Xmas Amp - Dibya's TDA7293 by Jhofland

Hi Folks,
Members Dibya and Jhofland have designed a new amp using the TDA7293 chip amp. I have not heard it myself, but I trust Dibya's ears when he says it sounds exceptional.

Dibya said that despite this chipamp sounding so womderful, it was surprising that there is not already an existing design on DIYA. So we teamed up with Jhofland who did the design and layout of a mono amp. Jhofland added a DC servo to control the offset and provided some regulated power for the opamp. The board is pretty compact and I am sure easy to build. The best part is that it's inexpensive. The full BOM from Mouser (shopping cart below) is only $26 per channel (not including the home made inductor using 18ga magnet wire wrapped 12 times around a AA battery as a mandrel).

Some of the notable mods developed by Dibya and perfected with Jhofland's help include:

  • Reduced gain of 28db for improved sound quality (default is 32dB)
  • Improved feedback optimizations for better LF & HF sound quality
  • DC offset servo for improved LF performance
  • Addition of Thiel Network for improved stability
  • Tweaks for improved HF response
  • Bootstrap mod for improved bass response
  • Optimized values of decoupling caps for best midrange sound quality

The optimizations for the gain, bootstrap, and PSU decoupling were found using a CRO by Dibya. The lower gain setting was found by extensive listening tests.

Recommended PSU would be a 150VA 25v 0v 25v trafo with 15,000uF per rail for mono, or 300VA 25v 0v 25v with 20,000uF per rail for stereo. Note that if on-board DC servo is not used, then up to 35v 0v 35v trafo's can be used for +/-50v rails for the full 100w output power. However, that will require some really big heatsinks. It is much better to run no higher than +/-40v per Dibya's recommendation. Some recommendations for affordable trafos and heatsinks here.

Note that if populating the DC servo, C17 and C2 should be replaced with jumpers. The on-board voltage regulators are +/-40v max rails so please keep that in mind when choosing the PSU.

The design is free for your personal use and the Gerbers, BOM and schematics are below. Jhofland's designs are superb and I have enjoyed many of his creations. I have not yet built the verification board yet (still waiting for PCBs to arrive) so at this point, you would be building it at your own risk as a beta tester. However, it is quite a simple design and mostly follows the factory datasheet except for the DC offset servo.

If you don't want to order boards for yourself, I can provide them for cost of shipping. First come first serve 25 pairs of boards maximum. Please add your name to the free board interest list below and once we verify they work, I can order boards and get them out to you. This is a holiday special offer that will end by Jan 31, 2021. Boards will be 2oz copper HASL finish with green solder mask.

Special thanks to Jhofland for the wonerful design and layout, and to Dibya for the inspiration and for putting us on this path to inexpensive yet great sound.

Happy holidays and enjoy!
:santa:

Closeup of pdf schematic, main amp portion (note that R15 should be replaced by 47k or as low as 10k to get better zero DC offset tracking and C1 should be closer to 4.7uF to get the deepest bass extension):
904725d1608921278-xmas-amp-dibyas-tda7293-jhofland-tda7293-amp-rev1-1-schematic-main-amp-jpg


Closeup of pdf schematic, opamp PSU portion:
904726d1608921278-xmas-amp-dibyas-tda7293-jhofland-tda7293-amp-rev1-1-schematic-opamp-psu-jpg


Output stage topology from datasheet. Note that it looks like a quasi-complementary topology, could this be the secret to the great sound?:
904727d1608921278-xmas-amp-dibyas-tda7293-jhofland-tda7293-datasheet-output-stage-detail-jpg


PCB renders:
904728d1608921278-xmas-amp-dibyas-tda7293-jhofland-tda7293-rev2-render-top-png


904732d1608921829-xmas-amp-dibyas-tda7293-jhofland-tda7293-rev2-render-bottom-png


Mouser Shopping Cart:
Mouser Electronics

#### TDA7293 Xmas Amp Free PCB Interest List (maximum 2 boards please) ####

for example:

Name / Country
-----------------------------
xrk971 / USA

Here is the thread for handling the logistics of the giveaway.
https://www.diyaudio.com/forums/swa...3-xmas-amp-jhofland-giveaway.html#post6487628


Edit Jan. 13, 2021: Final design files (Gerbers, Schematic, BOM) are here.

Edit Feb 13, 2021 - cleaned up the grounding on the measurement and here is 10W case, THD is 0.0014%:
922086d1613269769-xmas-amp-dibyas-tda7293-jhofland-tda7293-10-0vrms-crc-10ohms-fft-jpg


Here is 40W case, THD is 0.005%:
922087d1613270322-xmas-amp-dibyas-tda7293-jhofland-tda7293-20-0vrms-10ohms-fft-jpg


My implementation using surplus Dell CPU coolers:
919834d1612715079-ready-run-rtr-ssr-dc-speaker-protection-delay-gb-b37b96fb-d787-48c7-b1cd-b2618eb956e0-jpeg
 

Attachments

  • TDA7293_ Schematic_12_06_20.pdf
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  • Gerbers_TDA7293_ver1_12_06_20.zip
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  • TDA7293_amp_BOM_Dec6_2020.zip
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  • TDA7293-Rev2-Render-Top.png
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  • TDA7293-datasheet-output-stage-detail.jpg
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  • TDA7293-Amp-Rev1.1-Schematic-opamp-psu.jpg
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  • TDA7293-Amp-Rev1.1-Schematic-main-amp.jpg
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  • TDA7293-Rev2-Render-Bottom.png
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  • Dibya-8ch-TDA7293.jpg
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Last edited:
Picture seems to show isolated devices, yet there is no isolated version of the TDA729x AFAIK?

What do you mean by isolated? Monoblocks vs stereo amps?

The datasheet is here:

https://www.st.com/resource/en/datasheet/tda7293.pdf

The boards actually made it to NY (Vunce ordered the verification build set for me). But they seem to be lost in transit between NY and Virginia due to delays from Covid19.

They look nice.
 

Attachments

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maxreboband

New member
2020-12-02 8:13 pm
I've been looking for a good amplifier for my friends system, and it looks like this is a perfect fit. Thanks so much for doing this.


MaxReboBand / 2 amps / USA


as8912 / 2 Amps / USA
ahtllc / 2 Amps / USA
dBel84 / 2 boards / USA

Flamethrower1 /2 boards/ USA
Signal Lost / 2 boards / USA
 
I have a request to everyone of you , please at least get active components from Mouser/Digikey.
Fake TDA7293 ( Rebranded TDA7294S ) are out in wild & I wont be shocked if people from china fakes TL071. I found even fake NE5532 from ebay so wont be shocked.
When populating servo , C17 and C2 shall be replaced with jumper, You can use scrap leads from other resistor and capacitor.
Cheers Everyone ,
 
Last edited:

Hiten

Member
2010-06-29 2:54 pm
India
withdrawing. Thanks

copy following list and move forward.

MaxReboBand / 2 boards / USA
as8912 / 2 boards / USA
ahtllc / 2 boards / USA
dBel84 / 2 boards / USA
Flamethrower1 /2 boards/ USA
Signal Lost / 2 boards / USA
diy.tiger / 2 boards / NZ
MShipmanPE/ 2 boards / USA
Angchuck / 2 boards / Singapore