First issue is that there's a "pop" on power up. I'm aware this is a thing with class D amps, but unsure how to rectify it on this circuit. Has anyone experience with adding something to this board for removing start up pop (image below).
I'm sure I can probably get a time delay power on circuit from Aliexpress, but not sure how to work it into this circuit.
The second issue is that it appears the Google home mini goes to sleep when not in use and (guessing) turns off the audio output. This seems to leave a horrible ground hum on the system. What's the best way to get around this without modifying the Google home mini circuit? Can I do something like put a high value resistor across the amplifier input to pull it to ground?
I'm sure I can probably get a time delay power on circuit from Aliexpress, but not sure how to work it into this circuit.
The second issue is that it appears the Google home mini goes to sleep when not in use and (guessing) turns off the audio output. This seems to leave a horrible ground hum on the system. What's the best way to get around this without modifying the Google home mini circuit? Can I do something like put a high value resistor across the amplifier input to pull it to ground?
I use a similar 6 channel amp for my TV audio. There are no pops at all. Things to try. Disconnect the audio
inputs to the board. Does it pop at turn on with no input signal? If it sill pops, try connecting all the inputs
to ground and try it again. If it still pops, do ALL the channels pop or only some?
My preamp driving the TPA amp is balanced power (+ / -5V) so there is no DC on the signal feeds.
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inputs to the board. Does it pop at turn on with no input signal? If it sill pops, try connecting all the inputs
to ground and try it again. If it still pops, do ALL the channels pop or only some?
My preamp driving the TPA amp is balanced power (+ / -5V) so there is no DC on the signal feeds.
G²
Before I answer your questions, I have to explain this setup. I'm using this to drive some old speakers in a mono configuration to put together a cheap audio setup for my shed. The centre channel is tied to ground. Both rears and fronts are bridged together for mono input. I have a secondary circuit board which is a low pass filter for the subwoofer. This is being fed from the same input signal and then into the subwoofer input.
I've found these on Aliexpress, but I'd have to buy three of them and it's adding a lot of complexity... It's also mildly happening on power down and it's not clear if this circuit attempts to fix that as well:
Yes
Same outcome.
All.
I've found these on Aliexpress, but I'd have to buy three of them and it's adding a lot of complexity... It's also mildly happening on power down and it's not clear if this circuit attempts to fix that as well:
If it's coming from a stereo pair maybe put a preamp inbetween the google home and the first instance of connection to your amp set up?
It's a bit of a guess but I have had problems with amps humming without a live input present so maybe a preamp before it would make the difference since the google home seems to shut down its audio outputs? I'm no expert but it might be worth a go if you can find something like this in whichever region you are in:
NE5532 Amplifer Board OP AMP HIFI Preamplifier Signal Bluetooth Amplifer Preamplifier Board In Stock|bluetooth board|board bluetoothboard board - AliExpress
NE5532 Amplifer Board OP AMP HIFI Preamplifier Signal Bluetooth Amplifer Preamplifier Board In Stock|bluetooth board|board bluetoothboard board - AliExpress
At that price it's worth a try alright! I can probably change the resistors on it to set the gain to 1.
Doesn't solve the startup pop issue though :/
Doesn't solve the startup pop issue though :/
My unit is powered from a 19V 180W laptop supply. It draws a big enough inrush that the Polk powered sub
does a thump from the power line dip. I fixed that with a 1 second delay to the sub power. I don't think you want
a slow ramp up supply with a class-D amp.
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does a thump from the power line dip. I fixed that with a 1 second delay to the sub power. I don't think you want
a slow ramp up supply with a class-D amp.
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How did you delay powering on the sub? It's all my speakers that pop. It's physically moving the speaker a fair amount, so I'm afraid it may also be causing damage.
I was considering looking at a circuit that would slowly ramp up the voltage, but yes, apparently that's not good for class D amps?
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I use a time delay relay like this.
It's an eBay item that uses a 555 timer to turn on a 10 amp relay. I put it inside an "old work" plastic electrical box
with a duplex outlet. The relay then powers up the sub 1 second later. The relay needs 12V to run it so I have a
12V wall wart that turns on with the system and then starts the delay.
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It's an eBay item that uses a 555 timer to turn on a 10 amp relay. I put it inside an "old work" plastic electrical box
with a duplex outlet. The relay then powers up the sub 1 second later. The relay needs 12V to run it so I have a
12V wall wart that turns on with the system and then starts the delay.
G²
Attachments
Yup. Basically took the speaker output and put a 10:1 resistor divider on it to bring the max volume down to line level. It works perfectly when there's audio playing. It's just when it goes to sleep that I get massive hum.
With no better suggestions, I've went ahead and bought a bunch of relay protection boards based on the UPC1237 to fix the pop on startup.
For the hum, I bought a small preamp with adjustable gain, bit of a gamble, but hopefully it works like GhramGhram thinks it will 🙂
For the hum, I bought a small preamp with adjustable gain, bit of a gamble, but hopefully it works like GhramGhram thinks it will 🙂