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1、OWNERS 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 Page 1 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 99
2、9 Pre-preamplifier Manua. RadioFans.CN 收音机爱 好者资料库 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 Prepar
3、ation for use .(7) 2.5 Repacking for shipment.(7) OPERATION 3.1 Introduction .(9) 3.2 Controls 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 s
4、hipping 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 settle
5、ment. 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 certi
6、fied 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 th
7、e 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 r
8、ear 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 Connectors to your audio interconnect cables. We u
9、se 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. I
10、nitially 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) Rep
11、acking 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 pa
12、cking 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
13、 its controls and its Page 6 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 999 Pre-preamplifier Manua. connections. Controls the Left Channel Signal, Ground, the Case Ground (a green binding post) and the Right Channel Signal Ground. The Tone Arm Ground
14、 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 switche
15、s 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 r
16、esistances: 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 shou
17、ld 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. Dont loose these screws as they have drilled and
18、tapped heads to accept the screws on the connector cables 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 Page 9 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 99
19、9 Pre-preamplifier Manua. 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 RESISTORRESISTOR USED IN CLIPS 100 Oh
20、ms 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 lev
21、el 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 overlo
22、ad 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 e
23、xcept 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
24、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 conventio
25、nal moving iron or moving magnet phono cartridge. Connect this up (hopefully to the second) to the phono input, and adjust the preamplifiers 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 outpu
26、t 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
27、 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
28、Pre-preamplifier requires about 10 seconds after turn Page 10 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 999 Pre-preamplifier Manua. on to function and another minute or two to stabilise. Attempts to use it before that period is over will result in h
29、igher 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 onl
30、y 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.
31、 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
32、early 170s when Dayton Wright Associates and Mark Levinson both introduced units designed to operate from very low source impedances. While Audio dealers were skeptical about the potential market, Audiophiles were very impressed with the improvement over transformers and sales were excellent. As a r
33、esult 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-preampli
34、fier 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 p
35、re- 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 collecto
36、rs 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 tr
37、ansistors 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 PNPS, or from 250 to 400 ohms in NPNS) a reduction in the effective resistance can be obtained Page 1
38、1 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 999 Pre-preamplifier Manua. by using Fowlers technique of operating several transistors in parallel. This lowers the amount of noise generated, both by reducing the aggregate base spreading resistance, and
39、 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 inducta
40、nce, 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 de
41、veloped 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 tra
42、nsistor. 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
43、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 configu
44、ration 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 metho
45、d 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 si
46、nk 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
47、Diagram 4.3 The DW 999 Pre-preamplifier block diagram: Page 12 of 26DW 999 Pre-preamplifier Manual 12-12-2019mhtml:file:/C:UsersSlgerDownloadsDayton-Wright 999 Pre-preamplifier Manua. (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 paral
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