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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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In Reply to: Mono tuner questions... posted by Monkeypunch! on July 19, 2003 at 02:30:21:
I am not sure that mono FM tuners (tube type) are superior to solid state tuners because they are mono, but for distance listening (DX) stereo signals are too noisy to be of any practical use. Also, by the time FM stereo came into use, most new tuners being sold (tube and solid state) were offered with an FM stereo multiplexer circuit (if only as an option) to be able to decode the stereo signal.The mono signal is frequency modulated (FM) on the broadcast signal. The stereo portion of the signal is amplitude modulated (AM) on a 38Khz sub-carrier frequency centered around the broadcast frequency. This 38Khz sub-carrier is processed into the two stereo difference signals (L-R, R-L) that when mixed respectively with the original mono (L+R) signal yield true stereo (L) and (R) audio channels.
The downside of this AM modulation technique used with the (L-R) and (R-L) audio program is that while the mono signal is very immune to signal interference, noise, and multipath distortion the AM-modulated stereo signal is quite inferior in this regard. Also, FM broadcasts could have had a wider frequency response than the current 15Khz upper limit, but the nature of the stereo broadcast made it necessary to cut off the high frequency response above 15Khz due to the 38KHz sub-carrier scheme and also to avoid interference with the 19Khz pilot signal used as part of the stereo broadcast.
Any FM stereo tuner (tube or solid state) will provide it's best possible mono signal tuning performance by selecting FM mono instead of FM stereo. The only FM stereo tuner I know of that does not have a switch for mono reception is the Carver TX-11 series. These use a proprietary Carver circuit that processes the stereo broadcast in a way that the resulting noise and distortion of the stereo output is almost as clean as the mono signal, so no FM mono option is provided.
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Follow Ups
- Re: Mono tuner questions... - mkmelt 07/19/0304:37:31 07/19/03 (2)
- Sounds good to me... - realistico 07:44:08 07/19/03 (1)
- Re: Sounds good to me... - tubetwang 12:56:18 07/20/03 (0)
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