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Author Topic: Poor S/n on headphone audio output  (Read 11180 times)

Richard

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Poor S/n on headphone audio output
« on: January 09, 2017, 12:02:02 pm »
Hi guys,

Love the little P275 analyzer and it's Windows program.

The only thing I really don't like about the analyzer is the poor stereo audio quality from the headphone
output.  When the unit goes into stereo decode, the background hiss in the headphones is terrible.
And it doesn't matter how strong the off-air signal is, the hiss is always there.

Is there any way you can improve the S/n on the demodulated stereo output?

Thanks :)
Richard
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Jan

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Re: Poor S/n on headphone audio output
« Reply #1 on: January 09, 2017, 12:34:57 pm »
In order to reduce the development time and meet the demand for such measuring equipment, there are many routines taken from the older device which are only slightly adapted and sometimes do not utilize all features of the new hardware. This is a temporary solution. We are working on a fully new MPX software component especially for this device.
The stereo decoder can be switched off in the menu. It is not required for common measurements.
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Richard

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Re: Poor S/n on headphone audio output
« Reply #2 on: January 29, 2017, 08:40:17 am »
Thanks Jan :)

I am sure this unit will be very popular (I note that it is sold out again already) and I look forward to future DSP and firmware updates.

Well done anyway :)

Richard
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mimu

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  • Posts: 12
Re: Poor S/n on headphone audio output
« Reply #3 on: March 24, 2018, 06:58:43 pm »
Hello.
Are there any news about this?

Thank you
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Jan

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Re: Poor S/n on headphone audio output
« Reply #4 on: March 27, 2018, 07:59:40 pm »
This work is already done, however we decided to put these improvements into a bigger package of updates, incl. the FM Scope control software. This caused some delay but I'm sure you'll like the result. A link for trying will be published here in a few days.
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Jan

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Re: Poor S/n on headphone audio output
« Reply #5 on: April 21, 2018, 11:53:53 pm »
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Richard

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Re: Poor S/n on headphone audio output
« Reply #6 on: June 17, 2018, 01:02:34 pm »
Thanks Jan,

The new Firmware has improved the headphone audio.

There are still some low level noise products in the demodulated audio, but it is a lot better
than before.

Great to see improvements are happening :)

Kind Regards,
Richard
 

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Jan

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Re: Poor S/n on headphone audio output
« Reply #7 on: June 17, 2018, 09:23:40 pm »
Being a measuring equipment, the P275 does not contain extra audio demodulator. Doing so would need adding independent second tuner for audio only - unnecessary for all typical applications.

The audio is taken from the measuring tuner and its performance is limited by input A/D converter resolution. The A/D converter, which processes clipped IF signal, has 1-bit resolution and has sampling rate of 70 MHz. This sampling rate is converted to 169 kHz in several decimation stages while the demodulated MPX resolution increases to 9-10 bits @ 75 kHz FM deviation.

The audio output is 2x PWM, effective resolution 12 bits @ maximum volume.
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