Sherwood tuner S-3000 III FM

Description

Sherwood Tuner S-3000 III FM: Full Description and Specifications

The Sherwood S-3000 III is a vintage FM mono tuner from the early 1960s, part of Sherwood's acclaimed S-3000 series of tuners. Known for its quality construction and excellent sound for its time, the S-3000 III was a popular choice for audiophiles seeking reliable FM reception. While it is a mono tuner, it was designed to accommodate an optional multiplex (MPX) decoder for stereo reception, which would have been a separate unit at the time. Key Specifications:

• Tuning Range: 87.5 - 108.5 MHz (FM)
• Sensitivity:
  • 0.95 µV for 20 dB quieting
  • 1.8 µV for 30 dB quieting
  • 3.6 µV for 50 dB quieting
• Frequency Response: 20Hz to 20kHz (FM), ±0.5 dB (likely a specification for the S-3000 IV, the S-3000 III spec might be slightly different but within a similar range).
• Signal to Noise Ratio (S/N): 60 dB (FM) (likely a typical value, may vary slightly).
• Distortion: Less than 1/3% IM @ 100% modulation (60/7000 cps: 4/1 w/std. preemphasis). Less than 1% harmonic @ 100% mod., 400 cps.
• Selectivity (Typical): 200 kHz @ -6dB
• FM Discriminator: 600 kHz peak-to-peak
• Hum and Noise Level: 60 dB below 100% modulation
• FM Drift:
  • ±2 kHz with AFC (Automatic Frequency Control)
  • ±15 kHz without AFC
• AFC Correction: 16 dB
• Output: 2.0 Volts @ 100% FM (cathode-follower audio output)
• Antenna Input: 300 ohm balanced (came with two lengths of plastic-covered wire for basic antenna)
• Tuning Scale: Analogue with a "Feather-ray" tuning eye (likely a dual magic eye tube for precise tuning indication).
• Tubes: Likely utilizes around 11 vacuum tubes, including types like 12AT7, 6BS6, 6CB6A, 6AU6, 6AU8, and 6BN8 (tube complement can vary slightly based on specific production runs and service history). It also likely has a solid-state rectifier in later versions.
• Power Consumption: 40 watts, 110-120V, 50-60 cps.
• Dimensions: 14 x 10.25 x 4 inches (W x D x H approximately)
• Shipping Weight: 16 lbs

Key Features:

• Delayed AGC (Automatic Gain Control): Applied to the RF stage for stable reception of varying signal strengths.
• Cascode RF Amplifier: For improved sensitivity and lower noise.
• Triode Mixer: A tube-based mixer for signal conversion.
• Two-Stage IF Amplifiers: For increased gain and selectivity in the intermediate frequency stage.
• Cascaded Limiters: To remove amplitude modulation and improve FM signal quality.
• Foster-Seeley FM Discriminator: A common and effective circuit for recovering the audio signal from the FM carrier.
• Cathode Follower Output: Provides a low-impedance output for better compatibility with amplifiers.
• Level Control: Allows adjustment of the output signal level.
• AFC (Automatic Frequency Control): Helps lock onto the center of the FM station and reduces drift. Can be switched on or off.
• "Hush" Control (Likely present on later versions like the S-3000 IV): A muting circuit to reduce inter-station noise.
• Provision for Optional Multiplex Decoder: Designed to be compatible with external stereo decoders when FM stereo broadcasting became more widespread.
• Attractive Vintage Aesthetics: Typically features a clean front panel design with the tuning eye as a prominent visual element.