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Class D Switching Power Amplifiers and Power D/A conversion

My 7498 Class D Amp
My 7498 Class D Amp
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Old 14th September 2019, 02:01 PM   #1
claredes is offline claredes  Brazil
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Join Date: Nov 2014
Location: Belo Horizonte MG
Default My 7498 Class D Amp

Hello.
This is my little integrated amplifier that I set up buying parts on Aliexpress.

TDA7498 from the black board.
SMPS 26V 8.5A (221W) power supply for use in industrial equipment.

Digital preamp with 3 line-in and 2 line-out, Bass, Treble and Loudness control and remote control.
Hot glue as a temporary feature to attach the display to the panel until I buy a tool to thread the front panel aluminum.

Speaker output terminal I left RCA until
Purchase the appropriate terminal for the speaker cords.
Hope you like it.

Ps: I bypassed the 2.2ohm resistors.

Ps: I don't know why some photos were inverted.
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Last edited by claredes; 14th September 2019 at 02:09 PM.
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Old 14th September 2019, 02:26 PM   #2
FauxFrench is offline FauxFrench  France
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Join Date: Dec 2017
Location: The mountains, calm and quiet.
Looks like you are a fine craftsman. Any noise issues?
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Old 14th September 2019, 02:43 PM   #3
claredes is offline claredes  Brazil
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Thanks.
I did nothing but integrate the parts I was buying.
A slight noise when no signal.
By injecting signal even at very low level the noise ends completely.
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Old 14th September 2019, 04:38 PM   #4
jimk04 is offline jimk04  United Kingdom
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Location: North Notts
Can I ask of the digital pre amp and display?

Great build. Well done. I use similar amp with 24v smps and an Ebay es9038q2m dac, Google chromecast, through Faital 3fe22. Sounds lovely . Overall cost well under 100gbp
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Old 14th September 2019, 05:41 PM   #5
Mark Tillotson is online now Mark Tillotson
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Location: Cambridge UK
Quote:
Originally Posted by claredes View Post
A slight noise when no signal.
By injecting signal even at very low level the noise ends completely.
Probably your source - many digital players power down the output amp chip when idle, causing the impedance to rise to very high, generating noise. Its annoying (a good feature with earphones and when battery operated though)


You can cure this by adding a low value load resistor (few kOhms) on the input of the amp, on the assumption all the sources these days with be very low impedance. You could add such a resistor to a set of phono leads alternatively.


I've used some of these TDA7498 boards and they seem pretty good, though I'm sure there are some very cheap ones with inadequate filter components. The 2 ohm resistors are there for 4 ohm loads as the chip is rated down to 6 ohms. Its best to bypass the resistors and use only with 8 ohm speakers.

Last edited by Mark Tillotson; 14th September 2019 at 05:45 PM.
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Old 14th September 2019, 06:33 PM   #6
claredes is offline claredes  Brazil
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Join Date: Nov 2014
Location: Belo Horizonte MG
Quote:
Originally Posted by jimk04 View Post
Can I ask of the digital pre amp and display?

Great build. Well done. I use similar amp with 24v smps and an Ebay es9038q2m dac, Google chromecast, through Faital 3fe22. Sounds lovely . Overall cost well under 100gbp

This is the digital pre amp with display.
R$ 64,09 18%de desconto | Frete Grátis DC9-24V PT2313 Soundboard Digital Preamplifier Board (Conjunto Completo) Siemens Capacitores De Acoplamento de Áudio
AliExpress

I like him, but it's the simplest on Aliexpress. I must say there are some that should be better.
Beware of some that are with 5.1 input. It has neither bass nor treble adjustments. They are usually called PGA2311 / PGA2310.
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Old 14th September 2019, 06:37 PM   #7
claredes is offline claredes  Brazil
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Join Date: Nov 2014
Location: Belo Horizonte MG
Quote:
Originally Posted by Mark Tillotson View Post
Probably your source - many digital players power down the output amp chip when idle, causing the impedance to rise to very high, generating noise. Its annoying (a good feature with earphones and when battery operated though)


You can cure this by adding a low value load resistor (few kOhms) on the input of the amp, on the assumption all the sources these days with be very low impedance. You could add such a resistor to a set of phono leads alternatively.


I've used some of these TDA7498 boards and they seem pretty good, though I'm sure there are some very cheap ones with inadequate filter components. The 2 ohm resistors are there for 4 ohm loads as the chip is rated down to 6 ohms. Its best to bypass the resistors and use only with 8 ohm speakers.
Hello!

I'm really enjoying the amplifier and this noise has not bothered me yet. But I will do what you said.
About the 2.2ohm resistor, I jumpered under the board, I use 6ohms and 8ohms speakers.
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Old 17th September 2019, 12:01 PM   #8
claredes is offline claredes  Brazil
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Join Date: Nov 2014
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YouTube
Video of TDA7498 amplifier with Philips bookshelves.
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Old 17th September 2019, 12:54 PM   #9
Kay Pirinha is offline Kay Pirinha  Germany
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For safety reasons I would tie the case to that empty IEC socket's PE tab and replace those RCA output terminals by ones that really are apt to cope with the current.
Best regards!
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Old 17th September 2019, 01:13 PM   #10
claredes is offline claredes  Brazil
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The output terminals I'm going to change.
Since the grounding will not help, I have no grounding in my house.
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