DSA Phono III User manual

DYNAMIC SOUNDS ASSOCIATES
Phono III
USER MANUAL
120/240 VAC Operation
Naples, Florida

WELCOME
Dynamic Sounds Associates LLC (DSA) welcomes you to our world of the finest possible audio
electronic products. We thank you for your purchase and we assure you many years of musical
enjoyment. We are always available to answer your questions and we welcome comments
regarding our products. Feel free to contact us at any time through our website at
www.dynamicsounds-assoc.com or by sending messages directly to info@dynamicsounds-
assoc.com. We look forward to your feedback and will gladly respond to all questions and
comments.
IMPORTANT INFORMATION
1. All units are set to operate on 120VAC ONLY unless a label is applied to the back panel
under the power plug indicating 240VAC operation. Operating a unit set for 120VAC on 240VAC
will cause permanent damage and void the warranty.
2. Dynamic Sounds Associates LLC reserves the right to make changes or modifications to
future units without prior announcement. Any such changes or modifications will be for the
purposes of improving the mechanical or sonic performance. Dynamic Sounds Associates LLC is
under no obligation to incorporate any changes or modifications into prior units; however, it
may be possible to provide upgrade packages for prior units—if desired—for a reasonable
charge.
3. Registering your component with us by using the form at the conclusion of this manual,
will allow us to contact you with potential product upgrade information. Information regarding
upgrades may also be requested by e-mail to [email protected].

INTRODUCTION TO THE DYNAMIC SOUNDS-ASSOCIATES PHONO III
Many times over the years since I founded Dynamic Sounds Associates (DSA), I have been asked why did
I chose to design a phono preamplifier as the first component of what has become a multiple
component line of products? My response has always been, “... because the phono preamplifier is the
most critical component in the electronic chain of components in your listening system.” Why is it so
critical? Because, if the phono preamplifier degrades the audio signal in any way, that information is
lost or altered in a way that can never be corrected in any of the subsequent amplifier stages. It is gone
forever; and, unfortunately you may never realize that it is gone. I started Dynamic Sounds Associates
so that I could design a phono preamplifier that was totally faithful to the input signal in every respect,
and honor my “Hippocratic audio oath” of, “First, do no harm to the signal.”
Designing a really good phono preamplifier is not easy, it must be able to provide amplification factors
as low as 100 (40dB), to as much as 2000 (66dB). It must have a dynamic range of 40-60dB at any gain
setting, and a frequency response that exceeds the audio range of 20 Hz –20 kHz by over an order of
magnitude. And, when everything else is done, it must also have very low distortion and noise. This is a
tall order for any piece of electronic equipment, but through a process of careful design and analysis,
combined with using only the finest component parts in the finished product my goals were achievable.
My first phono preamplifier, the DSA Phono ONE, established the basic “architecture” on which the
Phono II and now the Phono III are based. Within this architecture I was able to achieve the competing
goals of high gain and high dynamic range, combined with a “flat” bandwidth of >500 kHz. Also, since I
dislike using coupling capacitors in the audio chain, I was able to produce a design that is essentially “DC
coupled”, and remains stable with respect to DC drifts and offsets at the output without resorting to
feedback systems for correction. Finally, to eliminate the occurrence of transient harmonic distortion
(THD), there are no inter-stage or “global” feedback loops in the preamplifier; and, all of the playback
equalization is performed though passive low pass filters between the gain stages.
The end result of this “no-compromise” design approach is the DSA Phono III that combines all of the
original goals and “lessons learned;” but, combined into a package which offers unmatched operational
flexibility. Through the use of a remote control, the listener can now make adjustments in gain, phase,
and cartridge loading from the comfort of their favorite listening chair. The DSA Phono III also has four
playback equalization curves, in addition to the standard RIAA curve, that are user selectable and
designed to provide proper playback compensation for many LPs produced prior to the adoption of the
RIAA standard.
The ability to adjust cartridge loading from the listening position lets the listener make alterations in the
sound at the LP level by “shaping” the response of the phono cartridge in order to enhance the sound
from the listener’s perspective. Yet, the internal memory will retain the “baseline” value of the
loading unchanged so that it is easily recalled when required.
I believe that you will find the DSA Phono III listening experience as enjoyable as I found the
design process.
Douglas Hurlburt, Ph.D.
Founder and Principle Designer
Dynamic Sounds Associates

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1.0 GETTING STARTED
We know you are eager to get your new Phono III into play. This section will provide preliminary
information on the features of the Phono III and familiarize you with the layout of the controls and the
connectors. Section 2.0 will guide you through the process of the initial setup of the Phono III and
making the proper connections. Section 3.0 will provide additional information on the operation and
use of the features of the Phono III, plus instruction on setting the internal memories for gain and
cartridge loading. Section 4.0 will provide more detailed information on the overall design and
capabilities of the Phono III and can be reviewed at your leisure. Section 5.0 will provide information on
how to balance the outputs of the Phono III to maintain its high degree of performance. The Phono III
comes pre-balanced and, during normal operation, should not require checking and adjusting the output
balance more than once/year.
1.1 Unpacking
The Phono III should be carefully removed from the packaging material in the shipping box. The
following items should also be found in the Phono III shipping box:
Shielded power cord
Four Critical Mass Isolators
2mm slotted screwdriver
XLR female connector with three wires
One pair of RCA (unbalanced) to XLR (balanced) adapters
Plastic bag containing:
o1/16” Hex key wrench
o0.050” Hex key wrench
oFour threaded adapters for mounting the Critical Mass Isolators
o¼ watt resistor
1.2 Installing the Critical Mass Isolators
Remove the Phono III from its plastic protective bag.
Screw the large-diameter end of the threaded adapters (from the above plastic bag) into the
Critical Mass isolators. (It is recommended by Critical Mass that the paper disk on the top of the
isolators be left in place.) NOTE: The threaded adapters are made of titanium and are
specifically designed for the Critical Mass Isolators.
Screw the small diameter end of the threaded adapters into the threaded holes in the bottom of
the DSA Phono III. (These should be screwed in firmly such that the top surface of the isolators is
in direct contact with the bottom of the DSA Phono III.)
1.3 First Look at the Phono III
After unpacking your Phono III, installing the four isolators, and ensuring that all of the parts are
provided, you should take a few moments to familiarize yourself with the features on the front and back
panels.

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1.3.1 Front Panel
The front panel of the Phono III is shown in Figure 1.
Figure 1 –Phono III Front Panel
The front panel is divided into three sections identified as: right, left, and the center column which has
an upper and lower part. The functions located in each section are described below:
Right Section (Push buttons)
oStandby –amplifier is turned on but the output drivers are not operational
oMute –amplifier and output drivers are powered, but output is muted
oRun –amplifier is fully operational
oMode –Stereo/Mono selection
oPhase –Non-Inverting/Inverting operation
oL-R/R-L –Channel differencing (only operational in mono mode) (See Sections 3.2 and
3.5)
oFilter –High Pass filter for suppression of excess low frequencies from source
material
Left Section (Push buttons)
oInput selection (A, B, C)
oGain selection referenced to 1kHz (40dB, 46dB, 50dB, 56dB, 60dB, 66dB)
Note: The input selection and gain selection functions are operational ONLY when the unit is in the
Standby or Mute mode.
An internal memory retains the gain setting for each input and, when that input is selected, the gain will
be set to the stored value. The Phono III comes with the gain for each input set to 40dB and the user
must select the desired gain for actual use (see Section 3.3). Once selected, that gain will be saved—
even if the unit is turned off (for up to a 5 year period of time)—and will be applied the next time that
input is selected. Note: After turning the Phono III power on, and until an input is selected, the unit will
always show the “default” gain of 40dB.

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Center-Upper Section (See Figure 1A)
oThe LED display indicates the value of the loading for the selected input.
oThe “Loading”LEDs indicate if the display is showing “Ohms”(for MC) or “pF”(for MM).
In addition, the “100K”loading LED indicates if the resistive loading for an MM cartridge
is 100Kohms instead of the default 47Kohms. The type of loading (Ohms or pF) is
selected via switches on the Center-lower section for each input. (See following section.)
oThe “Equalization Indicator LEDs”indicate what form of playback equalization has been
selected for that input using switches on the Center-lower section. (The equalization
options are discussed in more detail in Section 4.4.) The “EQ Group LED”shows which
equalization group is selected (RIAA is the default and will show a blue color.) The LEDs
“EQ1”and “EQ2”indicate which of these has been selected within the selected EQ
group. These are not illuminated if RIAA is selected. (See following section.)
Figure 1A –Center-upper Section
Center –Lower Section (See Figure 1B)
This section is a hinged door (swings to left) that reveals the controls that select the type of
cartridge loading, and the desired playback equalization, to be used for each input. Also there
are Up/Down buttons that can be used for setting the cartridge loading value for each input. It
will be seen that there are three rows of switches, one for each input. Only those switches for
the selected input are “active” at any one time.
oLoading type –The first switch selects whether the loading is for a MC (ohms) or MM
(pF) cartridge at that input. In the MM position the second switch permits selecting
47Kohms or 100Kohms as the resistive load. If MC is selected, the second switch is not
operative. NOTE: The first switch for input A has a center “off” position that allows the
user to use a custom loading value instead of the internally selected loading. (See
Section 2.2 for details.) If a custom loading is to be used for input A, the LED display in
the Center-upper section will show “– –––“.

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Figure 1B –Center–lower Section
oEqualization –The first switch selects the equalization group (G1 or G2). The center
“off” position selects the RIAA playback equalization for that input. The second switch
selects either EQ1 or EQ2 within the selected group and is inactive if RIAA is selected.
(See Section 4.4 for details of the other equalization curves)
oThe load adjustment buttons may be used instead of using the remote control to adjust
the actual cartridge loading; however, the internal memory ONLY stores the loading
value for each input when selected using the buttons shown here in the Center-lower
Section. The stored loading value will be applied whenever that input is selected. (See
Section 3.4 for more detail.) When using a MM cartridge, the input capacitance of the
Phono III (120pF) is automatically added to any selected value. Thus, the minimum
capacitance shown on the LED display for a MM cartridge will be 120pF.
oA small opening labelled “Reset” clears the loading memory for the selected input
without using the buttons or remote. The LED display will then show either “0 ohm” or
“120pF”. (Use the provided 0.050” hex key wrench for this purpose instead of a
paperclip.)
Notes:
(1) When powered on it takes approximately 30 sec for the main amplifier power supplies to reach
operating voltage and stabilize. During this time the Standby LED will show a red-orange color and
will blink at a 1Hz rate. (If the Standby LED shows a red or green color only, turn off the unit and
contact DSA.)
(2) An input selection cannot be made, nor can the Phono III be switched to the Mute or Run mode,
until after the power supplies have stabilized which will be indicated when the standby LED stops
blinking.
(3) When switching between the Standby and the Mute mode, there is a delay of a few seconds for the
Phono III to come out of the Standby mode, and before the Mute LED will illuminate. This is due to a
startup delay in the output stage for each channel.
(4) Once in the Mute mode, switching between the Mute and Run modes is instantaneous, as is the
response when switching from Run to Mute.

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1.3.2 Back Panel
The back panel of the Phono III is shown in Figure2. To the right there are three inputs labelled “A, B, C”,
and each input has both an RCA (unbalanced) and XLR (balanced) connector for both the Left and Right
channels. At each input there is also a ground binding post for use with input cables that have a
Figure 2 –Phono III Back Panel
separate lead for the external shield. At each input there is a switch to select either the unbalanced
(RCA) connector or the balanced (XLR) connector. When one of these connectors is selected, the other
connector is disconnected from the input.
The output connectors are to the left of the input connectors, and each channel has unbalanced (RCA)
and balanced (XLR) output connectors. It is possible to use both output connectors simultaneously, if
desired, without damage to the unit. (For example, you can provide audio to a line stage and a separate
sub-woofer amp using both output connectors.)
At the far left is the AC power connector with integrated power switch. The AC connector also houses
the AC line fuses in a plug-in module located between the AC connector and the power switch.
NOTE: The fuse holder can be removed only when the power cord is detached from the AC receptacle.
Two replacement fuses are contained within the fuse holder (see Section 2.1).
The binding post labeled “Turntable Ground” should ONLY be used for attaching a grounding lead from
your turntable (if required) to the Phono III. Do not connect other grounding wires to this terminal or
ground loops and AC hum may occur.

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1.4 Remote Control
The Phono III remote control is shown in Figure 3. The remote control will operate the following
functions:
Mute and Run
Load adjustment
Blue LED intensity
Gain selection
Phase
The cluster of five buttons in the upper- center of the remote is used for load
adjustment, muting the unit, and adjusting the intensity of the blue LEDs.
The “Mute”button, in the center of the cluster will mute the unit when
pressed. Press the “Run” button in the upper left to return to the run
mode.
The vertical buttons with the “up” and “down” arrows will adjust the
loading in 10ohm or 10pF increments, respectively; however, the
selected values will NOT be saved in memory. (See Section 3.4.)
The “left” and “right” arrows adjust the Intensity of the blue LEDs.
Pressing the left button will dim the LEDs, and pressing the right button
will increase their intensity. There are 16-possible LED intensity settings
from full brightness to totally off. Holding either button down will scan
through these settings in the appropriate direction.
Pressing one of the gain buttons will change the gain for the chosen input
to the selected value and store it in memory—but ONLY if the unit is in
the Mute or Standby mode. (See Section 3.3.)
The phase can be switched between non-inverted and inverted, and back
again, using the button in the upper- right marked “Phase.”
Figure 3 –Remote Control
There is a small blue LED in the upper-left of the remote which will blink every time a button is pressed,
indicating that the remote is transmitting data to the receiver on the front panel of the Phono III. If this
LED becomes dim, or fails to blink, it is probably necessary to replace the batteries. Using the 1/16” hex
key (provided) remove the two screws holding the cover at the bottom end of the remote. Remove the
cover and pull out the battery holder. Replace the batteries with two new AAA size batteries and slide
the holder back into the remote. Replace the bottom cover and tighten the two retaining screws.
2.0 INITIAL SETUP AND INSTALLATION
This section addresses those setup steps that can be performed with the unit unpowered. Because the
initial settings for the gain and internal loading can only be set when the unit is operating, these steps
will be addressed in Sections 3.3 and 3.4, respectively.

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2.1 Connecting the Cables and Selecting Cartridge Type
The cable from each phono cartridge is connected to the respective RCA or XLR input connector for the
desired input (A, B, or C) to be used. In accordance with convention, the Right Channel uses connectors
with a Red band and the Left Channel uses connectors with either a White or Black band. Note that
each input has an associated ground terminal. This should be used only when using input cables that
have separate ground leads for the shields. Any ground lead from the turntable should be connected to
the ground terminal to the right of the AC power connector.
Since the Phono III has a fully balanced input stage, the XLR connector may be used for the cartridge
leads; however, the wiring of the cable from the cartridge is critical in this case, or the balanced
capabilities of the Phono III will not be realized. See Appendix A for information on how to properly
modify your input cables (or prepare a custom cable) for use with the balanced (XLR) input connector.
Failure to use properly wired input cables with the balanced (XLR) input may result in a faulty
connection and may also cause an increase in the hum level. Alternatively, a pair of specially wired
adapters is provided with each Phono III to properly adapt an unbalanced cable for use with the
balanced input. These adapters are the ONLY adapters that can be used for this purpose. Other
commercially available adapters do not properly convert from unbalanced to balanced and will result in
the Phono III operating in the unbalanced mode, NOT the balanced mode. If you are properly using the
XLR input connector for your cables, be sure to move the input connector selection switch to the “Bal”
position. Otherwise, it should be in the “Unbal” position.
Once the input cables have been connected, the cartridge type for each input should be selected using
the switches on the front panel (See Figure 1B). The left-most switch for each input is used to select
either MC cartridge (resistive loading) or MM cartridge (capacitive loading) for the input in question.
1
This determination should be made before proceeding with the setup. If a MM cartridge is selected, the
adjacent switch permits selection of 47Kohms or 100Kohms for the loading resistance. If a cartridge
requires a “Custom” load, it should be connected to input “A”, because the cartridge type switch for the
“A” input has a center “off” position that bypasses the internal loading networks in the Phono III. (See
Section 2.2 for instructions on installing a custom load.)
The switches for playback equalization should be checked to ensure that the first of these is in the
center “off” position which selects the RIAA equalization curve. Additional information on the use of the
equalization switches will be found in Section 4.4 and Appendix B.
The choice of output connector depends on whether balanced or unbalanced output cables are to be
used. If unbalanced cables are to be used, they are connected to the Left and Right channel RCA
connectors, respectively. Balanced output cables are connected to the respective XLR output
connectors. The Phono III can drive separate amplifiers using both the balanced and unbalanced
outputs, providing that the combined loading impedance does not result in total output currents
exceeding 30mA.
2
1
The basis for this selection also applies to moving iron and other types of phono cartridges.
2
This corresponds to a load of approximately 235 ohms when the Phono III is operating at its maximum 7VRMS
output level. At lower levels, the allowable loading will decrease correspondingly.

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The AC power cord plugs into the connector on the left-hand side of the AC power module on the back
panel.
3
This power module also contains the power on-off switch and two line fuses housed in the
center section of the module.
NOTE: This module can accommodate either 120VAC or 240VAC supply voltages; however, supply
voltages are NOT interchangeable without internal changes on the power supply board. Unless
indicated otherwise, all Phono III units are set to operate ONLY on 120VAC, and connecting to 240VAC
will cause failure of the unit. Those units that are set to operate on 240VAC are so indicated by the
application of a label indicating use for 240VAC on the back panel.
The fuses are accessible by removing the power cord and then prying the fuse holder out of the center
portion of the AC module using a small flat blade screwdriver. (The provided flat-blade screwdriver is
too narrow for this purpose and, if used, may be damaged and unable to perform the adjustments in
Section 5.0). There is a slot to be used for this purpose on the edge of the module adjacent to the
location of the power plug. Extra fuses are provided, and are located in small compartments that are
integral to the fuse holder. These are accessible once the fuse holder is removed. Be certain to only use
replacement fuses that are of the 20 mm size, and 1.5 amp capacities such as the Buss Type GMC fuse.
(If you wish, “Audiophile grade” aftermarket fuses may be used provided they are of the same size and
amperage rating.)
2.2 Installing a Custom Load
The internal loading networks of the Phono III can provide resistive loading for MC cartridges over the
range of 10 ohms to 2550 ohms in 10 ohm increments. The capacitance loading for MM cartridges
covers the range from 120pF to 1400 pF, in 10pF increments. However, if these ranges are not
sufficient, and a custom load is required for a specific cartridge to be installed on input A, proceed as
follows.
Using the provided 2mm slotted screwdriver, undo the two captive screws on the cover plate at
the left end of the Phono III top panel (see Figure 7) and remove the cover plate. (The two
screws are captive and will not come out of the cover plate.)
Using a small light look down into the unit and what you will see is shown in Figure 4. The two
circuit boards are the modules for the internally controlled MC cartridge loading. On each board
is a pair of pin sockets, shown by the red arrows, for a custom resistor or capacitor to be
inserted.
Having determined the proper value of resistance or capacitance to be used, insert the
component leads into the pin sockets on each board.
Replace cover plate.
The loading thus inserted will be used whenever input A is selected and the cartridge type switch for “A”
is in the center “off” position. If this switch is in either the MC or MM position, the custom load will be
3
The supplied power cord is a shielded cord; however, users may prefer to use their own power cord having a
standard IEC connector.

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out of the input loading circuit. Also, when using either input “B” or
“C”, the custom load will be ignored.
NOTE: There is a fixed 100Kohm resistance across the input of the
Phono III.
4
Thus, if the desired custom load resistance is RL, then
the actual value of resistance to be inserted, RX, is given by
RX = [ RL 100K ] / [ 100K –RL ] ,
( “” implies multiplication, “K” = 1000) .
Thus, if RL = 10Kohms, RX = [10K 100K ] / 90K = 11.11Kohms .
Based on available resistor values, it may be necessary to use an RX
that is not the exact value as calculated above. If a custom
capacitive load, CL, is required, the value of capacitance to be
inserted, CX, is given by
CX = CL –120,
where the values of capacitance are given in pF (pico farads = 10-12
farads).
Figure 4 –Layout for Installing Custom Load
3.0 OPERATING THE PHONO III AND SETTING THE MEMORIES
You are now ready to finalize some of the initial setup procedures that can be performed only when it is
operational, and start enjoying your DSA Phono III. The Phono III should be placed on a sturdy shelf that
will provide adequate support for the unit and permit access to the back panel for cable connections.
Clearance at the ends of the unit should be at least 1 inch, and the top panel clearance should be at
least 3 inches to permit adequate air circulation for cooling.
3.1 Turning on the Phono III
After connecting the input and output cables, and inserting the power cord into the AC module, you may
turn on the Phono III using the power switch on the AC module on the back panel. The Standby LED on
the front panel will show a red-orange color and will blink at approximately a 1Hz rate. This blinking will
continue for about 30 sec during which time the voltages on the internal amplifier boards are ramping
up to their operating values. Until this LED has stopped blinking, indicating that the amplifier operating
4
The 100K internal load is the same regardless of whether the input is balanced or unbalanced.

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voltages have been reached and have stabilized, selecting either Mute or Run will have no immediate
effect.
NOTE: If this LED shows either a red or a green color only, it indicates that one of the power supplies is
not active. Turn the unit off and contact DSA for instructions.
Once the Standby LED has stopped blinking, the Mute position can be selected by pressing the Mute
button on the front panel or remote control. When first moving from Standby to Mute, there will be a 4-
6 second delay while the output driver voltages are applied and before the Mute LED will show a light
green color. Also, you may observe that the Standby LED will show either a brief green or red color prior
to the Mute LED showing a light green color. This is perfectly normal and does not indicate any problems
with the Phono III. In the Mute mode the Phono III is fully powered, but the muting relays at the output
are open. This mode represents the mode in which the Phono III can be left operating for long periods
of time, if desired, and is the mode in which thermal equilibrium will be obtained most readily.
Switching to the Run mode, using the front panel or remote control button, closes the output muting
relays and the Run LED will show a blue color. There is no delay between selecting the Run mode and
the Run LED turning blue. Switching back to Mute from Run will turn off the Run LED and illuminate the
Mute LED again. Switching back to the Standby mode turns off the output stage voltages but not the
amplifier board voltages so the Standby LED will glow but will not blink.
NOTE: If either the Mute or Run button is pressed during the initial 30 sec period after AC power on,
the Phono III will advance directly to the operating mode that was selected once the Standby LED has
stopped blinking. However, there will still be the initial 4-6 second delay while the output stage is
powered up.
Once operational, the Phono III should be left in the Mute or Run mode for about two hours to reach
thermal equilibrium. While it can be used and enjoyed during this warm-up period, there is the potential
for small DC voltages to appear at the output connectors and some of the switch functions—if
activated—may cause unwanted “pops or thumps” in your speaker system. These will be greatly
reduced after the Phono III has fully warmed up and thermally stabilized, at which point the top panel
should be slightly warm to the touch. For those who wish to listen on a regular basis, it is advised that
the Phono III be left running in the Mute mode since this will maintain the optimal thermal equilibrium
condition.
3.2 Front Panel Functions
The functions available on the right-hand-side of the front panel are described in detail below.
Mode: This function toggles between stereo and mono operation. In the Stereo mode, the Phono III is a
true stereo preamplifier with > 60db channel separation. In the Mono mode, the left and right channels
are summed to provide a true mono mode (the identical signal applied to both channels). The mono
mode works best with mono LPs, but can also be used when playing stereo LPs if desired. NOTE: Some
mono cartridges will cause excess hum due to internal wiring that creates a ground loop. Selecting
the "Mono" mode in this instance will largely cancel this hum.

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Phase: This function selects either normal or inverted absolute polarity of the audio signal. The default
condition is non-inverting from the input to either the unbalanced output or the positive side of the
balanced output. Repeated pressing of the button on the front panel or remote control toggles between
non-inverting and inverting operation. This function can be used in any of the Phono IIIs operating
modes.
Filter: This function is either “on” or “off”. The LED is illuminated when the high-pass (HP) filter is “on.”
This function is used to reduce low frequency rumble or resonance from the turntable, or other
undesirable very low frequency content from the source. When selected, the filter response shown in
Figure 5 is added to the overall response at the selected gain setting and playback equalization curve.
Figure 5 - Relative Filter Response
L-R/R-L: This function operates only when in the Mono mode of operation and it differences the left (L)
and right (R) channels as indicated. This function works in conjunction with the phase selection. If the
phase is non-inverted, pressing the button will select the L-R function, and pressing it again will revert to
mono mode only. If the phase is inverted, pressing the button will result in R-L, and pressing it again
reverts to the mono mode. If the unit is operating in the L-R condition, then pressing the phase button
repeatedly will “toggle”between L-R and R-L. (See Section 3.5 for a description of how to adjust the
azimuth angle using this function.)
3.3 Setting the Gain Memory
The Phono III has a memory that stores the gain setting for each input, and this memory must be
“initialized” when the unit is used for the first time. The gain values can ONLY be set when the unit is in
either the Standby or Mute modes of operation. When powered on, the default gain will always show
“40dB”until an input is selected. The gain required for each input can be selected, and stored, using the

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buttons on the front panel, or the remote control. To select and store the gain for each input into
memory, proceed as follows:
Note: The Phono III comes with the gain memory set at 40dB for each input. If this is the desired gain
value for a specific input, no further action is required.
Ensure that the unit is operating in the Standby mode (LED not blinking) or the Mute mode. The
40dB gain LED will be illuminated.
Press the “A” input button and then press the button on the front panel, or remote control, for
the desired gain. This stores the desired gain in the memory for the “A” input.
Repeat the above process until all desired inputs have been assigned a gain value. If the default
gain value of 40dB is correct, the 40dB button does not need to be pressed since 40dB is already
stored in memory.
Table 1 provides guidance regarding the appropriate gain for various cartridge output levels. If you find
that the gain initially selected is too low or too high, place the unit in either Standby or Mute mode and
using the front panel buttons, or the remote control, select the new gain for that input. This will store
the new value in the gain memory for the selected input. Do not be afraid to experiment with gain
settings, but try different ones to get the desired listening level for your system. It is almost impossible
to overload the Phono III, and even if overloaded, it will not damage the unit.
TABLE 1
Cartridge output (mV) RMS at 1KHz
Gain
>3mV
1mV –3mV
0.5mV –1mV
0.3mV –0.5mV
< 0.3mV
40 dB
X
X
46 dB
X
50 dB
X
56 dB
X
X
60 dB
X
66 dB
X
3.4 Setting the Cartridge Loading Memory
The internal loading circuits are divided into two sections:
One section provides the capacitive loading for MM cartridges as well as the 47Kohm/100Kohm
selection for resistive load.
The other is a plug-in module that controls the resistive loading for MC cartridges (this module
can be seen in Figure 4).
These modules are controlled by a “master” up/down 8-bit binary counter that is “clocked” either by the
“Up/Down” buttons shown in Figure 1B or by the “Up/Down” buttons on the remote control shown in
Figure 3. The loading range and incremental steps are as follows:

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MC cartridge –0 ohms to 2550 ohms in 10 ohm steps (Using 0 ohms will result in a shorted
input and very little, if any, signal.)
MM cartridge –120pF to 1400 pF in 10pF steps. Also the resistive load can be 47Kohms or
100Kohms.
For MM cartridges, the minimum 120pF represents the input capacitance of the Phono III, and the upper
limit is restricted to 7-bits on the counter.
When the Phono III is turned on by the user for the first time, the loading memory has all “0s” stored for
each input, so it is necessary to provide “baseline” loading data for each input.
5
The baseline data can
be set in any of the operating modes (Standby, Mute, Run). To store the “baseline” data, proceed as
follows:
With the unit turned on, and in either the Standby or Mute mode, select an input to be used.
(You have already selected the cartridge type in Section 2.1).
The display will show “0”ohms if you selected a MC cartridge, or “120”pF if a MM cartridge was
selected. If a MM cartridge was selected, the selection of 47Kohm or 100Kohm resistive loading
should have also been made.
Using either the “Up” button on the front panel, shown in Figure 1B, or the “Up” load button on
the remote control, shown in Figure 3, increase the loading to a “baseline” value as
recommended by the cartridge manufacturer, or based on previous listening experience. (If you
overshoot the desired value, use the “Down” buttons to make corrections.) This will be the
“baseline” loading value for that input.
Press either the “Up” or the “Down” button on the front panel to store the “baseline” loading
value. NOTE: The “baseline” loading data is ONLY stored using the buttons on the front panel.
Using the up or down buttons on the remote control will NOT store any data in the loading
memory. (See following paragraph for using the load buttons on the remote.)
Repeat the above process for the other inputs that will be used.
Having put the “baseline” data into the loading memory, it is now possible to use the remote control to
make loading adjustments while listening and not alter the “baseline” data. This permits the user to
make minor changes in the cartridge response for the purposes of enhancing the listening experience
for a particular recording by using the “Up”/”Down” buttons on the remote without changing the
“baseline” data. To return to the stored “baseline” loading value at any time, press the “mute” button
and then the input selection button for the input being used, followed by pressing the “run” button. If
the listener believes that an improved “baseline”loading was obtained by using the buttons on the
remote while listening, it is only necessary to use either the “Up” or “Down” button on the front panel
to store the newly obtained loading value for that input (pressing “mute” is not required).
5
The “baseline” data represents the load values that will be stored in memory for each input/cartridge
combination based on manufacture’s recommendations or listening experience. This value can be easily changed
if listening experiences offer a better value.

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Note: Using the “reset”, shown in Figure 1B, will “zero out” the “baseline”loading values in the memory
for the selected input.
3.5 Adjusting Cartridge Azimuth Angle
The “L-R/R-L” function can be used to adjust cartridge azimuth alignment; however mono source
material is required for this adjustment. The approach relies on the differencing of the signals from the
left and right channels. Azimuth alignment is set when there is zero (or equal but very low) signal in
both the L-R and R-L settings.
6
The steps to be followed are as follows:
1. Place a monophonic record on the turntable
2. Switch the Phono III to the mono mode
3. Push the “L-R/R-L” button and play the record
4. While “toggling” the phase button, listen to the speaker output and adjust the azimuth angle of
the cartridge to obtain a minimum sound level in each position (L-R and R-L).
5. When satisfied, switch back to the stereo mode.
4.0 DESIGN PHILOSOPHY AND IMPLEMENTATION
The solitary goal of the Dynamic Sounds Associates (DSA) Phono III is to provide the finest possible
reproduction from LP recorded media. To achieve this goal, the Phono III is based on a “no-compromise”
dual channel design using best engineering principles and the finest of components. The Phono III does
not employ any form of loop feedback to achieve the desired throughput gain or the proper playback
compensation. Instead, each gain stage of the Phono III has internal feedback to ensure that all forms of
distortion are held to very low levels. The playback compensation is provided through the use of passive
low-pass networks, with the proper time constants, located between the gain stages of the amplifier
chain. This approach provides low distortion plus a very high dynamic range. It also eliminates transient
inter-modulation distortion, which is a common byproduct of configurations where the throughput gain
and playback compensation are achieved through the use of inter-stage loop feedback.
Furthermore, because even the finest of coupling capacitors can cause minor, but perceptible,
degradations in the reproduction of the audio signal, the Phono III has no coupling capacitors in the
audio chain from input to output. Yet, through the use of an innovative design it remains very stable
and resistant to DC drifts. Additional advantages of the design approach are the ability to provide easy
polarity inversion of the audio signal and a true monophonic capability for the proper reproduction of
monophonic LPs. Combining these two capabilities leads to the L-R and R-L capability in the mono mode
which is used, as described, in Section 3.5.
6
There are other methods for adjusting the azimuth angle that rely on minimizing channel cross talk. The use of
these approaches may be beyond the capabilities, or resources, of many audiophiles; and, we believe that the
approach described in Section 3.5 will prove satisfactory in most instances.

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5.1 Amplifier Chain
The block design of the Phono III is shown in Figure 6. It consists of four all JFET balanced (differential)
amplifier gain stages, two of which can be adjusted to provide the required gain to accommodate
virtually any phono cartridge. In addition, each gain stage employs its own precision, temperature
compensated, low noise constant current source and voltage regulator for the ultimate in stability,
signal control, and isolation.
Figure 6 –Phono III Block Diagram
As can be seen from Figure 6, the first and second gain stages, as well as the third and fourth gain stages
are differential pairs. The fourth gain stage is also connected differentially to the unity gain output
driver which provides a balanced output through a standard XLR connector and a single-ended output
via a standard RCA type phono jack. The two switches shown at the input represent the process that
allows the input stage to accept either unbalanced or balanced inputs. The solid lines represent the
unbalanced mode configuration and the dashed lines the balanced configuration.
Using two differential pairs of gain stages has significant advantages for noise reduction which will be
discussed in more detail in Section 4.5. The downside of differentially coupling the first and second gain
stages is that two matched LP filters are required for the HF component of the playback equalization
curves. However, the filters are of a simple design and can be easily balanced to ensure proper playback
equalization. The balancing and calibration of these filters is performed by DSA during the “break-in”
period after a new unit is assembled and is not a user accessible adjustment. Once balanced and
calibrated, there is no requirement to perform any further adjustments on these filters.
While the Phono III has no coupling capacitors in the signal path, it still does not have any significant
response at DC which prevents the propagation of DC drifts and offsets. This “DC block” occurs at the
input to the third gain stage, the first stage in the second differential pair shown in Figure 6. This “DC
block” combined with the gain dependent low frequency response of the first stage results in a
frequency “roll-off” at very low frequencies as shown in Figure 7. This very low frequency roll-off is
relative with respect to the absolute gain and any playback equalization being used. If the filter function
has been activated, that response will be added to the frequency response shown in Figure 7.

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Figure 7 –Relative Low Frequency Response of the Phono III
4.2 Output Driver
The Phono III uses a separate high bias current Class A output driver for each polarity of the amplified
audio signal. The output stage supply voltages are fully regulated and are powered separately from the
voltage rails that power the amplifier chain of the Phono III. The output impedance for each polarity at
the output connectors is 75 ohms.
Because of the high rail voltages, and the inherent linearity of the Phono III design, it is capable of
providing an output drive voltage of >20 volts peak-to-peak without any clipping of the audio signal. The
output stages of the Phono III can provide up to 30mA of drive current without distortion, and can drive
amplifiers with input impedance as low as 1kOhm, or long cable runs that have a capacitance of greater
than 30nF, without any problems
7
.
4.3 Power Supply
The Phono III employs a dual, fully regulated power supply, and the individual supplies are isolated from
each other. The power supply for each channel provides ± 60V rail voltages for the operation of the
7
This is based on a 20kHz signal at 30V p-p. At lower frequencies or drive levels, the Phono III can drive significantly
higher values of capacitance without difficulty.

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amplifier section as well as separate rail voltages of ± 47V for the associated output stage. In addition, it
also generates regulated ±12VDC for internal use by the regulator, and +5VDC that is used to operate all
of the control functions.
To accommodate the fact that the Phono III contains no coupling capacitors within the audio path, and
to prevent damage to components that could occur if the rail voltages were applied suddenly, the
Phono III power supply is designed with an approximate 30 sec ramp from about ±5VDC at turn-on to
the full ±60VDC. As the voltage slowly increases, the value of both positive and negative rails are
monitored by comparison circuitry in the power supply. Only when both rails have achieved the proper
final values of ±60VDC, and the regulator section has “clamped” indicating that it is in the fully regulated
mode, is a turn-on signal generated that permits the output stage to be turned on when the “Mute” or
“Run” button is pressed. In a similar manner, the voltage rails for the output stage are monitored to
ensure that they are correct before the “Run” function can be enabled. This prevents operation in the
event of a failure within the power supply or amplifier board that could result in applying a large DC bias
to the output connectors.
4.4 Playback Equalization
As seen in Figure 5, the playback equalization is divided into two parts. The high frequency (HF) (>1kHz)
compensation is located between Stages 1 and 2, and the compensation for frequencies <1kHz is
located between Stages 2 and 3. The compensation is designed in this manner to ensure that HF signals
from the cartridge which enter the preamplifier at levels greater than those at lower frequencies are
correctly attenuated before passing to the other gain stages of the Phono III. This approach ensures high
dynamic range over the full frequency spectrum as well as significantly reducing the output noise power.
Because of the inherent flexibility of this approach, it was decided to incorporate additional playback
equalization curves in addition to the RIAA curve which has become the recording industry standard.
Appendix B provides an in-depth discussion of playback equalization curves and information on their
incorporation into the Phono III architecture.
As shown in Appendix B, the playback equalization curves are determined by a set of three “time
constants”, where each time constant can be represented by a combination of a resistor and capacitor
of specific values. Table 2 (also Table B.1) shows the time constants for the equalization curves that
have been incorporated into the Phono III, and the recording labels that they are associated with.
TABLE 2
The choice of equalizations based on Columbia and Decca/FFRR was based largely on their early
dominance in the production of the LP record, and that information regarding the equalizations they
GROUP
EQ Curve
NAME
t1
t2
t3
---
--
RIAA
3180 μsec
318 μsec
75 μsec
G1
EQ1
Columbia-Pre RIAA
1590 μsec
318 μsec
100 μsec
G1
EQ2
Decca/FFRR - Pre RIAA
1590 μsec
318 μsec
60 μsec
G2
EQ1
Columbia 78RPM
---
530 μsec
100 μsec
G2
EQ2
Decca/FFRR 78RPM
---
530 μsec
25 μsec