Dynaco PAT-4 Preamplifier

View the
parts/PC board layout
for the PAT-4.


The Dynaco PAT-4 is an all silicon solid state control center and preamplifier which must be used in conjunction with a basic power amplifier, such as the Dynaco Stereo 70 or Stereo 120, and a pair of loudspeakers. In addition, the PAT-4 provides sufficient power for a pair of 600 ohm headphones. When headphones only are to be used, a power amplifier is not required.

All input signal sources, such as a phonograph, radio tuner, tape recorder, etc., are connected to the inputs of the PAT-4 and this preamplifier is the control center for all mono and stereo signals. Thoughtful planning has provided exceptional flexibility to accomodate future requirements for such sources as a second phonograph or a microphone, television sound, musical instruments requiring electronic amplification, etc. A standard phone jack input and output on the front panel enables convenient connection of a tape recorder or headphones, even when the preamplifier is installed in a cabinet.

The components in the PAT-4 are the highest quality to protect against failure, and all parts are operated conservatively with close tolerances to assure continued proper operation. The transistors have been specially selected for minimum noise and distortion in sustained use and the etched circuit modules have been pretested in the circuit to ensure that every unit, after assembly, will meet the specifications normally associated only with laboratory prototypes.

The specifications of the PAT-4 speak for themselves. The distortion and noise, up to levels well beyond those required to drive any conventional amplifier, are comparable to the finest tube designs and below the levels which can be accurately measured with commercial grade test equipment. Specifications cannot define all the facets of superior audio performance, however. In use with varying program material, the PAT-4 achieves its design goals of sonic ease and naturalness always sought but rarely achieved in solid state designs. Ther eis remarkable clarity and an impression of direct contact with the original without the extra brightness or stridency which, unfortunately, is sometimes attributed to high fidelity sound.


Frequency Response:

High level inputs: ±0.5 dB from 10 Hz to 100 KHz
Low level inputs: ±1 dB from 20 Hz to 20 KHz

Distortion at rated 2 volt output:

THD less than 0.05% 20 Hz to 20 KHz
IM less than 0.05% with any combination of test frequencies

Hum and Noise:

Magnetic Phono: 70 dB below a 10 mV reference signal
High level: 85 dB below a 0.5 volt signal


Magnetic Phono: 54 dB at 1000 Hz
High Level: 20 dB

Tone Control Range:

±16 dB at 50 Hz
±12 dB at 10 KHz

Maximum Output: 10 volts into high impedance; 5 volts into 600 ohms.


Magnetic Phono: 47,000 ohms
Tape Head: 100,000 ohms
High level: 100,000 ohms
Audio Output: 600 ohms
To Tape:
From low level inputs, 600 ohms ohms.
From high level inputs, same as source

Amplifier input: Nominal load 10,000 ohms or higher


Low level or high level RIAA magnetic phono or ceramic phono
NAB 7-1/2" tape head
Special (normally microphone)
Tape amplifier
Spare high level or TV, etc.
Front panel high level

Outputs: Tape output ahead of controls; 2 Audio outputs (one switched by front panel jack); Front panel outout.


Selector switch
Volume control
Balance control
2 Bass controls
2 Treble controls
High filter switch @ 15 KHz, 10 KHz, and 7 KHz
Loudness compensation switch
Tape Monitor switch
Low Filter switch
paired Stereo-Mono switches to provide A or B channels independently or combined (A+B) with 6 dB blend for 3rd channel output, or stereo
Illuminated power switch

Semiconductor complement: 8 transistors; 2 diodes.

Dimensions: 13-1/2" wide by 4-1/4" high by 9" deep.

Shipping Weight: 10 lbs.

Power Consumption: 5 watts.

Designed by:

Ed Laurent

Year Introduced:



$139.00 kit
$229.00 assembled


Dyna's first solid-state preamp, incorporating front-panel tape in/out jacks and a variable high filter.

This page created and maintained by Greg Dunn.
Copyright © 2000-2001 Greg Dunn