What is stereo?




There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.




H.H. Scott '59





Pioneer TX-6800

 Pioneer TX-6800
Stereo FM/AM High Fidelity Tuner
Improved Performance-to-Cost Ratio Gives You Lower Tuning Error for Lower Price in This new Pioneer Model.
Clean Audio Output: Flat 20 Hz to 15 kHz +0,5 dB, -1,0 dB.
Extra-Long Tuning Dial with LEDs
Straight-Rule Twin Tuning Meters
Pioneer-Exclusive ICs with Automatic Pilot Canceller.
A Very Clean Audio Output
When designing the TX-6800 stereo FM/AM tuner, Pioneer put sound quality first on the list of objectives. We made sure the audio output is as clean as possible – free of distortion and noise. Our goal was achieved the frequency response reaches from the almost inaudible low of 20 Hz to the upper reaches of your hearing at 15,000 Hz. Plus 0,5 dB, minus 1,0 dB or better. Special ICs developed exclusively for Pioneer are used throughout, wherever it was possible to eliminate bulky discrete parts without harming performance quality. In fact, these special ICs anable us to reduce cost and improve performance quality, not only in this model but in our most expensive tuners and receivers as well.
FM Front-End Section FET Assures High Sensitivity.
Radio-frequency signas entering the tuner via the antenna are passed throughthe front end. It is here that the broadcast signal to which you have tuned on the 3-gang variable capacitor (via the tuning system) is sorted out fromall the others. Pioneer has employeed an FET in this section to see that the signal selected is stripped of noise and distortion, this permits us to step up the sensitivity of the sectionto achieve more “reach”. The usable sensitivity in FM mono, for instance, is a respectable 10,8 dBf (1,9 uV). At the same time, the spurious response ratio is improved to 70 dB.
The FM IF Section The First Pioneer Exclusive IC
A one-stage buffer amplifier and the Pioneer developed IC No. PA-3001A team up here to amplify the IF or Intermediate Frequency. The special advantage of the IC here is low-noise performance; the signal-to-noise ratio obtained is an excellent 80 dB (mono) or 74 dB (stereo).
Phase-Linear Ceramic Filters
Also, in the IF section, a pair of phase linear ceramic filters are put on line amomg the IC and IF amplifier. Without them, the high frequencies in the final audio output would be far less clean and clear. A further advantage is that the ceramic filters offer excellent interference rejection characteristics.
Our New Quadrature Discriminator.
We call this new circuit a One-Pack Phase Shifter because it packs the conventional micro inductor and the discriminator with new bobbin material in one shielded case. The benefits include the following:
Positive protectionagainst distortion
Improvement of input vs. distortion characteristics
reduction of noise for a better S/N
Increased stability against temperature/humidity changes.
 FM Stereo Section
in the multiplex section of the TX-6800, we use a microelectronic integarted circuit (the Pioneer exclusive IC No. PA-1001A) which contains a throughly reliable PLL or Phase-Locked Loop circuit. Unlike the old-fashioned “demodulators” which were subject towide errors in performance depending on outside influences like temperature and humidity, our PLL is entirely error free. Always-stable, very wide stereo separation in FM is the result.
A Built-In Pilot Canceller Circuit.
The multiplex switching signal mentioned erlier is a 19 kHz signal which is broadcast along with the two stereo channels. Its only function is to “trigger” the multiplex section to separate the left and right channels; once that function is done, it must be removed entirely lest it interferes with the audio signals processed in the following sections of the tuner. Old-fashioned tuners used a low-pass filter for removing that “switching signal”, now called the “Pilot”. But such filters tend to “chop off” desired audio frequencies, too. We ve avoided this with the use of a built-in Automatic Pilot Signal Canceller, quite different in concept and operation from the “active filter” type another advantage is an improvement of carrier leakage by 20 dB over conventional types. Also, it should be pointed out that this Automatic Pilot Signal Canceller is incorporated within the PA1001A itself and thus enjoys the same high reliability and protection from outside influences.
 AM Fidelity Is Improved
Better Frequency Response - A high-density IC (HA-1138) is used in the AM section of the Pioneer TX-6800 to contribute greatly to improved frequency response, permitting a flatter, more faithful reproduction over a wider range.
AM Distortion Reduced - The IC likewise serves to reduce the sound- spoiling distortion in AM reproduction especially in the very low frequencies around 100 Hz.
Variable Capacitor - Our use of a 2-gang system in the variable capacitor for AM permits liner tuning and higherlinearity. AM sound you might once have thought to be “lo-fi” is received and reproduced with more pleasant results.

Still More Advantages
Extra Long Tuning Dial - It's unusual to find a tuner in this price range with such a good tuning “feel”. The major contribution to more convenient and accurate station selection in the Tx-6800 is its long (300 mm) tuning dial for AM/FM. The FM band, by the way, is “frequency linear” - divided into equidistant sections.
Srtaight-Rule Meters The Twin Tuning Meters on this model reflect Pioneer's policy of providing maximum readability and impeccable accuracy. The staraight-rule scales of the Signal meter (for AM/FM signal strength) and the Tuning meter (for FM center-of-channel) are calibrated for easy reading and finished in Pioneer blue for eye appeal.
FM Muting Switch - This front-panel feature permits you to cut out inter-station tuning noise while tuning FM stations. in the Off/Mono position the muting circuit is taken off line to permit tuning of distant/weak stations; reception mode is then switched to monophonic.
LED Indicators - These long-life Light Emitting Diodes let you know tuner status for AM, FM and Stereo FM at a glance.
Function Switch - Select FM or Am ; a special back-up circuit prevents pop noise as the switch is used. 
Specifications
FM Section
Usable Sensitivity:  10,8 dBf (1,9 µV) [Mono]
50 dB Quieting Sensitivity:
Mono :  15 dBf (3,1 µV) / Stereo :  38 dBf (44 µV)
Signal-to-Noise Ratio:
Mono :  80 dB / Stereo :  74 dB
Distortion:
At 100 Hz :  0,1% (mono) / 0,2% (stereo)
At 1 kHz :  0,1% (mono) / 0,2% (stereo)
At 6 kHz :  0,15% (mono) / 0,25% (stereo)
Frequency Response:  20 – 15,000 Hz +0,5 dB, -1,0 dB
Capture Ratio:  1,0 dB
Alternate Channel  Selectivity:  60 dB
Spurious Response Ratio:  70 dB
Image Response Ratio:  60 dB
IF Response Ratio:  80 dB
AM Suppression Ratio:  55 dB
Muting Threshold:  17,2 dBf (4,0 µV)
Stereo Separation:  40 dB (1 kHz) / 35 dB (30 – 15,000 Hz)
Subcarrier Ratio:  50 dB
SCA Rejection Ratio:  50 dB
Antenna Input:  300 Ω  balanced,  75 ohm  unbalanced
AM Section
Sensitivity:  300 µV/m (IHF, ferrite antenna) / 15 µV (IHF, external antenna)
Selectivity:  35 dB
Signal-to-Noise Ratio:  50 dB
Image Response Ratio:  40 dB
IF Response Ratio:  70 dB
Antenna:  Buil-in ferrite loopstic antenna
Semiconductors:  1 FET;  3 ICs;  8 Transistors;  15 Diodes
Power Requirement:  120 -240 V,  50/60 Hz
Power Consumption:  14 watts
Dimensions (W x H x D):  451 x 151 x 284 mm (17-3/4” x 5-15/16” x 11-3/16”)
Weight:  5,3 kg (11 lb 11 oz) net


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