OWNER'S MANUAL
THE DAYTON WRIGHT Model 999
PRE-PREAMPLIFIER
Mark 1

DAYTON
WRIGHT GROUP LTD.

97 Newkirk Road North, Richmond
Hill,
Ontario L4C 3G4,
CANADA

Revised: February 22,
1985

TABLE
OF CONTENTS

Section
Title  (Page in printed manual)

GENERAL
INFORMATION
1.1
Introduction....................................(4)
1.2
Description....................................(4)
1.3
Warranty........................................(4)
1.4
Identification .................................(5)
1.5
Inquiries ........................................(5)

INSTALLATION

2.1
Introduction................................. (6)
2.2
Initial Inspection......................... (6)
2.3
Claims............................. ...........(7)
2.4
Preparation for use ...................(7)
2.5
Repacking for shipment............(7)

OPERATION

3.1
Introduction ............................................(9)
3.2
Controls & Connectors........................ (9)
3.2l
Use of BNC Connectors……….. (9)
3.22
Making up cables........................(10)
3.23
Adaptors……………..…….........(10)
3.24
Control Location………….....….(11)
3.25
Load Resistors.. .........................(11)
3.26
Opening the Case.......................(12)
3.27
Custom Loading .........................(13)
3.28
Output Level Adjustment............(13)

3.3
Power Supply Module..........................(14)
3.4
Hum & RF Problems............................(14)

PRINCIPLES OF OPERATION

4.1
Introduction............................................(15)
4.2
General Theory.....................................(15)
4.3
Block Diagram ....................................(16)

4.4
Specifics.................................................(17)
4.4l
Input Cascode Stage................(17)
4.42
Current Sink .............................(18)
4.43
Buffer & Second Cascode Stage. (18)
4.44
Output Stage............................ (18)
4.45
Regulators.................................(19)
4.46
Power Supply Module............. (19)

(page 2)

PERFORMANCE CHECK

5.1     Introduction
.............................(20)
5.2     Equipment Required
.............(20)
5.3     Distortion
Measurement....... (21)
5.4     Frequency Response
Measurement (21)

REPLACEMENT PARTS

6.1
Introduction........................ (22)
6.2
Parts List........................... (23)
6.3
Ordering Information ........(25)

SCHEMATICS & TROUBLE
SHOOTING

7.1     Introduction
.......................(27)
7.2     Schematics
......................(28)
7.4     Circuit Board
Layout....... (30)
7.5
Troubleshooting............... (31)
7.51   DC Voltages
...................(32)
7.6     Dis-assemble&
Reassembly (32)
7.7     Switch
Maintenence.........(32)

(page 3)

SECTION
1
GENERAL
INFORMATION
Introduction:

1.1     This manual covers the
installation, operation, and servicing of the Model Dw 999
Pre-preamplifier.

Description:

1.2     The DW-999 is a
Infranoise (very low noise) Pre-preamplifier which is designed to amplify the
low level low-impedance signals from a moving coil type of phono cartridge to
the level where they are sufficient to drive the phono input of a conventional
preamplifier.  This unit permits the user to select among several
cartridge load resistances, and if necessary, to install a special resistor to
match the required load.

The
circuit components are mounted on a double sided MIL-Grade-Epoxy Glass Circuit
Board which is housed in a robust welded aluminum case.  The Circuit Board
is selectively coated with a solder resist on both sides in order to prevent
solder bridging.

The Power
Supply is built into a separate case and supplies 30 volts DC to each channel of
the pre-preamplifier.  Both sections of the supply are electrically
isolated from each other.

The Left
and Right Channels of the Pre-preamplifier are both electrically and physically
isolated from each other on the circuit board in order to minimize any
interaction.  Both channels have individual and separate grounds.

As
supplied, the unit operates off 95 to 130 volts, 50 to 60 Hz mains.  The
power supply cord supplied is suitable for use in Canada and the United States
of America. Other operating voltages and cords can be supplied upon
request.

Warranty:

1.3     The DW999 is
warranted in the Continental United Statesof America and Canada under a LIMITED
WARRANTY as follows:

This Dayton Wright
Product is warranted against defects in both materials and
workmanship
for
a period of Two Years from the date of manufacture, or from a period
of
up to two years from the date of customer Purchase, the latter
in no
case
to exceed three years from the date of manufacture and in no
case
to be valid unless the customer has his original Bill of Sale
clearly
showing
the Date of Purchase and the Name and address of the dealer

from whom this unit
was purchased.  This warranty is voided
where this unit has been subject to
misuse or abuse.
Any usage of acid-core solder on this unit void the warranty as
does any
attempt
to modify the circuit and/or the components used in its
manufacture.
Once
return is authorized and the unit returned prepaid to the factory,
we
will repair or replace any parts which prove to be defective
within normal usage
and provided the warranty has not expired.  The Dayton
Wright Group Ltd.,’s decision
as to whether a unit has been abused shall be final and
binding.
No
other warranty is expressed or implied and The Dayton Wright Group
Ltd.
is not liable for consequential
damages.

Exclusion for damage
due to a lightening strike or power surge. Our warranty does not cover
anything that is damaged by any incident like this. As transistors or other
components may fail if subjected to a voltage spike, even after some months have
passed, if we are called on to effect a repair, any such work will be excluded
from any subsiquent warranty repair. It must be understood, in advance, that
should we attempt a courtesy repair, tat it is NOT under any warranty
whatsoever!

You may have additional warranty rights in
certain States.

Outside the United States and Canada your
warranty will be with the designated import agent for this product.

In the Continental United States and Canada, for
Warranty return authorization contact:

This information is
given only as it was supplied with the 555 Pre-preamplifier and may no longer be
current!

The Dayton Wright Group Ltd.

Customer Services

3-97 Newkirk Road

Richmond Hill, Ontario,

L4C 3G4, Canada,

Old number:(416) 884-8586

New number: (905 508-7500

Identification:

1.4     This manual applaes
to the DW999 Pre-Preamplifier only.  The Unit may be identified by the
1999" on the top of the case, the model and serial number located on the back of
the case, and the serial number on the circuit board itself.  The date of
manufacture is also on the circuit board.  Any attempt to alter any of
these numbers will void the warranty.

INQUIRIES:

This information
is given only as it was supplied with the 555 Pre-preamplifier and may no
longer be current!

1.5     Direct any inquiries
to:

The Dayton Wright Group Ltd.,

Customer Service,

3-97 Newkirk Road ,

Richmond Hill, Ontario L4C 3G4

Canada.

Always
identify the unit by the serial number and model number.  Shipments to the
above address will not be accepted unless prior arrangements have been made and
a return authorization obtained. Out of country customers are advised that it is
their responsibility to file the necessary export documents so that they will
have proof of export and thus avoid payment of duties upon the basic value of
the unit upon its re-entry to their country.

(page 5)

Section
2
INSTALLATION

Introduction:

2.1     This section
contains the information needed to perform an initial inspection of the DW 999
Pre-preamplifier as well as the installation steps normal to its use in an audio
system.  Also covered are the procedures to be followed if initial
inspection reveals damage to the unit, as well as repacking of the unit for
storage or reshipment.

Initial inspection:

2.2     This
pre-preamplifier was inspected both electrically and mechanically before it was
shipped to the dealer.  While we advise the dealers that all shipments
should be inspected for damage immediately upon receipt so that shipping damage
can be noted on the manifest and a claim made against the carrier, we have no
way of verifying that this has been done.

It is
wise therefore, to perform a careful physical inspection of the pre-preamplifier
prior to its initial use.  Inspect the packing material to see if there is
any physical damage to the carton.  If carton damage is present, make a
note of it's location and extent.  Also note any signs that the carton has
been exposed to excessive moisture.

The
pre-preamplifier case should be free of scratches or burnish marks.  The
interconnecting cable from the power supply should be free of cuts or
blemishes.  The connector screws should be in place on the connector or
should be packedged separately.  Four (4) sets of BNC Connectors are packed
(In plastic Bags) with each pre-preamplifier.

The
chassis mounted BNC Connectors should not be damaged or bent.

An
inspection of the internal Circuit board may be done by removing the two screws
on either end of the power connector at the rear of the case.  This will
allow the PC Board to be slid out.  There should be no sign that any
components have been broken, cracked or knocked free of the circuit board.
Re-insert the board in the case and secure with the two screws that had been
removed.

If the
Pre-preamplifier is connected and operated outside the case remember that
certain board traces if shorted together or if short-circuited to ground, can
cause the transistors to be blown.  Location of these damaged parts and
their replacement is not covered under your warranty.  If it is necessary
to operate the unit uncased, be sure that it is resting on an insulated
surface.  As there is no power switch on this unit. up to 35 volts will be
present in the power supply section of the board.

(page 6)

Claims:

2.3     The warranty is
printed in paragraph 1.3 on pages 4 and 5. If shipping damage is present and you
took delivery of the unit up at a dealers; it was his responsability to inspect
the incoming material after shipment, any claim for damages must be setled
between yourself and the dealer.

If the
unit was shipped to you by the dealer, and you find shipping damage, it is your
responsibility to make a claim against the carrier involved within a period of
14 days for hidden damage, or 7 days for visible damage.  If you failed to
inspect the material upon receipt and gave the carrier a 'clear' signature you
might have difficulty in procuring a settlement.

Nevertheless it is your responsibility to notify the carrier in writing within
the statutory period (which is best done by registered-return receipt requested
mail) and to insure that he arranges an inspection of the goods as soon as
possible.  Your dealer should assist you by providing a certified true copy
of the Bill of Lading and the Invoice so that you can then make a written
claim.  Upon receipt of your written claim the carrier generally has 120
days in which to negotiate a settlement.

The
Dayton Wright Group Ltd. has packed your unit carefully in a manner sufficient
to withstand the normal rigors of shipment.  We therefore assume no
responsibility for shipping damage.

Preparation for Use:

2.4     The unit should be
unpacked and placed on a surface removed from any power transformers or other
sources of magnetic AC interference.  The power module cable may then be
plugged into the rear of the pre-preamplifier and secured with the screws
provided.  We do not advise leaving these loose as inadvertent
disconnection could cause a damaging transient to go through your audio
system.

See
section 3.21 on instructions for attaching BNC Connector's to your audio
interconnect cables.  We use these rather than the more common phono
connectors as we have found that they not only are more reliable, and have lower
distortion and noise but that as their ground connects first and disconnects
last, there is far less possibility of an inadvertent disconnection damaging the
other equipment.

Initially it is wise to place the unit in an easily accessible location as you
may wish to alter the load resistor settings and the output level
controls.  Be sure that you know what load your cartridge requires.
Remember that the "OUTPLIT LEVEL" controls are twenty turn (20)
potentiometers.

(page7)

Repacking for Shipment or Storage:

2.5      ALWAYS
SAVE THE ORIGINAL PACKING MATERIAL!  Whenever you wish to store the
unit or re-ship it the pre-preamplifier must be packed securely.  The
Factory will not accept responsibility for units that have been returned to them
and damaged in shipment due to faulty packing techniques and/or materials.
Make sure that the cable connector is positioned so that it will not mar the
finish on the pre-preamplifier or the power supply module.

(page 8)

Section
3
OPERATION

Introduction:

3.1         This
section covers the general operation of the DW 999 Pre-Preamplifier including
its controls and its connections.

Controls & Connectors:

3.2         As
noted, the DW 999 employs BNC Connectors for all Audio Signal Path
Connections.  As both these as well as phono connectors are used in video
recording, BNC-to-Phono cables are usually available from dealers handling video
accessories.  We do not advise the employment of phono adaptors as these
simply re-introduce the problems that we tried to avoid by using BNC units in
the first place.

Use of BNC Connectors:

3.31         The
BNC Type of connector is in use world-wide as a wide-bandwidth low-noise
connector in applications ranging from avionics to test equipment.  As
such, it may be readily obtained from electronics parts houses.  While
lower cost units are nickel plated, the better quality units are plated with
either silver or gold.  Besides the aforementioned advantage of making the
ground connection first (upon connection) and breaking it last (upon
disconnection) the BNC unit has a bayonet type locking device to hold it in
place.

In
general, the cable-mounting portion of the connector system consists of a
machined body upon which the positive bayonet-type-locking sleeve
revolves.  This body also has the slit sleeve ground connection which in
turn surrounds a plastic insert which separates the outer grounded body and the
inner live center pin.  From the rear, a bushing screws into the main body
and through of a tapered metal washer, a flat washer, and a rubber ring, connect
the outer braid of the coaxial cable used to the connector body.  This
bushing is available in several different sizes and a size can usually be found
that will fit whatever audio interconnect cable is being employed.  Several
manufacturers offer prefabricated cables with BNC connectors already attached at
one or both ends.

(page 9)

Making up Cables:

3.22         A
bushing should be used that is a snug fit over the insulation of the coaxial
cable being used.

(page10)

Adapters:

3.23
Because of the amount of Video equipment that uses BNC connectors, most
retailers who sell video recording equipment have a selection of BNC to Phono
cables and adapters.  While these are generally satisfactory for the
connection of the Pre-preamplifier to the preamplifier (providing the length of
the cable is not too long) they exhibit the usual noise problems when used in
the very low impedance input circuits encountered in moving coil
cartridges.  While an adapter may serve to get a system ‘up-and-running’,
we would respectfully suggest that it be replaced as soon as possible.

Control Location:

3.24         The
DW 999 has two user adjustments. (NOTE: THE REGULATED
VOLTAGE AND
THE
TRIMMER CAPACITOR ADJUSTMENTS (if the latter is used) HAVE BEEN PRESET AT THE
FACTORY AND MUST NOT BE TOUCHED!

These
user adjustments are both accessible from the front panel.  They are: The
Cartridge Load Control Switch and the Output Level Control.

The
Load is set by means of the small DIP-type switches set on either side of the
input connectors.  The output level control are screwdriver-adjustment
units whose bushings are located adjacent to the output connectors.  As
would be .expected, the left channel is to the left of the case, while the right
channel is to the right of the case.  The three binding posts in a line
are, from left to right; the Left Channel Signal, Ground, the Case Ground (a
green binding post) and the Right Channel Signal Ground.  The Tone Arm
Ground lead should be connected to whichever of the three ground terminals that
results in the lowest noise figure being obtained.

Load Resistors:

3.25         Six
Load resistors are located on the circuit board for each channel, and even more
may be added using the spring clips provided.  When all the DIP switches
are OPEN or OFF - then the load will be 499 ohms.  The first switch section
is 83 ohms, the second is 65 ohms, the third is 28 ohms, the fourth is 14.5
ohms, and the fifth is 9.8 ohms.  The sixth is for the resistor clips
located internally.  The switches may be used in combinations to achive
other resistances:

Opening the Case:

3.26         The
Pre-preamplifier case may be opened by unscrewing the two screws on either side
of the power connector.  Slide the 'unit carefully out of the case.
The Custom Load Clips are between the Load Selection switch and the Input
Connectors.  The lead on the resistor should be trimmed back so that it may
be clipped in place-the clip is opened by depressing the projecting cap on the
clip.

The
case is closed-by sliding the board assembly back into the case and securing it
in place with the screws that had been removed.  Don't loose these screws
as they have drilled and tapped heads to accept the screws on the connector
cable's "D" Connector.

(page12)

Custom Load:

3.27         A
custom Load may be used by inserting a resistor in the spring clipd
provided.  Remember that there is always a 499 ohm load in place, the
formulae for summing of parallel resistors must be used:

1
=
1
+       1
DESIRED
R
R
499

Thus to achive a load of l00 ohms, use a
125 ohm resistor in the clips
and
switch the last switch on.

DESIRED LOAD RESISTOR   RESISTOR USED IN CLIPS

100
Ohms
125 Ohms

50
Ohms
56 Ohms

40
Ohms
43.5 Ohms

30
Ohms
32 Ohms

20
Ohms
20.85 Ohms

10
Ohms
10.2 Ohms

5
Ohms
5.05 Ohms

2.5
Ohms
2.51 Ohms

1.0
Ohms
1.002 Ohms

Under 2.5 Ohms use the exact load resistor you
wish to use on the cartridge ... the error will be negligible.

Output Level Adjustment:

3.28         The
level adjustments are normally used to lower the output level so that the
preamplifier is not overloaded by the output of the DW 999.  As the DW 991
Pre-preamplifier has an maximum signal output in excess of 2 volts at anywhere
from 20 Hz to 20 kHz it would require a preamplifier having a .2 volt overload
at 1 kHz to accommodate its capabilities.  As there is about-20 db of
equalization from 20 kH z down to 1 kHz in the RIAA curve, 2 volts at 20 kHz
-20dB (or divided by 10) = .2 volts at 1kHz (200 millivolts).

In
practice the full 34 dB voltage gain of the DW 999 pre-preamplifier is rarely
needed except with the very few ultra-low voltage moving coil units.  Once
the screwdriver-adjusted volume control is fully clockwise, the gain of the
pre-preamplifier may be lowered 6 dB by rotating each of the two controls 10
turns counterclockwise.

While
an oscillator, voltage divider (remember that most oscillators do not respond
well to the 4 to 100 ohm load imposed by the pre-preamplifier), and RMS
voltmeter CAN be used to both set and balance the output levels of the left and
right channels of the pre-preamplifier a more humble and practical method
involves borrowing a turntable with a conventional moving iron or moving magnet
phono cartridge.  Connect this up (hopefully to the second) to the phono
input, and adjust the preamplifier's volume control to a comfortable
level.  Switch over to the moving coil unit/pre-preamplifier.  Playing
the same part of the same record, adjust both of the output levels on the DW 999
Pre-preamplifier to produce the equivalent playback level.  The channels
may be balanced by adjusting one of them up or down until equally good balance
is produced on several different recordings.

(page 13)

Power Supply Module:

3.3         The
Power Supply Module contains a transformer having a double and isolated set of
secondary windings.  Each of these is connected to a bridge rectifier and
thence to a large filter capacitor.  The output DC is led to the
pre-preamplifier via a power cord and 'DI connector.  The proper fuse MUST
be used to protect the power transformer.

The DW 999
Pre-preamplifier requires about 10 seconds after turn

on to function and
another minute or two to stabilise.  Attempts to

use it before that
period is over will result in higher than normal
distortion and
noise levels.

The pre-preamplifier
MAY be left turned on all the time.

Hum and/or RF Problems:

3.4         It is
often difficult to distinguish between AC Power line induced Hum and TV
Inter-channel Sync-Interference.  The former is usually lower in pitch and
will change only when interconnect cables or equipment is moved away from power
cables, power cords, or power transformers.  RF hum changes with very small
movements of cables and is more of a buzz than hum.  It requires a real
expert to deal with RF interference, as its elimination is more of an art than a
science.  Contact the factory for assistance.

(page 14)

SECTION
4

PRINCIPLES  OF
OPERATION

Introduction:

4.1         This
section provides a brief overview of the theory of operation of the DW 999
Pre-preamplifier.

General Theory:

4.2         The
use of a Pre-preamplifier or 'Head amp' rather than a transformer dates from the
early 170's when Dayton Wright Associates and Mark Levinson both introduced
units designed to operate from very low source impedance’s.  While Audio
dealers were skeptical about the potential market,, Audiophiles were very
impressed with the improvement over transformers and sales were excellent.
As a result the number of pre-preamplifiers proliferated.

However, because the input voltages were in the microvolt range and the gains of
the units ranged from about 22 dB to 32 dB, most designers did not appreciate
the need for low distortion at higher output levels.  They forgot that as
the pre-preamplifier is used before the RIAA equalized section of the
preamplifier, the 20 kHz output level will be about 20 dB (ten times the
voltage) than the 1 khz output.  Many conventional cartridges have an
output of 100 millivolts at 1 kHz on very loud passages, and if the equivalent
output is needed from a pre-preamplifier; that is, 100 mV @ 1 khz, then it must
be capable of a I Volt output at 20 kHz.  Very few pre-preamplifiers had
this capability.

The
usual design used two PNP and two NPN transistors with their emitters tied
together and used for the input.  The bases were AC grounded -and the
collectors capacitativly taken to the output.  This yielded a low imput
impedance due to the common base operating mode and a typical gain of about 22
to 26 dB.  Typical distortion figures at 100 mV output would be about .04%
Harmonic; rising to over 3% at 1 volt.  More advanced designs employed
several PNP transistors in parallel with an emitter follower output.  Some
had feedback as well.  As the noise generating resistance in the transistor
is the Base Spreading Resistance (and is from 50 to 200 ohms in PNP'S, or from
250 to 400 ohms in NPN'S) a reduction in the effective resistance can be
obtained by using Fowler's technique of operating several transistors in
parallel.  This lowers the amount of noise generated, both by reducing the
aggregate base spreading resistance, and by allowing a better impedance match
between the source and the transistors.

One
danger is present.  With very low base resistances, there is little local
feedback to stabilize the transistor, and parasitic oscillation can take place
if the cartridge has a very low resistance and appreciable inductance, when
feedback is used.  Thus it was not uncommon to find pre-preamplifiers that
were unstable with certain moving coil cartridges.

(page15)

Other
factors also intrude.  Transistors operated at very low signal levels
suffer f rom Early Effect distortion.  This can be eliminated using a
technique developed by us at Dayton Wright called the bootstrapped cascode.
(This has been copied extensivly by other manufacturers such as Sony, etc.,
without crediting us as the source).  Here, a portion of the emitter
signal from the lower transistor of the cascode pair is applied to the base of
the upper transistor.  While this raises the input impedance of the emitter
input of the upper transistor (now more voltage swing is present at the
collector of the lower transistor and the slightly higher charging/discharging
current of the collector capacitance does lower the bandwidth slightly) and much
lower distortion results. we have employed this technique in all out
pre-preamplifiers (and in some of our preamplifiers as well) since 1971.

While
an op-amp type of input using a 'long-tailed-pair' is less sensitive to
cartridge loading induced changes in the effective feedback characteristics this
configuration raises the noise level by a factor of 1.4 and is rarely used where
noise is critical.  Even feedback has limitations insofar as distortion
reduction is concerned in pre-preamp2ifiers.

Dayton
Wright Group has been developing the technique of 'tracking complimentary
transfer functions  ‘as a method of distortion reduction.  Two
stages, each with a known non-linearity are set up so that the non-linearity of
the first stage is canceled out (or almost so) by the complimentary nonlinearity
of the following stage or stages.

Obviously operating point tracking is required, and we employ a current sink set
up with a 'soft" buffer to ensure that thermal tracking takes place between the
stages.  In addition, the very low impedance require correspondingly low
value feedback components, and this in turn requires an output stage that can
handle the current demands of this low-impedance feedback.

Block Diagram

4.3         The
DW 999 Pre-preamplifier block diagram:

(page16)

Specifics:

4.4         The
following sections cover the operation of the stages in more detail.

Input Cascode Stage:

4.41         The
input stage consists of ten bootstrapped cascode stages operating in
parallel.  Each stage has a loo ohm resistor as a current equalizing
resistor in its emitter bypassed with a .33 uF polypropylene capacitor and a
220 uF Aluminum Electrolytic.  The input signal is fed to all ten bases in
parallel.  The base of the upper transistor of the cascode pair is biased
through a 82k resistor, and has the signal from the lower transistor's emitter
fed to it through a .33 uF polypropylene and a 22 uF tantalytic in
parallel.  The collectors of the upper transistors are operated in
parallel.

The
biasing network consists of a 4k3 resistor from ground down (the ground rail is
positive) to a pair of silicon diodes in series, followed by a 4.75 resistor to
the 15.2 volt negative rail. The lower transistor bases are biased through a
common 7k5 resistor from the junction of the 4k3 resistor and the start of the
diode pair, while the upper transistor bases are biased by individual 82k
resistors tied to the junction of the diode pair and the 4k7resistor.  Both
bias taps are bypassed up to ground with 35uF tantalytic capacitors, and the
latter tap is also bypassed with a .33 uF Polypropylene as well.  The stage
uses 2N4058 PNP Devices selected for low shot-noise and low base spreading
resistance.

INPUT STAGE

The
100 ohm emitter resistors are commoned and feedback from the output is applied
at this point via a 100 ohm series resistor.  The AC shunt is a 2 ohm
resistor in series with a 10,000 uF capcaitor (bypassed with a .33 uF
Polypropylene).  In    order
to    stabalize  the DC operating point and to prevent
latch up, a 499 ohm resistor is also used as a shunt element.

The input loading network consists of 5 switch
selectable resistors, as well as a 499 ohm resistor.  A .33 uF
polypropylene in parallel with a35 uF tantalytic serve as the input coupling
capacitor.

(page17)

Current Sink:

4.42         This
is a single NPN transistor
using a
100 ohm emitter resistor and a
base biasing network of 2
lN916 diodes
to the negative rail
(bypassed with a
22 uF tantalytic
to lower noise),
pulled up by a
5k6 resistor up to the
ground
rail. The current sink is
bypassed
with a 33 pF in series with a
499
ohm resistor.

Buffer and Second Cascode
Stage:

4.43
The current sink is followed by a
'Soft' buffer consisting of an emitter

follower with a unbypassed 3k9
resistor
in its collector circuit.
The emitter
load is 1k82 ohms, and
the emitter
signal is fed to the
lower NPN
transistor base (of a
cascode). This
cascode has a loo
ohm emitter resistor
bypassed with
470 uF, and the bias for
the upper
base is derived using a lN916
diode pair from the lower
emitter to
the upper base; this is
pulled up
towards ground with a
15k resistor.
The collector load
is a 4k75 ohm
resistor. The
dominant pole
compensation is
applied around these
stages in a
manner designed to hold the
stage
tracking at high frequencies.
Thus 68 pF runs to the buffer
input,
47pF runs to the cascode
input and a
68 pF trimmer runs to
the negative
rail.
(this may be replaced with a 9
27pF caapacitor in some units). The

trimmer is used to adjust the
loading
on the cascode stage at
higher
frequencies.

The Output Stage:

4.44         This
stage is a PNP emitter-follower using a PNP current source and is quite
conventional.  It is necessary to ensure that there is adequate drive for
the feedback loop as well as the
output
load.

(page18)

The
output is isolated by a 2.2 uF capacitor and a 20 k 20 turn trimpot is used to
set the output level.  A 499 ohm resistor defines the minimum output
impedance.

The Regulators:

4.45
Three regulators are used in series in order to isolate the pre-preamps stages
from: A) Line Voltage 'Bumps', B) Line voltage changes, C) A.C. component Hum,
D) Regulator noise.  The DC input is fed to a MC7924BT regulator which has
an output of 24 volts and is loaded with a 4700 uF capacitor (slowing down the
regulator).  Then a MC791SBT regulator follows with a 2.2 uF capacitor
across its output.  A LM104H is used as the final regulator with a 2N2905A
PNP as a current boost device.  A trimmer pot allows the output voltage to
be set at 15.2 volts, while a 4r7 ohm resistor defines the

maximum current that can
be drawn before the regulator goes into current limiting protection.  The
use of a 2200uF electrolytic capacitor in parallel with a .33 uF polypropylene
gets rid of the noise generated by the LM 104 H regulator.

The Power Supply Module:

4.46         This
consists of a transformer with two secondary windings.  Each winding is
connected to a bridge rectifier with a large capacitor across its output.
The two DC voltages are led to the preamplifier by a cable and 'DI
connector.  While no switch is provided, a fuse is in the primary of the
transformer.

Power
on indication is provided for each channel by a LED mounted back in the power
supply section.  A light pipe leads the light to the front panel.
This avoids having power present near the sensitive input section.

(page19)

SECTION
5

PERFORMANCE CHECK

Introduction:

5.1         This
section covers a simplified procedure useful for establishing the proper
performance of the DW 999 Pre-preamplifier.  While the factory uses
computer controlled test equipment, this is probably beyond the financial means
of many who wish to verify the proper performance of the
pre-preamplifier.

One of
the most difficult aspects of the Performance Check is the measurement of
distortion in the pre-preamplifier as it is below the noise level of the
measuring equipment.  The technique that can be used is to use a harmonic
distortion measuring set that has a output after the fundamental removing notch
filter.  This output is fed to a spectrum analyzer and that instrument used
to separate the harmonics from the noise; the latter will be wide band.

Nevertheless, it must be remembered that this will yield the total distortion of
the measuring system and the pre-preamplifier; so a second measurement must be
made with the pre-preamplifier load on the oscillator, but of the oscillator
itself.  The difference between the two is the distortion of the
pre-preamplifier.

The
measurement is normally made with the pre-preamplifier output running about 3 dB
below overload although 1.5 volts is satisfactory. otherwise the noise is too
great f or even the spectrum analyzer to be able to resolve the harmonics.
The distortion at 1.5 volta, at 1 kHz should run under 0.0006% using a 400 Hz LF
Cutoff and a 30 kHz HF cutoff.  This drops off rapidly as the output level
is lowered.

The
frequency response is such that excellent 100 khz square waves are passed, the
rise time of the unit into a 47 kHz load being in the order of 350
nanoseconds.

Equipment Required:

5.2         The
equipment required will be:

a)   Distortion Test
Set          Sound Technology
1710A

Note: this must have an output after

the fundamental has been filtered from

the returned waveform.

b)   Spectrum
Analyzer
Hewlett Packard 3580A

c)
Dual Trace 25 mHz oscilliscope  Advance Gould OS1000A

d)
Function
Generator
Hewlet Packard 3314A

e)   RMS
Voltmeter
Hewlet Packard 400GL

(page20)

Distortion measurement:

5.3         The
distortion analyzer feeds the pre-preamplifier through a network consisting of a
499 ohm resistor in series with a 4.9 ohm resistor; the pre-preamplifier load
switch being set for 9.8 ohms.  The output signal monitor line from the
test set feeds input A of the dual trace scope, and the scope is set to sync
from this.

The
output from the pre-preamplifier feeds back to the input of the Distortion
Analyzer, and the monitor of this input after the fundamental has been filtered
out is fed to channel B of the scope AND to the Spectrum Analyzer. (The output
level on the pre-preamp should be fully up)

Let
the DW 999 warm up for 15 minutes, then set the output for 1.5volts RMS as
indicated on the Distortion Analyzer.  The analyzer is setup so that the
Hum filter (400 Hz) is on, the noise Filter is set at 30 kHz and on, and a
frequency of 1 kHz has been selected.  The distortion should read about
0.0014 percent on the meter of the Distortion Analyzer and will be very
noisy.

Use
the oscillator-direct button on the analyzer to read the oscillator's
distortion, resetting the set-level-control as necessary.  The distortion
reading on the meter should be about the same.  Use the spectrum analyzer
set for a 1 kHz interval and a 30 Hz bandwith to display the harmonics of the
oscillator/distortion analyzer and record the scale readings for each
harmonic.  Then switch in the pre-preamplifier and reset up the
analyzer.  Record the new harmonic levels.  If the second harmonic
drops instead of rising, then invert the phase of the input so that the
pre-preamplifier is not canceling the even harmonic distortion.

Use
the usual formulae to find the relative difference between the two readings on
each harmonic.

The oscillator/function generator
and RMS voltmeter can be used to inject a signal of known level into the
Spectrum analyzer in order to calibrate its graticule.

The indicated
difference in distortions should run from 0.0002 to 0.0006 per-cent with 75% of
it being second, and 25% of it being third harmonic.

Frequency Response:

5.4         There
is nothing special about the technique of frequency response measurement save to
be sure that: a) Pre-preamplifier is not overloading, and b) the oscillator load
is acceptable through using the 499 ohm/5 ohm voltage divider mentioned
earlier.

(page21)

Section
6

REPLACEMENT PARTS

Introduction:

6.1         There
are few if any exotic parts used in the production of the DW 999
pre-preamplifier and there should be little need for replacement parts.
It should be possible to obtain anything needed (save PC Boards and/or Sheet
Metal Work at a local Electronics Parts supply house.

If you
cannot obtain the needed part locally, the Dayton Wright Group Ltd., does carry
a complete supply of replacement parts.  Customers should be forewarned
that our prices are probably going to be higher by 50 to 90% that the use of a
local source.

We
have used the manufacturers name rather than his Federal Supply Code
Number.  Please note that several manufacturers manufacture metal Film
precision resistors and substitutions can be made here although some slight
increases in noise level could result.

Note
that while the component value is screened on the circuit board along with its
component type and number, from time to time,, The Dayton Group reserves the
right to make changes without notifying the prospective or actual user.
Engineering change notices are available that cover these.

When
writing for parts, use the Model Number, the Revision number on the circuit
board,, the part number AND description!  We will advice if there has been
any change in the design!

(page 22)

6.2 Parts
Listing

Quan.
DW-Stock No.     Value
Description      Mfg.
Mfg. No.      Part Designation

2
50-469-C330        33pF Ceramic
Cap       Philips
63810339      C99,109

2
50-469-C470        47pF Ceramic
Cap       Philips
63810479      C102, 112

2
50-469-C680        68pF Ceramic
Cap       Philips
63810689      C103,113

2
50-456-T650         5.5-65PF Trimer
Cap   Philips
010GA60E     C104,114
48
50-415-B337        0.33uF 63V Polyprp Cap
Acushnet N1862Z.35 Cl,3,4,6,

C8,9,12,13,16,17,20,21,24,25,

C28,29,32,33,36,37,40,41,44,45,

C48,49,52,53,56,57,60,61,64,65,

C68,68,72,73r76,77,80,81,84,85,

C88,91,94,97

4
50-413-225C      2.2uF 100V  Polyest Cap
Philips    344CHA2M2   C105,107,

C115,117
24
50-422-D336      22uF 16 V Tant Bd
Cap
ITT
TAP22Ml6      C7,11,15,19,

C23,27,31,35,39,43,47,51,55,59,

C63,67,71,75,79,83,100,106,110,

C116
6
CSR13D356K-L 35uF 15V Sld Ttl Cap
Mallory   CSR13D356KL   C2,5,89,90,

C95,96
20         50-426-227A
220uF     10V AI.EL R Cap
Philips    426UP10220
C10,14,18,22,

C26,30,34,38,42,46,50,54,58,62,

C66,70,74,80,82
2
50-470-C471 470uF 10V
Al.El.Cap
Philips
437EID470
C101,111

2
50-470-E222 2200uF 16V
Al.El.Cap
Philips
437ETE221
C92,98
2
50-470-C103 10,000 uF 10V Al.El. Cap
Philips
437E7DlO3
C87,93
2
50-398-F472 4700 uF 25V Al.El.R
Cap         Philips 2222
16472
C100,110

16
lN916
lN916        Sil
Diode
Motorola
lN916
Dl,2,3,4,5,

D6,7,8,9,10,11,12,13,14,15,16

4         45-350-1
Com-Female  BNC
Jack
Amphenol
31-10
Jl,2,3,4
2         16-16-03 Bndg
Post Blk Bndg
Post
Johnson 1110403001       J5,6

1        16-16-04 Bndg Post Gm Bndg
Post
Johnson 1110404001
J-

1
45-150-09P  9 P D Con     PCB Mtg 9P
D     Winchester
47-1109P         J7

2
103-95-5
LED          LED -
Yellow
National
NSL5352A
LED1,2

(page 23)

6.2
Parts Listing Continued

Quan.
DW-Stock No.     Value
Description      Mfg.
Mfg. No.      Part Designation

40
103-153-2     2N4058 S PNP Low
Noise
T.I.
2N4058
Ql,2,3,4,5,

Q6,7,8,9,10,11,12,13,14,15,16,

Q17,18,18,20,21,22,23,24,25,26,

Q27,28,29,30,31,32,33,34,35,36

Q37,38,39,40

8
103-150-3 2N5429 S NPN Low
Noise
Motorola    2N5429
Q41,42,43

Q44,48,49,50,51
6     2N2905A   2N2905A PMP Metal
Can
National     2N2905A
Q45,46,46

Q52,53,54

2
40-97-2ROOF       2 Ohm    1% Mtl
Film Res   Philips
MR30F2r
R9,65
2
40-97-4R75F    4r75       1% Mtl
File Res   Philips MR30F 4r75  R82,95
2
40-97-IOROF 10 Ohm 1% Mtl Film Res    Philips
MR30Flor      R9,17
2
40-97-15ROF 15 Ohm 1% Mtl Film Res    Philips
MR30Fl5r      R8,16
2
40-97-16R2F 16r2 1% Mtl Film
Res           Philips
MR30Fl6r2   R83,96

2
40-97-30R0F 30 Ohm-1% Mtl Film Res    Philips
MR30F30r   R7,15
2
40-97-75R0F 75 Ohm 1% Mtl Film Res    Philips MR3oF75ro
R6,14

28
40-97-1000F 100 Ohm 1% Mtl Film Res  Philips MR30Fl00r
R5,13,20,22,

R24,26,28,30,32,34,36,38,40,42,

R44,46,48,50,52,54,56,58,61,67,

R72,76,85,89
8
40-97-4990F     499 Ohm 1%  Mtl Film Res Philips
MR30F499r   R3,10,11,

R18,60,66,76,89
2
40-97-1821F
1k82         1% Mtl Film Res Philips
MR30FlK82    R74,R87

2      40-97-2431F
2k43 1% Mtl Film Res Philips
MR30F2K43
R81,94
2      40-97-3321F 3k32 1%
mtl Film Res Philips MR30F3K32 RI,2
2      40-97-3921F 3k92 1%
Mtl Film Res Philips MR3oF3K92 R79,92
2 40-97-4371F 4k32 1% Mtl Film Res Philips
MR3OF4K37 R63,69
6 40-97-4751F
4k75 1% Mtl Film Res Philips MR3OF4K75 R64,70,

R77,78,90,91

2 40-97-5621F 5k62 1% Mtl Film Res Philips
MR3OF5K62 R71,84
2 40-97-7501F
7k5o 1% Mtl Film Res Philips MR3OF7K50 R63,68
2
40-97-1502F 15kO 1% Mtl Film Res Philips MR3oFl5KO R75,88

2 61-60-203P 20k Long Trimpot Bourns
3009P-1203 R4,12
2 61-107-W203
20k Square Trimpot Boums 3299W-1203 R80,93

20
40-97-8252      82k5 1% Mtl Film
Res   Philips   MR3OF82K5 R19,21,
R23,26,27,29,31,33,35,37,39,

R41,43,45,47,49,51,53,55,57,59

2 117-79-40A Neg Volt Reg Adjustable
National LM104H Ul,4
2 117-279-20
IS Volt Neg Volt Reg Motorola MC7918Cr U2,5
2
117-279-24 24 Volt Neg Volt Reg Motorola MC7924CT U3,6

(page24)

Model DW 999
6.2
Parts Listinq , Continued
Quan.
Stock No.       Value
Description
Mfg.      Mfg.  No. Designation
2   15-84-6A     6PST DIP
DIP
Switch
Greyhill 76SBO6      SW1,2

mechanical Parts

4 23-201-1 .187 mtg Bushing Heyco
B-187-125-062
2 18-2900-01
Plastic Rod rw 14-2900-01
1
14-1558-12A Circuit Board Unpopulated  SPECIAL  ORDER
ONLY

1 M803-15-lB Circuit Board Populated
SPECIAL ORDER ONLY
1 Y18-2055-02A
Panel For Pre-preamp Case SPECIAL ORDER CNLY
2
Y18-2055-02B Cheek Inserts SPECIAL ORDER ONLY
1
Y18-2055-03A Pre-preamplifier Case SPECIAL ORDER CNLY
4
22-55-01 Feet, Adhesive
1
Y18-2057-02A Cover, Power Supply SPECIAL ORDER CNLY
1
Y18-2057-03A Case, Power Supply SPECIAL ORDER ONLY
1
M803-10-02 Power Supply 120 v SPECIAL ORDER CNLY
1
M803-10-05 Pgwer Supply 220 v G.B. SPECIAL ORDER ONLY
1
M803-09-01 Cable, Power Supply SPECIAL ORDER ONLY
1
14-1559-04 Power Supply Board Unpop. SPECIAL ORDER ONLY
1
MB03-12-02 Power Supply Board Pop. SPECIAL ORDER CNLY

4
22-28-3      Rubber Feet / Power Supply ont Rbr

2   23-112-10
Strain Relief Bushing PS
Heyoo     5N-4

1 8X280202 Power Supply Transformer Hamond
SPEC ORDER CNLY
2 103-151-18 400
PIV    Rectifier DIP Vero VM18/VM48

2 50-399-9  AI.EL. Cap Philips SPEC
ORDER CNLY
1 24-236-2 Line Cord
120 V North America SPEC ORDER ONLY
1 24-1236-2 Line Cord 220 V Great Britain SPEC
ORDER CNLY
1 69-9-2 Fuse
Holder  Buss HKP
1 69-4-XX
1/2 Amp Fuse Buss AGC3 1/2

6 2-574-6 6-32 1/4 Screws B Hd A Spae Naur
HX251
1 2-1200-19 Screw Set for
Preamplifier Case Closure / D Connector

Ordering Information

6.3 Orders for replacement parts may be placed
with The Dayton Wright Group although we would advise contacting the Order Dept
first to obtain prices.

All orders should be accompanied with a
certified check or money order for the amount quoted by the Parts
Department.  Note that Quotations are good for a maximum of 30 days but
that we reserve the right to changes prices and parts designations without
notice.  DO NOT SEND CASH IN THE MAILI

Prices will be quoted FOB Richmond Hill,
Ontario; shipping, insurance, and handling costs will be quoted
separately.

(page25)

Model DW 999

Because of parts shortages in the industry,
parts may be unavailable from time to time.  The Dayton Wright Group Ltd.
accepts no responsibility for delays caused by strikes, civil insurrections and
the like.

Parts prices should be obtained by
phoning:

(416) 884-8586 - ask for the Parts
Department

NOTE: BE SURE TO
INCLUDE THE MODEL AND THE SERIAL NUMBER OF 999 AS IT WILL BE ON OUR
RECORDS.

Please be advised that records are kept of
quotations, and orders; from time to time we are aware of people trying to buy
the special parts necessary to build a piece of equipment themselves.  We
therefore reserve the right to refuse to accept any order.

Orders should be placed with:

Dayton Wright Ltd.
Parts
Department
3-97 Newkirk Road
North
Richmond Hill, Ontario L4C
3G4
CANADA
Phone:
(905) 508-7500

(page 26)

Model DW 999

Section 7

SCHEMATICS

Introduction

7.1 This section covers some of the information
needed to locate faults and to repair them.  The schematics for the left
and right channels are supplied along with a drawing of the circuit board
layout.  Please note that the board is approximately (but not exactly)
symmetrical and there is complete electrical isolation between the two channels
irrespective of whether the power supply is plugged in or not.  This
section also covers troubles-hooting as well as DC voltages.  By measuring
certain voltages, the proper operation of individual stages can usually be
verified.

(page 27)

Model DW 999

Troubleshooting

7.4 The first thing to verify is that there is
power reaching the board.  Check the voltages across the large filter
capacitors (Cl09, & C110) at the Left Rear and Right Rear of the Circuit
board.  Remember that the Left side of the board as you f ace the front
panel is the Left Channel, while the Right side of the Board is the Right
Channel.  C109 is therefore, in the left channel’s power supply, while Cll0
is in the right channel power supply.  The voltages should be about 24
volts plus or minus 3/4 of a volt.  If one of these voltages is near zero,
then check the first two pins of the power supply connector on that side of the
board.  The voltage here should be above 30 volts; if not, the power supply
module is faulty on that channel.

If the power supply is OK but the voltage across
the capacitor is low, then the MC7925CT may be bad on the corresponding channel;
or the filter capacitor may be shorted.  If the MC7924CT (U3-Left or
U6-Right) is hot to the touch, the filter capacitor (Cl00-Left or C110-Right)
might be shorted.

If the voltages are OK on both channels move on
to C107 (Left) or C117 (Right).  The voltage across these should be about
20 volts.  If not, check the IC's U2 (Left) and/or U5 (Right).

Then check the voltages across C92 (Left) and
C98 (Right).  This should be about 15.2 volts.  If it off slightly,
reset to 15.2 volts using the corresponding trimmer R80 (Left) or R93
(Right).

If the voltage is below 8 volts and does not
respond to the trimmer adjustment then the series pass transistor Q47 (Left) or
Q54 (Right) may have been blown.  These have heat sinks on them.
Check these by measuring the Emitter to Base voltage which should be
approximately 0.6 volts.  Replace if below 0.4 volts.  If the voltage
is about 5 volts the LM104H might be damaged and these are U1 (Left) and U4
(Right).  However if the output voltage is about 1 to 1.5 volts then the
stage might be in current protection mode.  Measure the voltage drop across
the 4.7 Ohm resistors R87 (Left), R95 (Right).  If this is over .65 suspect
a short in the corresponding channel which is causing excessive current to be
drawn from the power supply.

A quick check should be made of the voltage on
the negative rail to collector of the current sink,  these are transistors
Q43 (Left), Q58 (Right).  This voltage should be between 1.48 and 1.60
volts.  If substantially higher, suspect the buffer stage transistor Q44
(Left) or Q 59 (Right) and check its emitter to base voltage which should be
about .6 volts.  If almost zero, replace the transistor. if still off
substantially then check the lower transistor of the second cascode stage,, Q41
(Left) or Q48 (Right) for proper emitter to base voltage (around .58 to .62
volts).  If this is very low, replace the transistor.

High noise levels will normally be caused by
failure of the buffer stage transistors Q44 (Left) or Q59 (Right).  This
will also cause some distortion and lead to very strange (and high) voltages
across the current sink transistors Q43 (Left) or Q58 (Right).

Excessive low frequency noise might be caused by
a failure of one of the input capacitors, either the tantalytics C2 (Left) or C5
(Right) which might show excessive leakage, or the polypropylene capacitors C3
(Left) or C6 CI0         (Right).

A general malaise could be caused by a failure
of one of the transistors in the paralleled-cascode input stage, that is either
the input or upper transistor of the pair might fail.  Remember that these
PNP devices have a different pinout than the NPN'S.  The Emitter is towards
the center of the board, the Base is towards the edge.  The collector is
the center lead if the transistor.  The enmitter to base voltages should be
the same for all of the transistors in both of the stages, if not,, check the
capacitors for that section.  The base currents drawn by the upper
transistors of the casodes can be checked by taking a voltage drop reading
across the 82k resistors.

The plastic cased NPN transistors used for the
current sink, the buffer and the second cascode stage have a conventional pin
out.  That is, the emitters are nearest the edge of the board,, the base
connections are in the center, and the collector connections towards the
center.  However the metal cased PNP transistors are arranged so that their
collectors are nearest the circuit board edges, the bases in the middle, and the
emitters towards the center of the circuit board.  The collectors are also
connected to the metal cases so beware of shorting heat sinks together

If the collector loading capacitor C104 (Left)
or C114 (Right) is not set properly (or is off in value, about 27 pF is fitted
when a variable capacitor is not used), the distortion will be excessive.
Proper adjustment of the variable trimmer capacitor will cause a dramatic 'null'
in the distortion under the circumstances.

(page31)

DC Voltages:

7.4 These have been covered in the
troubleshooting notes.

Dissassembly and Reassembly:

7.5 The pre-preamplifier is disassembled by
removing the screws on either side of the nine pin "DI connector on the rear of
the case.  This allows the circuit board to be slid out of the case!

Do not let the circuit
board rest on a conductive surface,
and make sure that clipped component leads do not
fall
on a live circuit to cause a short circuit.

This is the way that
transistors get blown!

Reassembly consists of sliding the board back
into the case and using the aforementioned screws to secure the case to the
connector.

(page 32)

Switch Maintenance:

7.6 Because of the very low signal levels
present in the loading switch we commend the use of Stabilant 22
(TM) or Tweek (TM) on the switch contacts.  A co tube
of the former is packed with each DW 999 pre-preamplifier, and a drip of same
should be used on the ground and central pin of all the BNCIS, the cable pins
where the interconnect plugs into the phono arm, and on the cartridge
corrections themselves.  It can also be used on the interconnect cable
connectors between the pre-preamplifier and preamplifier, and between the
pre-amplifier and power amplifier as well.

The switches (SwlSw2) should be treated once a
year as well.  Either
Stabilant 22
or the original (concentrated) Tweek may be diluted with isopropanol or ethyl
alcohol so as to thin it out so that it can be introduced into the switch
housing via the rocker openings.
Alternatley, use Stabilant 22A which is already
diluted.

(page33)

© 1980, 1999, 2004, 2009 Wright
Electroacoustics

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