Millennium XP (discontinued)
Millennium XP class A/B modules have been discontinued. We recommend the excellent "ZapPulse 800XE" PWM modules for new designs...
Revolutionary non-feedback Power Amplifier!
Available as assembled and tested modules for DIY Audio.
| Taking DIY to the next level! |
Millennium XP is a series of Class A/B Power Amplifiers with very high sound quality, but moderate
power consumption. Millennium XP is built with the best possible parts: SANKEN ring emitter output
devices, Through Hole Plated circuit board, low impedance capacitors from Chemicon (Sprague) metal film power
resistors and Vertical Crystal 'Z' transistors. All this is necessary to invoke the special Non Feedback
technology where no feedback loops are present at all (Except optional DC Servo). In our kits we use
exclusively terminals from LC and Neutrik.
Input signals can be balanced or unbalanced (RCA Line Level). XP runs glue-less with any preamplifier,
even (with change of one resistor value) with tube preamplifiers.
The secret behind the very high sound quality is the special amplifier topology, only found in Millennium
XP and a few other very costly amplifiers. To explain how it works, first we
look at a normal Power Amplifier. In a normal amplifier The signal is amplified 1000's of times in
several stages all with some amount of non-linearity and time delay. To reduce the
distortions from this amplification, the output signal is fed back to the input stage, and compared with
the input signal. If differences are detected, they are corrected by sending an
inverse correction signal through the amplifier from the input. Theoretically this is a perfect
amplification technique, however in real life there are a few problems:
The input signal is compared with and corrected from the output signal when it is a few microseconds old.
So it is not the same signal that is compared. The errors can not be
compensated before they are actually present on the output, and then it is really too late. The signals
are modulated in the non-linear amplification stages, and this modulation is
attempted to be removed again in the feedback loop. All these effects contribute to loss of detail, load
dependent sound performance, and a hard, cold sound. And the reason why most
Japanese amplifiers have this kind of sound, because they often use heavy amounts of feedback to obtain
low THD. Feedback is higher at lower frequencies because the time delay has less
effect on the signal, and so the sound of the amplifier is different at high frequencies compared to low
frequencies.
In Millennium XP each stage amplifies the signal only enough to reach the desired level on the output.
The gain is limited, and non-linearities are avoided by replacing the emitter
non-linearity with a high grade metal film resistor, with ultra low distortion (Vishay MELF). The result is
that the signal is not compared with an old signal, but simply progresses through the circuit unchanged
to reach the output with high power. The sound of the amplifier is homogenous - the same at all
frequencies.
Worldwide more than 6000 Millennium amplifiers have been built in different versions, which proves the
reliability and quality of this platform. You will simply not
get this performance at a reasonable price anywhere else.
Like most conventional analog Power Amplifiers, the Millennium XP needs a huge capacitor bank to keep the
soundstage wide and open at any sound level. Therefore the cap bank
of the Millennium kits is totally 120.000 uF of ChemiCon (Former Sprague) low impedance capacitors. In
fact this is so much that a soft start circuit is necessary to break in
the power supply on the mains grid without blowing a mains fuse. This soft start is also standard in
every Millennium XP kit.
The core of all the amplifiers is the Millennium XP module: A 100% feedback loop free power amplifier.
It is primarily build with SMD components of premium grade.
Click to
enlarge photo
Each module is preassembled and tested at our production facility in Denmark. One Millennium XP module
can produce up to 350 Watts RMS of output power, into a 2 Ohms load, and
120 Watts RMS in 8 Ohms. If only 8 Ohms loads are used, the power supply can be adjusted to make one
module put out some 180 Watts RMS in 8 Ohms.
This amplifier will run stable with any supply of +/- 12V to +/-63 Volts DC. Look at the 'Millennium
Parts' page to see a table of Supply Voltage vs. Output power.
The stable and reliable quality Millennium, with high sound quality is already used with renowned
companies as Brüel and Kjaer and Danish National Broadcasting corp.
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enlarge photo
Millennium XP Technical Features:
4 stage driver chain gives overwhelming bass control.
Vishay Glass Substrate resistors reduces 3rd order distortion.
Gain building is made with vertical crystal Z transistors, with ultra low capacitance (< 2.5 pF).
Click to
enlarge photo
Advanced "Ultra Linear Core" voltage amplifier with very low harmonic distortion and no feedback
loops.
Double Layer Polypropylene capacitors support power supply definition at high frequencies.
All signal carrying circuit board traces are made with soft curve technique, without angles, to improve
high frequency performance.
Click to
enlarge photo
Separate power supply for power stage and voltage amplifier stage, so heavy loads does not affect the
sensitive voltage gain stages.
Optional DC servo on board ( one point 2nd order ).
Short Circuit Protection (non current limiting). If an overload occurs the signal is shut down for 3
second, and then back on again, until normal load is detected. This method is
developed for professional PA amplifiers and is so effective that the amplifier can be left with full
power and shorted output for days without damage.
Principle of Operation.
Click to enlarge
photo.
This simplified schematic shows how simple the circuit of this amplifier is. There are no capacitors in
the signal path, so there is full gain even at DC.
The frequency response is linear from DC to 500.000 Hz. (+0-3 dB).
The special technology and high quality parts in this amplifier give it world class performance in
liquid, clean sound, with detail and dynamics.
We recommend not using additional output devices in parallel, as this may inhibit the amplifiers focus
and definition in midrange and treble.
Technical Specs.
(For 120 Watt version with 2 x 33V AC transformer).
| Power Output in 8 Ohms | 120 Watts RMS |
| Power Output in 4 Ohms | 240 Watts RMS |
| Power Output in 3 Ohms | 300 Watts RMS |
| Frequency Response +0-3dB | DC-500.000 Hz |
| Phase Shift @ 20.000Hz | max. 2 deg. |
| THD | 0,0017% |
| Peak Current 1 ms | 46 Ampere |
| Output Impedance | 150 mOhm |
| Damping Factor(50 - 15.000 Hz) | 53 |
| Equivalent Input Noise | 20 uV RMS |
| Signal / Noise Ratio | min. 110 dBA |
Piecing together an amplifier based on Millennium XP.
If you need to buy all parts to your new Millennium XP amplifier, we recommend you go to the system page,
hit the button on
the left side. You can combine Millennium XP modules with many different types of applications and parts,
if you have say a
transformer or good capacitors on stock, you can use them with a couple of Millennium XP modules to build
a true high
performance audio amplifier. You can also build active speakers, by simply building Millennium XP modules
into the speaker
enclosure, where en most cases you will find ample space for power supply, heat sinks etc.
The criteria for the parts that will successfully combine with Millennium XP are:
Main transformer: min. 2 X 12 - max. 2 X 40 Volt AC min 300 VA
AUX transformer: min. 2 X 12 - max. 2 X 42 Volt AC min 30 VA
Electrolytic Caps: min. 2 X 10.000 uF min Voltage according to Main transformer
secondary voltage.
Enclosure: Only requirement is for air to flow freely around the heat sinks.
Heat Sinks: Depending on the transformer secondary voltage and subsequent output
power:
| Transformer of 2 X: | gives in 8 Ohms: | Requires a heat sink of: | And no. of
ext. boards: |
| 12V AC | 15 W | 4 K/W | 0 |
| 15V AC | 24 W | 2,5 K/W | 0 |
| 18V AC | 36 W | 1,7 K/W | 0 |
| 24V AC | 50 W | 1,2 K/W | 0 |
| 27V AC | 79 W | 0,7 K/W | 0 |
| 33V AC | 128 W | 0,5 K/W | 0 |
| 39V AC | 180 W | 0,35 K/W | 1 |
| 24V AC bal. | 200 W | 0,3 K/W | 0 |
| 27V AC bal. | 300 W | 0,2 K/W | 0 |
If 4 Ohms load is used, the power will be doubled, and the heat sinks must also be doubled.
The two 'bal' fields are for a setup with two bridge mode Millennium XP modules.
This is easily accomplished by connecting the input signal to + on one module, and to - on the other.
No extra circuit is required.
Heat Sink Temperature.
The Heat sink table above does not refer to the point of destruction of the module, but rather the point
where the amplifier will comply with IEC 65121 safety regulations, and maintain maximum temperature of 60
Centigrade
on the anodized surface of the heat sink.
Destruction point is significantly higher, and reached where the junction temperature of the power
transistor
reaches 125 C. What is translates into as a heat sink temperature, depends on the output power.
As the transfer of heat from the junction to the case gives a 'thermal resistance' of 0.5 K/W and Case to
Heat Sink
gives additional resistance of 0.2 K/W, there is a combined 'resistance' of 0.7 K/W from Junction to Heat
Sink.
If we dissipate i.e. 50 Watts in the junction, (corresponding to 200 Watt output power) the temperature
difference between
junction and heat sink is : 50 * 0.7 = 35 C. So in this case the break point is with a Heat Sink
temperature of 90 C
( 90 + 35 = 125 C ). Quite hot! And this is just the guaranteed limit of the manufacturer. In real life
these devices
can take even more pounding!
In another example if we dissipate 100 Watts in the device the Junction to heat sink loss is 70 K, and in
this case the
max. Heat Sink temperature is only 125 - 70 = 55 C. This corresponds to 400 Watts audio power in one set
of (2) devices.
More than you would normally subject a single device amplifier to. In this case you would need to
dissipate 2 x 100 Watts =
200 Watts with a Heat Sink temperature rise of 55 - (ambient) 25 C = 30K. 30K / 200W = 0.15 K/W. A very
big heat sink... By
adding more power devices your Junction to Heat Sink loss is reduced, so the heat sink can be much
smaller.
Please note due to thermal inertia, the Heat Sink will not reach its final temperature level before about
1 - 2 hours
has passed at full dissipation.
Safety Margin.
The above calculation is as stated a worst case scenario. In real life the Sanken Devices used in
Millennium XP have proven to be extremely rugged. We have verified 48 hour tests with devices
subjected to twice the specified load, (120 Watt per device and 100 C Heat Sink temperature).
This torture load is NOT what we endorse you to replicate in your amplifier, but it shows that
the device can take the load of the most remarkable situations.
For professional P.A. applications we encourage you to dimension your Millennium XP amplifier the
above table.
Second Breakdown
A Sanken output Device (2SA1216 or 2SC2922) has a maximum power dissipation limit of 200 Watts. However
this max limit decreases with higher temperature, because of the thermal resistance discussed above, and
also
a phenomenon called Second Breakdown. This is a property of any bipolar transistor, but not MOSFET's thus
their
popularity for high load P. A. amplifiers. MOSFET's are cheap and abundant on the market but have
negative
properties that has dismissed them from use in our power amplifiers, their high Source impedance simply
don't
allow for as good sound quality as bipolar transistors, in a linear power amplifier. (Different in a PWM
amplifier
like ZapPulse, where the device is switched entirely on with low impedance or off).
Electrolytic Caps Voltage.
Remember that the capacitor voltage is marked in Volts DC, while the transformer secondary voltage
is in AC. The capacitors voltage must be (slightly) higher than the resulting DC voltage from the
transformer, in order to keep safe operation of the amplifier for many years. Better quality caps are less
sensitive to intermittent over voltage surges. So a good cap will not explode if you run it at slight
overvoltage,
Say 65 V DC on a 63 V cap. It will in time lose some of its capacity though. If you run a 63 V cap at 80
V
it will most probably explode after a while.
To convert the value from AC to DC simply multiply the AC voltage by 1.4. Example a 40 V AC will result
in:
40 * 1.4 = 56 V DC. (Roughly). Add 10% mains line tolerance, and your max. voltage on the caps will be:
61.6 V, perfect for a set of good 63 V caps.
In the old days you would say that the caps should have 20-50 % higher specified voltage than the actual
voltage
applied. This rule still applies if you use very cheap and poor quality caps. In other cases use to the
limit!
Low Impedance Speakers.
Millennium XP can be configured to drive low impedance speakers, down to say 1 Ohm. A subwoofer with i.e.
9 pcs. 8" 8 Ohms drivers can be constructed to fit in a flat area, above a ceiling, under a couch or
similar, and
due to the large membrane area still produce immense sound pressure using a Millennium XP as driver
amplifier.
Dimensioning of the amplifier is simple, use a 27 Volt transformer, one set of ext. output devices,
at load
impedances of 1 - 1.3 Ohms your output power is 400 - 500 Watts RMS.
We have done some 11 units of
1.3 Ohms speaker / Millennium amplifiers in the city of Holstebro. The units are
running
on 2 clubs, and half of them for more than 10 years. The trick of this system is that each
speaker only gets a maximum of 40 Watts even at max SPL of > 140 dB. Nothing that can kill it no matter
what signal is applied.
So we have provided a total warranty for any damage to speaker or amplifier for 5 years. And after a
operation
period of 10 years we had no repair visits so far.
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