Can I use GBUF with this setup?

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

Post by Hanzibal » Fri 2011-03-11 19:22

Hi!

I got a Netduino mini (basically a fast Arduino with .NETMF in firmware) controlling a vs1053 and an SD card as SPI slaves for digital music file playback.

Can I use GBUF when connecting line out (headphone connectors) of vs1053 to a class D amplifier, provided I feed everything from the same 12v (1.5A) dc wall outlet adapter?

What else do I need in terms of resistors and/or capacitors between the vs1053 and the amp?

Thanks!

russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Fri 2011-03-11 19:52

Iv been reserching the same question, from what iv read you should only ever use the GBUF when using head phones NEVER use it for lineout / amp

use the boards GND + left/right to connect to an amp

below diagram seams to be the suggested way
download/file.php?id=117

EDIT
just found this document
http://www.vlsi.fi/fileadmin/app_notes/ ... output.pdf

will be using the simple diagram (page 8) my self as i will be using a simple onboard amplifier

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Fri 2011-03-11 21:24

Thanks for your reply, I'll be looking into your suggested reading and get back when digested.

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Fri 2011-03-11 22:50

Meanwhile, any thoughts on this here problem of mine?

viewtopic.php?f=11&t=282&start=10#p893

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Sat 2011-03-12 10:16

For initial testing, I'll go with the simplified connection as described in chapter 3.2 of the pdf you referred to (same as you). I'll report back of the results from trying this.

russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Sat 2011-03-12 14:27

my project is a simple audio board for a slot machine where quality is not that important so i think it will be fine for me :)

look forward to your results :)

Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 1:59

Wired up according to the simple diagram at page 8 and tried connecting to a pair of amplified PC speakers.

No good at all, total lack of power and mostly high frequencies, hardly any bass at all. VERY far from what the headphones sounds like.

I'm lousy at analogue stuff though and I didn't know what values for C1 and C2 to use so I just took C1 = C2 = 4,7nF plus I only had ceramic ones.

Please let me know how it works out for you...

russdx
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Re: Can I use GBUF with this setup?

Post by russdx » Mon 2011-03-14 2:07

oh dear :(

Im very new to electronics my self but my dad is a charted engineer so he drew up the audio out /amp part of this schematic for me, im going to try this circuit my self when my sparkfun vs1000 / vs1053 boards turn up :)
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Panu
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Re: Can I use GBUF with this setup?

Post by Panu » Mon 2011-03-14 13:35

Hi!

If the D-class amp can accept input signals of up to about 2.5V, then I'd connect GBUF to the IN- pin of the D-class amp and LEFT to the IN+ pin. That way you can have good sound quality with a differential connection to the differential amplifier and you don't need the DC blocking capacitors! If you look at download/file.php?id=117, you need the RC filters marked as "sigma delta reconstruction" and the "high frequency grounding path". But you can leave out the "DC block for output".

-Panu
Info: Line In and Line Out, VS1000 User interface, Overlay howto, Latest VSIDE, MCU Howto, Youtube
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Hanzibal
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Re: Can I use GBUF with this setup?

Post by Hanzibal » Mon 2011-03-14 14:13

russdx wrote:oh dear :(

Im very new to electronics my self but my dad is a charted engineer so he drew up the audio out /amp part of this schematic for me, im going to try this circuit my self when my sparkfun vs1000 / vs1053 boards turn up :)
russdx, the schematics are similar to the one I tested and I need stereo output, your seem to be mono?
Panu wrote:Hi!

If the D-class amp can accept input signals of up to about 2.5V, then I'd connect GBUF to the IN- pin of the D-class amp and LEFT to the IN+ pin. That way you can have good sound quality with a differential connection to the differential amplifier and you don't need the DC blocking capacitors! If you look at download/file.php?id=117, you need the RC filters marked as "sigma delta reconstruction" and the "high frequency grounding path". But you can leave out the "DC block for output".

-Panu
Thanks Panu, I'll to try the suggested wiring instead but I want to use the stereo input to my class D amp that takes left, right and gnd. I'm a bit confused now, could you please clarify which wire goes where exactly?

I usually connect my iPhone to the D amp so it can probably take 2.5v but I'll check that.

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