I made 2 amplifiers using the red Sanwu tda7498e boards that are available at all the usual places. I'm using one with a pair of 2 way bookshelf speakers with 8" woofers made by TC audio and the other with 6.5" woofers and 3.5" tweeters. They both have developed a pretty loud noise floor that I never noticed so loud as it is lately. I can hear the static white noise sound from 8' away when it's quiet in the room. They both hiss even when the signal inputs are disconnected. What would cause this to happen?
Also I remember reading about some popular mods to these Sanwu boards but can't seem to find the thread anymore. If I remember correctly one of the mods was to remove and jumper some diodes but I don't know which ones.
Also I remember reading about some popular mods to these Sanwu boards but can't seem to find the thread anymore. If I remember correctly one of the mods was to remove and jumper some diodes but I don't know which ones.
Are the tda7498e chips known to be noisy, or could it be the high probability of the chip being a fake? I'll try asking them but I won't get my hopes up that they will answer.
Maybe you can check out this thread on the Class D forum...
https://www.diyaudio.com/community/threads/ebay-cheap-tda7498-boards.265387/
Also, check out JohnAudioTech youtube channel. He experimented with putting a resistor across amp input to remove the hiss. I don't have this board nor having problem like this, but I guess it is worth a try.
https://www.diyaudio.com/community/threads/ebay-cheap-tda7498-boards.265387/
Also, check out JohnAudioTech youtube channel. He experimented with putting a resistor across amp input to remove the hiss. I don't have this board nor having problem like this, but I guess it is worth a try.
I found that thread on the tda7498 and have been reading through it here and there(48 pages). So far most of the boards talked about on there aren't the one I have. I have watched the video from John audio tech on YouTube but don't remember anything about a reistor on the input. I'm going to go rewatch his videos now! Thanks
I think John's vdo is more about ground loop noise, not class D hiss.
Additionally, I've read somewhere that people suggests to reduce the gain of amp board to reduce hiss. I tried searching but mostly found complaints about hiss, not how to fix it!
Since some people experiences the problems, some not, it could be anything like bad board layout or bad chips? I think the last resort is to try another or different boards (e.g. TPA325X-based boards).
Additionally, I've read somewhere that people suggests to reduce the gain of amp board to reduce hiss. I tried searching but mostly found complaints about hiss, not how to fix it!
Since some people experiences the problems, some not, it could be anything like bad board layout or bad chips? I think the last resort is to try another or different boards (e.g. TPA325X-based boards).
I think I found the video you were talking about and it was to fix a buzz or noise associated with an unplugged line input. I haven't found any answers other than it being opamps in the preamp or a bad layout. What I find strange is that my noise developed slowly over time and the amp was silent when new months ago. The sanwu board doesn't use any opamps in the signal path just some 1uf poly caps and a 50k pot then onto an smd cap and into the chip. My gain is configured at 20db the lowest the board goes. I've tested it on a 24v lithium battery pack and with 3 different smps'. The hiss is there even without any input signal rcas plugged in and there's no Bluetooth.
AliExpress is having a big sale right now and I was thinking about ordering a bdm8 from the wondom store. It's the same tpa3255 that parts express sells under the Dayton name. I already have a 48v 10a amps that's adjustable from 0-48v that would be perfect for a tpa3255.