Dynaco PAT-5 Preamplifier

Pat-5 Bi-FET from eBay auction #404977011

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parts list,
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Frequency Response:

High level inputs: ±1 dB from 10 Hz to 50 KHz.
Low level inputs: 0.5 dB of RIAA curve.

Distortion at 2 volts output into 10,000 ohms in parallel with 1000pF:

THD: 0.007% or less, 20 Hz to 20 KHz.
IM: 0.007% or less with any combination of frequencies.

Hum and Noise:

Magnetic Phono: 70 dB below a 10 mV input, at 1000 Hz.
High level: 90 dB below a 0.5 volt input.


Magnetic Phono (LO) to Audio Out: 57 dB at 1 KHz.
Magnetic Phono (HI) to Audio Out: 63 dB at 1 KHz.
Magnetic Phono (LO) to Tape Out/E.P.L. Out: 37 dB at 1 KHz.
Magnetic Phono (HI) to Tape Out/E.P.L. Out: 43 dB at 1 KHz.
High Level to Audio Out: 20 dB.
High Level to Tape Out/E.P.L. Out: unity.

Phono Input Acceptance:

LO: Greater than 115 millivolts at 1 KHz.
HI: Greater 45 millivolts at 1 KHz.

Tone Controls:

Bass: ±16 dB at 50 Hz.
Treble: ±12 dB at 10 KHz.


Low: -4 dB at 10 Hz; 6 dB per octave. (Conforms to newly revised RIAA phono playback curve)
High: -10 dB at 10 KHz; 15 dB per octave.

Voltage Output:

10 volts into 10,000 ohms or greater.
4.5 volts minimum into 1000 ohms.


Magnetic Phono: 47,000 ohms in parallel with 220 pF.
High level: 50,000 ohms
Tape Output:
From phono inputs, 15,000 ohms or greater may be connected.
From high level inputs, same as source.
Audio Output: less than 600 ohms

Separation at 2 volts output into 10,000 ohms; undriven input terminated in 5K:

20 Hz: 70 dB minimum.
2 KHz: 70 dB minimum.
20 KHz: 45 dB minimum.

Semiconductor complement: 13 transistors; 2 integrated circuits; 3 zener diodes; 4 diodes.

Dimensions: 13-1/2" x 4-1/4" by 11-3/4".

Power Consumption: 12 watts, 120V or 240V, 50/60 Hz AC.

Shipping Weight: 13 lbs. (5.9 kilos)

Designed by:

Wade Burns

Year Introduced:



$239.00 kit
$399.00 assembled


Dyna's replacement for the venerable PAT-4, adding such niceties as a high-power switchable outlet, speaker selector and terminals, dual tape monitors, an external "processor loop" intended for EQs or other signal modifiers, and an op-amp high-level stage. The BI-FET term is a trademark of National Semiconductor for the JFET LF357H IC used in the PAT-5 BI-FET version. This replaced the NS LM301 opamp in the PAT-5 preamp in 1977, opening the door for numerous audiophile mods including the highly acclaimed Frank Van Alstine and Walt Jung upgrades.

Thanks to Rich Hollis for info regarding the LF357H.

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