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Old 25th November 2014, 05:15 PM   #1
tbj is offline tbj  United Kingdom
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Default Ebay cheap TDA7498 boards

Hi all,

I'm building a hi-fi for my wife for christmas and just bought one of these TDA7498 boards to do the heavy lifting of driving the speakers:

TDA7498 100W 100W Class D High Power Amplifier Board DC20V to DC36V | eBay

There seem to be tons like them on eBay.

Anyone had any experience with them? Any modifications that have to be made to make them sound good? They look fairly decent, with WIMA type caps on the output filter and a decent heatsink...
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Old 25th November 2014, 05:43 PM   #2
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I've just finished an amp with this board 100W TDA7498 100W High Power Digital Amplifier Board Amp Board with Radiator | eBay This board has way larger/better chokes which makes a big difference when played loud/hard. I would only recommend this board with 32V to 36V which gives you more power than a tpa3116 which has the potential to sound a bit more detailed. Tpa3116 has 400khz switching frekvency and the TDA7498 has under 200kHz which is a bit too low and gives white noise faster when pushed to the limit. But when driven at 36V the limit is way higher than on the tpa3116(maks25V) so its a lot more powerful when driven at 36V
The sound from the linked card is some of the best I've heard from any stock board mention earlier. No sibiliance and no harsh treble, but with a lot of punch in the bass! I highly recommend it!
Ofcourse you could swap out the ceramic smds with film smds which would probably make it more detailed. I also swapped out the powersupply cap to a better aluminium electrolytic for more current control. That cap was the only mod I did and I didn't listen to the board on beforehand. The chokes on this board bought seperately cost more than the entire board linked so I think its a great buy!
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Old 25th November 2014, 10:19 PM   #3
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I checked the specs again and switching frequency is about 310kHz and not 200kHz as I thought. But its still lower and white noise appear "earlier" on TDA7498 than TPA3116 boards.
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Old 25th November 2014, 10:37 PM   #4
tbj is offline tbj  United Kingdom
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One thing I have noticed from comparing photos of the board against the application note is that it does a weird thing in the output filter - only a single resistor per channel. What is it using the resistors for?
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Old 26th November 2014, 02:52 PM   #5
schdrag is offline schdrag  Switzerland
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Hi tbj
looks like yours, but who knows, which components are built.
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Old 26th November 2014, 04:24 PM   #6
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i own that board from the original post.
you can find it cheaper on ebay (it was like 11€ shipped to germany).
i had ordered the board from the second post, too.
but it never arrived and the seller is an a**hole.

yes, the output filter of the black board is really weird.
it actually is only "one half" per channel.
(i will look that up when i´m home and post the values; they also differ from the datasheet-circuit.)

BUT:
the amp sounds really good for its price.
the cheapest tpa3116 (red yuan-jing board and unmodded black yuan-jing) sounds definitely worse.
but a modded tpa3116 or a better board like that from sure-electronics might be better.
the tda7498 plays lower on the same fullrange speakers and the high mids are not that harsh.
there are not many options in that price range and the for 11€ that black 7498 is not the worst.
one thing to consider might be that the datasheet doesn´t suggest 4 ohm speakers.
some sellers say it would be possible to drive 4 ohmers with tda7498, but i didn´t try it yet.
another reason to consider the tda7498 might be that there seems to be no higher spl into 8 ohm speakers from single dc supply available.
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Old 26th November 2014, 04:24 PM   #7
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Quote:
Originally Posted by schdrag View Post
Hi tbj
looks like yours, but who knows, which components are built.
that´s a good price.
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Old 26th November 2014, 05:21 PM   #8
tbj is offline tbj  United Kingdom
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Thanks all.

One more question. Do these boards need to go in a shielded case, or do they not radiate that much EMI anyway?

I'm thinking of putting it in a perspex case along with a valve pre-amp. Should look cool.
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Old 26th November 2014, 05:32 PM   #9
schdrag is offline schdrag  Switzerland
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I will use a metall case and I will use short cables to my subwoofer, because the cables and the speaker influence the characteristics of the class d amplifier (by the way I bought the US $12.86 tda7498 from aliexpress, tzt trading including free transport to Switzerland). I read that class d especially tripath cause high frequency emi, hopefully I needn't add an elektor HF Filter.
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Old 26th November 2014, 05:37 PM   #10
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I do not hear any interferences between those boards and my pc although they sometimes are without an enclosure next to each other on my desk.
but you have to take all my statements with the grain of salt, because i have neither highest claims in sq nor do i hear everything that other guys describe when they talk about their amps and speakers and preamps and cables and so on.
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