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DIY Class D optical coaxial receiver with LCD and remote

What do you guys think about this work


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Joined
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#1
Intro
Hi guys this is Manoj from Chennai. A novice electrical guy who loves to build stuff on his own. So without much about myself let's jump into the project.

The quest:
On 19-jan-18 the quest for AV receiver started after buying a Vu Iconium 50" 4K LED TV. Wasn't having a large headroom for high end network receivers. Though a decent enough sound with deep punchy bass and soundstaging was my first preference
Friends were suggesting Sony's HT-Iv300 though after a visit to Sony centre I wasn't satisfied with overpowering muddy bass and poor soundstaging.
Then Yamaha's, as my budget was under 25k Yamaha's entry level receivers lacked features and it wasn't delivering deep yet punchy bass.
Puny 6.5 inch subwoofer was trying so hard and it never gave me what I needed.

Feb-18
Quest continued but on OLX for onkyo receivers.Most of them were old and had nothing regarding features least I was needing 4k upscale. It also ended up as failure.
At the end of February I came to know that my friend had a old Panasonic DVD recorder + hometheater. SA HT 740
The thing is that it was non working but I had other ideas.

Salvage
I went up to him salvaged the old thingy. Came home disassembled everything. Went to a Panasonic guy a friend of my grandpa. He lucky had service manual for those, took photo copy of the manual.
Now it was something from just a junk.

March-18 The build..
Found that the main CPU was the issue. It wasn't suffering from any physical damage but it was the firmware. Searched firmware from many sites and service centres, no luck.
Then came up using only the digital amplifier sector and power section.
Luckly it had two power sections one for standby circuit and an dedicated supply for digital amplifier sector.

Tracing:

Started tracing the outputs and inputs from pin to pin. Marked everything from data till signals for speaker protection delay and Prologic switching.
IMG_20180217_145652_20180419084802387.jpg
Even bought a cheap Samcon micro soldering station for tis project.
Further more research lead me to the detailed spec of the IC's and output figures.
Main class D amp.
RSN704D66 - P
It is a monolithic 6 channel hybrid IC from matushihita or Sanyo wasn't able to get a proper datasheet even.
unnamed.jpg
Sorry for images from internet as the IC had soldered heat sink and wasn't accessible.
So winding up the specs from the manufacturer's manual was able to get some numbers. Screenshot_20180419-085302.jpg
They stated RMS power of each channel at 10% THD, man it's 10% it would be clipping speakers so badly at 10% so taking the RMS power at 1% THD at 1khz test tone.( Real life scenario will be lower than that).
Front channel : 65w at 4ohm 1%THD
Surround channel : 65w at 4ohm 1%THD
Centre channel : 240w at 4ohm 1%THD
SUBWOOFER channel : 240w at 4ohm 1%THD

Googleed the DIN standard it was slightly stringent than traditional RMS saying 10% THD 1% is acceptable.

So these numbers were quite the same as current days receiver output figures.

The build:

Being a Chennai guy having Ritchie street is a great thing.
Went on to amplifier spares shops bought a cabinet for the whole thing. Luckly I came to know about 5.1 channel remote kits and much needed optical to analog converted boards.
The thing is that these remote kits can be paired up with those board with changes optical to coaxial from the remote control.

Shopping :

Went on to buy the remote kit they were kind enough to explain all the wirings and IC level functions.
Bought the matching cabinets for the display and remote kit.
It came with rotary encoder for volume and sound functions. Two of them one for source and other for volume and sound related functions.
IMG_20180404_213655.jpg
Just a assembled view to show the display and rotary encoder.

Purchase list as follows:
5.1 remote kit with display and remote
Suitable cabinet
Usb Bluetooth FM board (specifically vire brand)
Power switch
Speaker terminals
12v 3pin 80mm case fan
Power chord
7A fuse 4nos
Shielded wires
Multicolored wires
Speaker wires

Assembly :

Primary view is to have a clear layout for every component inside the cabinet.
My usual style is to mount large components first then to small. First of all installed the class D amplifier board then. Standby power circuit. IMG_20180403_120200.jpg
Mounted the display and USB Bluetooth module.
And wired everything, since the SMPS will cause lot of static noise into the signal lines I made a outer grounding shield for reduced EMI noise.
And a major advantage is it has inbuilt IC level protection from overload, short circuit protection and speaker protection delay.tandbymode turns off the main power supply for amplifier.

Crossovers and low pass filters :

Basically I don't want the 5 channels to be full range so I decided to have a 6x9 coaxial up front and 3in two ways on the back. Centre channel would contain 2- 3 inches and a tweeter.
Since it's a budget build I need to cut cost down by all means without compromising audio quality across all frequencies.
Primary objective is to have a balanced sound and best soundstaging with deep yet punchy bass.
Cross over frequencies
Front channel will be full range though having a cutoff below 100hz.
Surround 150hz - 20khz
Centre channel will be full range tough having a cutoff below 100hz.


Bass management
Added a subwoofer pre amplifier board such that it has isolated 6 channel inputs and a single output
Which filters off anything above 100hz.
And has a 3db boost at frequencies below 48hz, making deep bass regardless of my box design. This gain of 3db can be varied through a internal potentiometer.
IMG_20180404_122830.jpg
Assembled view with shielding for Digital amplifier.

Bass management makes the Subwoofer to work regardless of channel. This makes the LFE channel into Subwoofer channel. This reroutes sound below 100hz to the Subwoofer channel from all the speakers.
So I'll be getting a 6db gain from Subwoofer channel.
It can be tamed down from the remote kit as it has gain control for all channels.

DAC and optical DAC

This whole amplifier has its inbuilt 24bit 96khz DAC inbuilt in the Digital amplifier section. It's from Texas instruments don't know the exact IC details as it had a bonded heatsink on it.
As it had no digital inputs I had to buy a optical to analog decoder.
IMG_20180410_095142.jpg
Optical and coaxial to analog converter
The converter has Cirus logic digital decoder and Ti 24bit 96khz DAC.
Cirus logic decoder is renamed TRi JET usually Chinese manufacturers rename those for copyright.
Have tapped on to the digital out of the decoder IC to the DAC in panasonic's D amp board.
So that any digital decided data will be converted to analog within the Panasonic's board.
The remote kit only will select source and send volume data in terms of PWM to the DAC.

SPEAKERS

Got a pair of pioneer TSA 6975R 3way coaxial for front channel.
Dainty 3inch 30w RMS for surround with small piezo tweeters.
Tested things with local speakers and came out well and good.
Soundstaging was awesome and main part is the subwoofer
Got a second hand Logitech z906 it has a 8inch 165w subwoofer.
It's a THX certified unit has deep enough yet good punchy bass.

Ending things up

So after a brief period of 3months till date have spent nearly 6k on this project and came out to be pretty damn good.
I mean can't compare with branded one's as their integrity within each of them is completely out of reach.
This is more like a modular unit having good enough integration between each of the boards.
IMG_20180414_143026.jpg
No fuzzy hanging or bugs so far works quite good.
For the price I paid I got something unique that no one has and ample sound for filling a large hall.
Plz do help me out with the filters and crossovers
Expert comments and view are welcomed
Thanks everyone.....
 
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Joined
Apr 19, 2018
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#3
@tuff thanks buddy...

IMG_20180404_213700.jpg
Last image I added wasn't clear showing the functions
Soon I'll add more pictures showing the options and functions in the display....
 
Joined
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#7
You have done an excellent Job. Happy Listening

Sadik
Thanks sadik
I'm still trying to figure out the exact details for the DAC
Upon googling have found that it's a 24bit 196khz DAC from Wolfson (but the IC's are scratched on top)

This weekend I'll be getting my front channel and centre channel enclosures
Will update how it sounds after completing...
 
Joined
Oct 5, 2017
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#12
This weekend I'll be getting my front channel and centre channel enclosures
Will update how it sounds after completing...
Congrats you are making me to search my soldering iron and tools which i did not touched for past 4 years:cool:
your system is not creating ground loop hum?
Only you can find the hum or unwanted noise when there is no source is playing with mid/max volume connected with speaker box ( not speaker alone )
Most of the DIY will be creating hum/slight high freq noise/Power on sound if you pack it in single box.
Have to struggle to come out of the challenges.
All the best.
 
Joined
Apr 19, 2018
Messages
35
Likes
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Points
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Location
Chennai
#13
Congrats you are making me to search my soldering iron and tools which i did not touched for past 4 years:cool:
your system is not creating ground loop hum?
Only you can find the hum or unwanted noise when there is no source is playing with mid/max volume connected with speaker box ( not speaker alone )
Most of the DIY will be creating hum/slight high freq noise/Power on sound if you pack it in single box.
Have to struggle to come out of the challenges.
All the best.
Initially I had issues due to grounding as I used two SMPS for the build..
Later upon sorting out the ground issue. I found the noise is due to EMI due to high frequency switching (usually all SMPS do have these).
So used internal shielding for the primary (SMPS for the D amp).
Panasonic's manual stated that it's a must to use. I removed it for better thermal management, but eventually I had to use it.. pixlr_20180420213109765.jpg
And at max volume can hear some slight hiss (really negligible compared to ambient noise.)
 
Last edited:
Joined
Oct 5, 2017
Messages
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208
Points
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Location
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#14
Initially I had issues due to grounding as I used two SMPS for the build..
Later upon sorting out the ground issue. I found the noise is due to EMI due to high frequency switching (usually all SMPS do have these).
So used internal shielding for the primary (SMPS for the D amp).
Panasonic's manual stated that it's a must to use. I removed it for better thermal management, but eventually I had to use it.. View attachment 27096
IMHO If we use the low power smps Umph bass will miss( u will get more high freq but)
you may not feel what u r missing Unless you try the normal e core / toroidal trafo for power supply ( amplifier section - SUB/FL/FR/C)
 
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#15
IMHO If we use the low power smps Umph bass will miss( u will get more high freq but)
you may not feel what u r missing Unless you try the normal e core / toroidal trafo for power supply ( amplifier section - SUB/FL/FR/C)
Yeah but the specific D amp has its dedicated powersupply built onto it's PCB.
The main thing is it's a Hybrid power supply, it switches from 12-0-12 5A to 38-0-38 12A through a power sense pin on the IC
The IC sends 5V trigger PWM to the SMPS whenever it requires higher power, (it switches when it exceeds 20~25w per channel.)
So the particular IC was designed by Panasonic to operate with SMPS. Even the IC has got a thermal mgmt pin which control 3pin pwm fan.
If it was a TPA or TDA series I would definitely prefer torroidal trafos.
BTW the LFE or sub channel hits 15hz at lowest.
 
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#17
That is some great effort Manoj. Keep it up, I am sure bigger things are coming your way in the years ahead.
Thanks bro...:D

Update:
Sat Apr 21 A visit to Ritchie street
Bought 2 x Award 3 inch 8ohm 30w RMS speakers for centre channel.
Got the much needed soundstaging from those, yet the build quality could have been better. Can't complain much for a price of 150/- per piece.
Checked out Dainty (from Singh traders), Zipp (vipul traders) and Life (crown electronics).
All of them had pretty good build Polypropylene cone and rubber surround. Though they lack that openness when it comes to soundstaging. They all sound bassy and provide teeny weeny treble.
So felt Award speakers would do a good job providing good vocals.
Gonna parallel two 8ohm drivers and a small unknown brand tweeter. Will use 1.2uf 50v NP capacitor for filtering. IMG_20180421_122734.jpg
IMG_20180421_122745.jpg IMG_20180421_122618.jpg
 
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#18
Update : Apr-28 Speaker Enclosures
So after a brief period of 2 weeks the enclosure for the 6x9 pioneers arrived.
Went to the carpenter asked to use 10mm plywood for the rear to create more mid bass resonance.
Dimensions as follows
LxBxH = 15"x 9"x 8"
MDF thickness = 1" (10mm ply only rear panel)

Internal volume = 0.31 cubic feet approx
Sealed enclosure. IMG_20180429_105804.jpg
Used wood sealer to finish the enclosure, then sanded and used black Mica.
Used some Silicone caulking to seal the inside edges to keep things air tight. IMG_20180429_105724.jpg

Update May 1
Front channel and centre channel assembled

Got the enclosure for centre and surround channels.
After a two delay the guy made a decent looking enclosures
It isn't an eye candy but does it's work well.
The centre channel covers up vocals and provide good soundstaging.
The vocals are precise and tweeter only comes at above 8k freq range as intended.
Mid bass is carried out through 6X9 pioneer coaxials.
Speaker selection was a luck to me I got things right at first shot.
IMG_20180501_233743.jpg
Just a view of how the final unit looks like
IMG_20180501_233757.jpg
Dual award 3" 8ohm 30w drivers with a 25w PET balanced dome tweeter.
Next update will consist of surround channel and installation in my hall with the rest of the system..
 
Joined
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#19
Hi Manoj
What is the price of the optical board ?
Regards
Somak
Intro
Hi guys this is Manoj from Chennai. A novice electrical guy who loves to build stuff on his own. So without much about myself let's jump into the project.

.

DAC and optical DAC

This whole amplifier has its inbuilt 24bit 96khz DAC inbuilt in the Digital amplifier section. It's from Texas instruments don't know the exact IC details as it had a bonded heatsink on it.
As it had no digital inputs I had to buy a optical to analog decoder.
View attachment 27073
Optical and coaxial to analog converter
The converter has Cirus logic digital decoder and Ti 24bit 96khz DAC.
Cirus logic decoder is renamed TRi JET usually Chinese manufacturers rename those for copyright.
Have tapped on to the digital out of the decoder IC to the DAC in panasonic's D amp board.
So that any digital decided data will be converted to analog within the Panasonic's board.
The remote kit only will select source and send volume data in terms of PWM to the DAC.
 
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