Can I use GBUF with this setup?

Writing software for systems that use VLSI Solution's devices as slave codecs to a host microcontroller.
russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Mon 2011-03-14 14:25

ah yes sorry, forgot to mention i am using mono :mrgreen:

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Panu
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Re: Can I use GBUF with this setup?

Post by Panu » Mon 2011-03-14 14:48

Hi, Hanzibal!

If your stereo class D amp has IN+ and IN- for the both channels (as most do), e.g. it has INL+, INL-, INR+ and INR- pins, then the wiring is LEFT->INL+, GBUF -> INL-, RIGHT -> INR+, GBUF -> INR-.

-Panu
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Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 15:27

Great, thats clear. I'm looking forward to try the suggested setup tonight. I'll report back on the result.

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 15:30

russdx wrote:ah yes sorry, forgot to mention i am using mono :mrgreen:
Well, its a slot machine so it probably won't attract audiophiles :D

I saw you also have a vs1000 onboard - vs1053 for music and vs1000 for sound effects or just a means of mixing different sounds together?

russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Mon 2011-03-14 15:42

I need two audio channels so i am able to play two samples at once. ie the reels could be spinning with some sort of reel spin music then as each reel stops it needs to play a reel stop sample on top of the reel music.

so yeah basically just mixing two channels :)

so i think i will go down the route of having a vs1000 + vs1053 to achieve this :)

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 22:14

Maybe you could do with the vs1053 alone. Since you only use mono, maybe you could have different sounds in each of the two channels as stereo input to the vs1053 and then adding them together analoguewise afterwards. I guess another solution could be to have different sounds from two digital sources interleaved as input to the vs1053 and then write a custom dsp application to mix them together within the vs1053.

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 22:28

Panu wrote:Hi, Hanzibal!

If your stereo class D amp has IN+ and IN- for the both channels (as most do), e.g. it has INL+, INL-, INR+ and INR- pins, then the wiring is LEFT->INL+, GBUF -> INL-, RIGHT -> INR+, GBUF -> INR-.

-Panu
Hi Panu! Using the setup you suggested earliger, I got a very powerful and crisp audio from my 2 x 25W class D amp (Texas Instruments chip). Apart from my usual bleep /blop background noise I now got some low levelled 2 Hz "bip, bip, bip,...bip" and also present is a DC signal in ~D note. But apart from all that, sound was really great ;)

As said, I use a single 12V feed for the amp that also feeds a 5v regulator for the MCU and a 3.3v regulator feeding the vs1053 and the SD card. Ground is common for everything and so maybe there's a ground loop and I guess I will need to block out some DC too?

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Tue 2011-03-15 2:07

Got rid of the 2Hz "bip, bip, bip" by separating the D amp from the rest, i.e. no more single 12v feed plus I abondoned GBUF for regular GND and some r's and c's.

The latter don't do much good though, DC signal still present.

russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Tue 2011-03-15 12:35

could you post your audio out Hanzibal? so i can compare to mine before i bread board it

thank you :)

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Tue 2011-03-15 13:49

Do you mean the schematics or actual sound produced? The schematics are quite simple, right now I'm just passing left, right and gnd (not gbuf) straight to the external d amp (has its own 12v feed) so there's really nothing to it.

Audio is great when rendered on a pair of monitor speakers, except for a a low level background signal, which I suspect being what you would refer to as dc signal.

The dc signal is hardly audible when increasing volume to a pleasant listening level, but using your dad's scheme that'll probably go away too. I will try some similar measures and report back. Currently I'm at home with my 2 year old daughter who's hurling, so tonight at ealiest since I have the presentation tomorrow (for which sound is currently goog enough).

Til later!

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