Packburn 325 User manual

electronics inc.
AUDIO NOISE SUPPRESSOR
MODEL 325 OWNER’S MANUAL
Packburn is Registered in U.S. Patent and Trademark Office
REV 10-1

electronics inc
AUDIO NOISE SUPPRESSOR MODEL 325
A single-ended noise suppressor designed to eliminate or reduce noises due
to imperfections in and damage to sound recordings in all analog audio media
and their digital reproduction, including cylinder, disk, film wire and tape
recordings, both monophonic and stereophonic
Model 325 contains three processors designed to suppress
transient noises (ticks, pops, clicks, crackle, scratch)
encountered in some 100 years of phonograph recordings,
wherever and however made, as well as the audible hiss
familiar in all audio media prior to the development of
successful encode/ decode noise suppression systems and,
more recently, digital audio.
Model 325 also incorporates a number of
necessities and conveniences for the optimum playback of
disk and cylinder recordings for best quality of sound.
The Switcher:
The first noise reduction processor in the Audio
Noise Suppressor is the Switcher. This is designed specifically
for the reduction of noises from monophonic disk and cylinder
recordings, taking advantage of the redundancy that exists in
these media: the same signal is engraved on each of the two
side walls of the groove. However, the distribution of
particulate matter in the record material (one cause of noise) is
random. Also, dirt, mildew and scratches do not affect each
side wall identically.
Prior to the development of the Packburn Switcher,
a monophonic disk or cylinder, if played back with a
stereophonic reproducing system, was best played by
summing (in the appropriate polarity) the signals from the left
and right channels. The Switcher does this when in the rest
position. However, at any moment when the reproduction from
the left or right channel is quieter (more noise-free) than the
sum signal, the Switcher can elect to reproduce just the quieter
groove wall. The Switcher switches among these three
possibilities (left, right, or sum) at a very rapid rate with
astonishing results. At lower frequencies (from 300 Hz down)
where switching would not accomplish anything, the two
channels are mixed to minimize rumble.
The idea of using the Switcher on vertical-cut
recordings may seem strange at first since there is only one
signal engraved in the bottom of the groove. However, the
vertically modulated signal is affected by disturbances in the
side walls of the groove. The Switcher is not as effective for
vertical recordings but it has a part to play.
The switching process is generally not applicable for
noise reduction of stereophonic records or of monophonic tape
recordings or broadcast. For these, transient noise
suppression must be achieved by the Blanker alone.
The Blanker:
The second noise reduction processor is the
Blanker. This is designed to cope with transient noises from
any source: whether from the output of the Switcher, where
noises remain that were common to both side walls of the
groove, or from a stereophonic disk recording. Also, it is
applicable to a monophonic tape, a broadcast or a CD record
of a disk recording that has transient noises. Note that the
Packburn Blanker works from any program source, in contrast
to some devices that require the vertical component of a
stereophonic disk to trigger their action.
The Blanker clips the amplitude of each individual
positive-going or negative-going pulsation of the noise
transient whenever it exceeds a threshold value determined by
the peak program level in the vicinity of the transient.
The Switcher plus the Blanker comprise the
Transient Noise Suppressor of the Audio Noise Suppressor.
The Continuous Noise Suppressor:
The third noise reduction processor reduces audible
hiss-or white noise, whatever one prefers to call it. It is a
constant annoyance in just about every cylinder, disk, wire,
analog tape or film recording made prior to the development of
successful encode/ decode systems of noise suppression,
followed by digital mastering.
This noise is perceived by the human ear as being
of a fairly continuous nature in contrast to the pops, ticks, and
clicks of transient noise and therefore, we call our third
processor the Continuous Noise Suppressor. This processor
comes third because it is expeditious to suppress the transient

noises first. In the case of recordings containing no transient
noise, such as analog master tapes and copies thereof, the
Continuous Noise Suppressor will be the only one needed.
The Continuous Noise Suppressor is a variable low-
pass filtering circuit that responds in accordance with the
nature of the program material. When the program material is
quiet and contains little in the way of high frequency energy,
the high frequencies that the listener is aware of are almost
entirely those in the noise. The cutoff frequency of the filter
closes down to its lowest value. In loud and/ or brilliant
passages when the signal is effectively making the noise, the
cutoff frequency assumes intermediate values. The operator
controls the extent to which the filter closes down and opens
up, so a substantial reduction of hiss can be achieved without
audible degradation of the program material and without the
swishes and pumping that have been the undesirable by-
product of similar devices.
Metering of the input: The two input channels are metered to
assure that the proper signal levels are provided to the Audio
Noise Suppressor. Metering takes place after the input level
control and before the channel balance control.
Channel balance control and audition of difference signal:
the balance control is needed for balancing of signals into the
Switcher when playing monophonic disk or cylinder recordings.
In reproducing vertical-cut recordings, the balance control also
serves as a canting control. Audition of the difference signal
as well as of the sum signal allows one to set the channel
balance or canting adjustment with accuracy.
Test Switch: This switch enables selection of either the
quieter or noisier groove wall by the Switcher. It is useful for
demonstration and diagnostic purposes. Also, in the case of a
full-width monophonic tape recording in which the oxide is
flaking off, one can play it with a two-track head and use the
Switcher to choose the momentarily louder channel and thus
avoid dropouts.
FACILITIES ADDITIONAL TO AND SUPPORTIVE OF THE
NOISE REDUCTION PROCESSORS
A number of necessities and conveniences are included in the
Audio Noise Suppressor to assist the user in achieving
optimum performance with disk and cylinder playback as well
as other signal sources, as follows:
Playback from either channel: There is the ability to play
from either channel separately of a monophonic disk or
cylinder with the lower frequencies of the two channels mixed
so as to eliminate rumble. This is a necessity in reproducing
those occasional recordings in which one side wall is
consistently noisier than the other. Such a condition can
indicate that the optimum stylus is not being used, but some
recordings persist in this behavior with any stylus that one may
try. For these recordings it is preferable to play from just the
quieter side wall of the groove and use just the Blanker for
transient noise suppression.
Transient Noise Suppressor can be switched out:The
Switcher plus the Blanker, which constitute the Transient
Noise Suppressor, can both be switched out by means of a
single toggle switch whenever one wishes to process a
recording only through the Continuous Noise Suppressor
.
Eight position bass equalization switch: This allows
selection of the commonly used bass equalization curves for
78s manufactured prior to the recording industry’s
standardization on the RIAA curve in 1953. Also includes the
RIAA curve.
Six position treble equalization switch: This allows
selection of the commonly used treble equalization curves for
78s as well as for those long playing records that were
manufactured prior to the recording industry’s standardization
on the RIAA curve in 1953. Also includes the RIAA curve.
Cutoff frequency meter: This meter displays the ever-
fluctuating value of the cutoff frequency when the Continuous
Noise Suppressor is operating.
Bypassing the Audio Noise Suppressor: The Audio Noise
Suppressor is provided with a bypass relay. This connects the
output terminals to the input terminals when the power is OFF
or when the ANS switch is in the “0” position. Thus, the Audio
Noise Suppressor is easily removed form the circuit when it is
not needed.
HALF THE
HEIGHT
(3.5 INCH)
ATTACHABLE 19
INCH RACK
MOUNT EARS
THREE NOISE
REDUCTION
STAGES
EQUALIZATION
SETTINGS FOR LP
AND EARLY
RECORDS
(8 TURNOVER,
6 ROLLOFF)
TABLE TOP
DESIGN
ERGONOMIC
CONTROL
LAYOUT

SOME USERS OF THE PACKBURN AUDIO NOISE
SUPPRESSOR
Customers are telling us -
“Simple to use…just sit back and listen!”
“Good hiss, pop and click elimination!”
“Improved musical clarity!
“The controls are easy to operate!”
“Preserves the original sound – serves archival purposes
well”
And for those who have returned their Packburn machines
for upgrading to the model 325 performance level * -
“The blanker and continuous noise suppressor are more
effective even on LP records.”
“There is less low frequency rumble on older records
including vertical-cut records.”
* Consult factory for details
APPLICATION NOTES
78s: The success of the Audio Noise Suppressor is most
spectacularly demonstrated with noisy 78 rpm disks, as these
present a continuous stream of ticks, pops, etc. the
suppression of which is immediately demonstrable. The same
applies to excessively ticky, scratchy or dirty 45s and long play
disks. You can instantly hear how the Switcher reduces the
crackle. Next you can turn on the Blanker and hear the major
role that it plays in eliminating or reducing noise from
scratches and cracks. Then you can adjust the Continuous
Noise Suppressor for the final improvement. You can even
operate the TEST switch and hear the effect of choosing the
noisier groove wall.
45s and long play disks. You can instantly hear how the
Switcher reduces the crackle. Next you can turn on the
Blanker and hear the major role that it plays in eliminating or
reducing noise from scratches and cracks. Then you can adjust
the Continuous Noise Suppressor for the final improvement. You
can even operate the TEST switch and hear the effect of
choosing the noisier groove wall.
Long Play and Stereo Disks: The improvement of these
requires more patient observation if they have not been abused,
as these have only occasional and pops, some of which,
however, can reproduce as loud as a pistol shot. The Blanker
reduces the pistol shots to innocuous thumps. Lesser noises are
turned into slightly noticeable thuds when they are not totally
eliminated. The Continuous Noise Suppressor effectively and
unnoticeably reduces the hiss.
45s and polystyrene long play records, with their higher hiss
level, are nicely served by the Continuous Noise Suppressor.
Acetates: These can range from worn and deteriorating disks
to extremely quiet, mirror-surfaced beauties. The Audio Noise
Suppressor handles the difficult ones like bad 78s, the good
ones like fine long playing disks.
Vertical-cut Recordings: This includes acoustical disks and
cylinders and electrical broadcast transcriptions. Both the
Switcher and Blanker have a major effect in reducing transient
noises from broadcast transcriptions. With acoustical disks and
cylinders the Blanker plays the major role in reducing the
transient noises. The Switcher can be turned up slightly for some
assistance in the noise reduction. The Continuous Noise
Suppressor can be applied to good effect in reducing the
remaining hiss.
78 Transfers to tape or long playing records: Many tape
copyists and record producers mistakenly transferred 78s with
the RIAA curve, which reduced surface noise but also took much
of the life out of the sound of a voice or instrument. In playing
back from such a source, one can restore the treble equalization
and then use the facilities provided by the Audio Noise
Suppressor to suppress the noises in the proper manner.
Analog Master Tapes and Film: The Continuous Noise
Suppressor is very successful at unobtrusively reducing the hiss
level of analog master tapes or copies thereof.
CDs: We claim no applicability of the Audio Noise Suppressor
to CDs mastered from original digital tapes. However, CDs
derived from 78s, from old movie sound tracks or from master
tapes that antedate the introduction of encode/decode noise
reduction devices all are instances where the Audio Noise
Suppressor has a role to play, whether on the part of the CD
producer or the consumer. If the producer chooses to ignore
what the Audio Noise Suppressor can do to improve his
product, the consumer can do it on his or her own!
Broadcast reception in general can benefit from use of the
Continuous Noise Suppressor if there is audible hiss, whether
the source of the hiss is in the program material or in the
conditions of the reception. Broadcasts of historical material, if
equalized with the RIAA curve (as it often is) can be corrected
and transient noises can also be suppressed.
Regarding copies, In general: The Blanker has to be relied on
to provide whatever transient noise suppression is to be
achieved. However, it must be recognized that recordings
processed into long playing disks or into radio broadcasts are
subject to equalization, compression and limiting and probably
are also several copying generations removed from the original.
All of these circumstances can tend to soften the leading edge of
a noise transient with the result that the detectability of the noise
transient by the Blanker circuit is lowered. Thus, as a general
rule, the Transient Noise Suppressor will be at its most effective
when it can be applied to the original recording.
The Continuous Noise Suppressor will not be affected in the
same way. It will just have more to do.
Carefully made stereo tape transfers of a monophonic disk or
cylinder—especially a digital tape—can provide good results,
as the Switcher can be employed and there should be no
appreciable degradation of the noise transients that would
reduce the effectiveness of the Blanker.
Record Restoration: Application of the Continuous Noise
Suppressor is best deferred to the final stage of processing by
those doing record restoration. In such applications, one would
use the Transient Noise Suppressor at the start. After filtering,
equalization, volume expansion, adding reverberation, etc., one
can then use the Audio Noise Suppressor a second time, this
time by-passing the Transient Noise Suppressor and using only
the Continuous Noise Suppressor.
Quadraphonics — Surround Sound — Ambience Systems
— Electronic Reverberation: The spatial illusion of these
systems is seriously degraded when pops and "pistol shots"
disclose the presence of the ambience loudspeakers. With the
Audio Noise Suppressor one can even play 78s without any loss
of the spatial illusion.

Audio Noise Suppressor Model 325 Technical Specifications
Designed for professional installations and for quality home
sound systems
Outfitted to interface with 600 ohm balanced line systems or with the more customary single-ended Hi Fi systems;
Provided with XLR professional connectors as well as with RCA-type phono connectors for all signal input and
output terminations.
Power Line Voltages: U.S./ Canadian 105 volts 120 volts, 50/60 Hz
International: 210 volts-240 volts, 50/60 Hz (consult factory)
Power Consumption: 20 Watts
Size: Width: 19" (483 mm) for rack mount, 17” (432 mm) with mounting ears removed
Depth: 13" (332 mm), Height: 3.5" (89 mm).
Inputs and Outputs: There are two separate electronically balanced input channels. Separation throughout the
audio frequency range is maintained in processing stereo signals, in which each signal path
is provided with a Blanker, a Treble Equalization network and a Continuous Noise
Suppressor and then routed through a dual OUTPUT LEVEL control to the separate output
terminations.
In processing lateral-cut or vertical-cut recordings, the signals applied to the two input
channels are routed through a balancing circuit to the Switcher. Or, at the operator's choice,
with lateral-cut records, the signal of either channel may be individually selected for
processing. To reduce the audibility of low frequency disturbances, the bass portion of the
two input channels, is mixed in the proper polarity. The output of the Switcher is connected
to both of the Blanker + Equalizer + Continuous Noise Suppressor channels, and the fully
processed signal may be taken from either or both of the output channels.
Electronically balanced input. Single-ended input impedance is 100k ohms.
Electronically balanced output. Single-ended output impedance is less than 1 ohm.
Sensitivity: With INPUT LEVEL control all the way up, a 0 VU (1.23 v.) reading of the processing
level meters will be achieved by an input signal of — 6 VU or less from a 600 ohms line or
by 0.4 v. or less from a single-ended source. Range of control of INPUT LEVEL
potentiometer is 20 db.
With OUTPUT LEVEL control all the way up, there is unity gain from the metering circuit to
the output terminations.
Frequency Response: Bass response is within ± 1/2 db to 10 Hz.
Treble response is determined by the setting of the Treble Equalization switch and the
action of the Continuous Noise Suppressor.
Treble Equalization: is provided by the Audio Noise Suppressor by means of a six-position selector switch which
enables you to match the treble portion of published equalization curves of records, old and
new. Includes FLAT, FFRR, AES, RIM, LP.
Continuous Noise The Continuous Noise Suppressor is a low pass filter. Cutoff frequency varies from 2.5 kHz to 18 kHz
Suppressor Action: in accordance with the dynamics of the program material and the nature of the surface noise.
Alternatively, a fixed cutoff frequency may be selected. Meter on front panel reads the cutoff
frequency. Filter has a slope approaching 12 db per octave.
IM Distortion: 60 Hz and 7 kHz, 4:1 at + 4 vu (1.23v.) input: Less than .05%
S/N Ratio: (Unweighted) – At least 75 dB with reference to + 12 vu (3 v.).
Warranty: A full five year’s warranty on both parts and labor.
About your Record To take advantage of the Switching process, you must have equipment to play back discs or
Playback Equipment: cylinders stereophonically. The two channels of reproduction must be closely matched in
frequency response.
Demonstration CD: Available on request
electronics inc. P.O. Box 226 Syracuse, NY 13215 U.S.A.
Ph 315-476-9121
Covered by one or more of the following US patents: 4,151,471; 4,155,041; 4,259,742; 4,322,641; 7,035,417

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TABLE OF CONTENTS
Foreword
Pg: 3
Installation of the Audio Noise Suppressor
4
Controls (Front Panel Description)
7
Getting Started
12
Technical Principles of Operation
15
Suggestions for Optimum Processing of Historical Recordings
17
Vertical Cut Records (Edison Diamond Disc, Hill and Dale)
20
Recommendations for Preserving Historical Media
21
CD’s – Tapes – Broadcasts
22
The VU Meters
24
Optimizing Other Components in Your Audio System
25
Trouble-Shooting Procedures
28
Equalization Settings for Early Recordings
31
Interface Diagram
36

2

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Foreword
Packburn Electronics, Inc. has been in business for over 25 years, inspired by the late
Richard C. Burns. What got the company running was Dick’s passion for historical sound
recordings and inventive playback equipment that would rescue musical nuances in a safe
and effective manner from the assault of unwanted noise. Our modest goal was to improve
the sound quality of our personal record collections but it was quickly discovered that our
noise suppressor was of interest to others. Our founding principles of safe noise reduction
and ease of operation are still alive and carry into our latest patents and our Model 325
Audio Noise Suppressor.
We appreciate your purchase of our product, and we want this unit to work for you as well
as it has for us in the time that we have spent with it. The unit has gone through extensive
testing, a one week run-in, and a listening session with test records.
The instruction manual describes how to use the Audio Noise Suppressor with a wide variety
of historical sound recordings. For casual listening you will probably develop settings that
apply to a given recording format. For meticulous copying of records, you will want to
check the settings for each individual recording.
The Audio Noise Suppressor consists of three noise reduction stages called the ‘Switcher’,
the ‘Blanker’, and the ‘Continuous Noise Suppressor’ (or CNS.) As you gain experience and
confidence in its operation, you will learn that the Audio Noise Suppressor is perpetually on
guard, acting to suppress noises as they occur. Those who already have a reasonably well-
adjusted audio system usually get the unit quickly connected and working and proceed to
"enjoy".
Wishing you pleasurable listening,
Thomas N. Packard
President

4

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Installation of the Audio Noise Suppressor
A. The Turntable
A stereo cartridge needs to be used even for monophonic phonograph records. If a
monophonic record is played back using a monophonic cartridge, the first noise reduction
stage (Switcher) won’t operate to remove noise. For those using the PACKBURN for
playback of 78 RPM records, stylus suggestions are provided on p. 17.
B. The Pre-amplifier (for providing signal to the PACKBURN Audio Noise Suppressor)
The pre-amp needs to be stereo. Treble and bass controls should be set “flat”.
In the “phono” mode, some pre-amps come with “roll-off” and “turn-over” equalization
controls. The turn-over control should be set “flat” or to “0 dB” and the roll-off control should
be set to “RIAA” or “500 Hz”. These settings result in the most effective noise suppression
for all types of records. Equalization is then facilitated with the PACKBURN Audio Noise
Suppressor by way of its own rolloff and turnover controls.
Some pre-amps don’t have rolloff and turnover controls and thus don’t provide the optimum
flat rolloff for phonograph records. If you cannot have your preamp modified, there are
other options:
(a) Try using the pre-amp you have, being careful to boost by the same amount the left
and right treble controls. You may not achieve optimum performance, but the
PACKBURN will still accomplish a substantial amount of noise reduction.
(b) Install a stereo equalizer between the preamplifier and the Audio Noise Suppressor.
This is similar to option (a) but is a more accurate way to counteract the rolloff curve
of the preamplifier. For information on how to adjust the equalizer, refer to Stereo
Equalizer Ahead of the Audio Noise Suppressor on p. 25.
(c) Consult our factory. The PACKBURN Audio Noise Suppressor has a factory-
settable feature that accurately counteracts the roll-off curve in the pre-amplifier.

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(d) Install a pair of passive equalizers between the preamplifier and the Audio Noise
Suppressor. For an example of a design, refer to Installation of a Passive
Equalization Network Ahead of the Audio Noise Suppressor on p. 25.
C. Equipment Following the PACKBURN Audio Noise Suppressor:
Signal processing devices such as equalizers, filters and sonic enhancers may be connected
to the output of the Audio Noise Suppressor to further improve the signal that is being
reproduced.
D. Input and Output Connections to the PACKBURN Audio Noise Suppressor:
The Audio Noise Suppressor accommodates typical high fidelity systems and professional
audio installations. The stereo pre-amp output or other stereo signal processing device
connects to the input of the PACKBURN. The PACKBURN installs in the audio system much
as one would install a stereo equalizer.
The RCA connectors are used for a typical high fidelity system. For professional audio
systems, the three prong connectors are used. Pin 1 of the three prong connector is
grounded and for single-ended (unbalanced line) systems, signal may be provided on either
pin 2 or pin 3. For 600 Ohm balanced line systems, signal is provided on both pins 2 and
3. When utilizing the RCA connectors, it is prudent to insert the grounding adapters
provided by PACKBURN into the three prong input connectors. The adapters ground the
unused pin 2 inputs.

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Front Panel Controls
1 2 3 4 5 6 7 8 9 10 11
12 13 14 15 16 17 18 19 20
1L- left input level
11 Power - Packburn on/off
2 R- right input level
12 Mode - selects how input signals to be processed
3 Input Level - adjusts meter readings
13 TNS – transient noise suppressor (switcher and
blanker) on/off
4 Bal - balances inputs if Mode in Mon or Ver
14 Test - normally leave in “0” see instructions
5 Rate - Switcher sensitivity
15 Switcher - on/off
6 Rate - Blanker sensitivity
16 Blanker - on/off
7Low - CNS minimum cutoff frequency
17 CNS - continuous noise suppressor on/off
8 CNS cutoff frequency
18 Turnover - low frequency equalization
9 Rate - CNS sensitivity
19 Roll-off - high frequency equalization
10 Output Level - adjusts output terminal levels
20 ANS - audio noise suppressor (TNS and CNS) in
or out of system
A. Enablement Controls (INPUT/ OUTPUT LEVELS, POWER, ANS, TNS, CNS)
INPUT LEVEL is set for proper readings on the L (left input) and R (right input) VU meters.
Music or speech should have peak readings at about or slightly above 0 VU. If an occasional
tick causes the meter needle to go off scale or the meter readings to mismatch, do not worry
about it if the program levels are correct. The input level control boosts the input signals up
to +20 dB.
OUTPUT LEVEL sets an output level that is convenient for the user, the input level already
having been set for proper VU meter readings. The PACKBURN provides unity gain (input
and output terminal signal levels match each other) when the two controls are at 12:00 and
also for other settings.

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POWER provides line voltage to the PACKBURN. When in the off position, the left input
is directly fed to the left output and also the right input is directly fed to the right output.
This means that even when the PACKBURN is not powered, your audio system will have
signal continuity.
ANS (audio noise suppressor) sets the PACKBURN in or out of your audio system. When
switched out (‘0’) the left input is directly fed to the left output and also the right input is
directly fed to the right output. When switched to ‘1’ the left and right inputs are fed to the
outputs through the PACKBURN.
This switch allows the user to perform a full “A - B” comparison test on the PACKBURN.
However, in order for this test to be valid, the signal levels at the input and output terminals
of the PACKBURN must match one another and the PACKBURN equalization curves must
be flat (turnover control set to RIAA, and rolloff set to 0 Hz.) Further, for a comparison
involving the mode switch in “mon”, the amplifier following the PACKBURN should be
switched to monaural. All of this makes for a “complete in-out” comparison of the device.
There is a less complete but much easier alternative: An “A - B” comparison is performed
on just the noise reduction stages of the PACKBURN by simply turning the TNS and CNS
switches on or off, no other adjustments being needed.
TNS (transient noise suppressor) turns the Switcher and Blanker noise reduction stages on
or off, overriding the individual Switcher and Blanker on-off switches. These noise reduction
stages reduce ticks and clicks and may reduce hiss if made up of a succession of small
clicks, all of this referred to as transient noise.
CNS (continuous noise suppressor) turns the CNS noise reduction stage on or off. This
stage reduces hiss.

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B. MODE Switch
This switch determines how the PACKBURN is to process the input signal. In the ST
(stereo) position, the PACKBURN treats the input as having two different musical signals
and so feeds stereo to the L and R outputs. When the switch is set to all of its other
positions L (left), R (right), MON (monaural) or VER (vertical), the PACKBURN treats the two
musical input signals as having little and usually no stereo content and so converts the input
signals into a matched, monaural signal at the left and right outputs. The signal on each of the
two output channels is predominantly the following:
L Left input signal,
R Right input signal,
MON Mix of Left and Right input signals,
VER Mix of Left and Right input signals phased for vertical-cut (Edison)
cylinders and discs,
ST Left input signal provided to left output,
Right input signal provided to right output.
The “MON” position is normally used for monaural tape, film, 78, 45 or 33-1/2 RPM records
or signal sources.
The “VER” position is used for monaural 78 RPM vertical cut records such as Edison
cylinders or diamond discs.
The “L” or “R” positions are normally used for purposes of adjusting the BAL (balance)
control or selecting the correct stylus size for the most exacting work, as will be described
below. However, you may find occasions when the L or R positions provide best noise
reduction, so feel free to use them.
The “ST” position is used for CDs, tape, film, 33-1/3 or 45 RPM records, or other signal
sources having noticeable stereo imagery.
.
C. Switcher Controls (BAL, RATE, TEST, SWITCHER-on/off)
The Switcher is the first noise reduction stage. The Switcher reduces pops and clicks and
may reduce hiss if made up of a succession of small clicks, all of this being referred to as
transient noise. This stage is active only in the “MON” and “VER” positions of the mode
switch.

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TEST is normally kept in the off (‘0’) position. This switch provides a way to check the
effectiveness of the Switcher. In the off position the quietest input signal is always selected
by the Switcher for playback, whereas in the ‘1’ position the nosiest signal is always selected!
The comparison should be made with the Blanker and CNS stages turned off. The TEST
switch has some playback utility as well. Some customers have used it for monaurally
recorded reel-to-reel tape or film reproduced stereophonically. The “nosiest” input is always
selected, in this case the input not having a brief drop-out! Transient noise or continuous
noise on the tape or film is taken care of by the other noise reduction stages.
BAL (balance) matches the levels of the left and right input signals, something that is
important for optimum use of the Switcher. BAL. can be set by comparing the mode L and
mode R signals and adjusting until the two signals are equal. Alternatively, turn the
BLANKER and CNS off and MODE to “VER”. Set BAL. to the music null (cancellation of the
music). If the transient noise is canceling, the switcher won’t operate properly (see p. 15.)
Also, if there isn’t a null, make sure the treble and bass control settings in the pre-amp ahead
of the PACKBURN are the same. BAL. corrects up to a 6 dB mismatch between the input
signal levels.
(SWITCHER) RATE increases the sensitivity of the Switcher when it is adjusted clockwise.
As the sensitivity increases, the L, R, and M (mixed L and R) lights increasingly flicker,
indicating that the L and R input signals are being selected with increasing frequency over
the mixed monaural signal as the quietest signal for playback. If the L and R lights don’t
flicker to the same extent, make sure the input signals have been properly balanced. If the
balance is correct, the lights are just indicating that there is more noise in one input signal
than the other. The control is often operated at 5:00 (full clockwise rotation).
D. Blanker Controls (RATE, BLANKER-on/off)
The Blanker is the second noise reduction stage. The Blanker is a complimentary strategy for
reducing transient noise. The Switcher and Blanker form collectively the TNS (transient
noise suppressor).
(BLANKER) RATE increases the sensitivity of the Blanker when it is adjusted clockwise. As
the sensitivity increases, the L, R lights increasingly flicker, indicating that the left and right
input signals are being independently noise suppressed. These lights are conservative. It is

11
normal for them to respond to louder passages of music. A 3:00 control setting is a good
starting place for most records in fair condition. For 78 rpm records with hiss or long playing
records with scratches, higher settings are often beneficial.
E. Continuous Noise Suppressor Controls (LOW, RATE, CNS-on/off)
The CNS (continuous noise suppressor) is the third noise reduction stage. The CNS
reduces hiss, referred to as Continuous Noise.
LOW sets the lowest frequency in the input signals to be noise filtered. When the (cns) rate
control is set to 8:00 (fully counter-clockwise), LOW operates like a treble control and is set
to where the hiss is removed. The setting is best made during quiet passages of music. The
setting is displayed on the frequency meter. Typical LOW settings are 8:00 to 10:00.
(CNS) RATE sets how the CNS should react to louder or more brilliant passages of music.
The control is adjusted in the clockwise direction until these passages are not dulled. For
records in fair condition, the frequency meter should display a reading of 10 to 15 kHz during
loud or brilliant passages. It is okay for the frequency meter to go off scale. The optimum
setting of RATE may require LOW to be increased from its initial setting. Typical RATE
control settings are 10:00 and 12:00.
F. Equalization Controls (TURNOVER, ROLLOFF):
TURNOVER provides the most common eight low frequency (bass) equalization curves for
playback of 78, 45 and 33-1/3 RPM phonograph records, and also for cylinders. Refer to
Equalization Settings, pp. 31-35. For CDs, magnetic tape, video, film, broadcast or other
media, set turnover to “RIAA”. If you change the TURNOVER setting, it might be necessary
to change the input level setting.
ROLLOFF provides the six most common high frequency (treble) equalization curves for the
playback of 78, 45 and 33-1/3 RPM phonograph records, and also cylinders. Refer to
Equalization Settings, pp. 31-35. For CDs, magnetic tape, video, film, broadcast or other
media, set rolloff to “0”. If you change the ROLLOFF setting, it might be necessary to
change the CNS control settings.

12
Getting Started
1. Install the Packburn between your pre-amp and the stage of your audio system to
which the pre-amp was connected. Don’t connect the PACKBURN to the line
voltage just yet.
2. Preset these controls as shown :
POWER
INPUT LEVEL
BAL.
OUTPUT LEVEL
MODE
TURNOVER
ROLLOFF
TNS
TEST
SWITCHER
BLANKER
CNS
ANS
T
Off
12:00
12:00
12:00
ST
MON
VER
> >
> >
0
0
0
0
0
1
> >
Start with the power switch off.
For stereo music (CDs, tape, film, 45’s, 33-1/3 speed)
For monaural music (78’s, 45’s, 33-1/3 speed discs,film)
For vertical-cut (Edison) cylinders or discs
Set the bass equalization. See pp. 32, 34-35.
Set the treble equalization. See pp. 32, 34-35.
Start playing music. You should hear sound through your audio system
which is now bypassing the PACKBURN. If you don’t hear anything, check
your patch cables.
3. Connect the PACKBURN to 120 VAC (unless factory-set for 230 VAC).
POWER
On
At least one light should light. Also, you should still hear music, otherwise,
make sure that the output cable has not been plugged by mistake into the
input terminals.
4. Adjust the level controls:
INPUT LEVEL
OUTPUT LEVEL
> >
> >
Adjust the preamp ahead of the PACKBURN or INPUT LEVEL until the left
and right meters are reading 0 VU on the program (music).
Adjust OUTPUT LEVEL for level match when the ANS is switched
between ‘0’ and ‘1’, or to your liking.

13
5. Turn on just the SWITCHER (noise reduction stage 1)
MODE
TNS
TEST
SWITCHER
BLANKER
CNS
ANS
BAL.
(switcher) RATE
MON or
VER
1
0
1 ←
0
0
1
> >
> >
The switcher applies only to the MON and VER modes. Stereo records
not having much stereo imagery to sacrifice may be played in MON.
Stereo recordings are normally played in the ST mode. When the ST
mode is selected, the SWITCHER stage is automatically bypassed.
Select VER mode. Adjust BAL. for a null. Just the music should null, not
the noise, see p. 15. Alternatively, adjust BAL. for equal music levels
between mode R and mode L.
Adjust clockwise for best noise reduction without musical disturbance. It
is often set fully clockwise.
L, R and M lights should be flickering.
6. Turn on just the BLANKER (noise reduction stage 2)
MODE
TNS
TEST
SWITCHER
BLANKER
CNS
ANS
(blanker) RATE
L
R
MON
VER
ST
1
0
0
1 ←
0
1
> >
Select as desired.
Adjust clockwise for best noise reduction without musical disturbance. A
3:00 setting is typical for records in fair condition. L and R blanker lights
should be flickering.

14
7. Turn on just the CNS (noise reduction stage 3):
MODE
TNS
CNS
ANS
(cns) RATE
LOW
(cns) RATE
L
R
MON
VER
ST
0
1 ←
1
> >
> >
Select as desired.
TNS overrides the Switcher and Blanker switches.
Start at the 8:00 (full counter-clockwise) position.
Select a quiet passage of music. Adjust LOW as you would an ordinary
treble control to remove hiss. Ignore for the moment any dulling of the
music.
Select a loud passage of music. Adjust (CNS) RATE so the music is not
dulled. In newer recordings, the frequency meter should read about 10
kHz to 15 kHz during the most brilliant passages of music.
8. Turn on the noise reduction controls in combination (the Switcher, Blanker and CNS
stages are all turned on in the following example):
MODE
TNS
TEST
SWITCHER
BLANKER
CNS
ANS
MON or
VER
1
0
1 ←
1 ←
1 ←
1
Adjust switcher, blanker and CNS rates in combination
for the optimum result.
9. Turn on the noise reduction controls in combination for a Stereo recording (the
Blanker and CNS stages are turned on):
MODE
TNS
BLANKER
CNS
ANS
ST
1
1 ←
1 ←
1
When MODE is in ST, the Switcher is automatically bypassed.
Adjust blanker and CNS rates in combination
for the optimum result.