DW 999 Manuale utente
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
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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)
PRINCIPLESOFOPERATION
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)
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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
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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,
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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)
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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
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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.
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(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
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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
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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
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Indice
