Need tone to wake up DAC and Amp

[MCH]

Hi guys, my knowledge and capabilities in audio start and end plugging cables and installing piCorePlayer in a raspberry, so i need someone's help here.

I plan to use the following:

Pi(moode) 》DAC (D30pro) 》power amp

The D30pro can auto switch on when it receives a signal.
The power amp can do the same thing.

The problem is that most probably i will be missing the first couple of seconds of music...

As i have no idea the only solution i can think of is to generate a sort of 3-5 seconds signal that consists on two weak and ideally inaudible tones, the first to wake up the DAC and the second to wake up the amp. I could save it like if it was a song and put it first in my playlists, so when the real music starts everything is up and running.

Now my questions for the forum are:

Is there another way of doing it?

Could someone be so kind to explain how could i generate such a file or even better (and i feel this is asking too much but...) do it for me? I and dozens of artists that don't like to hear their masterpieces amputated would be eternally grateful.

 

[MCH]

Actually i don't know if i actually needs a tone to wake up the DAC, maybe it just needs to receive data, so maybe one single tone after a couple of seconds of silence might suffice (?)

 

[JayGilb]

What happens now when you start playing a file from the Pi ?
You should test out your audio chain and see how much music is lost before the dac and amp wake up.

 

[MCH]

4 seconds in total will suffice

 

[NiagaraPete]

I have a similar setup. PI Dietpi > D30Pro > Power amp. The Pi will wake the DAC and my power amps. No delay. The same goes for Airport Express to DAC. It also switches input automatically.

I only use GMediarender in Dietpi.

 

[Apesbrain]

I'm not sure this is the best way to accomplish your goal, but feel free to unzip and use the attachment. It's a second of -90 dB noise followed by three seconds of silence.

A better way might be to figure out how to add a delay in Moode. For instance, LMS has this control:

 

[MCH]

Thank you Apesbrain, i will surely try it an report
Delayed startup wouldn't work becausr the amp needs to receive a actual signal to trigger the switch on mechanism and the it takes a couple of seconds to be ready to send signals to the speakers (and hence the lost music)

 

[MCH]

I have a similar setup. PI Dietpi > D30Pro > Power amp. The Pi will wake the DAC and my power amps. No delay. The same goes for Airport Express to DAC. It also switches input automatically.

I only use GMediarender in Dietpi.

That means your amp is super fast!

 

[NiagaraPete]

I’ve reread your post a couple times. Are you thinking you might loose a couple seconds or you are loosing a couple seconds?

I think you’ll find that it all works seamlessly.

 

[MCH]

I already loose 0.5 seconds with the D30pro alone (that is, having the D30pro in stand but the amplifier on by the moment I press play in moode), and that's already very noticeable with songs that have a quick start.

The amplifier with the autostart I will get it to test in a few days, but they already told me that it takes a couple of seconds from the moment it detects the signal until being up and running.

BTW, @Apesbrain your archive works perfectly to wake up D30pro, and I need to max the volume to hear the noise (only the second half of it makes it through), so all good there, thanks again. Will see if it is strong enough to wake up the Amp too at a reasonable volume.

 

[AnalogSteph]

I sort of doubt it, tbh. The way typical analog signal detection circuitry works, I would assume it takes at least something in the tens of millivolts to trigger it. I might try generating 5 s worth of 20 Hz sine at a peak amplitude of 0.03 (~-30 dBFS), fading in and out the first and last 200 ms or so. (Should be easy enough e.g. in Audacity.) Increase amplitude if that still doesn't do it. Going down to 10 Hz is also worth a shot, detection sensitivity down there may be little worse but hearing threshold would be substantially higher still.

I presume the power switch is not physically accessible?

 

[MCH]

I sort of doubt it, tbh. The way typical analog signal detection circuitry works, I would assume it takes at least something in the tens of millivolts to trigger it. I might try generating 5 s worth of 20 Hz sine at a peak amplitude of 0.03 (~-30 dBFS), fading in and out the first and last 200 ms or so. (Should be easy enough e.g. in Audacity.) Increase amplitude if that still doesn't do it. Going down to 10 Hz is also worth a shot, detection sensitivity down there may be little worse but hearing threshold would be substantially higher still.

I presume the power switch is not physically accessible?

Thank you Steph!
What is that you doubt, that the signal is strong enough? I know that the auto off needs less than 1 mV (that is, while receiving 1 mV or more, it won't switch off) but didn't ask about the auto on, i assume the same (?). Of course i dont want to wake it up with the volume maxed, so maybe something like 10 or 20 mV or more, if still not super audible, would be ideal
Yes, the idea is to hide the amp in a cabinet and forget.
I see Audacity is free, will try to see what can i do.
Why fading in and out the signal?

 

[AnalogSteph]

I see Audacity is free, will try to see what can i do.

It's really quite handy to have around as a Swiss army knife type audio editor. The tone generator works perfectly, and it's got SoX VHQ level resampling available.

Why fading in and out the signal?

Just to avoid clicks / pops, particularly if the waveform does not end in a zero crossing (which it should in my example as 5 s will fit an integer number of 20 or 10 Hz periods).

 

[MCH]

Hi guys, i think i owe you a follow up. So i got the Amp and even had the chance to discuss this subject with the designer. He suggested me to generate a 1 kHz instead of 20 Hz and so i did with Audacity. The tone looks like that:

0.2 seconds fade in - 1.2 seconds 1kHz 0.1 amplitude - 0.2 seconds fade out - 3.4 seconds of silence (to make sure the amp is up and running when the music starts.

It works perfect, both the DAC and the Amp wake up and by the time the sound gets to the speakers the tone is over so i cannot hear anything.

Thanks all for your suggestions