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Do's and Don’ts for ZapPulse amplifiers.
A ZapPulse based amplifier is a remarkably stable and rugged solution, which can function reliably for
many years.
Still it is a very easy technology to work with, and will work every time. However there are some
precautions, that
are not normally considered with traditional analogue amplifiers. At this point around 3000 ZapPulse
modules are
in service around the world, and this has given us knowledge of potential pitfalls, which we pass on to
you below
on this page. If you follow the advice given, you will never have problems using a ZapPulse amplifier.
Should you
be as unlucky to experience a breakdown anyway, our 100% warranty will cover new modules under any
circumstance, and
also we will be at your service to find the cause for the problem encountered.
If you follow the given advice you can keep clear of any known problem associated with the use of a PWM
amplifier.
Avoid DC on the input.
| ZapPulse is frequency linear from 0 to 150.000 Hz. This means 0 Hz - or DC is amplified as any other
signal.
When DC comes out of the amplifier, and there is a load connected to the amplifier, the output stage will
start
functioning like a reversed switch mode boost regulator. This means it can generate plus voltages from the
minus rails.
(Or opposite depending on the polarity of your applied DC voltage). Since no current is drawn from the
plus rail in
this condition, voltage will start building up. This | | is called Power Supply Pumping. The voltage will
rise until
leakage in the main caps is bigger than the current through the speaker load. At this point your caps are
in
danger. Excess of 200 Volts have been encountered.
To avoid this problem, simply avoid DC on the input. If you are using a tube preamp, or soundcard, that
is likely
to apply DC to the input of your ZAP amplifier, simply connect a capacitor in series with your input
signal. 1-2.2 uF
is adequate (not bigger!). Use a good quality!
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Do NOT remove the load at full Volume!
| The output choke of ZapPulse will in function try to maintain a stable current through the load, as
given by the
output signal. If you remove the load, during a power peak of say 10 Ampere, the coil will do anything to
try and
keep the 10 Amps flowing. We have chosen a very capable choke type, so you can be sure it will succeed in | |
making the
high current flow, even if it can not flow in your speakers, it will end up as a small lightning in
ZapPulse's filter
capacitor.
This is not healthy for the filter capacitor, though it will actually withstand some of these
sparks.
The solution i simple: Do not remove your speaker load at high volumes.
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Start-ups with no output loads.
| Many diy'ers are inclined to start the amplifier first time without speaker load, until they are
confident
the amplifier is working correctly. We don't recommend this procedure with a ZapPulse amplifier. When we
build
amplifiers in house using ZapPulse
modules, we take into account the system stability even with no loads, but in DIY the situation is
different.
The setup varies from amplifier to amplifier, and this might affect stability. The speaker load on the
other
hand helps keep the amplifier stable under almost any condition, because it dampens | | the Q of the output
filter.
We recommend you start your amplifier with speaker load (or similar resistor load), and keep a good eye
on
the membranes of your bass drivers. If they behave strangely simply cut the power off immediately to
troubleshoot.
If you don't leave the speakers with full DC for long periods, they will not take any damage from this
procedure.
You can easily see if something is not right. Lastly the modules are 100% tested from our side, so you
can be
fairly sure they work every time, providing you got plus minus and GND right.
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Never attempt to enlarge the holes of the PCB.
| You want to make your amplifier as good as possible, so you have cut out half meter of your expensive
heavy duty speaker cable, to use for power supply connections. But unfortunately the holes in the PCB
pads are only
2 mm in diameter, so you take out your power drill, and make a nice big hole to fit the cables in, right?
Wrong! The ZapPulse modules are built on 4 layer circuit boards, meaning there are 2 invisible copper
planes inside
the | | PCB. These planes distribute power supply and GND to the parts on board. The solder pads are
connected to the
power planes in the middle of the PCB section. If you drill a hole in it, the connection is lost, and the
module
is destroyed. In fact the gauge of Power Supply cable is not so important
mainly because of the short run, more importantly is the length that should be kept to a minimum to
reduce the wire inductance. Maximum 10 cm / 4 inches.
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Mono-Blocks can be a Problem.
| Traditionally mono-blocks are popular because that way you are sure the channels don't interact with
one another,
keeping a good clean perspective of sound stage. With ZapPulse modules it can be very hard to
electrically separate
two channels. The input GND's are connected through the preamplifier or signal source, and most probably
the power
GND's can see each other, noise wise through the mains transformer's internal capacitance of typically 1-2
nF.
You can isolate the way modules can | | see each other if you make a good effort of HF filtering the mains,
but it is
not the best way to go.
If you try to separate two channels, and the run off each others frequency by just a few hundred HZ, you
may experience
a slight background tone, of high or low pitch.
The best solution is to not build mono-blocks.
Better place the
modules closely together, and connect the two ground planes together with a short heavy wire, so shorting
out the
source of the switching noise.
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Use a sync. generator in multi channel amps.
| ZapPulse is an obvious choice for a small sized home cinema amplifier with cruel amounts of power! If
you mount 5 or 7
free running channels in one enclosure, you will most surely find that the many independent switching
frequencies will
lead to interchannel disturbances - and in turn to higher background noise and high | | pitch tones.
The solution is to place the modules closely together, connect their ground planes tightly together, and
use
a sync generator so all modules run at the same frequency. This eliminates all problems with channel
interaction.
All modules in the setup must be connected to the (same) sync. generator.
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Don't short the output...
| ...if you have disabled the short circuit protection. This may sound like a joke, but several users
have done
just this and witnessed a total crash of a module. If you have | | not disabled the short circuit protection
however you
may short the output as much as you like under any condition, this the module will withstand with no
problem.
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