Is the noise hum? if so, it could be due to a subtlety in the lay-out of the pcb, particularly in the area of the power supply. It could also be due to the proximity of the power supply and signal circuits. That's to say, it could be either conducted or radiated noise.
One way to tell would be to feed power in from a separate board.
For general hum troubleshooting and analysis, this link might be useful:
www.updatemydynaco.com/documents/GroundingProblemsRev1p4.pdf
One way to tell would be to feed power in from a separate board.
For general hum troubleshooting and analysis, this link might be useful:
www.updatemydynaco.com/documents/GroundingProblemsRev1p4.pdf
I tried the V- to the bolt and heatsink and there is nothing so its not connected. I clipped on a wire from the heatsink to the ground and done nothing as expected after the last test.
Well I'm getting lots of crackle and pop if I move the rca connectors. My only two sources of input have been from my phone and my laptop. even without any external input connections I have noise. So basically nothing connected and only power cable I have noise.
This is my first ever amp build and I'm kind of thinking it sounds like it does because I have no volume knob / potentionmeter. So at the moment I'm restricting the volume from the source like my phone or laptop and my amp is full on. I have a 50k pot here I havent tried yet maybe this will help? Also I noticed some other LM3886 builds when I googled earth rca & lm3886 and they had some sort of resistor or cap on the rca terminals. is this like using a pot? sorry for the questions.
It reminds me of a guitar amp hum.
Well I'm getting lots of crackle and pop if I move the rca connectors. My only two sources of input have been from my phone and my laptop. even without any external input connections I have noise. So basically nothing connected and only power cable I have noise.
This is my first ever amp build and I'm kind of thinking it sounds like it does because I have no volume knob / potentionmeter. So at the moment I'm restricting the volume from the source like my phone or laptop and my amp is full on. I have a 50k pot here I havent tried yet maybe this will help? Also I noticed some other LM3886 builds when I googled earth rca & lm3886 and they had some sort of resistor or cap on the rca terminals. is this like using a pot? sorry for the questions.
It reminds me of a guitar amp hum.
Huh?
I just cut the green wire and sound is heaps better! Now I just have a hiss now.
Your thinking is basically sound. You effectively have the amp at full volume all the time, you must wire in a pot. It sounds like you also have a bad connection at the sockets. Short the inputs, that is connect the inner pin to the outer. This has the same effect as turning the volume right down to zero
well my input cable is a 3.5mm to Left & Right RCA. Its cheap and nasty. Makes noise as the 3.5mm is jiggled in the phone and same with in the computer.
So if I hear you right I should now.
Use single core cable that has copper shield. Attach 1 cable to each left and right rca with copper shield to earth of rca and inner cable to signal in.
Now I have to run this wire to the new pot that is a LOG 50k stereo with 6 terminals. then run them back to the input on the amp board.
My amp board only has [L-In, GND, R-In] should I now connect both these earthed sheilds to GND?
Thanks for all the help too
Yes, that all sounds goodAre you confident how to wire the pot?
I haven't done my research yet but I have 3 of them here, all are Stereo Logs with 6 pins but they range in quality.
50k EIZZ Gold plated stepped
50K Jaycar cheapy
10k ALPS RK27
Whats the best way to connect them, I had my rca connections soldered onto the board underneath but I do have a white plastic connection on top that I can use but I dont know what they are called and where I would get them or that cable in one.
I'm really not looking forward to running the wires from the back rca to the front of the box then back to the board. I have a proper enclosure I'm building but this is all a test fit to iron out the floors like the grounding issue hums etc.
Sorry if I dont make sense its 1am here and about to fall asleep. You have been a great help.
A 6pin two channel vol pot needs 8 copper wire connections.
Two for Left input.
Two for Right input.
Two for Left output.
Two for Right output.
Each pair should either be twisted or a coaxial. BOTH ends of each coaxial need to be connected.
Mounting the vol pot next to the input RCAs is best. But that requires a long operating rod from front to back.
If you can't do that, then you have to run long wiring to the vol pot.
Each two wire connection requires a LOW LOOP AREA at the terminations. Make an effort to achieve that.
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Yeah, it's $300 for the two bare boards, and the total parts cost for two boards is approximately $200--so it's $500!!! for the stereo bi-amp.wtf
unbelievably, here come all ebay kits into play, even "try them and fail" is very cheap in comparison
.. and I am shipping PCBs for my amp free
An other BS reply, China bashing, What fake components? Every component today are made in China, including 99% of the audio kits. $38 for a stereo amplifier must be a good deal. To make an amplifier with a LM3886 is not rocket science. May be care to point out the faults in the PCB design?
Actually, mounting the pot closer to the OUTPUT connectors is better. The input signal to the pot tends to be line level (0.9-2.0 V RMS). The output from the pot is often attenuated by 40 dB or more (so 9-20 mV RMS). Thus, the output connection is the more sensitive node.
Mounting the volume pot by the rear panel and using a connecting rod to reach the volume knob is good advice, though.
Tom
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