Re: Remote Power Supply Connection

-- 
Trevor Wilson
www.rageaudio.com.au
"keithr" <keithr@[EMAIL PROTECTED]
> wrote in message 
news:4830aed2@[EMAIL PROTECTED]
>
> "Patrick Turner" <info@[EMAIL PROTECTED]
> wrote in message 
> news:48303804.A765B189@[EMAIL PROTECTED]
>>
>>
>> Trevor Wilson wrote:
>>>
>>> "flipper" <flipper@[EMAIL PROTECTED]
> wrote in message
>>> news:2e1v24tp96nb7n7dopacuig5rv7hubtiru@[EMAIL PROTECTED]
>>> > On Sun, 18 May 2008 09:04:49 +1000, "Trevor Wilson"
>>> > <trevor@[EMAIL PROTECTED]
> wrote:
>>> >
>>> >>
>>> >>"flipper" <flipper@[EMAIL PROTECTED]
> wrote in message
>>> >>news:oolu249l2p19arj95g2it4fhjag238ajfl@[EMAIL PROTECTED]
>>> >>> On Sun, 18 May 2008 07:36:56 +1000, "Trevor Wilson"
>>> >>> <trevor@[EMAIL PROTECTED]
> wrote:
>>> >>>
>>> >>>>
>>> >>>>"Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
>>> >>>>news:g0mu6g$2vgp$1@[EMAIL PROTECTED]
>>> >>>>> Trevor Wilson wrote:
>>> >>>>>> **Asked and answered. Use AC. Do not use DC.
>>> >>>>>>
>>> >>>>>
>>> >>>>> In practice that is perhaps not such a good idea as it sounds.
It
>>> >>>>> means
>>> >>>>> the rectifiers will be at the end of a fairly long piece of
cable. 
>>> >>>>> The
>>> >>>>> large rate of changes of current caused by rectifiers
(especially 
>>> >>>>> the
>>> >>>>> semiconductor type) combined with the series inductance of the 
>>> >>>>> cable
>>> >>>>> is
>>> >>>>> a
>>> >>>>> recipe for noise, interference and possibly stability problems.
>>> >>>>
>>> >>>>**I fail to see how. In practice rectifiers are already at the end

>>> >>>>of
>>> >>>>very
>>> >>>>long cables and are supplied by devices with prodigious
inductance. 
>>> >>>>In
>>> >>>>any
>>> >>>>case, there are measures that can be taken to reduce the problems
>>> >>>>associated
>>> >>>>with noise from diodes. There are even (easy) measures which can
be
>>> >>>>taken
>>> >>>>to
>>> >>>>reduce the inductance of those connecting cables. What I am very
>>> >>>>concerned
>>> >>>>about is the extreme ignorance displayed about the dangers 
>>> >>>>associated
>>> >>>>with
>>> >>>>DC arcs and connectors. This, as opposed to your hypothetical, is
a 
>>> >>>>very
>>> >>>>real possibility. Read this:
>>> >>>>
>>> >>>>http://www.arcadvisor.com/faq/dc_direct_current_arc.html
>>> >>>>
>>> >>>>Trevor Wilson
>>> >>>>
>>> >>>
>>> >>> The connector isn't a switch, relay, or fuse.
>>> >>
>>> >>**Indeed. If it is unplugged, whilst 'hot' a disaster could result.
>>> >
>>> > While I'm not particularly enamored with the idea of HVDC umbilicals
>>> > it doesn't take too much thought to come up with at least one means
to
>>> > prevent manual disconnect while hot and I'm sure a few minutes more
>>> > could produce others.
>>>
>>> **I've not seen any solutions proferred yet. However, the use of AC
>>> eliminates any problems. There is no downside.
>>>
>>> >
>>> >> Using AC
>>> >>eliminates any possibility of such a disaster.
>>> >
>>> > So does preventing disconnect while hot and you seem to have
>>> > completely missed the entire discussion about how to ensure 'no
touchy
>>> > hot pins'. And, if done right,  no 'touchy hot' could also mean no
>>> > 'arcy disaster hot'.
>>>
>>> **Then present your solution and explain why is is better than using
AC.
>>>
>>> >
>>> >> Using DC is just dumb.
>>> >
>>> > You really should look for a more congenial means to salve your ego.
>>>
>>> **Just dealing in the facts. Inconvenient that they are. Using AC is 
>>> much
>>> smarter, safer and simpler. Using DC is dumb, unsafe and
inconveniently
>>> complex.
>>>
>>> Trevor Wilson
>>
>> Trevor, you wouldn't know a fact even if one bit you on the arse.
>>
>> Thr trouble is you are unaware of solutions because you've never
>> had to find solutions.
>>
>> AC is fine where possible, but what us tubies like to keep
>> OFF THE AUDIO CHASSIS is the whole PSU, ie, mains PT, diodes, first
>> electro filter caps, and
>> chokes, and second electro filter caps.
>>
>> The sensible thing is to transfer the Vdc by cable, but on the
>> audio chassis the Vdc has a small amount of C between say the OPT CT
and
>> 0V, say about 2uF only, plastic type.
>> This will shunt the inductance of the cable, and it is 5Amp rated wire,
>> its dc resistance is totally insignificant.
>> One can have a diode in series with the Vdc input at the amp to prevent
>> say +600V causing current flow from the live pin to something earthy.
>> One can also rig up the feeds so that if the cable becomes unplugged
>> from the
>> PSU a relay closes and a resistance is connected to the
>> Vdc rail and 0V. Because only 2uF is present, the decline in Vdc to
safe
>> levels
>> can be very fast even without tubes drawing current.
>>
>> Patrick Turner.
>
> Lets face it the whole safety thing can be fixed. You put the connectors

> at each end under covers. The covers can only be lifted by removing a 
> screw (or two), under the cover is a micro switch. Long before anybody
can 
> access the actual connectors, the power is switched off by the 
> microswitch. I have seen this on a number of pieces of professional 
> equipment, for the safety of both the operator and the equipment itself.

**Except that such a solution only works with AC. DC power requires that 
capacitors be discharged as well (I need not remind you that microswitches

are spectacularly unsuited for high Voltage DC).

AC power cables make far more sense. Using DC is dumb.

Trevor Wilson