FPGA based digital signal synthesizer

Project Title

FPGA based digital signal synthesizer

Project Area of Specialization Information & Communication TechnologyProject Summary

An audio synthesizer is a device that takes in an audio signal from a source and processes it using its internal combination of hardware and software to produce a desired audio output. This type of audio-processing is widely used by musicians around the world.

The concept of audio-signal processing roots from the idea of effects that musicians need in order to produce a very specific type of sound which can only be achieved by processing the original audio of the instrument. One example of such effects can be heard in rock music which is more commonly known as overdrive/distortion.

Previously these effects were incorporated by using an effects unit or “pedal” which were analog and used a variety of analog components such as transistors and vacuum tubes. These are replaced by digitized effect units which utilize IC’s which combine several effect units eventually creating the all-in-one software based Multi-effect units which we can see today.

Our aim to develop and implement the same effects that musicians require using FPGA which will cut down the cost of the overall procedure as well as improve the performance of complicated effects which were previously achieved using the digital effects unit.

   

Project Objectives

The effects that these digital synthesizers imitated were of the analog pedal that were previously being used but only the effects that were mathematically linear in terms of signal processing could be implemented effortlessly.

Non-linear effects such as distortion and overdrive were more complicated to handle by just the digital synthesizer to match the performance of its analog counterpart.

Mainly there are three ways of achieving these effects

1. Built-in effect units inside a guitar amplifier
2. Sole software solutions which run on a PC and need an external interface for the guitar (or any other instrument) to be connected to the PC for the audio input.
3. Physical Multi-effects units consisting of a guitar as and input and amplifier for output and a chip based DSP core with a hard architecture that cannot be changed.

Our project uses an FPGA board that can implement every single logical operation and since it is a direct implementation of a digital circuit it allows many audio channels to be processed together which improves real-time performances.

Modern FPGAs provide a high performance and flexible alternative to other application-specific products, allowing us to implement system-on-chip designs that eliminate the need for separate components to perform audio processing tasks, thereby reducing costs, particularly for multi-channel audio applications.

Project Implementation Method

• Conversion of audio signal from analog to digital using ADC in the FPGA board.
• Understanding the basics of VHDL and the Verilog codes used to synthesize the audio signal.
• Process the audio signal using the intel FPGA board and veri-log codes in VHDL.
• Conversion of the processed signal with effects to analog.
• Playing the music signal back using an amplifier and possibly displaying the signal on a screen.

Benefits of the Project

In this project, we to intend to experiment with the idea of implementing audio-processing algorithms on an FPGA, instead of the common CPU/DSP-based platforms. Since this approach is not commonly used in the guitar-effects industry and only a few private individuals have experimented this using different FPGA boards around the world.

We aim to develop a device that can replicate the effects unit being commonly used and make it into a more friendly experience for the user using FPGA board and improve the performance of the sound effects as well as transform it into a more compact and high performance solution for musicians everywhere.

Technical Details of Final Deliverable

In our project we are using Max 10 neek FPGA board having

 Audio Codec:

The MAX 10 Plus offers high-quality 24-bit audio via the Texas Instruments TLV320AIC3254 audio CODEC (Encoder/Decoder). This chip on MAX 10 Plus supports, line-in, line-out and microphone-in ports with adjustable sample rate from 8KHz to 192KHz.

ADC:

The board has a 2x10 ADC header with sixteen analog inputs connected to FPGA ADC1 and ADC2 respectively. The 1x3 header J12 is used to select pin 18 of 2x10 header J7 or potentiometer input to be connected to the channel 8 of FPGA ADC2. Short pin 1 and pin 2 of J12 to select potentiometer, short pin 3 and pin 4 to select pin 18 of 2x10 header J7. The 1x3 header J13 is used to select pin 16 of 2x10 header J7 or on-board microphone to be connected to the channel 7 of FPGA ADC2. Short pin 1 and pin 2 of J13 to select on-board microphone, short pin 3 and pin 4 to select pin 16 of 2x10 header J7.

 DAC:

The board provides a Texas Instruments DAC8551 16-bit digital-to-analog converter (DAC). It is a small, low power, voltage output DAC. The DAC8551 used a versatile 3-wire serial interface that operates at clock rates to 30MHz and is compatible with standard SPI, QSPI, Microwire and DSP interfaces. The analog voltage output of DAC8551 is connected to a SMA connector.

MIDI (Input)

The standard protocol for communication between music devices and computers is Musical Instrument Digital Interface (MIDI). Data transmitted using this type of protocol is of 3 bytes, sent asynchronously over a serial communication port as 24-bits of data.

Effects we are implementing on our board.

Distortion:

This effect is actually amplitude clipping or compression in which the top and bottom peaks of waveform are capped at a maximum absolute value. An ideal system is designed such that the amplitude of a waveform never able to exceed the full-scale range of its output.

Delay:

This effect actually includes two things one is delay and the other is echo delay module store previous values of a signal for a variable length of time, usually up to for several seconds.This is actually a simple delay between user input and system output.

Vibrato:

The vibrato effect modulates the frequency of the signal at a user defined rate and depth. The functionality of this effect was confirmed audibly as well as visually on the oscilloscope. Using a maximum depth parameter to exaggerate the frequency change of the signal, many different frequencies can be observed on the oscilloscope for a single input note. 

Final Deliverable of the Project HW/SW integrated systemCore Industry MediaOther IndustriesCore Technology Clean TechOther TechnologiesSustainable Development Goals Industry, Innovation and InfrastructureRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	69000
MAX 10 NEEK FPGA	Equipment	1	56000	56000
Speakers	Equipment	1	3000	3000
Shipping Charges	Miscellaneous	1	10000	10000