkfun or at your local electronic store, assemble it, and come back to the Shruthi-1 afterwards. It is better to destroy a small LED blinker than an almost fully populated Shruthi-1 filter board. Here is a soldering tutorial we recommend.
Also, while assembly is easy, troubleshooting an assembly mistake can be difficult and might require more skills (using an oscilloscope, following a schematics, unsoldering parts). If you are a beginner, make sure that there is someone around you willing to help in case things do not go as expected.
Can I order a pre-assembled unit?
Depends on what kind of pre-assembly you have in mind!
If you think of industrially, mass-produced units sold at the same price as kits, the answer is no. Because it is primarily a project intended for DIY, the Shruthi-1 only uses through-hole parts (pins and leads inserted and soldered through holes on the circuit board) to make it easy to assemble with a limited amount of equipment and experience. However, this technology is not ideal for industrialized production.
If you think of hand-assembled units, the answer is yes. Some hand-assembled units are regularly available on the shop.
Why aren’t there detailed build instructions for the filter boards based on vintage chips? Why aren’t there kits for the CEM3379 board?
We make these boards less attractive to build in order to avoid “rushes” on vintage chips, as it was the case with the CEM3379 when the first Shruti-1 was released.
We believe that some modern and widely available chips have an equally high potential for great sounding filters than original CEMs or SSMs, and we will produce more filter boards in the future based on common OTA or VCA chips. It’s time for new classics!
Which filter board is the best?
Here is a very subjective evaluation:
| Filter board | Response to loud signals | Self oscillation shape | Q loudness drop | VCA quality | Extra features |
|---|---|---|---|---|---|
| SMR4 mkII | Slight distortion | Sine | No | Good | 2-poles switch, mod points for BP modes |
| SVF | Clean signal | Sine, overdriven at very high-frequencies | No | Good | Second filter, LP/BP/HP mode selection |
| POLIVOKS | Large distortion | Dirty triangle | No | Average | LP/BP mode selection, distortion, filter FM |
4 knobs, seriously? What’s the point of making a complex synth if you make it that hard to edit!
User interface is a very subjective matter, but all the Shruthi-1 users agree that it is a very intuitive and easy to program synth, and that the pages / parameters layout can be learnt very quickly (that is the reason why we don’t label the 6 switches – the same way note names are not written on piano keys). But if you insist, yes, it’s possible to build a “1 knob per function” programmer for the Shruthi!
8-bits? Does it mean it sounds like a gameboy?
8-bits has been used a lot recently to refer to the aesthetics associated with early 80s gaming consoles and home computers. Those computers used dedicated sound chips (such as the AY-3-8910, MOS 6581 or C012294) featuring high-frequency (clocked at several MHz) digital oscillators, and in the case of the SID, an integrated analog filter.
8-bits also refers to the resolution (fairly low by modern standards) of a digital circuit storing or processing audio signals. Early 80s wavetable synths and samplers (CMI Fairlight, E-mu Emulator , PPG Wave, Ensoniq ESQ-1, Kawai K3) all used 8-bits sound generators.
The Shruthi-1 is closer to the latter than the former.
Is the Shruthi-1 related to the Arduino?
The Shruthi-1 uses the same line of chips as the Arduino boards (8-bits AVR), but that is pretty much where the similarity ends. The chip runs at 20MHz and does not use a serial bootloader – so the Shruthi-1 cannot be reprogrammed with the Arduino development tools.
We found that bare gcc and avril, our own hardware abstraction library based on compile-time configuration gave us more satisfying performances than the Arduino libs.
C++, you must be kidding? Real hackers write assembly or C.
We found that, at the exception of short signal processing building blocks, assembly language was not a necessity. The best optimization we found were always algorithmic/structural rather than instruction micro-management. C++ provides compile-time abstractions / evaluation which allows a clean separation between system and application level code at no interfacing cost.
Why using such a puny chip?
Yes, 8-bits, 20 MHz, with a very generic RISC instruction set is totally silly for audio. But the alternatives are either SMT (ARM), or do not have free/open-source compilers/development tools (dsPIC).
If there’s enough interest in buying kits with a pre-soldered microcontroller chip, we might switch to STM32F in the future.
What is the origin of the name?
The Shruti-1 originally was an all-in-one tampura/shruti box/lehera machine based on phase distortion synthesis – but after adding some menus to tweak the sound parameters it quickly morphed into a synth. The “ShruTHi-1” spelling was coined during discussions with Tim Parkhurst about the use of the TH-201 (aka Mankato) VCF design in the Shruti-1. At this point, the decision to redesign the product with an “open-ended” analogue section was taken. Shruti means “what is heard” in Sanskrit and refers to the pitch class in the context of indian music. Shruti is also a common (girl) first name. Like many common indian names, Shruti is often transliterated with an aspirated consonant in South India, so Shruthi is commonly seen as a name too.
