MUSICAL DESIGN
SP-2B/C
SP-2B/C Signature
SP-2B/C Platinum
MUSICAL DESIGN
SP-2B/C
Thank you for purchasing the Musical Design SP-2B/C. This vacuum tube line stage preamplifier
is the result of years of research into 'listener-oriented' design. There are many worthy design approaches
from a pure engineering perspective, but it is much more difficult to design a preamplifier with great
sound quality than one with great specifications. This fact is evident from the small number of truly
'classic' designs developed over the years. In our view, the Musical Design SP-2B/C meets the
requirements of a classic design. We believe that the sound of a 'classic' reflects timeless values. In other
words, a classic design of today will be considered to meet sophisticated musical tastes of audiophiles
for years to come. The sophisticated audiophile appreciates the classics of yesteryear as much as the finest
present-day designs. We are sure that you, as a discerning listener, have heard a classic design and
appreciate the merit of 'timeless' quality. There are classics in fine clothing, the arts, and other areas of
human endeavor that can be matched in the art of electronic design. Accomplishing these goals is the most
respected achievement in any design endeavor. We are proud of the achievement represented by the classic
Musical Design SP-2B/C. We know you will spend many satisfying years enjoying this extraordinary
preamplifier.
TABLE OF CONTENTS
INTRODUCTION ................................................................................................................................ 1
DESIGN CONSIDERATIONS ............................................................................................................ 2
INSTALLATION ................................................................................................................................. 3
OPERATION..................................................................................................................................... 4,5
CARE AND MAINTAINENCE .......................................................................................................... 6
AUDIOPHILE DISCUSSION ............................................................................................................. 7
WARRANTY ....................................................................................................................................... 8
NOTES ................................................................................................................................................. 9
SCHEMATICS ............................................................................................................................ 10 - 12
©copyright Musical Design 1999
1
DESIGN CONSIDERATIONS
The Musical Design SP-2B/C is a direct result of
years of investigation which revealed how topology and
component parts affect sound quality. At Musical Design,
we believe that there is great virtue in simplicity. Therefore
our preamplifier has the minimum of stages and complexity. The Musical Design team has a great depth of experience in selecting the essential passive parts that make up a
great audio design.
It should be clear, to even casual observers, that
traditional measurement techniques fail to predict the sound
quality of a preamplifier. Given this argument you might
think we are suggesting that audio design still smacks a bit
of alchemy. You would be right! However; there are
technical details to explain, so read on!
CIRCUIT DESCRIPTION
The input signal is DC coupled . This vacuum tube
line stage preamplifier uses only two tubes, one for each
channel. Each twin triode(6DJ8/6922) in the SP-2B operates
as a single push-pull voltage gain stage. Therefore; the
active circuitry is essentially composed of one stage per
channel - not two. The same operation is used in the SP-2C
with the Electro Harmonix 12AU7EH.
The circuitry operates in Shunt Regulated Push
Pull(SRPP) mode. This has been called "The most linear
circuit design possible for vacuum tubes." SRPP operation
provides extremely wide bandwidth and low distortion
without global feedback.
POWER SUPPLY
Separate B+ voltage pass transistors and capacitor
reservoirs are used in each channel. Very large capacitors
are used for the 'raw B+' and outputs of each regulator.
These capacitors are larger than those used in many tube
power amplifiers. Filament voltage is heavily filtered and
then regulated. A huge capacitor is used for the 'raw' heater
supply and heater voltage regulation ensures no variation in
cathode emission during operation. The power transformer
is custom manufactured. It's windings are wound side by
side, not one on top of the other like conventional designs.
This is a so-called 'Split Bobbin' design which minimizes
the intrusion of sonically harmful RFI energy. The overall
power supply design emphasizes RFI attenuation and
minimum wideband noise.
2
ENCLOSURE
The cabinet is fashioned from heavy-gauge, damped
steel which has good vibration absorption characteristics.
The cabinet is solid and quite acoustically dead. The cabinet
feet are not just ordinary rubber feet, but are especially
designed to minimize acoustic feedback transfer to the
preamplifier chassis from the supporting surface. We all
know the importance of minimizing component vibration. It
is important to reduce the vibration of the vacuum tubes,
since the tubes are susceptible to mechanical vibration
known as microphony. The faceplate is machined from
0.250 inch aluminum which is brushed and then anodized
either silver or black. The handles, which can be purchased
as an option, are custom extrusions especially designed by
and made for Musical Design.
FEATURES
Many features of the SP-2B/C are unique and expensive.
When it comes to value received, we believe the SP-2B/C
is in a class by itself.
'DIRECT' input switch is hard wired to "DIRECT"
jacks. This input bypasses "SELECTOR" switching
and the "MODE" control for a more pure signal path.
SPLIT BOBBIN POWER TRANSFORMER with
metal casing minimizes RFI transmitted via power
lines, while reducing hum to vanishing levels.
DUAL 'MAIN OUT' jacks simplify the connection of
bi-amplified systems.
'MUTE' switch provides full muting of the output at
your command. The output relay mutes the output
signal for the first 30 seconds following turn-on and
instantly at turn-off.
TEFLON® insulated, Gold-Plated RCA jacks are
used for all input/output connections
IEC power cord socket allows experimentation with
aftermarket power cords.
INSTALLATION
It is recommended that the SP-2B/C be installed in
an 'open' installation, i.e. on a table or cabinet top. This
allows easy access to the rear-mounted power switch. A
preamp as visually pleasing as the SP-2B/C likes being
shown off. If you must install it in a cabinet, you can leave
enough room above the preamp to reach in with your arm
and activate the power switch. At any rate you should leave
a few inches above the preamp for adequate ventilation and
this may provide vertical clearance to reach the power
switch. If access to the power switch is difficult, you should
use a high current 'power strip' with a built-in power switch
to energize the SP-2B/C. Of course, you must leave the
power switch of the SP-2B/C 'on' for this to work. The SP2B/C is equipped with a time delay relay, so it will not
produce thumps from the loudspeaker even if it is turned on
sequentially after the power amplifier. This relay switches
off the main outputs within 0.5 seconds at turn-off ensuring
that no thumps appear at the loudspeaker at any time.
LOCATION
The power transformer used in the SP-2B/C minimizes
external hum fields, but any sensitive low-level equipment
should not be 'stacked' atop the preamplifier. In other
words, do not set a moving coil headamp or any other low
level amplifier such as a microphone preamplifier on top of
the SP-2B/C. To minimize induced hum pickup in the SP2B/C itself, allow a foot or more of space between the SP2B/C and any power amplifier, isolation transformer, or any
other device containing a large transformer.
PROPER VENTILATION
The SP-2B/C will become noticeably warm in use.
It will remain cooler if it is operated in an open area with
unrestricted air flow. Since the SP-2B/C has been provided
with ventilation slots on the side and a see-thru front panel
vent, it has adequate ventilation in almost any installation. If
it must be used in an enclosed cabinet, allow about 2-3" of
air space above the preamplifier. In addition, it is a good idea
to have some ventilation in the rear of the cabinet enclosure.
Please observe the following precautions:
Do not obstruct the ventilation holes in
the top cover or front panel.
Do not place records, CDs or other
temperature sensitive materials on the
top cover.
Do not install in a tight space lacking
ventilation provisions.
3
OPERATION
The SP-2B/C is activated by pushing in on the upper
half of the rear panel 'rocker' switch. The vacuum tubes
visible through the front panel light up over a 10 second
period. If the tubes do not light at turn-on, see the section
in this manual called PROBLEMS. When the SP-2B/C is
turned off, the tubes go dark slowly.
MAKING CONNECTIONS
AC
The AC power cord is an IEC removable type. Note
the one way insertion pattern and insert the cord into the
rear-mounted IEC receptacle. Seat the cord firmly into the
receptacle. Before plugging this cord into your wall socket
make sure the on-off switch is in the off position, i.e. the
bottom of the switch is pushed in. The AC power cord must
be connected to an outlet providing 120 VAC at 50/60 Hz.
If your AC line voltage is not 120 VAC, 50/60
Hz, you must use the 'export' version of the SP-2B/C
with the transformer voltage adjusted properly. Alternately, you may use a voltage conversion transformer of
at least 50 watts capacity.
INPUT/OUTPUT
Shielded 'RCA cables are required to connect the
input/output signals with the SP-2B/C. The SP-2B/C has
low output impedance and will drive high capacitance interconnects up to 30 feet in length, but we recommend that you
keep your interconnect length as short as possible.
Keep both channels of the interconnect close to each
other throughout their length to minimize hum.
Do not run interconnects parallel to AC cords; cross
them at right angles to each other.
The MAIN OUTPUT jacks of the SP-2B/C provide a
signal of inverted absolute phase. Reverse the connections on both speaker cables at either the power amp or
the speakers to maintain proper absolute phase response.
GENERAL OPERATION
'DIRECT INPUT'
The component that is connected to the rear panel
'DIRECT' inputs has a direct connection to the STEREO/
MONO switch then onto the volume/balance control - the
SELECTOR control is not in the signal path. This reduces
signal degradation for your favorite reference component.
To use DIRECT inputs, simply connect your favorite high
level component into the DIRECT inputs on the back panel
and put the DIRECT/SOURCE switch in the DIRECT
position. No adjustment to the SELECTOR switch is necessary. The 'DIRECT' input is not available at the 'TAPE OUT'
jacks for recording.
4
SELECTOR SWITCH
The function of this control is very straightforward.
The labeled inputs on the rear panel correspond to the
labeling on the selector switch. For example, simply connect your tuner to the TUNER input on the rear panel, then
select TUNER with the SELECTOR switch. The DIRECT/
SOURCE toggle switch must be in the SOURCE position
to activate the SELECTOR switch. Please note that the SP2B/C does not have a phono stage. If you have an outboard
phono stage such as the MUSICAL DESIGN PHONO ONE,
it can be connected to any input.
MODE SWITCH
In the normal STEREO mode, the MODE switch
presents the sound in normal stereo as found on modern
audio recordings. Many historical recordings are only
available in monophonic sound even in CD format. It is
preferable to replay these recordings with the MODE switch
in the MONO position. The REVERSE position is handy
for making certain system tests. In addition, if you borrow
a new component for a brief evaluation and you accidentally
get the connectors backwards, the REVERSE position makes
life easier.
BALANCE SWITCH
The BALANCE control provides trimming of the
output of each channel and then complete attenuation of
each channel at the maximum positions. In center position(0), each channel has maximum output. Then, for
example, if you rotate the switch counterclockwise it begins
to attenuate the right channel and finally cancels the right
channel output in fully counterclockwise rotation.
OPERATION
MUTE/LISTEN SWITCH
VERY, VERY IMPORTANT!
This toggle switch allows you to silence the main
output jacks at any time, except for the first 30 seconds of
on time. The output is automatically muted for the first 30
seconds after activating the power switch. Simply move the
switch to MUTE position to silence the output and then
return to the LISTEN position to continue listening. This
provides a full muting of the output signal, not a partial
muting. When the mute relay is activated it simply shorts the
output to ground. The relay is not directly in the signal path.
Do not use the MUTE/LISTEN switch as a shortcut when you desire to change one of the input cables,
although you may do this as a safeguard. We recommend that
you switch the input SELECTOR or the DIRECT/SOURCE
switch, from the active input to an unused input when switching interconnect cables to avoid stress on the vacuum tubes.
In other words, if you are in source mode and wish to change
the input wires for the tuner, then set the SELECTOR
switch to CD while this is done. Then reselect TUNER to
listen to the cable change. If you want to change the wires to
the DIRECT input, simply move the DIRECT/SOURCE
switch to SOURCE. Simply turning the volume all the way
counterclockwise will provide the same level of protection
to the vacuum tubes, but you will lose your reference volume
level.
NOTE: The muting relay is a quality device and is very quiet
in operation. If you doubt that it is working, simply move the
MUTE/LISTEN switch very slowly so that the noise of the
switch does not mask the sound of the clicking relay.
Few people make the decision to purchase a highend product without quite a bit of thought on the subject. So
don't you think it is also worth your time to make sure your
purchase is as good as you thought it was when you made the
decision. Well, what are we getting at here? You just plop
the thing down, plug it in and go, right!
Well it just isn't so easy. For instance, we recommend that you burn-in the SP-2B/C for a minimum of three
days. Thats right, just leave it on, play it and don't take the
sound too seriously for a few days. Ok, so it does clobber the
preamp you had, just remember it will get better! You can
even play it while you sleep. Just put a CD in your player and
put it in repeat mode. Set your SP-2B/C to the same input the
CD player is connected to, put the SP-2B/C in MUTE mode
and turn the volume up about half-way. You could even use
the special CD from Sheffield Labs, designed to break in a
system.
ON/OFF SWITCH
The ON/OFF switch is located on the rear panel.
When the top of this switch is pressed, it activates the
preamplifier. After 30 seconds the internal relay activates
the output and listening can begin. The power switch has no
'on' indicator, the lighted vacuum tubes, which are visible
thru the screened 'viewing window' in the center of the front
panel, are the only 'power on' indicator required.
CHASSIS GROUND
A post is provided on the rear panel for grounding
other components to the SP-2B/C. This may prove useful if
there is a hum problem in the system. If an outboard phono
stage is used with the SP-2B/C and hum occurs, then grounding it to the SP-2B/C may help. Experimentation is the only
way to defeat hum problems. The SP-2B/C should be
completely free of hum in most installations, if the grounding is optimum.
5
INFORMATION
A great deal of care has gone into the design of this
product. Musical Design engineering guidelines called for
a minimum design life of 15 years for all parts (except
vacuum tubes)used in a typical audiophile system. In other
words, this product has not only been designed to sound
great today, but to sound just as good in the next century.
The resistors used are known for their staggeringly low
noise and long term reliability. The electrolytic capacitors
have generous safety margins and low impedance to further
reduce heating effects. In this age, when audiophiles seem
programmed to think that great sounding products are
necessarily unreliable, the Musical Design SP-2B/C is a
breath of fresh air. It is a preamplifier designed to stand the
test of time in terms of reliability and musical naturalness.
CARE
The SP-2B/C needs little maintenance, except for cleaning.
Never use harsh detergents, solvents, oven cleaner or
abrasives to clean any surface.
Never apply a liquid spray cleaner through the front
panel or top cover ventilation ports.
Never allow a solvent used to clean the RCA connectors, to touch painted surfaces.
Always enclose the SP-2B/C in the original plastic bag,
when moving or shipping, to minimize paint abrasion.
Clean external surfaces with a moist cloth or chamois. A small amount of mild detergent may be added to the
water, but follow this cleaning with a distilled water wipe/
rinse. A silicone cloth may be used to enhance surface lustre.
REPLACING VACUUM TUBES
The SP-2B requires replacement tubes of the
following types: 6N1P or 6DJ8, 6922, 7308, 6ES8, ECC88
and E88CC. The SP-2C utilizes the new Electro Harmonix
12AU7EH. There is no recommended replacement for that
tube. The Electro Harmonix 12AU7EH is a new design that
is actually slightly different than the traditional 12AU7/
ECC82. We have taken advantage of it's new linearity in the
SP-2C. Yes, a 12AU7 will work but will lack the naturalness
the preamp can convey. Both triodes within each tube
should be matched and each tube matched to the other for
low distortion and consistent gain from each channel. The
tubes must have matched 'MU' or channel balance will be
affected, since the SP-2B/C operates without global negative feedback, which would normally 'set' the gain, regardless of tube parameters. Obtain replacement tubes from
your MUSICAL DESIGN dealer. If you elect to replace the
tubes, remember to carefully align the pins of the new tube
to the socket when installing, never use excessive force
when putting the tube into the socket! Always respect the
risk of electrical shock - remove the IEC power cord from
the back panel before removing the cover.
6
PROBLEMS
BOTH VACUUM TUBES DO NOT LIGHT
Make sure the power cord is firmly seated in the rear
panel IEC socket and the wall socket.
Is upper half of rear panel power switch pushed in?
Is AC voltage available at wall socket? Plug in a lamp
to test the socket, if in doubt.
If the above conditions are met, it is possible that the
internal AC line fuse is blown(1/2 Amp AGC). This normally
indicates a need for factory service.
NO OUTPUT FROM ONE SPEAKER
Check the speaker fuse, if present, in both the speaker
and power amplifier.
Make sure the problem is not in speaker wires; reverse
them if unsure, also swap amplifier channels to eliminate
the amplifier.
Make sure the interconnects for the affected channel
are firmly seated; always turn amplifier off before
handling interonnects to avoid speaker damage.
If the problem persists reverse the input cable to see if
the problem switches channels. If it does, the preamplifier is okay and the problem is in previous wiring or
components.
NO OUTPUT FROM BOTH SPEAKERS
Make all applicable tests from above lists, testing both
channels for blown fuses etc.
Is the MUTE/LISTEN switch in the mute position?
Have you selected an unused input with the SELECTOR or DIRECT/SOURCE switches?
If all of the above tests fail to pinpoint the problem,
consult with your dealer.
SERVICING
If the SP-2B/C is determined to need factory
service, repackage in the original shipping carton. Be sure
to enclose the preamplifier in a plastic bag. Get a RMA
number from the factory. Send the preamplifier along with
a note stating the problem and return shipping address to the
factory via a reliable carrier. Do not send via parcel post.
AUDIOPHILE DISCUSSION
There are numerous topics that come under the
above heading, but our focus here is how to get the most out
of the SP-2B/C. This is not meant to be an all encompassing
discussion, but covers some points worthy of consideration
and a bit of philosophy.
Long ago, William Congreve wrote "music hath
charms to soothe a savage beast". Well, after a hard day
at the office there is a bit of savage beast in all of us. Coming
home to a great stereo system can be like finding the
proverbial desert oasis. It can be a source of recreation, that
for many of us, is relaxing and involving. Most audiophiles
begin the avocation with a simple attitude of either liking a
certain sound or not. Then they 'progress' to a stage where
they think in terms of audiophile adjectives like 'speed',
'slam' and a real favorite 'information'. Those that stay with
it, develop a really good system and get back to the essential
enjoyment of music for it's own sake. Once again, they get
back to the point where they either like a certain sound or
not. Actually, the SP-2B/C was designed for the first or last
group mentioned above. It is not the kind of preamplifier
with a clearly discernible character that grabs you in the
showroom, but lets you down at home. It is the kind of
preamplifier that you grow with slowly, discovering all of
it's virtues along the way. It is capable of exceptionally
natural tonal balance, realistic imaging and simply astonishing dynamic range. If your system fails to achieve an
extremely realistic sound, uniform frequency balance and a
sense of intimate relationship with the performance, the
reason is unlikely to be the SP-2B/C.
SPEAKER AND ROOM
In our experience, the two most common reasons
for poor sound are improper speaker placement and poor
room acoustics. Of the two, speaker placement is usually
the most troublesome. It is usually possible to find a good
speaker placement even in lively or dead rooms. In our
experience, a live room is preferred to a dead one. Many
otherwise good speakers sound mediocre when placed even
an inch from their optimum room position. In addition, if
they are not toed in properly, the stereo stage is crowded
into a congested clump in the center. If you are unsure of
your speaker setup, start with the speakers about 3 feet from
the rear wall(to the back of the speaker) and at least 1 foot
from the side walls. By moving the speaker around in
reference to the two room boundaries, you will achieve an
acceptable balance. At this point you will notice that by
moving the speaker straight back and forth from the rear
wall you can control the depth to a degree. Further from the
back wall gives more depth, closer gives less. Get a good
sense of depth by moving back and forth, then to gain
control of smoothness in the lower octaves try moving the
speaker in relation to the side wall. Most speakers sound
better when 'toed-in' at the listener or slightly in front of the
listening position, i.e. lines through the center of the speaker
would make an 'X' just in front of your listening chair. If you
have a good system and an even mildly decent room, you
will notice quite astounding differences in sound as you
reposition the speakers. Hey, you don't have to do this at
one sitting, this is supposed to be fun. If you achieve some
improvement and then get a little burned out, come back to
it later after you enjoy some of the good sound you've
already achieved. If you persevere, you will achieve quite a
fine tonal balance and impressive realism. It is unlikely that
you will finish this process in less than 3 hours, and you
must be totally relaxed or forget it. There are a few
unspokens here. Namely, that square rooms are often trouble
and that you should choose the short wall of the room to set
up the speakers. It is usually much more difficult to get
cohesive realism when using the long wall. One problem in
using the long wall is that you have only the back wall
available to balance out the lower octaves. Suddenly, the
achievable sense of depth is tied in with the requirement for
smooth bass/midbass.
BI-AMP OPERATION
If you want to use two amps in the system, go the
bi-wire route and use one amp for each channel, i.e. use one
channel for bass and the other for mid/treble in each
amplifier. This is very affordable and astonishing sounding with the new MUSICAL DESIGN D-75B and DM100B amplifiers. This gives you exceptional channel
separation. The SP-2B/C has dual MAIN OUTPUTS for
this purpose. Try to keep the interconnect lengths to a
minimum, since this doubles the capacitive load on the
preamp.
POWER CORDS
If you have reached a state of near bliss with your
system, perhaps you are ready to experiment with IEC
power cords. However, if you are not extremely satisfied
with the overall sound, it is most unlikely that a power cord
will solve any problems. Power cords do not suddenly make
you happy with a system that is not, at the outset, satisfactory. If your system is not wide open, holographic and
extremely smooth, it is not the fault of the power cord that
was shipped with the SP-2B/C.
It is through experimentation and concentrated
effort that a system is really improved. Don't get off on the
wrong tangent.
7
MUSICAL DESIGN
LIMITED WARRANTY
FIVE YEAR PARTS AND LABOR WARRANTY
This warranty gives you specific legal rights. You may also have other rights which vary from state to state.
Parts and Labor Coverage
Warranty Exclusions
For five years from the original date of purchase, Musical
Design will replace parts found to be defective and will
repair product defects free of charge to the original purchaser, except for vacuum tubes which are warranted for
90-days. This warranty extends protection to the original
retail purchaser. The warranty is not transferable.
The warranty does not cover:
What Must the Purchaser Do?
A product used for commercial or institutional purposes
(including but not limited to rental units.)
Before sending your unit to be serviced, check the owner's
manual. Refer to the 'Problems' section in this manual to be
certain that your problem requires factory service. In some
instances, a call to our service department may reveal a
solution to the problem.
Set-up and installation charges or any adjustments to customer preference.
Repair and/or part replacement due to misuse, accident,
unauthorized repair, product modification or other causes
not within the control of Musical Design.
Incidental or consequential damages arising from use of the
product. This includes, but is not limited to copyrighted
material. Certain states do not allow the exclusion of
incidental or consequential damages; the above exclusion
may not apply to you.
How To Get Warranty Service
In order to get warranty service, it is necessary to:
1. Return the unit to the dealer where purchased
ready for shipment. Your dealer will return the unit
to Musical Design. Consult your dealer first.
2. Contact Musical Design directly; get a RMA number. Return the unit directly to Musical Design in
the original packing material, via a reputable carrier; do
not use 'Parcel Post'!
Whichever party ships the unit, it must be accompanied by
evidence of the original purchase date and a complete
description of the problem. Do not ship 'freight collect'!
ALL IMPLIED WARRANTIES, INCLUDING IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE, ARE LIMITED TO THE
DURATION OF THIS EXPRESS WARRANTY. Some states
do not allow period limitations on an implied warranty, so
the above limitation may not apply to you.
Important Reminder
Please fill out and mail your customer registration card
promptly.This makes it easier to notify you of any product
updates and insures that you will receive any newsletters
that are issued. Return of this card is not required as a
condition of your warranty.
MUSICALDESIGN
189 JACOBS WAY
SAINT PETERS, MO 63376
636-474-9266
TO OBTAIN OUT-OF-WARRANTY SERVICE
1. Contact the dealer where purchased. Your dealer may prefer that you send the unit directly to Musical Design.
2. Package the unit securely in the factory carton. Obtain a new factory carton if necessary. Products arriving in a nonstandard carton, which appear damaged, may be refused. Shipments received 'freight collect' will be refused!
3. Product must be shipped to above address with a letter stating the return shipping address and description of problem.
4. Your unit will receive quality service and will be returned transportation prepaid. Out-of-warranty billing will be
determined by nature of required repairs.
8
NOTES
Please enter important information about your product in the spaces below.
MODEL NO.__________________________________
SERIAL NO.__________________________________
PURCHASE DATE:____________________________
PURCHASED
FROM:_____________________________________________________________________________
TUBE REPLACEMENTS(TYPE/DATE):
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
_____________________________________________
FACTORY SERVICE DATES/PROBLEMS:
_________________________________________________________________________________________________
____________________________________________________________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________
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