Line out, Line in and Headphone connections

Designing hardware that use VLSI Solution's devices as the system controller for the entire design.
Hannu
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Re: Line out, Line in and Headphone connections

Post by Hannu »

I believe you saw the image on first page? Line input stuff naturally can be removed, R40, R41 also as there aren't that kind of resistors in the datasheet of the amplifier. SHDN pin should be connected to some GPIO to filter out the click when DAC turns on.

The blue circle of HF ground paths are needed. What you can tweak also is C24 and C25 with value and type. It will determine the low end of the frequency response for amplifier. High end can be tuned R38 and C1.

Have you tested if VS1010 can drive the element directly? Connect L and R to the speaker terminals and run auomono in differential mode. auomono can be found from here viewtopic.php?f=15&t=2767

DAC output is max 250 mW If I calculated correctly and depends heavily on the element.
iaburn
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Re: Line out, Line in and Headphone connections

Post by iaburn »

Hello,

I bought the following Arduino shield based on VS1053B to make an audio book player for my nice.
The board only has a headphone jack output, so I bought a mini 5V-3W PAM8403 amplifier and a pair of small suitable speakers and I'm now trying to find a way to connect the amplifier.

I saw the diagram that Panu linked about how to connect a D class amplifier, but that's too complex for my knowledge.
I found another diagram on page 8 from this document: http://www.vlsi.fi/fileadmin/app_notes/ ... output.pdf
which seems easier to understand, but: is it what I need in this case?
There are also 2 capacitors that I marked in red (C1 and C2) that don't have values. What would be the capacity for those?

Thanks a lot in advance
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pasi
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Re: Line out, Line in and Headphone connections

Post by pasi »

Hi,

Do you have schematics/datasheet for PAM8403?

It might be possible to connect LEFT/RIGHT/GBUF i.e. the headphone output to it directly, as long as it provides an amplifier reference input that is not the same as ground. (Its PCB shows "G" though....)

If not, for C1 and C2, I think the bigger the better... The VS1000 Audio Module uses 10uF and 100k to ground.
Edit: Also see the first post of this thread, which seems to use the same...
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iaburn
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Re: Line out, Line in and Headphone connections

Post by iaburn »

Thank you for your answer.
I could find this document:
https://www.mouser.com/datasheet/2/115/ ... 247318.pdf
And the board itself looks like the attached picture.
I'm just trying to make it as safe as possible. Everything will be powered by a 5V USB adapter and I got sacred about this "ground loop" problem :s
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pasi
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Re: Line out, Line in and Headphone connections

Post by pasi »

It looks like the PCB has the DC-block and series resistors, so you can connect LEFT and RIGHT directly.

I'm not sure from the image how VREF is connected. There is a DC block capacitor on that line, and it looks like from the routing of the +5V that VREF might not be connected to the negative power supply terminal. If this is the case, you can connect GBUF to the "GND" input of the board.

You can use an Ohm-meter and measure between pin 8 of the IC (or the capacitor end next to the "R" on the PCB) and the "-" terminal of the supply. If the resistance is near 0, they are connected and the above speculation doesn't hold. You would then be better off connecting the actual GND of the vs10xx board to the GND input.
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iaburn
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Re: Line out, Line in and Headphone connections

Post by iaburn »

I realised that my board looks slightly different (actual photo attached), but the components seem to be similar.
I've measured between pin 8 and negative terminal and the resistance is 570 Ohms. Would it be safe in this case to make a direct connection from the VS1053 shield headphone output to the amplifier inputs? :?:
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pasi
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Re: Line out, Line in and Headphone connections

Post by pasi »

Wow. I'm not sure what the designer has been thinking with that board layout/schematics.

The _|_ terminal seems to have a series capacitor (DC block) and then connected to the positive supply (PVDD and VDD). (I can't see how VREF is routed.)

You won't have ground loops due to the DC blocks, but I'm not sure how you would get the best sound out of that board.

a) connect LEFT, GBUF, RIGHT to L, _|_, and R
b) connect LEFT and RIGHT to L and R, and GND to the - supply (common ground for vs10xx and USB power). With this you'll probably get a power-up click/pop. The board has MUTE connected to PVDD/VDD.
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iaburn
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Re: Line out, Line in and Headphone connections

Post by iaburn »

That's super helpful, thank you!!
Knowing that I'm not risking a short circuit or something that could set it on fire, I feel more confident testing.
I will let you know my results! :geek:

EDIT:
I've just tried and, to my ears, both ways give the same noise levels and same volume. The important thing is that it works perfectly! :mrgreen:
SJS
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Re: Line out, Line in and Headphone connections

Post by SJS »

Hello Panu and @all,

i am designing a VS1053 pcb with stereo line in connection and looking for some help regarding the coupling capacitors (please look at the yellow marked 1µF capacitors in the picture below).

What is the recommendation for this capacitors? In different schematics different types occur (ceramic MLCC, film)...and i am wondering why there are no electrolytic types are used (like at the output side).

What i have learned already: the reason not to use MLCC at the output side is to prevent distortion because of the capacity unstability with biasing voltage and the piezoelectric effects of ringing. But will this not appear at the input side also? Is there any benefit to use electrolytic types instead?

Additionally i would like to know why 1µF seems to be a recommended "standard" (and not 10µF e.g. like in the output path)?

BTW: My aim is not to reduce costs, but get maximum audio performance.

Thanks in advance for your help!
Stefan
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SJS
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Re: Line out, Line in and Headphone connections

Post by SJS »

Hello @all,

nobody here who can help ? :)

Regards,
Stefan
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