Mains
filters, Surge protection and Isolating transformers.
You may have wondered why our mains power distributions blocks
are devoid of an on/off switch fuse or any of the above devices.
No doubt you would have read many technical articles on such devices
or technically qualified to be aware, so you may find our views
too simple however;
Filters and Anti Surge Protection
use either a capacitor or a choke of one type or another or both.
Both devices cause a drop in current and voltage, very small and
has no effect on the working of your item of equipment. This small
drop does however cause audible differences, usually a loss of dynamics
especially in CD/DVD players, Pre amplifiers and items that draw
very low levels of current. This is a well known fact and whilst
the filter has done it's job of removing all or most of the AC noise
and you hear an improvement in the sound, there is the down side
or detrimental effects too!
The best protection against power surges is your household insurance
policy! Check with your insurer if your equipment is covered against
damage caused by power surges and spikes.
Isolating transformer is a good way
of both cleaning up the AC mains supply, but to provide a continuous
supply of 13 amps of current requires a transformer of 3kva rating.
That is to say the transformers must be rated at 3kva continuous
and not peak output. Such a transformer is large, heavy (22 kg)
and expensive. Yes, you can for most systems use a transformer of
a lower rating but you must always check to make sure you do not
exceed the rating of the transformer. Not so good if you add items
of equipment or upgrade your amplifier to one more powerful. The
other problem with an isolating transformer is that it can get hot,
so ventilation or a thermal switch must be fitted. Ventilation means
vent holes in the casing, not good as it allows RF and EMI in and
out . A thermal switch is perhaps a better compromise together with
an oversize casing with heat sinks.
There are ways to overcome the problem of drops in voltage and
current, but as yet a cost effective and simple way of doing so
is to be found.
We are awaiting delivery of 1, 2 and 3 kva isolating transformers
for testing. The transformers are bespoke made for us and are of
audio grade quality. Pricing will be every competitive, lower than
any of the competitive product large due to the larger volume of
product that we will order from our UK supplier. Casing for the
transformers is at design stage and will incorporate eight UK outlets,
include a 15 or 20 amp filter, possibly some form of surge protection
and fitted with a two meter length of mains cable rated at 20+ amps.
To negate the audible detrimental effects of the active filter and
surge protection devices, the transformer will be connected inline
after the devices. There will be no on off switch or fuse fitted
and the mains lead hard wired to the unit.
Switches/Fuse/Silver plating
The inclusion of the either a switch or fuse introduces contact
resistance in the path of the AC supply and so we omit both. It
is for this same reason the cord is hardwired to the block.
Hardwiring the system into the mains supply would be the best option
but there is the small matter of safety and practicality Whilst
most or all items of equipment are designed for use in countries
where the mains plug does not have a fuse (Europe, Australia, USA
etc use different methods of protection), it should be safe to use
in the UK without a fuse but this is a matter that you must check
and seek approval from the equipment manufacturer.
When using a fused UK plug make sure that it is fitted with a correctly
rated fuse.
Accepting that a UK plug with an appropriate rated fuse is a must,
the best we can do is omit the on/off switch, fuse on the distribution
block and suggest the use of our MK plugs with silver plated contacts.
The use of silver plated contacts reduces contact resistance which
is a good thing.
Fuses - unfortunately it is not possible to silver plate the end
caps of the fuse not unless there is someone out there prepared
negotiate a special order run of a six figure number of units. There
are some silver plated fuses (which is what we use) but the plating
a more a flash plate and no anti-tarnish protection. We would not
describe it as a silver plated due to the very thin coating of silver.
Ideally the mains sockets should also be silver plated but disassembly
and re-assembly would be much too costly and troublesome.
More to added to this saga at a later date!
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