PiGRRL - Now with sound.

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dnelms
 
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Re: PiGRRL - Now with sound.

Post by dnelms »

Sounds as if it's some feedback or picking up some garbage via the Vdc+, the common ground, or the i2c port.
I guess do as you were planning and bypass the power directly to the amp and see if that fixes it.

Also I'm not sure changing the value of your pot will make a difference as it's just a passive component and shouldn't be generating any high-pitched tone, it's probably just increasing the resistance until the interference is no longer audible.

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dnelms
 
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Re: PiGRRL - Now with sound.

Post by dnelms »

Man something wonky is going on with the forum today, I replied and it seems to have created a new thread? Anywho as I was saying...

Sounds as if it's some feedback or picking up some garbage via the Vdc+, the common ground, or the i2c port.
I guess do as you were planning and bypass the power directly to the amp and see if that fixes it.

Also I'm not sure changing the value of your pot will make a difference as it's just a passive component and shouldn't be generating any high-pitched tone, it's probably just increasing the resistance until the interference is no longer audible.

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Bel_Z_Bub
 
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Re: PiGRRL - Now with sound.

Post by Bel_Z_Bub »

lol no we just entered a new page! :) did you notice my last post on the previous? would that power converter do it? (although there's nothing to convert, it could isolate the problem?

you probably right about the pot, becuase when there's nothing connected at all, (like disconnecting the 3.5mm jack or disconnecting the pot the tone is at loudest. But when the pot isnt there and the jack is connected or when the pot is set at loudest the tone is completly gone, at least to my ears. In my previous version I could control volume with just a regular 10k pot, probably because that weird circuit's input (I copied from the beta version) is pulled up to the vcc as well as to the ground with 10k resistors. I kinda thought that caused it. But then the tone was really loud when I muted the sound with the 10k pot. When I switched amps the 10k pot didnt work no more, well not as linear as it did before and the tone was still there. Then I got the 50k linear pot and I thought that solved it at first. I didnt notice it for a week I think. untill everything was silent (pc off etc) and I was close to it with my ear I could hear it again. So its really neglactable I guess. Anyway this is why I think a slightly bigger pot would rule it out completly.

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dnelms
 
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Re: PiGRRL - Now with sound.

Post by dnelms »

It couldn't hurt to give it a try if you've got one sitting around. We use 100k pots in our mixer which is part of a power amp that we produce in limited quantities (its a specialized bit of kit).

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Bel_Z_Bub
 
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Re: PiGRRL - Now with sound.

Post by Bel_Z_Bub »

I've been messing with adjusting the tpa2016's gain with i2c, It worked perfectly for me before as I never went below 0. but it doesnt seem to take the negative values. I also cant find a datasheet link to it to confirm it actually goes below zero. According to the arduino driver it should go from -28 to 30 but I only notice changes from 0 - 30. ) ) 0 is far from muted. It doesnt make sense to me in the first place to have negative gain. I wonder if there was maybe an address wrongly or not covered by the arduino library as I also see a noisegate variable that is unused in the functions. I'll keep messing and let you know.

edit: I found the datasheet lol. The gain is only adjustable from -28 to 30 when compression is enabled. and from 0 to 30 when compression is disabled. The arduino library made me believe it was the other way arround, in the example file it disables compression and releasecontrol, while commenting its to adjust gain, then loops from -28 to 30 in gain. :P

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dnelms
 
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Re: PiGRRL - Now with sound.

Post by dnelms »

My eyes just crossed while trying to comprehend this :)

I'll do some googling and see if I can find anything.

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Bel_Z_Bub
 
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Re: PiGRRL - Now with sound.

Post by Bel_Z_Bub »

well all the result and facts are a bit dissapointing compared to the promises this amp makes:

in the datasheet it clearly states both:
-Digital I2C Volume Control
and
-Selectable Gain from –28 dB to 30 dB in 1-dB Steps (when compression is used)

but nothing further on Volume control in the sheets i2c section, only fixed gain. with fixed gain set to -28, its still far from muted, as no matter what I do, with compression enabled and AGC disabled it still keeps trying to set AGC and the higher the compression the slower it responds to the fixed gain setting. also with attack,release and hold set to 0. Maybe we can adjust the input signal in order to it, or shut down both channels at the lowest setting but its far from ideal. The sheet also doesnt make you believe the fixed gain is used to adjust volume. they have a few ideal settings graphs for all kinds of sources, jazz, radio voice etc. and they all include the fixed gain to a certain fixed setting. Also I think the db scale isnt linear to the human ear so that could also be a problem maybe. I havent tried using a 8ohm speaker yet, maybe that would help. as all numbers in the datasheet seem to be set for that.

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Bel_Z_Bub
 
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Re: PiGRRL - Now with sound.

Post by Bel_Z_Bub »

still no go on muting the sound with the fixed gain settings, I tried all kinds of limit settings as well to see if that maybe changed the range of the fixed gain.. it seems to work fine its just not realy noticable from lets say -28 to -14 and from arround +14 and up. all my other adjustments also seem to work fine, also found out how to adjust the noisegate level. I'm starting to believe its just not possible to mute it totally, if only I found a confirmation on the web that its possible.. I wont give up easily though lol

in the meantime I fixed the high tone produced by the piglow in my project, After I tried everything but a power isolator, but everything just made it worse..! even powering the amp from an external source now added the i2c activity to the speaker lol. (it was obvious as it was timed exactly to what was happing with the i2c devices in my code. I was about to order a power isolator, maybe I still will its not that expensive, but in one of my drawers I found a brand new linear mono pot, the same I use now but a 10K version, I thought I'd give it a go and to my surprise it works. only when the sound is halfway and I put the speaker to my ear I can hear it really soft. totally exceptable for me.

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