I bought one of these:
New TPA3116 50W*2+100W 2.1 Channel Digital Subwoofer Power Amplifier Board J4H8
The PCB has the Sanwu marking on the underside; the anti-static bag has a Sanwu label with a QR code, and the bag was sealed with a "Sanwu" embosser, so it's either a real Sanwu or someone went to a lot of trouble to try to make it pass as real.
They solved the power on/off pop issue on this one by not including an on-off switch.
I have the board hooked up to a pair of mini-Tabaq speakers (one 2" 4 ohm driver in each) for the left and right, and to a Cambridge Soundworks 8 ohm bookshelf speaker on the subwoofer channel.
The left and right channels work as expected. However, I am only getting output in the subwoofer if I have the "Bass Freq" control set to nearly full-to-full clockwise, and the "Bass Vol" control nearly full counter-clockwise. Within the very small range on each control where I'm getting a signal, there is an audible difference when I turn them slightly, so it's not quite as if it's an "all or nothing" situation. On the Bass Freq, the ramp-up to where I start hearing something is somewhat gradual, but on the Bass Vol, the cut-off is very sharp - go a smidge beyond a set point, and the signal turns off. Turning the Freq control rapidly will occasionally and irregularly produce a pop or two through the speaker.
With the Bass Freq and Vol controls set so that I'm getting a signal, the balance between the left and right channels and the sub seems reasonably good, and the bass level seems to track the left/right level appropriately as the main Volume is turned up or down, so I guess I could just use it as-is and declare it a qualified success -- but I'm curious if anyone has any idea why this thing is behaving like this? Are they all like this? Is it possible that the person who assembled this one used the wrong value pots for the two Bass controls? All three are marked B50K. (He/she managed to do a crap job of getting the three pot shafts all pointing forward.)
Any thoughts/theories/experiences appreciated.
New TPA3116 50W*2+100W 2.1 Channel Digital Subwoofer Power Amplifier Board J4H8
The PCB has the Sanwu marking on the underside; the anti-static bag has a Sanwu label with a QR code, and the bag was sealed with a "Sanwu" embosser, so it's either a real Sanwu or someone went to a lot of trouble to try to make it pass as real.
They solved the power on/off pop issue on this one by not including an on-off switch.
I have the board hooked up to a pair of mini-Tabaq speakers (one 2" 4 ohm driver in each) for the left and right, and to a Cambridge Soundworks 8 ohm bookshelf speaker on the subwoofer channel.
The left and right channels work as expected. However, I am only getting output in the subwoofer if I have the "Bass Freq" control set to nearly full-to-full clockwise, and the "Bass Vol" control nearly full counter-clockwise. Within the very small range on each control where I'm getting a signal, there is an audible difference when I turn them slightly, so it's not quite as if it's an "all or nothing" situation. On the Bass Freq, the ramp-up to where I start hearing something is somewhat gradual, but on the Bass Vol, the cut-off is very sharp - go a smidge beyond a set point, and the signal turns off. Turning the Freq control rapidly will occasionally and irregularly produce a pop or two through the speaker.
With the Bass Freq and Vol controls set so that I'm getting a signal, the balance between the left and right channels and the sub seems reasonably good, and the bass level seems to track the left/right level appropriately as the main Volume is turned up or down, so I guess I could just use it as-is and declare it a qualified success -- but I'm curious if anyone has any idea why this thing is behaving like this? Are they all like this? Is it possible that the person who assembled this one used the wrong value pots for the two Bass controls? All three are marked B50K. (He/she managed to do a crap job of getting the three pot shafts all pointing forward.)
Any thoughts/theories/experiences appreciated.
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I have the same board, unless there is some subtle difference in components that is not obvious to me.
You're lucky if there is indeed no 'pop' on power on or off - mine had a very healthy 'bump' on power off, I solved that by putting an additional circuit into the output. Maybe the power supply that I use is responsible for the pop.
I think what you're experiencing with the bass output has more to do with the response of the Cambridge cabinet than the amp itself. What range can that cabinet output?
I had a full range cabinet on my system, just to test the bass output, and I was baffled by the response I was getting from the bass volume/frequency pots. I then built a bucket sub and it became very obvious that the full range cabinet was limiting the bottom end - badly.
I've run some test tones through the bucket sub, it responds very well from 20Hz up. Cut-off seems to be about 180Hz. I run it full, ie up to 180Hz, bass volume is pretty sensitive and I have it set at about 11am. Sounds great.
You're lucky if there is indeed no 'pop' on power on or off - mine had a very healthy 'bump' on power off, I solved that by putting an additional circuit into the output. Maybe the power supply that I use is responsible for the pop.
I think what you're experiencing with the bass output has more to do with the response of the Cambridge cabinet than the amp itself. What range can that cabinet output?
I had a full range cabinet on my system, just to test the bass output, and I was baffled by the response I was getting from the bass volume/frequency pots. I then built a bucket sub and it became very obvious that the full range cabinet was limiting the bottom end - badly.
I've run some test tones through the bucket sub, it responds very well from 20Hz up. Cut-off seems to be about 180Hz. I run it full, ie up to 180Hz, bass volume is pretty sensitive and I have it set at about 11am. Sounds great.
Thanks for the response. The Cambridge speakers have 8" woofers and good enough bass extension to handle the jazz and rock tunes I've been playing (nothing with really low bass).
Has yours, with either the full range speaker or the bucket, exhibited the complete, sharp cut-off of the signal I described above (with the Bass Vol knob turned passed, say, one and a half on a 1 to 10 scale)? Are you able to tell me the values of the pots on yours (they're molded into the back wall of the casings)?
Has yours, with either the full range speaker or the bucket, exhibited the complete, sharp cut-off of the signal I described above (with the Bass Vol knob turned passed, say, one and a half on a 1 to 10 scale)? Are you able to tell me the values of the pots on yours (they're molded into the back wall of the casings)?
Pots on this amp are all marked B50K. Maybe one of your pots is a little damaged - when my amp arrived here one of the pots was well out of alignment, it had been bent out of position, in transit. I very carefully put it back into its proper position and it works fine. no sudden cutoff, just a progression.
It's doing the same thing whether I use a 16 volt laptop brick or a 12 volt one from an old LCD monitor.
The Bass Vol pot on mine was soldered on crooked, and the overall volume one is scratchy in operation. Next time I order some parts I will try to get some good name brand pots and see if I have better luck with them.
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