I almost hope it was fake chip, then it means no fault on my side..!
The thump maybe from the Bluetooth chip; from other peoples experiences, there is little can be done about this. But you have to short the inputs to ground first to check if this is the issue. Often the board makers are not so good and maybe the mute/standby capacitor is wrong or missing...
The thump maybe from the Bluetooth chip; from other peoples experiences, there is little can be done about this. But you have to short the inputs to ground first to check if this is the issue. Often the board makers are not so good and maybe the mute/standby capacitor is wrong or missing...
I am using the sanwu blue board with a very cheap 24v 5a psu (7 USD). And the vocal is very nice. Just put a 1000uf capacitor at the input of the power on the board. Harshness will go away.
Thanks wiz geek. I have read the entire thread over several days time. I have 2 7498 boards, 1 with surface mount caps and one with thru holes. Also have a subwoofer board and now the Bluetooth board. What exactly is the current improvements that work safely for these boards? Hard to sift back thu the many posts. Power supply input cap bank with decoupling protection, values or links. Bypass polarity diode, etc. sorry just want to be clear on subject. I already like stock sound but kno there is room for improvements and am excited! I have adjustable smps 12-24v 10A and laptop bricks 19.5v 3.3A and 19v 4.74A to try. All speakers 8ohms except 4ohm passive sub. Thanks for any help
i bought just the sanwu red board...on page 43 #422 some measurements are listed. i just started with diy.
please post some pic from your board.
the experts here know very well the mods.
Ebay cheap TDA7498 boards
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oh...sorry to hear that....but can you post a pic? i know it hurts if something is bunring but i want to see the manufactoring quality. mine was realy good made (maybe there is a difference ...mine is from amazon...i´m not willing to discuss over CN if there is a problem...)
chris
Hi Whizgeeek
my 2 cents.
before starting with power up a board with check for
shortcuts VCC GND,
Speakers terminals,
an visual control,...etc.
if you have no psu with current limiter build a fuse for the first time switch on.
if i build myself something ....i dont trust what i have done...
---> ....so i measure 
Sorry about poor quality, I cant get much closer..
I cut the remaining Legs to remove from the board easily.
This is where it lived, i used it very lightly for a couple of months as a sort of Proof of concept, the final plan was into a suitcase type box with wheels.
The Board sans smokey the bandit.
Inside the box.
A PCB with short and wide PCB tracks will improve the performance.
Be aware that the ripple filter circuit you showed was part of a larger circuit with 47000uF rectification buffer capacitors.
The photo you show here seems not to include large rectification buffer capacitors. Then you cannot rely on Juma's performance when you start drawing higher levels of current because the voltage feeding the ripple filter may dive below the voltage needed to keep the FET active.
Be aware that the ripple filter circuit you showed was part of a larger circuit with 47000uF rectification buffer capacitors.
The photo you show here seems not to include large rectification buffer capacitors. Then you cannot rely on Juma's performance when you start drawing higher levels of current because the voltage feeding the ripple filter may dive below the voltage needed to keep the FET active.
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24V supply voltage leaves a maximum of 64 Watt in a 4 Ohm speaker (clipping point). To get 85 Watt (clipping point) you need to use less than 4 Ohm as the load.
With 4 ohm loads, you need twice 64 Watt and some margin for losses in the amplifier. Thus about 150 Watt from the power supply.
With the crest factor for most music, you may do with a 24V/6A "brick" which you can find for a decent price.
Add some extra power line decoupling (10000uF-20000uF/35V) at the output of the brick and your amplifier will sound better.
With 4 ohm loads, you need twice 64 Watt and some margin for losses in the amplifier. Thus about 150 Watt from the power supply.
With the crest factor for most music, you may do with a 24V/6A "brick" which you can find for a decent price.
Add some extra power line decoupling (10000uF-20000uF/35V) at the output of the brick and your amplifier will sound better.
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ok FauxFrench. I am humbled as you are a very smart poster I have read all over the posts regarding amps and power. the load will be 8 ohms so now what? I have a 24V 6A in shopping cart. THis will be for a college dorm amp in a few years. I tried the amp on 19V 4A power brick and no decoupling cap bank. I was loud and a bit compressed, that's why I'm asking what to get? I have 24V 10A smps but just too large form for small spaces amp. THanks
I am using 24V 6A. With this psu the max clean sound you'll get is around 26w per channel for 8 ohm speakers. And if you use 36V psu, you'll get 80w per channel at 10% THD which isn't listenable, 62w at 1% THD, 45w good clean sound. You can never reach 85W for 8 ohm with this chip. Another point is, you have to be sure that your board is optimized for 8 ohm speakers. A link or a picture might reveal more about it.
45w with good quality speaker (and efficient) and with onboard gain settings these amps will be pretty loud if you need that.
45w with good quality speaker (and efficient) and with onboard gain settings these amps will be pretty loud if you need that.
thanks r, that info helps sum it up well. Not sensitive speakers for the dorm room build. JUst Zaph audio bargain mini monitor 2 ways. I think 84db or so. All these chip amps tend to distort when turned up. I will post a pick of board. I think gain is pretty high as it played loud on 19v4A brick through Klipsch floorstanders. they are prob 90+db? I also want it to be super safe for the granddaughter!
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