PAS-4 Vacuum Tube Preamplifier Owner's Manual VACUUM TUBE PREAMPLIFIER R PAS-4 CD VIDEO AUX SOURCE TUNER 2 to 1 SOURCE TAPE 1 1 to 2 TAPE 2 LEFT RIGHT EPL PHONO IN INPUT TAPE DUBBING TAPE MONITOR BALANCE PAS-4 Vacuum Tube Preamplifier MONO IN VOLUME POWER
Contents Introduction ...................................................................................... 3 Rear Panel Inputs and Outputs ....................................................... 4 Fuse ................................................................................................. 4 Operation ......................................................................................... 5 Tube Replacement ..........................................................................
Introduction Congratulations on your purchase of the Dynaco PAS-4 preamp. This preamplifier was designed to provide the highest combination of quality and value available, which is the Dynaco tradition. Only very high quality components have been used in manufacturing the PAS-4. Examples of this are the low noise metal-film resistors, polypropylene film capacitors, and selected (tested) vacuum tubes.
Rear Panel Inputs and Outputs Inputs - Phono These inputs will accommodate "moving magnet" or high output "moving coil" cartridges which have output levels of 1.0mV or higher. In the lower right hand corner of the rear panel is the preamp's chassis ground terminal. This thumbscrew is provided for attaching the separate ground wire often provided on turntables. (see Minimizing System Noise on page 11) Inputs - Tuner, CD, Video, Aux.
Operation Turn-On Delay and Visual Indicator When you turn on the PAS-4, the lamp above the PWR (power) switch glows GREEN and a timer circuit is evoked which keeps the preamp outputs at zero volts during the warm-up period. This 45-second warm-up period allows the tube filaments to fully heat, the high-voltage section of the power supply to reach full potential, and for the preamp output circuitry to settle, (avoiding loud turn-on "thumps").
Balance Control This adjusts the proportion of left and right channel signals going to the preamp's line level amplification stage (and therefore to the preamp's main outputs). Only the left channel signal will be heard with the Balance Control turned fully counter-clockwise, and only the right channel signal with full clockwise rotation.
Tube Replacement CAUTION: Before replacing tubes on your PAS-4 ensure the AC power cord is un- plugged from its AC (wall) outlet (or that the AC power cord is unplugged from the back of the unit) and wait for three minutes to allow the high voltage power supply to discharge. Gloves may be worn when changing tubes. Never touch live circuit elements in vacuum tube equipment because lethal voltages are present when these are turned on. The tubes in your PAS-4 could provide 5,000 to 10,000 hours of use.
Alternate Tube Types It is true that vacuum tubes made by different manufactures can actually sound different. The amount and type of sonic differences can be subtle or fairly obvious to a discerning listener. Also, tube reliability and longevity often varies according to manufacturer. Vacuum tube manufacturers are still introducing new versions of older tube designs. These new designs are commonly labeled with partly or wholly new part numbers.
Minimizing Noise in the System Hum is caused by amplification of the 50 or 60 Hz AC power line signal that is transmitted via the magnetic fields around power transformers and power cables. RF interference usually comes from inadequate shielding of cables or components.
Warranty For three years from the date of purchase (one1 year for tubes) Dynaco will repair, for the original owner, any defect in materials or workmanship that occurs in normal use, without charge for parts or labor. It is the owner's responsibility to provide transportation to the authorized Dynaco service representative who will perform warranty service, and to present proof of purchase in the form of a dated sales slip when requesting service.
PAS-4 Specifications Phono Section GAIN: 40 dB RIAA ACCURACY: +/- .5 dB from 20 Hz to 20 kHz PHONO OVERLOAD: 500mV RMS @ 1kHz MAXIMUM OUTPUT CAPABILITY: 60V RMS @ 1kHz THD: INPUT IMPEDANCE: 50V RMS @ 20kHz (for 1% THD) less than .025% @ 2V RMS Output 47k shunted by 10pF TAPE OUTPUT IMPEDANCE: 2k NOISE: -86 dB below 10mV RMS Input ABSOLUTE PHASE: Non-Inverting TUBE COMPLEMENT: 2ea 6DJ8 (6922); 2ea 12AX7 (ECC83) Line Section GAIN: 18.
EQ IN EQ OUT TAPE 2 IN TAPE 2 OUT TAPE 1 IN TAPE 1 OUT AUX VIDEO CD TUNER PHONO RIGHT INPUTS EQ IN EQ OUT TAPE 2 IN TAPE 2 OUT TAPE 1 IN TAPE 1 OUT AUX VIDEO CD TUNER PHONO LEFT INPUTS 2K R102 2K R101 2K R2 2K R1 8 9 8 7 9 10 1 2 3 2 3 4 16 SW4A SW2A 22 12 11 10 SW4B SW2B TAPE DUBBING 19 SW1B INPUT SELECTOR ACTIVE INACTIVE EQUALIZER 19 7 11 5 6 4 TAPE DUBBING 13 SW1A INPUT SELECTOR ACTIVE INACTIVE EQUALIZER 13 1 5 8 2 7 9 1 3
1 2 4 G L N 2A /100V 2A /115V 1A / 230V F1 FAST BLOW POWER ENTRY MODULE C204 C203 R201 100 C201 .01uF 1.4KV BLK 100V 0.0V .01uF 1.4KV (x 2) AC POWER SW7A BRN WHT 115V 230V BRN/WHT 50/60 Hz 100/115/230 VAC T1 GRN GRN R206 30K R205 20K RED RED D4 D3 C206 33uF 450V 470 3W R202 C219 4700uF 25V FWB1 600V 35A C207 1000uF 6.3V I 19.5V @ 1A R204 1M 1W R203 332K O C220 22uF 25V G U1 7812 -3.
PAS-4 PC Board Parts List DESCRIPTION DESIGNATORS Resistors 100 ohm, 1/2W, metal film R201 140 ohm, 1/2W, metal film R28, 128 221 ohm, 1/2W, metal film R21, 25, 121, 125 249 ohm, 1/2W, metal film R12, 112 301 ohm, 1/2W, metal film R9, 11, 20, 23, 109, 111, 120, 123 470 ohm, 1/2W, metal film R210, 211, 212, 213, 214, 215, 218, 219 1.37K, 1/2W, metal film R4, 104 2.0K, 1/2W, metal film R1, 2, 101, 102 5.6K, 1/2W, metal film R18, 118 6.
PAS-4 PC Board Parts List (cont.) DESCRIPTION DESIGNATORS Capacitors (cont.) 10.uF, 25V, alum electrolytic C222 22uF, 25V, alum electrolytic C220, 223 22uF, 250V, alum electrolytic C212 33uF, 450V, alum electrolytic C205, 206 470uF, 25V, alum electrolytic C221, 224 1000uF, 6.
