Is it Stereo?

I have a number of FM radios, including ones that can play MP3 files from media. Some are also Bluetooth speakers. But are they stereo? Only one has stereo speakers, but most have headphone jacks. In this article, I’m testing my radios’ stereo capability .

Methodology

How does one know whether something is stereo or not? It’s easy with MP3 files since one can make a simple audio file that has sound on one channel and then on the other, like this recording I made myself:

For FM, I’m using an inexpensive FM transmitter hooked up to a known stereo device playing the MP3 file. I verified that this Beinhome FM Transmitter I bought in 2022 transmits stereo. My Degen DE23 radio is stereo for both FM and MP3. Because it will play an MP3 file over and over, I selected it to supply signal to the FM transmitter. The pair makes a potent broadcaster.

Special care was taken to make sure radios with the ability to switch off FM stereo will be set appropriately on.

For Bluetooth, I just play the test file from my Windows computer paired to the device.

Expectations

My expectation is that most of the devices, both FM, MP3 and Bluetooth, will reproduce stereo.

Results

The result is one huge table. Radios that do not have headphone jacks will be obviously excluded.

Radio	FM Stereo	MP3 Stereo	Bluetooth Stereo
AMNVOLT ATS Mini	Reversed	n/a	n/a
Degen DE1131	Y	Y	n/a
Degen DE15	Y	n/a	n/a
Degen DE23	Y	Y	n/a
Eton Elite Executive	Y	n/a	n/a
HanRongDa HRD-908	Note 2	Note 2	Note 2
HanRongDa HRD-757	Y	Y	Y
Jazmm 213	N	Y	Y
Kaide KK-MP903	Reversed	Y	n/a
Kaito KA29	Y	Y	n/a
LiJiANi Rd239	Y	Y	Y
LiJiANi Rd908	N	n/a	n/a
Mesqool CR1015	N	n/a	n/a
Prunus J-429SW	Note 1	Y	n/a
Qodosen DX-286	Y	n/a	n/a
Qodosen SR-286	Y	n/a	n/a
Raddy RF75A	N	Y	Y
Raddy RF760	Y	n/a	n/a
Sansui F50	N	Y	Y
Sihuadon R-108	Y	n/a	n/a
SM-616	N	Y	Y
Tecsun PL-118	Y	n/a	n/a
Tecsun PL-330	Y	n/a	n/a
Tecsun PL-660	Y	n/a	n/a
Tecsun PL-990	Y	Y	n/a
Tecsun Q3	Y	Y	n/a
XHDATA D-109	Reversed	Y	n/a
XHDATA D-109WB	Reversed	Y	n/a
XHDATA D-219	N	n/a	n/a
XHDATA D-608WB	Note 1	Y	Y
XHDATA D-808	Y	n/a	n/a
Zhiwhis ZWS-603	Y	Reversed	Reversed

Notes:

1. While there seemed to be some channel difference, the crosstalk between the channels was extreme and the main impression is that the two channels appeared nearly the same.
2. Left channel has very low volume.

Observations and Conclusions

I was surprised that some of the devices reverse left and right channels for stereo FM and in one case even reversed it on MP3 play. I cannot explain the handful of devices that seemed to drop a significant portion of the left channel. It was always the left channel, never the right.

I was disappointed by the SM-616, the big fancy multimedia player. It handled stereo for media, but not for FM radio; similar to its smaller cousin, the Sansui F50. The Zhiwhis ZWS-2415 doesn’t have a headphone jack.

The ATS Mini channel reversal applies to V1, V2 and V3, according to a post on GitHub that someone sent me, in addition to the V3S I tested.

The Degen 1131 was rather expensive when it first came out, not the bargain blow out price under $20 I paid for mine. I didn’t know how good this one sounded with quality headphones. As Dan Akroyd once said: “Wow, that’s terrific bass!”

I did not generally test the ability for a radio to record FM stereo, but I did try the HanRongDa HRD-757 and the LiJiANi Rd239; both recorded stereo onto the MicroSD card. I’m confident the Tecsun Q3 would also capture FM stereo. To my knowledge, the ZWS-603 is the only radio in the collection with the capability to record from Bluetooth.

Afterword

This exercise grew out of another project, to convert some stereo cassette tapes to digital. I found that some (most?) converters on the market don’t convert stereo. So far I haven’t found a product that works.