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Class D Switching Power Amplifiers and Power D/A conversion

Ebay cheap TDA7498 boards
Ebay cheap TDA7498 boards
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Old 11th October 2018, 09:45 PM   #621
jimk04 is offline jimk04  United Kingdom
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Join Date: Jul 2018
I recently got this one

Promotions TDA7498 high-power digital amplifier board (100W 100 W) Finished amplifier board
Promotions TDA7498 high power digital amplifier board (100W +100 W) Finished amplifier board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

Very pleased and is fine as is. No mods required for a decent overall sound.

Runs very cool on 24v. Has negligible noise from the 3.5mm stereo Jack from my Samsung S9. Noisier from my pc soundcard
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Old 12th October 2018, 10:39 AM   #622
t-minik is offline t-minik  France
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Join Date: May 2006
Location: Montpellier
I agree that board is a good one .
perhaps noise can come from the inbuilt potentiometer.

On TDA7498 input impedance is 69k and, if i remember, on that particular board potentiometer is 50kB, should be better to fit 10kA to reduce impedance mismatch.
also there is no 1nf cap on input going to ground like on ST schematics, perhaps something to do here.

on mine i sorted the dual 50k pot, the two 1Uf ceramic cap going to inputs (shorted), an soldered a pair of 1uF+1nf film cap directly on the old pot pinout.
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Old 14th October 2018, 07:51 AM   #623
StevieF is offline StevieF  India
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Join Date: Aug 2013
Thanks guys for the recommendations. Will be looking into getting of them boards next month i hope.
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Old Yesterday, 04:03 PM   #624
StevieF is offline StevieF  India
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Join Date: Aug 2013
Quote:
Originally Posted by Yatsushiro View Post
I'd happily recommend this one (ignore that it says Aiyima, it's actually made by Feixiang). Of the 4 7498/7498E boards I have, this works best with my source (RPi, Allo DAC) and speakers (Q Acoustics 2050i)

Aiyima TDA7498E 160W*2 High Output Power Digital Amplifier Board Dual Channels Audio Stereo Amplifiers-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
What is the trimmer box for in the corner. Is it for supplying power to a fan for cooling?
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Old Yesterday, 04:45 PM   #625
Yatsushiro is offline Yatsushiro  France
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Join Date: Mar 2016
Location: Normandie, France
Quote:
Originally Posted by StevieF View Post
What is the trimmer box for in the corner. Is it for supplying power to a fan for cooling?
Supposedly it is to vary the output of the adjacent 2 pin connector from 0 to 13v, from memory.
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Old Yesterday, 05:00 PM   #626
jimk04 is offline jimk04  United Kingdom
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Join Date: Jul 2018
My trimmer just spins round. Output seems stuck at 8volts ish
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Old Yesterday, 07:12 PM   #627
FauxFrench is online now FauxFrench  France
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Join Date: Dec 2017
Quote:
Originally Posted by jimk04 View Post
My trimmer just spins round. Output seems stuck at 8volts ish
You tried to turn several times clock-wise and several times counter clockwise and the voltage didn't change?
What is the marking on the black IC next to the trimmer? LM2575S?

Last edited by FauxFrench; Yesterday at 07:15 PM.
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Old Yesterday, 07:56 PM   #628
StevieF is offline StevieF  India
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Join Date: Aug 2013
Yeah sometimes with those box shaped trimmers turning them both ways doesnt do much but after awhile in one particular direction they start to show an effect. If its stuck at 8V then i feel that is the max output for it but it should be possible to reduce it to a lower value, might need to turn for sometime in either direction till the V reading changes on the DMM.

I did a quick search for cpu cooling fans & it seems there are quite a few of those availble that run at 12V dc, so i believe that extra voltage outlet on these boards above is for an external fan to run.
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Old Yesterday, 08:31 PM   #629
FauxFrench is online now FauxFrench  France
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Join Date: Dec 2017
Quote:
Originally Posted by StevieF View Post
Yeah sometimes with those box shaped trimmers turning them both ways doesnt do much but after awhile in one particular direction they start to show an effect. If its stuck at 8V then i feel that is the max output for it but it should be possible to reduce it to a lower value, might need to turn for sometime in either direction till the V reading changes on the DMM.

I did a quick search for cpu cooling fans & it seems there are quite a few of those availble that run at 12V dc, so i believe that extra voltage outlet on these boards above is for an external fan to run.

I agree very much with you. Apart from supplying the fan-circuit, I guess it also serves to step (the up to) 39V input voltage down to the input of a linear 3.3V regulator used for control inputs. Such a 3.3V linear regulator will hardly appreciate up to 39V at the input.
Yes, these multi-turn trimmers do not always react right away.
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