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My Digital Audio Processor

Ravindra Desai

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#1
Hello all,

After working long years in analog, I was impressed by the offerings of a digital signal processor dedicated for audio applications.
I was fascinated by the possibilities of making a board and then re-programming it as many times as possible for the purpose of tweaking an application or using the same board for different applications.
It is the SigmaDSP which I have been on for some years now and have a matured board.
I am listing its features. I hope you guys like it.

- Digital audio Processor based on SigmaDSP platform that supports 2 Analog Inputs, 6 Analog Outputs (On board Stereo DAC for 2 additional outputs)
- On board 3.3V linear power supply (that supports 190V to 270V AC variation) for the processor, DAC and house keeping
- On board 9V linear power supply (that supports 190V to 270V AC variation) for media player that supports MP3, Flac, WAV, WMA through USB, Bluetooth and FM. The media player also has AUX input and comes with a small IR remote control
- On board interface for programming the DSP
- Front panel header (Front panel has 4 x Alps potentiometers, 1 Status LED and Universal IR Receiver. IR Rx is currently not used and is just a placeholder)
- Back panel header (Back panel has 2 x Analog Stereo inputs, SPDIF Co-axial/ Optical inputs that is jumper selectable. All the inputs are summed to form one composite Stereo Input)

Applications:
1. Stereo Audio Processor/ 2.1CH Stereo Audio Processor
2. 2.1CH Surround Sound Decoder and Post-processor
3. 2/3-Way Active Crossover
4. Audio Processor for PA Systems

I will post the photos of the Processor board, Back Panel, Front Panel, and the enclosure soon.
I will also detail out each of the application listed above and what role the DSP application firmware is playing.

Regards,

Ravindra.
 
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goldyrathore

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#2
Very good project. A few questions

1) What are the devices being used?
2) How are you planning the interface, is it standalone or to be configured from PC?
 

sadik

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#3
Looks a very good Project. Post the photos soon, I am watching this thread.

Secondly its very nice to know someone here staying close to Ratnagiri. I am from Ratnagiri but at present in Vadodara (Gujarat).

Sadik Bhatkar
 

Ravindra Desai

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#4
I am attaching photos of My Digital Audio Processor. Kindly excuse me for the quality of the photos.
As you can see, the boards are mature but the enclosure is still in DIYish state.

As I stated above, it can be used for a number of applications. What changes is only the firmware.

In the following posts, I will detail out each of the 4 applications stated in post #1 and explain how the same processor adds value.
It can be argued that similar hardware exists elsewhere. Which is OK. I am NOT claiming mine to be the best. All I have done is bring completeness by not throwing just the motherboard to the DIYers or end users but also give them the full story in the form of front panel interface, back panel interface and a media player. Soon I will start new threads similar to this to showcase my amplifier and speaker system and how the three (processor, amplifier and speaker system) should be able to nicely sit besides good branded systems.

I will help you understand the role of all the three components of the sound system and how the firmware can help solve everyday problems related to sound.

I am not perfect nor is my approach. So kindly treat this proposal as work in progress.

To help non- engineers, I will keep things simple and non- technical. However the technical minded can ask for more information.

GoldyRathore:
1.The processor IC is ADAU1701 which supports 2 input and 4 output channels. DAC for the 5th and 6th output channel is PCM510X
2. The processor is firmware driven. It can be suplied with a blank EEPROM to someone who wants a ready hardware platform. He can develop his own algorithms and application firmware. Programming interface is provided. It can also be supplied as a stand alone product (pre-programmed EEPROM) that a common man can start using straight out of the box without waiting for a technician to arrive.

Sadik:
On your way to Ratnagiri, come over to Kolhapur for a demo. Your review comments will be of much value to me.

Regards,

Ravindra.
 

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reubensm

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#6
Though I have never built anything digital myself, i can't but stop and admire your thread. One aspect that keeps a lot of us away from digital DIY is dealing with SMDs and micro components. Did you use pre-fabricated and assembled PCBs or did you make these yourself and mount components? Very curious to see the rest of your DIY chain. Well done.
 

Ravindra Desai

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#7
Hello RubenSM,

Thank you for visiting my thread.
I did audio design in analog for long years. I got fed up with customers ever changing requirements. Technology around me was changing and that worried me.
Interestingly, it was soldering the SMDs made me prolong migrating to digital. But then I realized that it was not difficult at all.

But, all my amplifiers are analog.

One of the fascinating things about digital is re-programmability. e.g. the one single processor board allows me to handle any customer requirement by writing an application that suits his needs. Still better,I have to stock only one item for all my needs.

I have done the design, placement, layout and assembly all by myself. I suggest that you give it a try too. We are here to help you along the way.
We also have Andonstar ADSM201/ Andonstar ADSM302 HDMI microscope to ensure that we are not forced to retire anytime soon.

b.t.w. We have a Gerrard changer bought by my Dad when I was a kid and We love it.

Regards,

Ravindra.
 

elangoas

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#8
To help non- engineers, I will keep things simple and non- technical.
Applications:
1. Stereo Audio Processor/ 2.1CH Stereo Audio Processor
2. 2.1CH Surround Sound Decoder and Post-processor
3. 2/3-Way Active Crossover
4. Audio Processor for PA Systems
Great Build.. But curious, why no HDMI?.. Since you mentioned 2.1CH Surround Sound Decoder and Post-processor, i would like to ask, what happens when you play DTS HD MA / Dolby True HD (or) say lossless media playback?.. Does your amp have the decoders built in?
 

Ravindra Desai

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#9
Great Build.. But curious, why no HDMI?.. Since you mentioned 2.1CH Surround Sound Decoder and Post-processor, i would like to ask, what happens when you play DTS HD MA / Dolby True HD (or) say lossless media playback?.. Does your amp have the decoders built in?
Hello elangoas,

Great questions! It allows me to tell more about my system.
In the market, presently, there is virtually nothing that can take stereo input and give great (good is not acceptable) quality output. Be it stereo or surround. BigBrothers have kind-of succeeded in monopolizing HDMI. This leaves nothing for common man.

I have built a system that takes ANY stereo input and outputs great quality audio. Be it stereo or surround. My system is blind to the audio source. As long as it is stereo, it will give you stereo or surround with quality that matches HDMI. The vocals, the music the effects all with just the right amount of bass, mid-range and treble.

To answer your question: I don't need HDMI. (I may add it because of the ARC feature). My system takes ANY INPUT (analog, optical or co-axial) from ANY SOURCE (Web, STB, TV, Media player, Bluetooth) in ANY FORMAT (WAV, MP3, FLAC, WMA, 2CH, 5.1/7.1CH, DTS HD, Dolby Tru HD), decodes it, processes it and then re-encodes it to stereo or surround format. I use nothing proprietory and have developed my own algorithms to do this.

Since you picked out 2.1CH Surround, I promise you the following in terms of user experience:

Top-class sound straight out of the box with:
- No complicated set-ups
- No volume adjustments during commercials, action scenes or soft passages
- No complaining about weak dialogues
- No distracting surround
- Consistent sound field at all listening volumes.

The list above is in fact drawbacks of the present systems! At least for the common man!!
Take the last one as an example: How many systems in the market today maintain the same center to surround ratio at ALL listening volumes? Aren't we forced to listen at and above a certain volume to get the right feel and balance? How will you enjoy it with a TV, then, for prolonged listening, with elderly people in the room? My system maintains same feel and balance at all listening volume levels.
I have tried to reason it to some extent here: https://www.hifivision.com/threads/what-changed-with-digital-audio.69388/

If all this sounds too good to be true, then wait until I announce invitations to audio buffs like you and me to review my system, at ones own place. I am still framing the guidelines but it will be along the lines: Review it, PM me your report and pass the system on to the next in line.

Thanks again for your interest and be at it.

Regards,

Ravindra.
 

elangoas

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#10
In the market, presently, there is virtually nothing that can take stereo input and give great (good is not acceptable) quality output. Be it stereo or surround. BigBrothers have kind-of succeeded in monopolizing HDMI. This leaves nothing for common man.
Understand you don't need HDMI.. Just my views w.r.t HDMI only..

For surround, HDMI simplified it.. If you were to take component video out from a DVD player (3 cables) & then HD audio codecs processed output, which is 7.1 channel out.. Then it makes 10 or more cables between source device & the amplification device.. HDMI solved it with a single cable and still room to accommodate future requirements..

For stereo too, HDMI would be great connectivity between STB & AVR.. Just one cable for 1080p video & 2.0/5.1 or more output..

To answer your question: I don't need HDMI. (I may add it because of the ARC feature). My system takes ANY INPUT (analog, optical or co-axial) from ANY SOURCE (Web, STB, TV, Media player, Bluetooth) in ANY FORMAT (WAV, MP3, FLAC, WMA, 2CH, 5.1/7.1CH, DTS HD, Dolby Tru HD), decodes it, processes it and then re-encodes it to stereo or surround format. I use nothing proprietory and have developed my own algorithms to do this.
Ok.. Sorry.. But i didn't understand some part of your above explanation..I understand, that your system accepts digital inputs.. Lets assume, once connects a PC/DVD/BR Player to your system via co-axial.. Does it mean that the decoding of multi-channel has to be done at source itself?..

If one were to bitsream/digital out from source device (let multi-channel untouched) over co-axial (or) optical, then your system needs a DTS/Dolby decoder..

Take the last one as an example: How many systems in the market today maintain the same center to surround ratio at ALL listening volumes? Aren't we forced to listen at and above a certain volume to get the right feel and balance? How will you enjoy it with a TV, then, for prolonged listening, with elderly people in the room? My system maintains same feel and balance at all listening volume levels.
Yes.. you are right.. There are at times in a movie, where there is a sudden increase in volume depending on action scene, so you are forced to adjust volume.. especially during night time watching (or) elderly people around..

AVR with Audyssey has one function to handle this.. Audyssey Dynamic vol.. I have used this feature many a times to handle the above situation.. It unifies he vol across the full length of the movie.. Loud action scenes & quiet dialogues are the same output..

If all this sounds too good to be true, then wait until I announce invitations to audio buffs like you and me to review my system, at ones own place. I am still framing the guidelines but it will be along the lines: Review it, PM me your report and pass the system on to the next in line.

Thanks again for your interest and be at it.
Sure.. Thank you for considering me.. Yes..Looking forward..

Happy to experiment / experience products..
 
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Ravindra Desai

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#11
Ok.. Sorry.. But i didn't understand some part of your above explanation..I understand, that your system accepts digital inputs.. Lets assume, once connects a PC/DVD/BR Player to your system via co-axial.. Does it mean that the decoding of multi-channel has to be done at source itself?..

If one were to bitsream/digital out from source device (let multi-channel untouched) over co-axial (or) optical, then your system needs a DTS/Dolby decoder..
I convert digital input to analog or digital stereo. This is allowed and is free. If I try to decode digital to multi-channel, than I need a license. or I will not be able to sell it in open market.

AVR with Audyssey has one function to handle this.. Audyssey Dynamic vol..
It is a feature available in high cost AVRs only. Common man does not know Audyssey. He tends to pick a system up that fits a budget. He get fooled by the panned effects in demo content and believes he has what is needed.
But yes, Aydyssey does what it is supposed to.

I would like systems to be priced based on wattage, not quality. Give everything that is needed to produce great sound and price the systems based on wattage. Audio world will then become a better place than it is today. But that's just me....

Regards,

Ravindra.
 

elangoas

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#12
I convert digital input to analog or digital stereo. This is allowed and is free. If I try to decode digital to multi-channel, than I need a license. or I will not be able to sell it in open market.
Perfect.. Got it..

It is a feature available in high cost AVRs only. Common man does not know Audyssey. He tends to pick a system up that fits a budget. He get fooled by the panned effects in demo content and believes he has what is needed.
But yes, Aydyssey does what it is supposed to.
Audyssey is aval in entry level AVR too, but priced heavily here in India (All brands).. and the high end AVR have platinum suite of Audyssey & its functions..
 

tuff

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#13
Almost every AVR has built in DRC. Even my 3500 rupee LG Bluray player has built in DRC. They simply have different names like Night mode and what not. I am not sure this system that you have envisaged falls in that category. Could you place this system of yours in a category that i can understand.
On one hand there is the high end purist way of seeing things, one of which is no DRC at all. Then the AVR category comes in. After that all the new wireless plug and play from the likes of JBL, Bose etc and everything in between. I am having a hard time to place this system, at least in my mind as to what would drive some one to buy it? Do you mean more watts would equate to more money?What kind of speakers would they be able to drive?Sorry if i sound ignorant ,but heck i am in a lot of ways. It seems it could be a OEM product for manufacturer's if custom programming is allowed, Kind of like Hypex NCore technology or ICE powered amps by B&O? I apologize again if this does not make any sense.
 

Ravindra Desai

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#14
Almost every AVR has built in DRC. Even my 3500 rupee LG Bluray player has built in DRC. They simply have different names like Night mode and what not. I am not sure this system that you have envisaged falls in that category. Could you place this system of yours in a category that i can understand.
On one hand there is the high end purist way of seeing things, one of which is no DRC at all. Then the AVR category comes in. After that all the new wireless plug and play from the likes of JBL, Bose etc and everything in between. I am having a hard time to place this system, at least in my mind as to what would drive some one to buy it? Do you mean more watts would equate to more money?What kind of speakers would they be able to drive?Sorry if i sound ignorant ,but heck i am in a lot of ways. It seems it could be a OEM product for manufacturer's if custom programming is allowed, Kind of like Hypex NCore technology or ICE powered amps by B&O? I apologize again if this does not make any sense.
Sorry to have left you confused. Maybe I took a few things for granted and that is my fault. Sorry again!
I will try to answer your questions but not necessarily in the same order.

What is this product:

1. It is a digital audio processor hardware that the user can program to suit his own needs or that can be supplied with a pre-programmed application such as stereo, surround, 2/3-way crossover, PA system processor. I would like to add that since it is only the program that changes, the user only has to buy the one hardware and replace the socketted IC to change the application from one to another.
2. The digital audio processor when combined with the amplifier, can perform the same way as an AVR but only that there are no video functions supported. The supplied media player allows the user to play media using USB, Bluetooth.
3. Since it supports custom programming, it can also be looked as an OEM product

More background:

SigmaDSP is a well known audio platform, especially among DIYers. It is popular because it allows graphical programming where you don't have to write a single line of code. You just have to drag and drop library block.
e.g. Drag the input port and enable 2 channels. Then drag a 2CH volume control and assign it to a DC potentiometer. Then drag a 2 channel o/p port. Connect the elements that you have dragged to get a stereo volume control. For more information go here and here.

On many forums, there is a kit available for sigmaDSP e.g. FreeDSP and miniDSP. I designed one but in a more complete and universal way. (At least that is what I think) by adding a front panel, back panel a media player and two extra output channels. I put it here on this forum because this is an Indian forum and as an Indian I wanted to convey that we are capable of contributing to audio hardware as well as application firmware development as well.

Now, by nature SigmaDSP, is a blank when you purchase it. So you need to program it. In my case also, you can buy a blank processor kit and program yourself or I can supply you with a pre-programmed processor. Either way, you will be buying it from an Indian, in INR and there will be 1-1 support available. That is why I posted it in DIY forum.

Next, let's take the case of a pre-programmed processor where the application of this processor is Surround Sound System:
The processor can be pre-programmed as a surround sound processor and together with the amplifier presented here acts nothing short of an AV Receiver except that it is only an A Receiver (AR). As an AR, the 4 front panels controls become: Center channel volume control, Surround channel volume control, Sub-woofer volume control and Master Volume Volume Control. The factory setting is for the user to keep everything in its MAX position. If your room booms, reduce the SW volume. If your surround speakers are placed too close, reduce the surround volume, if you want to listen to music with suppressed vocals, reduce the center channel volume. An accordance to your TV/ Projector gain adjust the master volume.
The controls are upfront, not hidden in a menu. Making it easy to revert back to.
The back panel has connectivity options: Analog, SPDIF (optical/ co-axial) and outputs. In case of an intrgrated implifier, the outputs will be speaker connectors.

That's it. Everything else that is needed for the application is something that user need not bother with or even be aware of.
Thus you just unpack it, set all the front panel controls to full, connect the inputs and outputs and start enjoying it using the TV or the STB remote!!

When I say:
Top-class sound straight out of the box with:
- No complicated set-ups
- No volume adjustments during commercials, action scenes or soft passages
- No complaining about weak dialogues
- No distracting surround
- Consistent sound field at all listening volumes

....I am only explaining the underlying features , conveying to the forum here that I have taken care of some common issues.

Customers that I face everyday range from audio experts to housewives.
I have made a system that produces great sound that you can use by controlling only three buttons: VOL+. VOL- and MUTE.

Some don't like the simplicity. Some love it. Some come back after months agreeing that they want a system that they can enjoy listening to rather than setting it up. All are fine by me.

I hope things are more clear now. If not, don't hesitate.....

I will be in Mumbai around March 6 to 8. Would you like to experience it? As a stereo sound system or as a surround sound system or both? With my speakers or yours or both? Let me know.

Regards,

Ravindra.
 
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tuff

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#15
Thanks for the detailed explanation. Gonna try and dig into it, hopefully my non-technical brain can understand the concept.
 

gopib

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#16
Good going. Will be watching this space. I understand what you are attempting. I have seen the miniDSP types and was looking for more flexibility.
 

vkirti

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#17
Ravindra, let me post a scenario to you and let us see if we can find an answer. I only watch movies on my TV (a 50 inch plasma) via a blu ray player, in the form of Blu ray's, DVD's and Via the USB input on the Blu ray. The player connects to the TV via HDMI and the audio is from the speakers of the TV. As you can understand the audio is the weak link, I do not wish to add an AVR and 5.1 speakers here because I already have that setup connected in a different room with a projector and cannot justify the costs of the second system.

Can I use your sound processor + amplifier for the audio in this scenario ? Will it drive three front channel speakers ? Does it have an out for an active Sub ? What is the cost range we are looking at ?

Regards
 

Ravindra Desai

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#18
Hello VKirti,

Thank you for your interest in my project.

Can I use your sound processor + amplifier for the audio in this scenario ?
Yes!

Will it drive three front channel speakers ?
See the the attached pdf and the explanation below.

Does it have an out for an active Sub ?
It has a speaker out for passive sub!
See the the attached pdf and the explanation below for more clarity.

It seems that My Ampli-Decoder (Amplifier + Processor/ Decoder) + My Speaker system will be a will be a perfect fit for your requirements.
The system is capable of stereo and surround. However, since you mentioned that you want to watch only movies (STB as a source for movies is also OK), I will restrict the discussion to Surround only.

The wiring diagram and the speaker configuration is as shown in the attached pdf

Center channel will produce dialogues and music
Surround channel will produce special effects
Sub-woofer will produce low frequency contents

Unlike 5.1CH set up this does not have L and R for music. The content of L and R is merged in C

The proposed setup has the following advantages:
1. Unlike 5.1CH system, no set-up or calibration is required
2. Unlike 5.1CH system, no volume adjustments during soft/ loud passages is required
3. Unlike 5.1CH system, Surround channels maintains its relation with Center at ALL volumes. In a 5.1CH set up, you need to be at or above certain reference volume to enjoy all the channels
4. 2.1CH surround produces amazing vocals as the set up ensures 1 : 1 : 1 ratio for dialogue to music to effects.
5. The system does not need symmetrical speaker placement and so eliminates 'sweet listening spot.'

I hope that it meets your requirements.
Do let me know if you need any further clarifications.

Regards,

Ravindra.
 

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vkirti

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#19
Hi Ravindra,

Thanks for the response, will wait for your PM. Can your decoder also decode from the blu ray player connected via co - axial i.e. decode 5.1 or 7.1 down to 2.1 ?

Regards
 

Ravindra Desai

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#20
Hi Ravindra,

Thanks for the response, will wait for your PM. Can your decoder also decode from the blu ray player connected via co - axial i.e. decode 5.1 or 7.1 down to 2.1 ?

Regards
Yes, it can!
But connecting it directly to the bluray player could have one disadvantage: remote control of volume and mute. However, if the bluRay player outputs variable signal on digital output, then there would be no problem.
If the signal is taken from TV, then we can use the TV remote to control the volume, regardless of the source.

Regards,

Ravindra.
 
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