Hi,
I have an amplifier board that other member on this forum have examined and said the gain on it is set to 36db.
I'm going to be feeding it with a signal from a chopped apart Google home mini. The hacky part on this is taking the peak 3.3v speaker signal and using a voltage divider to take that down to 300mv peak. Now, if the TPA3116 based amplifier I'm using has a gain of 36db, is the line level I'm bringing this to correct or should it be lower?
Thanks for any input.
I have an amplifier board that other member on this forum have examined and said the gain on it is set to 36db.
I'm going to be feeding it with a signal from a chopped apart Google home mini. The hacky part on this is taking the peak 3.3v speaker signal and using a voltage divider to take that down to 300mv peak. Now, if the TPA3116 based amplifier I'm using has a gain of 36db, is the line level I'm bringing this to correct or should it be lower?
Thanks for any input.
Find max. output voltage of the TPA3116 amplifier at the speaker terminals. It has a full bridge output stage, so that will be close to the supply voltage. Now you have the 0-peak voltage. If you want the rms voltage at the speaker terminals, multiply by 0.707. If you want the peak-peak voltage, multiply by 2.
Next, compare to the available output voltage of the source, which will be the Google Home Mini. Make sure you compare apples to apples, so both must be given as 0-peak, rms or peak-peak. Dividing them will give you the required gain.
Compare the gain to the ampifier's gain. If they do not match, calculate how much attenuation you need.
One caveat: the amplifier output of the Google Home Mini is likely to have a full bridge output stage as well. That means that the output voltage is not referenced to ground. How do you plan to feed this voltage to the TPA3116? It might be easier to tap into the Google pcb before the signal goes through the amplifier chip.
Next, compare to the available output voltage of the source, which will be the Google Home Mini. Make sure you compare apples to apples, so both must be given as 0-peak, rms or peak-peak. Dividing them will give you the required gain.
Compare the gain to the ampifier's gain. If they do not match, calculate how much attenuation you need.
One caveat: the amplifier output of the Google Home Mini is likely to have a full bridge output stage as well. That means that the output voltage is not referenced to ground. How do you plan to feed this voltage to the TPA3116? It might be easier to tap into the Google pcb before the signal goes through the amplifier chip.
Last edited:
Simple rule: As low as possible but sufficient for you
Common rule: when input is at 0dB then set gain at output nearly clip
Common rule: when input is at 0dB then set gain at output nearly clip
OK, so I have a 3.6V peak (7.2 peak to peak) signal. I've attenuated it by 10 which should give me a 360mv peak.
The output of the amplifier (if I've understood you correctly) will be close to 24v.
This gives a gain of around 66. 36db is around 63. So I'm definitely in the ball park of getting this correct! I can always tune later, I just wanted to make sure I was in or around the correct value.
Hmmm. My inspiration for this was from a YouTube video which shows it working as a line out at the end. I'm new to this stuff, but I guess the issue could be a DC bias?
Here's the video actually:I DEFIED GOOGLE ? Hacked an Audio Port onto Google Home Mini (Mod Kit Available) - YouTube
The home mini has volume control? I've cut into the speaker output and reduced to line level, so it will still control the volume.