Bybee Music Rail

Transcription

Bybee Music Rail

4/19/2011
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
QUICK START GUIDE with HIGH-VOLTAGE INFORMATION
4 Pages
INSTRUCTIONS FOR THE 2AMP Music Rail™ and the 15AMP Music Rail™.
Performance data, power supply information, installation and mounting notes
and high-voltage information.
1
See high-voltage schematic on high-voltage information below
See app note J0409 for exceptions, Bypass Capacitors
3
See app note J0310 for exceptions, Tube Amp Applications
4
See app note J0308 for exceptions, DAC Applications
5
15A Music Rails require heat sinks and insulators
6
Actual output noise will be input noise after suppression, or noise floor, whichever is greater
2
Fig. 1. Pin-Out Guide
4/18/2011
MUSIC RAIL™
INSERTS HERE
Fig. 2. Simplified DC power supply
Read: 0.5V drop for 2A devices.
Read: 2.1V drop for 15A devices.
MUSIC
RAIL™
Fig. 3. Music Rail modified power supply
MUSIC RAIL Installation Notes
1.
Vin must supply 11.5mA idle current to the Music Rail circuit (plus an additional 5mA to
ZD1 when a high-voltage adaptor is used).
2. J1 is the AC ground that bypasses noise currents and input ripple to ground.
3. J12 is the DC ground that returns idle current to the input source.
4. J1 and J12 may be tied together or run separately to optimize noise floor (experimentally).
5. J2-J6 (Vin) can carry 3A each and should be ganged together to carry higher currents.
6. J7-J11 (Vout) can carry 3A each and should be ganged together to carry higher currents.
7. 15A Music Rails must use appropriate heat sink (Pd=2.1V* load current).
8. Transistor on 15A Music Rails must be isolated from ground with thermal insulator.
9. Output capacitor not recommended (see app note J0409: Bypass Capacitors).
10. After installing each unit, insure that correct voltage drop appears from input to output
(0.5V for 2A modules, 2.1V for 15A modules). See data sheet for additional test data.
MUSIC RAIL™ Quick Start Guide
Page 2
4/18/2011
11. When negative polarity modules are used above 30V, the zener clamps in the hi-voltage
adapter must be reversed. All other connections remain the same.
12. As a final test, ensure that the output noise is lower than the input noise (if not, see FAQ).
MUSIC RAIL Mounting Notes
1.
2.
3.
4.
5.
6.
7.
8.
Try to locate the high-voltage adapter parts within 6” of the associated Music Rail.
Try to locate each Music Rail within 12” of the stage it feeds.
Power resistors in high-voltage adaptors should be derated 5-7 times and should be at
least 10mm distance from noise cap. Leave resistor leads 10-20mm long for increased
cooling.
The Music Rails can be bypassed for demonstration purposes. Simply jumper the input to
the output. Wire guage must be appropriate for load current.
For coplanar PC board mounting, a set screw can be used to mount each module to an
existing board standoff.
The mounting collar in each module is isolated and can be mounted directly to the chassis.
The mounting collar accepts #4 screws, but can be drilled out to accept 6-32 screws if
required. Mounting screw heads and standoffs should be 0.25 diameter max. Do not
exceed mounting pad diameter unless nylon or fiber washers are used for isolation.
15A modules can be mounted to existing heat sinks. Simply drill and tap into the heat
sink. Use caution. Taps are hard and brittle. Take care not to over twist the tap.
MUSIC RAIL™ HIGH-VOLTAGE INFORMATION
All Music Rail applications above 30V require High-Voltage Adaptation.
YOU WILL NEED:
1. One or more resistors optimized for your app. (See selection chart on app note J0413).
2. Two 24V, 1W zener diodes (high-voltage clamps). For negative supplies, D1 and D2 must
be reversed.
3. One 1uF capacitor (noise drain). For a list of recommended parts and suggested suppliers,
please see app note J0412.
4. Two terminal strips for mounting parts. (See Mounting Instructions above).
Page 3
4/18/2011
*R1 = (Vin-24V) / (.005A + .0115A) = (D1 + Music Rail Current
*W = (Vin-24V) X (.005A + .0115A) X 5 (5X derating factor)
Fig. 4. Bybee High-Voltage Power Supply
Photos showing typical layouts
Diode location on PC board
High-voltage parts mounted & wired.
##
MUSIC RAILS are manufactured in the United States.
2011 Bybee Labs, Inc.
8390 East Via de Ventura F-110
Scottsdale, Arizona 85258, USA
1-480-998-2880 / [email protected]
Page 4
Bybee MUSIC RAILTM
Direct Current Power Conditioners
General Description
Applications
High-Fidelity Analog Components
High-Fidelity Digital Components
High-Definition Video Components
Test & Measurement Equipment
Linear Power Supplies
Switching Power Supplies
High-End Car Stereo
Medical Equipment
Any other applications where power
supply noise & signal-on-rail affects
equipment performance
The Bybee Music RailsTM from Bybee Labs are
small footprint, active DC power conditioning
modules. They are designed to be installed at the
terminus of DC linear & switching power supplies.
With their low noise and low impedance, they
produce a highly purified source of DC power for
any load within their ratings. Signal-on-rail is
reduced along with power supply noise. (See
noise chart, page 3).
There are two models available in two polarities:
2A +/- and 15A +/-. Only 0.5V is dropped by the
2A device and 2.1V by the 15A device. Any model
can be used to clean up the noise floor of
switching power supplies to levels representative
of the very best analog supplies. In linear supplies,
large banks of filter capacitors can be replaced by
simple ripple filters, allowing package size to be
reduced.
Features
Low Noise Floor: 20nV/root(Hz)
Low Output Impedance: 6mΩ typ
Wide Voltage Range: 4.5–550V
High Current Range: 0-2A / 0-15A
Low Dropout Voltage: 0.5V / 2.1V
Low Dissipation: 1W / 31.5W
Direct-Coupled Topology
Small Footprint: 1.7H x 1.5W x 0.4D
Fig. 1 Raw DC Power Supply
Fig. 2 Raw Supply + DCPC
Benefits
In Fig. 2 (above), a MUSIC RAIL module is inserted between the raw power supply and the active circuit. The
module now interfaces direct with the active circuit. Signals from circuit stages that share common power
supply rails are bypassed by the wideband, low impedance of the MUSIC RAIL. The DC current coming out of
the raw supply is at the same time highly filtered by the Module. This dual effect improves the definition of both
audio and video signals. The MUSIC RAIL operates safely up to 30V and is adaptable to high-voltage power
supplies by the addition of three external parts. See Fig. 5 (below) for high-voltage schematic and page 3 for
R1 derating chart.
1
Performance Characteristics
Fig. 3. Dimensions
Installation Notes
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
J1 bypasses noise currents & input ripple to ground.
Vin must supply 11.5mA idle current to the Music Rail circuitry.
J12 returns the Music Rail idle current to the input source.
J1 & J12 may be tied together or run separately to star.
J2-J6 (Vin) should be ganged together to carry more
current.
J7-J11 (Vout) should be ganged together to carry more
current.
15A devices must use appropriate heat sink (Pd = 2.1V *
load current).
15A device transistor must be isolated from ground
with thermally conductive insulator.
Output capacitor not recommended (see app notes).
C1 must withstand the full input voltage with headroom for
line surges.
Fig. 4. Hook-up Guide
Typical Test Voltages
*R1 = (Vin – 24V) / (.005A + .0115A) = (D1 + Music Rail current)
*W = (Vin – 24V) X (.005A + .0115A) X 5 (formula 5X derating factor)
Positive polarity shown. Zener must be reversed for negative Music Rails.
2
Noise Suppression vs Frequency
Resistance vs Input Voltage, 30V to 150V
Resistance vs Input Voltage, 150 to 550V
3
Bybee MUSIC RAILSTM Hi-Voltage Adaptation
If your project is high-voltage, above 30V, and you need help,
e-mail or call us.
[email protected] 480-998-2880
Or download information from the “Product” section at the
Bybee Labs web site.
For high-voltage adaptation you will need:
1. One or more 20W resistors optimized.
2. Two 24V, 1W zener diodes (high voltage clamps).
3. One 1uF, 630V polypropylene capacitor (noise drain).
4. Two terminal strips for mounting parts.
5. A schematic showing value(s) of R1 (Fig. 5) on page 2.
6. Photographs showing typical layouts. (Fig. 7) (Fig. 8)
Fig. 7. Diode location on PC board.
Fig. 8. High-voltage parts mounted & wired.
Bybee Labs, Inc. Information and Ordering
Bybee MUSIC RAIL TM
Doug Hall
1-480-998-2880 | 1-480-907-2894 Fax
[email protected]
Scottsdale, AZ 85258
Music Rail In – Noise Out!
www.BybeeLabs.com
© 2010 - 2011 Bybee Labs, Inc., Scottsdale, AZ 85258
4
BYBEE MUSIC RAIL™
White Paper
What are they? How do they work? Why do I need them? We hear these questions all the time. The short answer is: Bybee
Music Rails actively increase the resolution and definition of both audio and video signals by removing noise and unwanted
signal from DC power supplies. This paper will explain conceptually the function and purpose of the new, active-circuit
Music Rail™.
I. The Vibrating String Analogy
You probably think this section is going to create a tie-in to quantum string theory. Not exactly. Remember the talking string
we used to play with as kids? The one with a tin can attached at each end? One person speaks into the first can while the
other person listens into the second one. The vocalized air in the first can causes the string to vibrate. This in turn causes the
second can to move air into the ear of the listener. So far everything is clear. Now imagine that a sandstorm blows up. The
sand impacts the cans as well as the string. There is now a granular surf noise constantly impacting everything that is spoken
or heard. This granular noise alters the vibrations of the string in unpredictable ways. This noise is analogous to power supply
noise in audio systems.
II. The Niagra Falls Analogy
Imagine a sheet of crystal clear water falling over a glass wall. You can see right through the water, through the wall, and into
the next room. In that room are rows of flower pots. All kinds of flowers in many colors. You can see all the details of the
flowers. The colors, the petals, the pistils, the pollen–every detail is crystal clear. Now imagine that there is a box of sand at
the top of the waterfall that begins slowly sifting into the falling water. The sandy water will degrade the pattern of the floral
details in unpredictable ways. This granular sheet of sand is analogous to power supply noise in video systems.
III. The Rusty Pipes Analogy
Imagine a thin stream of pure water flowing smoothly out of a faucet. The stream is clear, calm, and continuous. We can see
right through it. Now imagine that the pipes are rusty and that the water has become tinted by a brownish muck. Tiny specs
of rust cause the water to fizz and flicker. Everything we look at through the water now takes on a fuzzy, brownish tint. When
we install a charcoal filter in line with the pipe, the water turns clear again. This filter is analogous to the effect of a Bybee
Music Rail.
1 of 3
IV. Vibrating Strings Again
Before explaining what actually happens in the power supply of an audio amplifier, we must first string these analogies
together. It has been shown mathematically by many practitioners over many decades that electric current is analogous to
flowing water and vibrating strings. Let's now combine the two concepts of the vibrating string and the water faucet.
Imagine a thin stream of pure water flowing smoothly out of a faucet. The stream is clear, calm, and continuous. We can see
right through it. Now imagine that a piano string has been pulled tightly from one end of the stream to the other. The piano
string runs right down the middle of the stream, affecting all of it. A tap on the piano string makes it vibrate. This in turn
causes the stream to vibrate. If there is rust or sand in the water, the audio vibrations will intermix with them in
unpredictable ways, causing distortion. The sound is then no longer pure and transparent. It is polluted by noise.
In an audio amplifier, the stream of water is replaced by a stream of electrons. The electron stream originates in the power
supply. There is no piano string, but the effect is the same. The audio signal (music or voice vibrations in electrical form)
enters the electron stream through tubes or transistors, which act as gates. The audio signal causes the electron stream to
“vibrate” (the stream is actually modulated by the signal, and forced to conform to the pattern of the signal). So far all is well,
but what happens if the electron stream is impure? You can be sure that it is.
V. The Electron Stream
The power supply electron stream originates from the wall socket (long before that, but let's start there for now). The
electron stream from the wall is a polluted sine wave (AC + noise). A sine wave looks in many ways like a rope that has been
yanked at one end. When it jumps, the rope ripples from one end to the other. This ripple, in electronic form, is what actually
enters the power supply from the wall socket.
The first task of the power supply is to smooth out the ripples in the electron stream. We want the electron stream to behave
like “pure water flowing smoothly out of the faucet.” That way, when the audio signal enters the stream through tubes or
transistors, there will be no interference by the ripples. We want the stream to remain clear, calm, and continuous, so we can
hear right through it to the music.
This is critical, because if there is any kind of noise on the power supply rails, that noise will intermix with the audio,
distorting it in unpredictable ways. Noise on the rails can appear in many forms: it can be ripple; emi; rfi; unwanted audio
signal; etc. All of these noise sources can degrade the audio signal.
VI. Getting the Noise Out Lets the Music In
There are many ways to block, filter, suppress, and bypass noise from the power supply rails. The question is, which way is
best? The standard method is to use large banks of filter capacitors to bypass noise around the rails. Capacitors, however,
quickly consume space. Electrically they are far from ideal. The Music Rail is designed to replace excess filter capacitors. It
performs the same function as filter caps, but it does so actively, efficiently, and in far less space.
The Music Rail can also improve the performance of voltage regulators. Regulators operate by locking down the rail voltage
at some specific value. In so doing, the regulator samples the output voltage and compares it to a reference voltage. If there
is a difference, the output voltage is pulled back to the reference voltage. The reference voltage is most often provided by a
zener diode, which is itself a source of noise. The zener flickers constantly and emits a stream of low-level noise that
interferes with the sampling process. The net result is that the electron stream exiting the regulator can be jumpy. The Music
Rail will smooth out this jumpiness.
Switching power supplies behave similarly, but are worse, because the electron stream is polluted with high-frequency
switching spikes. The Music Rail can smooth out switching power supplies to levels representative of the very best analog
2 of 3
supplies. This is readily measured: up to 45dB of power supply noise is eliminated (depending on the level of input noise–see
Datasheet for performance data and installation instructions).
VII. How it Works in a Nutshell
When a Bybee Music Rail is installed in any kind of DC power supply, the electron stream passes through it. Power supply
noise is then actively filtered out of the electron stream and returned to the wall socket (earth). The electron stream itself,
however, is barely affected. The Music Rail drops only 0.5V for any load up to 2A, and drops only 2.1V for any load up to 15A.
The electron stream enters the Music Rail in polluted form, and exits as a pure stream of clarified current, ready to be
modulated at high resolution by the music signal.
### December 28, 2010
Scott Frankland, Senior Development Engineer
Jack Bybee, Senior Research Physicist
CONTACT: Doug Hall
480-998-2880 / 480-213-1450 Cell
[email protected]
© 2010-2011 Bybee Labs, Inc.
8390 East Via de Ventura, F-110
Scottsdale, AZ 85258
3 of 3
FAQ
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ Frequently Asked Questions
4 Pages
Three Most Common MUSIC RAIL™ Questions
Q: What are they? How do they work? Why do I need them?
A: Download the White Paper from this web site to get the full story. Other helpful
information is also available in the Apps & Data section.
Q: I’ve read the White Paper. (Helpful reviews are also available on this web site.)
How can I confirm the performance of these devices for myself?
A: There are two ways: by ear or by instrument. It is possible to strap the device from
input to output, effectively bypassing it. The strap can be opened via connector or switch.
By this means, the Music Rail can be auditioned in and out of the circuit. To test the device,
see Testing & Troubleshooting (below).
Q: I’m sold. Where can I find installation information?
A: All installation information, including the datasheet, app notes, and layout examples, is
available in the Apps & Data section of this site. We recommend starting with the Data
Sheet and the installation guidelines. Download the Technical Data followed by App J0331:
Installation & Mounting Notes.
Installation
Q: I have downloaded the Technical Data Sheet and the Installation Notes, but there is too
much information. I just want to get started right away. What do I do?
A: Download the Quick-Start Guide.
Q: I have downloaded the Quick-Start Guide but I'm still confused about some installation
details. What do I do?
A: Keep reading.
Q: My voltage rail is above 30V, so I need a high-voltage adaptor. How do I select R1
without doing math?
A: Download app note J0413: R1/R2 Selection Chart.
Q: How do I rate C1, the noise drain capacitor?
A: The C1 voltage rating should be the same or higher than the rail voltage.
More . . .
Q: I have selected R1 & C1 for my high-voltage adaptor. Where can I buy these parts?
A: Download App J0412: Parts, Suppliers, & Accessories.
Q: My voltage rail is above 300V, so I need to use both R1 and R2, but I don't have room for
two large power resistors in my chassis. What do I do?
A: You can use vertical mount resistors or you can use a single high-power resistor. Highpower resistors are available in 25W and compact 50W packages, but these require special
mounting techniques. Download App J0414: High Power Resistors to learn more. You can
also use TO-220 style resistors with heatsinks, such as those offered by Caddock and sold by
our distributors listed on this web site.
Q: My voltage rail is above 300V, so I need to use both R1 and R2, but I'm not sure how to
connect them in series. What do I do?
A: Download App J0417: >300V Power Supply Schematic, which shows a typical
configuration. You will need to adjust the R1/R2 values if your voltage rail is other than
300V. See App J0413: R1/R2 Selection Chart.
Q: What mounting hardware do I need and where can I buy it?
A: Download App J0412: Parts, Suppliers, & Accessories.
Applications
Q: How do I connect the Music Rail to a negative voltage rail?
A: Below 30V, the connections are the same as for a positive rail. Above 30V, you must
reverse the two protection diodes. All other connections remain the same. To see a
schematic for a negative installation, download App J0410: Negative Power Supply
Schematic.
Q: How do I connect the Music Rails for a bipolar (+/-) power supply?
A: Download App J0321: Bipolar Power Supply.
Q: How do I optimize Music Rails for a DAC?
A: A special low-voltage technique is required for DAC's.
Download App J0308: DAC Applications.
Q: How do I optimize Music Rails for tube amps?
A: A special high-voltage technique is required for tube amps.
Download App J0310: Tube Amp Applications.
More . . .
Q: I will be using 15A Music Rails. How do I know if I’m using enough heat sink?
A: If you are modifying a power amplifier you can use the existing heat sink. If not, you will
need to specify & supply one. In either case, you should run some numbers. Recommended
web resources are shown on the main Apps & Data page of the Bybee Labs web site.
Testing & Troubleshooting
Q: My Music Rail is in place. How do I know if it's working properly?
A: First check the voltage drops, then compare the input vs. output noise with a sensitive
AC meter or spectrum analyzer. You can also use a scope if the sensitivity is great enough to
display noise at the sub-microvolt level. To find voltage drops, see Figs. 2 & 6 in the
Technical Data information.
Q: The noise level has not dropped at the Music Rail output. Where’s the beef?
A: Even the Music Rail produces some noise. Sometimes the noise in front of the Music
Rail is just as low as the noise floor of the Music Rail. Wow! One of the interesting things
about the Music Rail is that it produces "good noise", i.e., the character of the noise that it
does produce is very smooth, like the sound of surf in the far distance. The character of a 3terminal regulator, on the other hand, is more spikey & jumpy, which can put an edge on
transients that makes them grating to the ear. So even if the PARD measures the same on
an AC voltmeter, it can still sound quite different in its effects on music. A spectrum
analyzer will show the difference quantitatively, but this does not always correlate psychoacoustically.
Q: The noise level has increased at the Music Rail output. What the frack?!
A: Under certain capacitive conditions a Music Rail may produce a low-level, nondestructive oscillation. This oscillatory energy adds to the noise floor, which can be seen on
a scope. This can occur when low-value capacitors are placed across the Music Rail output.
Oscillation may also occur when the input capacitor is too far away from the Music Rail (see
schematics for guidelines).
Q: My installation cannot avoid using capacitors across the Music Rail output. Is there
anything I can do?
A: Download App J0409: Bypass Capacitors.
Q: I have tried all the remedies provided in the app notes and I still cannot get my Music
Rail to operate as advertised. What do I do?
A: E-mail [email protected].
More . . .
Q: Shazaam! My Music Rail is in place and it passes all tests. How can I convince myself
was a wise choice?
A: Besides listening with & without a bypass strap, you can run some tests. After checking
the noise, run a signal (or music) into your component and increase the level until you can
see it on the rail. Be sure not to exceed the limits of your component and to properly load
your power amp. If you can’t see any signal on the rail, try increasing the frequency. High
frequencies will be stronger because there is less power supply rejection with frequency.
When you see the signal clearly—stop. Now try the same test at the same levels with the
Music Rail un-bypassed.
If you need additional help, please e-mail [email protected]
##
© 2011 Bybee Labs, Inc.
J0417
MUSIC RAIL™ APP NOTE: >300V Supply
1 Page
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
ADJUSTMENT FORMULAS
D1 current = .005 D2 current = none after C1 charges.
Music Rail current = .0115A
R1 + R2 = (Vin – 24V) / (.005A + .0115A)
R1 + R2 watts = (Vin – 24V) X (.005A + .0115A)
The above wattage must be derated. See app note J0413.
C1, C2 = Voltage rating must exceed input voltage.
D1, D2 = Reverse polarity for NEG supplies; otherwise same.
If you need additional help, please contact:
[email protected]
##
J0309
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: Benchmark DAC Installation
1 Page
Inside a Benchmark DAC 1, each Music Rail should be placed next to its associated
regulator. Use a 4-40 x 3/4"L extension (threaded standoff) to elevate each Music Rail. Use
4-40 set screws to fasten the extensions to the existing standoffs that support the
Benchmark PC board. These fasteners can be obtained from www.McMaster-Carr.com .
Below are the part numbers:
93330A437
92311A110
91770A108
Aluminum Threaded Round Standoff, ¼” OD, ¾” Long, 4-40 Screw Size
Stainless Steel Set Screw, 4-40 X ½” Long
Stainless Steel Truss Head Phillips Machine Screw, 4-40 X 3/8” Long
There are four regulators in the Benchmark DAC 1. The + / - 18V regulators supply the
analog output stage. The +5V & +3.3V regulators supply the DAC chip. There are convenient
2-pin jumpers for each regulator. The jumpers are marked as follows:
+18V = JP1
-18V = JP5
+5V = JP2
+3.3V = JP6
In each case, the pin nearest the sidewall connects to the Music Rail input (Vin). The output
(Vout) of the Music Rail connects to the other jumper pin.
Note: the 2A Music Rail drops 0.5V so this insertion loss will have to be compensated in the
low-voltage regs (+5V & +3.3V). To recover this voltage, lift the ground pin from each lowvoltage regulator and insert a diode (the ground pin will have zero volts on it, and will be at
ground potential, which you can confirm with an ohmmeter). The diode will boost the
output of each regulator by 0.6V, making up the insertion loss of the Music Rail. For positive
regulators, the diode should be inserted with the banded end toward ground (reverse it for
negative regulators). You can use a 1N4001 diode, or any equivalent diode with a forward
current rating of 100mA or greater.
Each Music Rail should have its two ground pins (the two outermost pins) jumpered. Next,
run a wire from either one of these ground pins to the ground plane of the corresponding
regulator (that part of the PC board that the regulator ground pin is, or was, soldered to).
This completes the installation.
After installation and power up, you should read a 0.5V differential from input to output on
each Music Rail. The RMS noise at each Music Rail output should read 25uV or less
wideband. You should also ensure that each regulator is working properly after the mod
(the output voltage of each regulator should remain stable when the AC line is decreased or
increased).
For further installation and performance details please see the Music Rail Technical Data.
App J0308 covers general considerations for installing Music Rails in DAC’s .
##
J0321
MUSIC RAIL™ APP NOTE: Bi-Polar Power Supply Schematic
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
BOM (one channel)
15A POS Music Rail
15A NEG Music Rail
Silicon thermal pad 2X
C1 1uF, 50V film 2X
C2 10uF, 50V film 2X
R1 1.1K, 2W 2X
D1, D2 24V, 1W zener 4X
Mounting hardware
*For Other Input Voltages:
R1 = (Vin - 24V) / (.005A + .0115A) = (D1 + Music Rail current)
R1 watts = (Vin - 24V) X (.005A + .0115A)
The above wattage must be derated. See app note J0413.
C1, C2 = Same capacitance; voltage rating must exceed input voltage.
D1, D2 = No change.
[email protected]
##
1 Page
J0308
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: DAC Applications
2 Pages
When installing a Music Rail after a low-voltage regulator (as in a DAC or other digital application),
you may wish to consider the insertion loss (dropout) of the Music Rail. A typical DAC chip is fed from
a +5V regulator and a +3.3V regulator. Note that the 2A Music Rail drops 0.5V. This dropout or
insertion loss can be compensated by the following technique:
To level-shift a 3-terminal regulator, lift the ground pin and insert a diode in series with it. The
diode will boost the output of the regulator by 0.6V, making up the insertion loss of the Music Rail.
You can use a 1N4001 diode, or any equivalent diode with a forward current rating of 100mA or
greater. For positive regulators the diode should be inserted with the banded end toward ground
(reverse it for negative regulators).
The level-shifting technique works well down to about 3V, even though our datasheet calls out a
4.5V minimum input voltage for the Music Rail. Here’s why: to produce the rated output current, the
input voltage must be 4.5V or higher. At lower currents, however, this rating can be relaxed. In other
words, although 3.3V is below the minimum rated input voltage, the Music Rail still functions
because the current draw of a DAC is very low.
You don't normally need to worry about level-shifting regulators that are >5V, but this will depend
on the application. Given these workarounds, there is no reason why you cannot benefit from using
Music Rails in several locations within your DAC.
Location, Location, Location
We have found that with a typical DAC, the most critical location is after the +5V regulator that feeds
the analog pins of the DAC chip. The +3.3V digital pin of the DAC is less critical, but still provides
benefits. Some of our customers also hear benefits when Music Rails are installed after the + / - 15V
regulators that feed the analog output stage (not the outputs of the DAC chip itself, but the op-amps
that buffer the DAC chip from the main output).
To summarize, the hierarchy of benefits is as follows:
1) +5V analog rail of DAC chip (5 stars)
2) +3.3 digital rail of DAC chip (4 stars)
3) + / - 15V rails of op-amp output stage (3 stars)
A full setup for a typical DAC would include the following:
1) 3 x 2A POS Music Rail
2) 1 x 2A NEG Music Rail
3) 2 x silicon rectifier diode
In a typical low-voltage application, each Music Rail should have its two ground pins (the two
outermost pins) jumpered. Next, run a wire from either of these pins to the ground plane of the
4/20/2011
corresponding regulator (that part of the PC board that the regulator ground pin is, or was, soldered
to). Try to position each Music Rail close to its corresponding regulator.
Post Installation Performance Check
After installation and power up, you should read a 0.5V differential from input to output on each 2A
Music Rail. Check the output noise with a scope or sensitive AC meter. The output noise should
always be less than the input noise. Under certain conditions a Music Rail may produce a low-level,
non-destructive oscillation. This oscillatory energy adds to the noise floor, which can then be seen on
a scope. This oscillation can occur when capacitors are placed across the Music Rail output.
Oscillation may also occur when the input capacitor is too far away from the Music Rail.
Occasionally, the use of a diode on the ground pin of a low-voltage regulator will adversely affect its
dropout voltage. This usually happens only with tightly cascaded regulators (e.g., a 5V regulator
feeding a 3.3V regulator). It may be necessary in these cases to add level-shifting diodes to both
regulators. For this reason, you should ensure that each regulator is working properly after the mod,
i.e., the output voltage of each regulator should remain stable when the AC line is decreased or
increased with a variac.
After confirming the performance of the regulators and Music Rails, listen!
Demo Straps
For those wishing to demonstrate the benefits of the Music Rail by ear, there is a simple method by
which the Music Rail can be bypassed: simply connect a bypass strap from input to output. This strap
can be switched, or a pair of quick-connects can be used. Just ensure that the strap, switch, and/or
connector are rated for the intended load. See app note J0412 for part numbers & suppliers.
Bybee Labs Resources
For further installation and performance details please see the Music Rail datasheet, which you can
download from www.BybeeLabs.com . You can also request our detailed installation procedure for
the Benchmark DAC 1 (app note #J0309). We are currently working on a procedure for the Music Hall
25.3 DAC, which will be available in April 2011.
[email protected]
##
DAC APPLICATIONS
Page 2
J0409
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: Bypass Capacitors
1 Page
The Music Rail performance, like many cutting edge IC’s, is bound by certain external
capacitive conditions. This vulnerability also affects three-terminal regulators, many of which
are subject to the same conditions. Therefore, to ensure best performance, we recommend the
following guidelines.
Input Capacitance
At least 10uF should be strapped from input to ground. Better to use 33uF or higher and
place it close to the module until stability is confirmed. You can use film or electrolytic, but if
electrolytic is used, you should use 33uF minimum. If the module is within a few inches of the
stock cap bank this part may be omitted.
Output Capacitance
Ensure that no output cap is present. If this is unavoidable, try to make the cap value less than
0.1uF or greater than 20uF. It is possible to go much higher than this, into the thousands of
microfarads, if certain precautions are taken. To avoid having the Music Rails self-protect,
ensure that the current rating is respected under all operating conditions. To do this you must
consider:
1) The load current at turn on
2) The peak capacitive current at turn on
3) The leakage current of the load capacitors
So long as the sum of the above does not exceed the Music Rail current
rating, it will operate.
Test Procedure
Under certain conditions a Music Rail may produce a low-level, non-destructive oscillation. This
oscillatory energy adds to the noise floor, which can then be seen on a scope. This oscillation
can occur when the above conditions are not met. Oscillation may also occur when the input
capacitor is too far away from the Music Rail.
If a problem is suspected, first check the voltage drops, then check the input vs. output noise
with a scope; or better yet, use a sensitive AC meter or spectrum analyzer. To find voltage
drops, see Figs. 2 & 6 in the Technical Data or Figs. 3 & 7 in the Quick-Start Guide.
If, after trying all of the above, you still fail to achieve proper operation, please contact:
[email protected]
##
April 20, 2011
J0331
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: Installation & Mounting
2 Pages
MUSIC RAIL Installation Notes
1.
Vin must supply 11.5mA idle current to the Music Rail circuit (plus an additional 5mA to
ZD1 when a high-voltage adaptor is used).
2. J1 is the AC ground that bypasses noise currents and input ripple to ground.
3. J12 is the DC ground that returns idle current to the input source.
4. J1 and J12 may be tied together or run separately to optimize noise floor (experimentally).
5. J2-J6 (Vin) can carry 3A each and should be ganged together to carry higher currents.
6. J7-J11 (Vout) can carry 3A each and should be ganged together to carry higher currents.
7. 15A Music Rails must use appropriate heat sink (Pd=2.1V* load current).
8. Transistor on 15A Music Rails must be isolated from ground with thermal insulator.
9. Output capacitor not recommended (see app note J0409: Bypass Capacitors).
10. After installing each unit, insure that correct voltage drop appears from input to output
(0.5V for 2A modules, 2.1V for 15A modules). See data sheet for additional test data.
11. When negative polarity modules are used above 30V, the zener clamps in the hi-voltage
adapter must be reversed. All other connections remain the same.
12. As a final test, ensure that the output noise is lower than the input noise (if not, see FAQ).
MUSIC RAIL Mounting Notes
1.
2.
3.
4.
5.
6.
7.
8.
Try to locate the high-voltage adapter parts within 6” of the associated Music Rail.
Try to locate each Music Rail within 12” of the stage it feeds.
Power resistors in high-voltage adaptors should be derated 5-7 times and should be at
least 10mm distance from noise cap. Leave resistor leads 10-20mm long for increased
cooling.
The Music Rails can be bypassed for demonstration purposes. Simply jumper the input to
the output. Wire guage must be appropriate for load current.
For coplanar PC board mounting, a set screw can be used to mount each module to an
existing board standoff.
The mounting collar in each module is isolated and can be mounted directly to the chassis.
The mounting collar accepts #4 screws, but can be drilled out to accept 6-32 screws if
required. Mounting screw heads and standoffs should be 0.25 diameter max. Do not
exceed mounting pad diameter unless nylon or fiber washers are used for isolation.
15A modules can be mounted to existing heat sinks. Simply drill and tap into the heat
sink. Use caution. Taps are hard and brittle. Take care not to over twist the tap.
##
Installation & Mounting
Page 2
J0414
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: High Power Resistors
2 Pages
For all installations above 300V we normally advise using two power resistors in series. If your
available space does not allow this, you can turn to 25W or 50W high-power resistors. Whichever
you choose, resistors should be conservatively derated* for several reasons:
1.
2.
3.
4.
Heat radiation to adjacent parts is minimized.
Power resistors can generate prodigious heat into solder joints. Thermal cycling causes
solder joints to alternately heat and cool over time. This cycle can soften the solder joint
and make it friable if heat is excessive.
PC boards can discolor due to excessive heat.
Resistors themselves require derating due to ambient heat.
25W Power Resistors
25W power resistors have flat mounting tabs that are designed to transfer heat more efficiently than
a wire lead. These tabs can transfer prodigious heat, and precautions must be taken when mounting
on terminal strips.
We recommend that you tack solder the tabs onto the terminal strip with minimal solder. Then wrap
the tab/terminal combination using 24AWG buswire. Finish up with several layers of solder. This will
provide a strong mechanical infrastructure, similar to concrete and steel construction.
4/20/2011
50W Power Resistors
50W power resistors are either very large or very compact. There is no in-between. Most
applications will not have room for the very large variety, so we will limit our discussion to the very
small variety.
We are talking here about chassis-mount resistors with built-in heatsinks. These are by far the most
efficient means of dissipating power, provided that the heatsink (or fan) is adequate. Heatsink
compound should be used, and fasteners should include lockwashers or kepnuts.
We recommend the following websites for advice on thermal design:
www.signaltransfer.freeuk.com/termegn.htm
www.sound.westhost.com/heatsinks.htm
##
HIGH POWER RESISTORS
Page 2
J0410
MUSIC RAIL™ APP NOTE: Negative Power Supply Schematic
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
ADJUSTMENT FORMULAS
D1 current = .005A
Music Rail current = .0115A
R1 + R2 ohms = (Vin – 24V) / (.005A + .0115A)
R1 + R2 watts = (Vin – 24V) X (.005A + .0115A)
The above wattage should be derated. See app note J0413.
C1 = Voltage rating must match or exceed input voltage.
D1, D2 = Reverse polarity for NEG supplies; otherwise same.
[email protected]
##
1 Page
J0412
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: Parts, Accessories & Suppliers
3 Pages
We recommend the following distributors for parts & accessories.
USA
Michael Percy Audio
http://www.percyaudio.com/Catalog.pdf
CANADA
Parts Connexion
http://www.partsconnexion.com/resistors_mills_mra5.html
UNITED KINGDOM
Audiocom International Ltd
http://www.audiocominternational.com
______________________________________________________________________
Power Resistors (R1)* Available from Distributors listed above.
For power resistors we recommend Caddock, Vishay, and Mills, available from the distributors listed
above. Alternates listed below.
For power resistors up to 3W we recommend the following series:
http://www.vishay.com/docs/28729/28729.pdf
For power resistors up to 5W:
http://www.koaspeer.com/products/resistors/leaded-resistors/mos/
http://www.ohmite.com/catalog/pdf/200_series.pdf
For non-inductive power resistors up to 50W:
For vertical mounting types:
http://www.ohmite.com/catalog/pdf/tww_twm_series.pdf
* To select R1 from a table, see app note J0413: R1 Selection Chart.
To calculate R1 see Bybee Technical Data
_______________________________________________________________________________________
Capacitors (C1) Available from distributors listed above.
For noise drain capacitors (C1) we recommend the following: any wideband or low-inductance
1uF film caps rated for the rail voltage. For compact high-voltage applications we recommend
Solen "Fast Cap" polypropylenes. These are rated at 250V, 400V, or 630V.
Specifications can be found at http://www.solen.ca/pdf/solen/fastcap.pdf
Other caps may be used, but to obtain maximum noise drain bandwidth,
they should be low-inductance film types.
_________________________________________________________________________
Zener Diodes (D1, D2)
24V, 1W zener diodes (D1 & D2) are common and can be found almost anywhere.
The generic part number is 1N4749A.
__________________________________________________________________________
Terminal Strips Available from distributors listed above.
For terminal strips we recommend Grennan, IAG, and Yammamoto.
Available from the recommended distributors listed at the top of this sheet.
For compact layouts we recommend the 3000 series from HH Smith (now Abbatron).
This strip has a top & bottom thru-hole on every contact, which allows component
stacking & staggering. The contact count is built into each part number,
e.g., 3003, 3004, 3005, etc. The 3006 can be seen at
http://www.abbatron.com
We recommend the 3008 or 3010 (10-lug) when stringing 20W resistors
in series for voltages above 300V (see app note J0417: >300V Supply).
All of these strips, and other electronic hardware, are available from:
http://www.electronichardware.com
For the most compact layouts vertical strips can be used. These have become nearly
obsolete, but are currently available from Antique Audio Supply.
They carry a 3-lug vertical terminal strip (P-0300V).
This can be cut down to 2 or 1 as necessary. Go to:
http://tubesandmore.com/
__________________________________________________________________________
Mounting Hardware
Fasteners for mounting are typically 4-40 or M3 and are available from
McMaster-Carr at:
http://www.mcmaster.com
__________________________________________________________________________
Fasteners & Standoffs
Below are some typical SAE fasteners & standoffs suitable for mounting Music Rails, along with their
McMaster part numbers:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
92311A108
92311A110
92311A107
92510A030
92510A420
91251A113
91770A096
91770A113
93330A463
93330A439
93330A437
93330A462
93330A435
91757A101
95584A200
1 Pack Type 18-8 Ss Cup Point Socket Set Screw, 4-40, 3/8" L
100 Ea Aluminum Unthreaded Round Spacer, 1/4" Od, 5/32"L, #4
100 Ea Aluminum Unthreaded Round Spacer, 1/4" Od, 1/8"L, #4
2 Packs Black-oxide Socket Head Cap Screw, 4-40, 3/4" L
1 Pack 18-8 Ss Truss Head Phillips Machine Screw, 4-40, 1/2" L
1 Pack 18-8 Ss Truss Head Phillips Machine Screw, 4-40, 3/4" L
10 Each Alum Threaded Round Standoff, 1/4" Od, 2" L, 4-40
10 Each Alum Threaded Round Standoff, 1/4" Od, 1" L, 4-40
10 Each Alum Threaded Round Standoff, 1/4" Od, 3/4" L, 4-40
10 Each Alum Threaded Round Standoff, 1/4" Od, 1-1/2" L, 4-40
10 Each Alum Threaded Round Standoff, 1/4" Od, 1/2" L, 4-40
Internal-Tooth Lock Washer #4, .27" OD, packs of 100
External-Tooth Lock Washer #4, 0.26" OD, packs of 100
_________________________________________________________________________
Demo Strap
Our recommended bypass strap for before & after demos is made by E-Flite:
http://www.e-fliterc.com/Search/Default.aspx?SearchTerm=ec3+connector
These 60A twin connectors can be clipped in half, giving two straps, or used in parallel.
The part numbers for pre-made 13AWG mating connectors are:
EFLAEC304
EFLAEC305
The part numbers for pre-made 16AWG mating connectors are:
EFLAEC309
EFLAEC310
_________________________________________________________________________
##
App Note J0413: R1 and R2 Selection Chart
Vin*
DCV
35V
40V
50V
60V
70V
80V
90V
100V
110V
120V
130V
140V
150V
160V
170V
180V
190V
200V
210V
220V
230V
240V
250V
260V
270V
280V
290V
300V
310V
320V
330V
340V
350V
360V
370V
380V
390V
400V
410V
420V
430V
440V
450V
460V
470V
480V
490V
500V
510V
520V
530V
540V
550V
R1**
OHMS
680
1k
1.6k
2.2k
2.7k
3.3k
3.9k
4.7k
5.1k
5.6k
6.2k
6.8k
7.5k
8.2k
8.5k
9.1k
10k
11k
11k
12k
12.5k
13k
13.5k
15k
15k
16k
16k
8.2k
8.5k
9k
9.1k
10k
10k
10k
10k
10k
11k
11k
11k
12k
12k
12k
13k
13k
13k
13k
13k
13k
15k
15k
15k
15k
16k
R1***
WATTS
1W
1W
2W
2W
3W
3W
3W
5W
5W
5W
8W
8W
8W
8W
8W
10W
10W
10W
12W
12W
12W
20W
20W
20W
20W
20W
20W
10W
10W
10W
12W
12W
12W
12W
12W
12W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
RECOMMENDED SOURCES
Audiophile quality power resistors are available from:
http://www.partsconnexion.com/resistors_mills_mra5.html
Industrial quality power resistors are listed below:
http://www.vishay.com/docs/28729/28729.pdf
http://www.koaspeer.com/products/resistors/leaded-resistors/mos/
http://www.mouser.com/catalog/specsheets/XC-600044.pdf
http://www.ohmite.com/catalog/pdf/200_series.pdf
For vertical mounting types:
http://www.ohmite.com/catalog/pdf/tww_twm_series.pdf
The above parts are available from:
http://www.mouser.com
http://www.digikey.com
http://www.masterdistributors.com
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
R2**
OHMS
R2***
WATTS
8.2k
8.5k
9k
9.1k
9.1k
10k
10k
10k
11k
11k
11k
12k
12k
12k
13k
13k
13k
13.5k
13.5k
15k
15k
15k
15k
15k
16k
16k
10W
10W
10W
12W
12W
12W
12W
12W
12W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
20W
FOOTNOTES
* For in-between voltage values select
closest resistor value corresponding
to your rail voltage (Vin).
** When R2 is called out it must be
placed in series with R1.
DERATING NOTES
*** Resistors are conservatively
derated for several reasons:
1) Heat radiation to adjacent
parts is minimized.
2) Power resistors can generate
prodigious heat into solder joints.
Thermal cycling causes solder joints
to alternately heat and cool over time.
This cycle can soften the solder
joint and make it friable if heat is
excessive.
3) PC boards can discolor due to
excessive heat.
4) Resistors themselves
require derating due to ambient
heat.
J0310
For additional
information,
please visit the
Bybee web site at
www.BybeeLabs.com
MUSIC RAIL™ APP NOTE: Tube Amp Applications
1 Page
Addresses issues associated with high-voltage apps.
For all installations above 30V high-voltage adaptors must be used. We have now recommend a
second 24V, 1W protection zener in the Hi-V adaptation (see Fig. 6 of Technical Data). This diode
should be placed from the input of the Music Rail to J1. This is in addition to the diode connected
from the input to J12.*
Whether high-voltage, or any other power supply, the best place to locate the Music Rail is at the
tail-end of the supply. The Music Rail is designed to interface directly with the audio circuit. In this
configuration, the Music Rail is best placed to filter input noise on one side, and to bypass circuit
signals on the other side.
The same is true for a switching supply. Just be sure that if you remove filtering components in the
raw supply you do not exceed the input ripple limit of the Music Rail (300mV for the 2A Rail and 1.8V
for the 15A Rail). This limitation includes any sudden shift in DC status that exceeds the input ripple
limit. When this input limit is exceeded, no damage will occur, just intermittent operation, which
means that the Music Rail will stop filtering until the peak input subsides. This ripple limit is why we
don't normally recommend using the Music Rail to feed output or driver stages in tube amps unless
certain precautions are taken.
In practice, this problem can be eliminated by using a long time constant ahead of the Music Rail. In
other words, if you observe the Music Rail output jumping around on the scope, slow down the input
(i.e., add more RC on the input side, or use regulation). For example, at a voltage of 300V in an
unregulated supply you might need to use 6.8K combined with 100uF shunt capacitance ahead of the
Music Rail. Of course, if a regulator is present, no time constant is needed, since the regulator will
provide a steady input voltage well below the ripple limit of the Music Rail.
This need for a long time constant in high-voltage applications is why it is usually more convenient to
use the Music Rails on the input stages and filament supplies of tube equipment. In filament
supplies, there is no need for a long time constant ahead of the Music Rail. Only in hi-V apps is this
required. That is because high-voltage transformers step up AC line transients, making them larger.
Also note that the 15A Music Rail has more input ripple headroom than the 2A Rail. This can be
useful in supplies where long time constants are not possible. You may also find the 15A Rail more
useful in low-voltage, unregulated supplies for this same reason. Just bear in mind that the 15A Rail
has a 2.1V dropout, so you will need to make this up at the input.
* For positive voltage the diode bands face the input of the Music Rail. For negative voltage, the
bands must be reversed.
##

Bybee Music Rail

Transcription

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