Line out, Line in and Headphone connections

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

Post by Panu » Wed 2014-03-05 13:45

Right. If you're really tight on PCB real-estate, you can do some experiments.. To prevent oscillation, it may be sufficient that the signals just see some resistive-capacitive load... it's not an official recommendation and I'm not even sure that it would work, but it might be enough to have the RC for the GBUF and then connect left and right to the same C via a 1Kohm resistor. That might be enough and you'd save two capacitors. I'll ask an analog chip engineer's opinion tomorrow, I'm a bit more digitally oriented myself.

-Panu
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lpmsr
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Re: Line out, Line in and Headphone connections

Post by lpmsr » Sat 2014-07-05 18:35

I am using the VS1000 Module and have a question about the outputs. Can I mix the L & R outputs together through suitable isolation resistors to provide a mono output? If yes, what value resistors would be a good choice? The external load in this case might be anywhere from 600 ohms to 10K ohms, although a fixed load could be added near the module.

Larry

Panu wrote:Hi!

The VS1053/VS8053 Simple DSP Board's application note is a great example for how to design a device with good analog performance (sound quality). It's good reading, and it's available at: http://www.vlsi.fi/en/support/evaluatio ... board.html. Look for the Application Note link at the top-right corner of the page.

Here's a small contribution to the discussion about the analog connections. I've annotated a section of the Simple DSP Schematic, showing what the various capacitors and resistors in the analog block are actually for.

Have fun examining!

-Panu

morpheus
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Re: Line out, Line in and Headphone connections

Post by morpheus » Wed 2015-02-11 15:17

Hello,
I have a standalone VS1063 mp3 recorder design that uses an onboard active microphone (ADMP504) and an optional passive one connected via mini-jack.
The active microphone (integrated amplifier) is connected to Line2 (pin 48) through an RC filter.
The external passive microphone jack is connected to the MICP/MICN pins using the schematic of the standalone player, see also attached image. The VS1063 MIC amplifier is enabled.
Unfortunately, because the active microphone level is low, I have to set the AGC on with a maximum gain of 20x (SCI_AICTRL2=20480) to have proper recording level. I have also set the encoder in dual channel mode to have separate AGC. (external mic = left, onboard mic = right)

With the optional external microphone connected (standard PC headphone used), the result is more or less OK. The external microphone channel (left) is louder and has much higher hi-frequency noise but none of these are critical. However, with the external microphone unconnected the left channel is full of a high level noise. I am suspecting that the AGC causes that since there is no input signal. Unfortunately I need the AGC in dual channel mode because the two microphones have very different levels. Is there a way to force the left channel to be empty (or at least not too loud) when there is no microphone connected? Otherwise I suppose I would have to detect the presence of the external microphone during startup and setup the encoder appropriately.

Thank you in advance,
Giannis

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Panu
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Re: Line out, Line in and Headphone connections

Post by Panu » Thu 2015-02-12 11:44

I'm not sure if I really understand your question. But I recommend that you adjust the parameters based on whether the other mic is present or not.

That said, you could try to see what happens if you would connect a 100 kOhm resistor across the optional mic so that there is some impedance between MICP/MICN. It might keep the noise in check, at least somewhat.

Of course, the best solution is to use an op-amp to make an external mic amplifier, but maybe that's overkill.

If high frequency noise is the problem, a low pass filter might be the solution. But I don't know how that would be added to the recording signal path; only that it's technically possible.

-Panu
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morpheus
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Re: Line out, Line in and Headphone connections

Post by morpheus » Thu 2015-02-12 12:02

Hi Panu,
the problem that I want to solve is the loud noise recorded in the left channel when the optional passive microphone is not connected.
I have thought of the resistor between MICP/MICN too, but haven;t tried it yet.
I too tend to believe that detecting the presence of the microphone and adjusting the recorder appropriately will be the best solution, but this will require another PCB version, so I was wondering if there is a way to at least partially solve the problem with the current board design.

Best,
Giannis

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Panu
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Re: Line out, Line in and Headphone connections

Post by Panu » Thu 2015-02-12 13:03

I'm having trouble understanding some of the details in your project. How do you handle the recording now? Is it a stereo recording with the mics in separate channels; or do you select which channels your record; or do you downmix a stereo recording into a mono one?

-Panu
Info: Line In and Line Out, VS1000 User interface, Overlay howto, Latest VSIDE, MCU Howto, Youtube
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morpheus
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Re: Line out, Line in and Headphone connections

Post by morpheus » Thu 2015-02-12 16:41

I record in stereo, with each mic to its own channel, so that I can later separate each microphone.

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devicedeveloper
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Re: Line out, Line in and Headphone connections

Post by devicedeveloper » Mon 2016-07-25 15:29

Hello, Support!

I want to connect MEMS microphone with VS1053, which has 3 line: Vcc, GND and OUT:
Image

Maximal output voltage this microphone: 0,4 Volts(RMS) AC + 0.7V DC offset.
How properly connect this microphone to MICN and MICP inputs ?

Is this right: MICN to GND, MICP to OUT thru 10uF condenser(for filter DC offset voltage), Vcc and GND to power and ground ?

With this microphone output level (0,4 Vrms) additional amplification need or not?

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Henrik
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Re: Line out, Line in and Headphone connections

Post by Henrik » Wed 2016-07-27 12:34

Hello,

The microphone is single-ended. Also the signal level (max 0.4 Vrms) is only 5.7 dB lower than the typical maximum line input level of VS1053 (which is around 0.77 Vrms) when Vref = 1.2 V (keep bit SS_REFERENCE_SEL of register SCI_STATUS at 0). This leads me to think it would be best if you connect your microphone to VS1053 using line input schematics.

Kind regards,
- Henrik
Good signatures never die. They just fade away.

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devicedeveloper
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Re: Line out, Line in and Headphone connections

Post by devicedeveloper » Wed 2016-07-27 15:09

Henrik, thanks for your reply!

VS1053 can be configured with a maximum gain and automatic gain control(AGC) at the same time?
What level of compression? (in dB or Ratio).

Early i planned use speech compressor SSM2167 (it has maximum compression level ratio 10:1) for over-gain protection when near sources of sound.
It plans to make a sensitive microphone.

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