<80°C max is a safe value. But don’t worry for the safety side there are 2 securities in case of overheat the dac will cut as well as the power supply.
Yes 6ohms will draw a bit more current.
There is also a way to increase the gain using JP trace under the board, but it will increase heat if you intend to use it without fan might not be a good idea.
@Raspiaudio - I received my mega amp today (via amazon). I’ve plugged it to the pi and usb-c power. In volumio I’ve set the DAC to HifiBerry Amp2. Music shows as playing on the app but I’m not able to get any sound out of the mega amp (either via headphones or speakers).
The fan on the mega amp is not spinning, my understanding from the thread is they will spin continuous, is that correct? Is there something I am missing?
Hello
Are you using the USB C on the Mega amp? you should
Are you using a USB C PD power supply? one that supports one of those voltage : 20v 15v 12v
thx
Yeah powering through the usb-c on the mega amp; the pi is working so power is going through to that at least. Just no other signs of action from the amp part. Is there anything I can probe with a multimeter etc?
Used 3 different usb-c PD adapters rated at 100W for 12/15/20V with the same results
the fan no spinning is stange, remove to plastic cover ant try it see the fan is not blocked by something, check also the fan is well connected
have done that now, fan spins freely if pushed gentle with a pick.
I unplugged the fan connector (with the power off) and plugged back in, seems solid. gave the wires a gentle tug and they seem well connected to the plug and solder joints. does not work under power though
Does the fan spin immediately with power; even if the mega amp board is not connected to the pi? Is the fan controlled directly from the board or the chip output? maybe i can follow the power trace to see where theres power etc
Yes, when you plug only the USB C on the Mega Amp and not connected to the RPI you should have the fan spinning. So please send it back thru Amazon, send me a private message if you need help.
Is limiting the hardware gain the best way to accommodate lower wattage speakers (10w-25w per channel)? Or would a smaller power supply (30w) be a safer way to do the same thing?
If limiting hardware gain is the proper method, are there recommended settings for different wattage speakers? Or is it just trial and error, dependent on the speaker?
I’m using Moode, upgrading from an older Mic+ with 5w/channel output to the Mega Amp
(BTW, a 2.1 channel mega amp would be a great future upgrade)
thanks
Hi, there is no hardware gain limiter on the Mega Amp, but you can limit volume by software
If you want to cap the maximum gain regardless of what applications do:
~/.asoundrc:pcm.limited {
type softvol
slave.pcm "hw:0"
control.name "SoftMaster"
control.card 0
max_dB -10.0
}
Then point your apps to pcm.limited instead of the default device. This forces a software gain stage with a maximum dB you choose.
You can also just us a 5v power supply like the official raspberry pi one it will limit power. And if you are using a USB C PD power supply the board will ask automatically to your charger the 12v profile then just play by hear and cap the volume before you hear any distortion.
I’m now powering my Mega Amp with a 65w power supply, and running Moode, which has a setting to limit max gain. I’m running a pair of 20w exciters that were almost workable with the older Mic+, but things are now sounding great with the extra power (no sub needed!)
Given that I’m not pushing the amp that hard, would it be possible or advisable to replace the fan with large heat sinks for a completely silent system?
Thanks again
yes purely passive heat sink can be done, but i can’t directly point you to a source, when I was designing the Mega it was my first intent by sink were too big to fit in the shell.