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Humm with the T4 and smps300r

Humm with the T4 and smps300r

Hello there i wonder if anyone can help.

I connected my smps300r and t4 together and all was working fine. I decided to replace the cheap mcaps with some more expensive mundorf ones as recommended in a hifi forum. Unfortunately this has caused some hum or hiss. this sound is very noticable when music is not playing but does not increase with volume levels. Strangely i replaced the original caps and the issue still remains. What have i dont to cause the hiss. Is it a ground loop problem? or cound it be something else. When i remove the rca cables the hiss still comes out of the speakers. Any help would be greatly appreciated.
here is a picture with the original mcaps
http://i1207.photobucket.com/albums/bb475/bostod/P1020774.jpg
Well i resoldered the new caps on both the same way as the originals( not sure this makes a difference). there also appeared to be a bit of a loose connection on the smps. tightened the clip and replaced. the hiss is completely gone but only the left channel is working. when i change the negative leads over on the speakers, both work but the hiss is back. when using the left negative to feed both speakers the hiss comes back too.
Hi,
first, do not use left negative for both speakers, that could harm the amp.
How did you connect the smps to mains? to the fuse? I don't have one here to check if that's possible, but normal would be to use the three connectors.

It could realated to some bad connection with the cap, or it could have nothing to do with the cap, just some other bad connection that appeared when you worked on it. Double check all connection. The white input connector can sometimes have bad connection.
If you don't find anything, try to disassemble everything and start over check all connections.
the picture is a little misleading. the three wires from the cable go into the 3 screwholes. i will check the white input connector. would it be possible to buy another of those leads with the white connector just in case it is that?
The connector should be easily fixed. Just by moving it around you should be able to check if it makes any difference. You could also remove it and solder the inpt cable directly to the pcb.
The connector should be easily fixed. Just by moving it around you should be able to check if it makes any difference. You could also remove it and solder the inpt cable directly to the pcb.
I have connected the cable directly to the board. still gettling one channel. should i test the speaker terminals with a multimeter for output?
I have connected the cable directly to the board. still gettling one channel. should i test the speaker terminals with a multimeter for output?

checked the supply voltage to all 4 speaker terminals each one is around 22.5 volts. so there is power going to all speaker outputs
checked the supply voltage to all 4 speaker terminals each one is around 22.5 volts. so there is power going to all speaker outputs



Hi, I suggest you check the pads of input caps. Some times the pads may be damaged when you remove the parts and they become OPEN, which will make noise.
PS: 22.5V from 4x ouputs terminals to ground or V+, that's quite normal. That means you use about 45V power supply.
Hi, I suggest you check the pads of input caps. Some times the pads may be damaged when you remove the parts and they become OPEN, which will make noise.

Checked the pads for the input caps. one appeared to be damaged from the soldering iron. I scraped some of the lacquer from the metal feed and resoldered. It is now working perfectly. Thankyou for the suggestion
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