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Class D Switching Power Amplifiers and Power D/A conversion

TDA7498 Hiss
TDA7498 Hiss
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Old 20th May 2020, 02:52 PM   #1
Apgar426 is offline Apgar426
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Default TDA7498 Hiss

I've tried 2 of these amps so far, one from SUCCA-audio, the latest is SMSL SA-89e. They both have floor noise problems. The first had a high pitched whine, the SMSL has a loud hiss. Even with no input. Tried multiple power supplies. I'm using infinity R152 speakers (100w 8ohm, 87db). I can't keep spending money trying out new amps.

I've searched for weeks online for a better alternative or a modification to help with this problem, but I've found nothing definitive. At best it seems a TPA3251 based amp, or a dual 3116 may have less noise floor, but I'm not sure. Can anyone here offer any advice? I'm not afraid to open this thing up and solder, either.

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Old 20th May 2020, 05:26 PM   #2
JonSnell Electronic is online now JonSnell Electronic  United Kingdom
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Location: The Jurassic Coast, England. GB
If these were sourced through fleabay, they are probably seconds and need to be returned as faulty.
Hiss is a noisy TDA7498 but whine could be poor filtering.
The power supply won't cause your issues.
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Old 20th May 2020, 06:33 PM   #3
Apgar426 is offline Apgar426
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Thanks for the response. Both the whine and hiss are plainly evident a few feet away from the speakers, even with ambient noise. However, I'm not sure it's enough to consider the units faulty. For reference, I tried another speaker, a Micca RB42 pair and there was was much less noise floor. The hiss disappeared only a few inches away. But, the Miccas did not have anywhere near the tweeter liveliness of the Infinity's.

These treble-sensitive speakers are probably making the problem worse, but now I am addicted to their sound. I'm hoping to find an amp to drive them cleanly, or modify the SMSL somehow.

Current ideas to reduce hiss:
-Try a 3251 based amp.. im suspicious- they are less than half the price of the SMSL

-Attenuate the tweeter inside the speaker.. I could live with toning it down a bit, but I may not have the experience to do this very well.

-Throw a shirt over the speaker. Cuts the hiss in half but muffles things a bit
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