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unknownprc: Super USB Cassette Capture EZCAP 218 - Operation behavior

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Foro » Radios etc. » MODELOS DEMONSTRADOS » unknownprc: Super USB Cassette Capture EZCAP 218 - Operation behavior
           
Jose Mesquita
Jose Mesquita
 
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15.Jul.22 10:02

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When I did the initial testing of this unit, I noticed the low level audio signal captured by the recommended Audacity software program. Audacity and Windows OS forums did not help. I followed the user guide, and have used earphones to monitor the audio to be captured by the computer software.

As a temporary solution, I have selected the captured audio section on the Audacity program, then selected the  Amplify option from the Effect menu, accepted the proposed settings and pressed OK. The captured signal is automatically increased and avoiding audio clipping.

After dismantling the unit, I found the reason and a better solution.

The audio signal captured by the stereo read heads is handled by U2, a UTC668 (LAG668 equiv.) Audio and Motor tape player IC, made by YW (Hangzhou Youwang Electronics). The dual channel signal is passed to the U2 pre-amp section and the output is directly feed into the U2 power amp section, where the volume level is handled internally and controlled by a external mono potentiometer, as seen in the IC datasheets.

The dual channel power output of U2 drives the stereo earphones socket, and also drives the input of U3, a 4558D Dual OpAmps IC, made by JRC, acting as dual channel audio amp.

The output of U3 is finally passed to U1,  a AS20BP0A201 A/D converter for audio with USB output, made by a popular, although not documented, Chinese JL brand.

As a result of this design, the digitalized audio signal level sent to the computer via USB port depends on the position of the U2 audio volume potentiometer, meaning that setting it for confortable level for earphones monitoring will result in low digitalized signal. 

This design has some advantages, as it is easier to avoid audio clipping by reducing the volume on stronger Cassette recordings, or increasing the signal on weaker ones

However, the drawback of this solution is that the audio level at the earphones used for monitoring can not be adjusted for confort listening as doing so may create issues on the digital recording quality.
One fix to this issue would be to enable the audio monitoring at the computer side in the software setup being used to capture the audio from the USB port (as I did in the Audacity program).

 

 

 

 

 

 

 

 

 

Este artículo fue corregido 15.Jul.22 10:08 por Jose Mesquita .

Michael Watterson
 
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15.Jul.22 19:40
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As there is a maximum level the tape can sustain, it would make more sense to drive the ADC from the input to the volume control via preset for Fe or Chrome or Metal levels.

However a decent vintage table top mains cassette player (with maybe new belts) via analogue to the stereo line in on a PC or an external quality USB audio box  to Audacity will give better results. I use a Sony TC-186SD and a either motherboard stereo in on tower PC or an old Creative Labs USB capture/play box on a laptop because the USB audio "dongles" are not great and most laptops now just have mono mic in, no stereo line in.

 

Jose Mesquita
Jose Mesquita
 
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15.Jul.22 21:06
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Hi Michael,

Thank you for your input.

Indeed, these usb low cost cassette devices can not compete with a proper tabletop or even a good Sony/Panasonic Walkman tape players.

I used my Nakamichi DR-2 for many years and I still have a good old Creative Labs converter stored somewhere.

I wanted to find out how these later cheap tape machines with integrated a/d converter perform. I would say it suffers a little hum that can be detected on silent passages, and the sound seems to be limited on the low and high bands. 

  
rmXorg