A solid-state stereo preamplifier developed as part of Dynaco’s early transition to transistorized audio equipment.
Overview
The Dynaco PAT-4 is a solid-state stereo preamplifier introduced during the late 1960s or early 1970s as the second series in Dynaco’s solid-state amplifier line, following the ST-120 power amplifier. It builds upon the design strengths of the PAS-3X while adding enhanced functionality. Marketed as an "all silicon solid-state control center," the PAT-4 was reviewed as one of the first solid-state preamplifiers available, with a 1968 review marking its early presence in the high-fidelity market.
Specifications
| Model Rating Type | Solid-state stereo preamplifier |
| Frequency characteristic | Aux : 10 Hz to 100 kHz ± 0.5 dB |
| Frequency characteristic | Phono : 20 Hz to 20 kHz ± 1 dB |
| Total harmonic distortion factor | 0.05% or Less (2 V Output, 20 Hz ~ 20 kHz) |
| Cross modulation distortion factor | Not more than 0.05% |
| Signal-to-noise ratio | Phono : 70 dB (10 mV input) |
| Signal-to-noise ratio | Aux : 85 dB (0.5 V input) |
| Tone control | Bass : ± 16 dB (50 Hz) |
| Tone control | Treble : ± 12 dB (10 kHz) |
| Output level | 10 V (Hi impedance) |
| Output level | 5 V (600 Ω) |
| Input impedance | Phono : 47k Ω |
| Input impedance | Tape head, High level : 100k Ω |
| Audio output | 600 Ω |
| Tape | 600 Ω |
| Input terminal | Mag (Hi, Low, one system each), Ceramic, Tape head, Tape amp Tuner, Spare (2 sets), Special (Mic, Phono 2) |
| Output terminal | For Audio (2 sets, 1 set with switch) |
| Front panel output | For tape recording |
| Semiconductor used | Transistor : 8 |
| Semiconductor used | Diode : 2 pcs |
| Power consumption | 5W |
| External dimensions | Width 345x Height 105x Depth 205 mm |
| Weight | 4.5kg |
Design
The PAT-4 uses only four transistors per channel to fulfill its functional requirements, minimizing sonic coloration through refined circuit design. It features a double-channel configuration allowing independent operation of left and right channels, and includes a high-cut filter switchable in three stages. The tone control circuit delivers a completely flat response at the midpoint. Designed for versatility, it can drive a 600 Ω load, making it suitable for professional applications. It also includes stereo/mono switching with Ach, Bch, and Blend functions operated via two rocker switches. A front-panel spare input allows connection of a tape deck or microphone. Dynaco provided a schematic for an optional input equalizer for the PAT-4.
Product Family
The PAT-4 was developed as the second series in Dynaco’s solid-state amplifier line, following the ST-120 power amplifier, and retains key advantages of the earlier PAS-3X preamplifier.
Market
Common issues reported include non-functional front panel lights and incompatibility with modern cables. Restoration resources exist, including service checks, control cleaning, and replacement parts available through specialty suppliers like Updatemydynaco.com.
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