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nilsonsound - an ongoing story

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nilspixel View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2021 at 1:43pm
sure it does ;) just for a completion of this diary here...
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Post Options Post Options   Thanks (1) Thanks(1)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 31 August 2021 at 5:42pm
One cabinet with a 150W input is going to run out of steam before your mids and tweeters, especially outdoors. Looks up ISO 226 to get an idea of relative SPLs.

And as bob mentioned, the empty cabinet next to it may absorb some of the energy radiated.


Don't worry about the THD, anything below 1% at amplifier is decent enough.


You won't be playing sine waves for long durations, so your cables will be quite overspecced'. You could potentially reduce their size if they're unmanageable (bend radii / mass). Shorter is always better of course.


Edited by infrasound - 31 August 2021 at 5:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 03 September 2021 at 10:26am
What i ordered today:

...LiFePo4 100AH 200A (400A max.) + Shunt
...Rage 1200.2
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 4:51pm
Update:

I installed the rage 1200.2 today. agm is replaced by lifepo4.

problem:
after ~1 min after I powered up the rage Amp the Pioneer starts to make a high frequency sound.. when I turn off the rage this tone disappeares instantly..

what's going on here?... any ideas?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 6:34pm
Feedback on the ground line / power heading down the signal ground is my guess.

Does it go away if you disconnect the signal connections? Try buying a ground loop isolator and adding it on the inputs to the rage amplifier.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 8:33pm
I was wrong! But thanks for your reply!

The probelm was the new rage itself. I opened up the whole thing to check if parts are loose. i tightened some screws, noise is gone.

But one problem remained:
As soon as i use the second amp (rage) my high speakes start to make weird noises even though there is no signal coming from the dsp. i wired both power cables directly to the battery +. When i disconnect the rage from the battery, noise is gone. My assumption is that both amps interfer with each other somehow... may a powercap solve the problem?

Any ideas on that?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 28 September 2021 at 9:48pm
Powercap, no. They are of questionable effectiveness to stop voltage drops - and you aren't pulling anywhere near enough to be in that realm anyway.

My answer to your last point is more or less the same, so not wasted. Because the power GND and signal wiring in 12v systems are often shared (or too closely related), it can be needed to isolate them to prevent interference. 

My suggestion is to try the isolator in various spots until the problem disappears.

Or, it may work to use a separate isolated DCDC power supply for the DSP


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Post Options Post Options   Thanks (0) Thanks(0)   Quote nilspixel Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2021 at 7:48am
thanks a lot infra! I'm going to try your suggestions today to see if it affects anything ;)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 29 September 2021 at 1:59pm
I'd guess that a high pitched whistle is gonna be due to the two Class D amp's oscillator frequencies interfering with each other and producing an audio-frequency tone. Most amps use a free-running oscillator whose frequency isn't particularly stable or locked to any reference clock, so if you've got two amps on the same battery bus, and one is running at 400kHz and the other one 405kHz, you're going to get signals of 5 and 805kHz appearing on the system ground. 
I've also experienced noise emanating from cheap Bluetooth reciever boards - this is due to the chip involved pulling very short, sharp pulses of current from the supply at a rate with at least some audio-frequency components. No amount of passive filtering (extra caps near the BT board) makes it go away. The only way is to use little 5v-5v isolated converter bricks to power the BT board. However of course you need to connect signal ground "around" the isolator somehow otherwise there's no circuit for the audio signal to flow. Using a 1000uF cap across the rail after the isolator and a 100r resistor to link BT ground to audio ground seems to work well for me - the 100r is enough to make most of the interference flow thru the 1000uF cap to the isolated ground rather than out onto your audio ground. Small transformers would also work but more expensive.
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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