Hi guys
I got a LM4780 Amp from AliExpress. It sounds really good but I wanted to skip the cheap volume pot and hocked up the wires directly to the coupling caps, but no sound at all.
I am feeding it from a Wiim Ultra with 2 volts rms output.
Anybody a clue what's going on?
I got a LM4780 Amp from AliExpress. It sounds really good but I wanted to skip the cheap volume pot and hocked up the wires directly to the coupling caps, but no sound at all.
I am feeding it from a Wiim Ultra with 2 volts rms output.
Anybody a clue what's going on?
Maybe you can build it back and see if it then works again?!
You know what is said about volume potentiometers and their protective features.
You know what is said about volume potentiometers and their protective features.
What's changed??
Did you only rewire the RCA inputs wiring straight to the terminal block?
OR, you did some other changes??
Can you check the resistance between the blue and red arrows?
Did you only rewire the RCA inputs wiring straight to the terminal block?
OR, you did some other changes??
Can you check the resistance between the blue and red arrows?
I only went streight to the Terminals.
It almost feels like the mute function is constantly on now. I just don't understand the logic of this otherwise simple change.
Check all connections again. There must be no signal short circuits to GND. There must be 0 ohms between each RCA connector and the first leg of the Wima input capacitors on each channel and there must be no connection between the channels. There must be 0 ohms between that bare GND wire of the amplifier and the RCA GND.
And one more thing, I would skip that terminal and solder the signal wires directly to the capacitor pins and the GND of the cable to the GND bare wire. Such connectors have a bad effect on sound, and maybe the problem you have is in them. If those are steel screws in the picture, then the sound quality will be even worse.
as didiet78 wrote, maybe speaker protection got active. Maybe you don't know LM3886 (and your double chip version) tend to oscillate without well defined input resistance, what you exactly did, removed pot resistance and amp is oscillating producing some DC voltage and protection won't switch on the speakers.
Put in my stepped attonator but problem remained.
Although the relay clicks it stays open.
Had to bridge it but I still want to find the cause.
As far as I can see the chip itself is not de/activating the relay.
Might have been a coincidence that the relay gave up when I skipped the attonator.
Boy this $ 220 China Amp really sings. Tried quite a few chip amps but this one takes the crown.
Expansive soundstage, dynamic and natural.
With my prefered coupling caps it might make it into my main system.
Greetings Klaus
Although the relay clicks it stays open.
Had to bridge it but I still want to find the cause.
As far as I can see the chip itself is not de/activating the relay.
Might have been a coincidence that the relay gave up when I skipped the attonator.
Boy this $ 220 China Amp really sings. Tried quite a few chip amps but this one takes the crown.
Expansive soundstage, dynamic and natural.
With my prefered coupling caps it might make it into my main system.
Greetings Klaus
Has the DC offset at the output been checked? There must be some reason why the speaker's DC protection kicks in.
Try putting resistors around the same value as the pots from the connection to the coupling caps to ground (temporarily, just hold them there for a sec.) The input from the previous stage may need a ground path or the input voltage might be too high since you are eliminating the input voltage divider - most anything like this is designed to have a terminating resistance.
Also: You know they make insulated wire, right? 😉
Also: You know they make insulated wire, right? 😉
The correct way to "skip the volume pot" is to short the moving contact to the "hot" side of the potentio meter. Then you just fix the volume at max while removing any potentio meter artifacts. And keeping everything else the same.
In addition, we are not clairvoyant so SCHEMATIC drawings of what you did please.
And if you are unable to draw those you should not mess with the inside of electronics and have confidence it will work.
In addition, we are not clairvoyant so SCHEMATIC drawings of what you did please.
And if you are unable to draw those you should not mess with the inside of electronics and have confidence it will work.