Manoj Sivaraman
Member
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.
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.
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.
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.
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.
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.
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.
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.
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.....
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.
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.
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.
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.
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.
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.
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.
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.
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.....
