Re: Remote Power Supply Connection

Ian Thompson-Bell wrote:
> 
> Trevor Wilson wrote:
> > "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
> > news:g0up1a$1ap1$1@[EMAIL PROTECTED]
> >> Trevor Wilson wrote:
> >>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
> >>> news:g0rmo0$27co$1@[EMAIL PROTECTED]
> >>>>
> >>>> I agree when the rectifiers are close to the transformer supplying
them
> >>>> but not when they are separated from it my a couple of metres of
cable.
> >>> **And again, it is not difficult, nor expensive to deal with such
issues.
> >>> A handful of capacitors will effectively deal with any problems.
> >>>
> >>>
> >> Definitely not. The point is that the caps normally used to suppress
> >> reverse spikes in semiconductor diodes do just that. The have no
effect on
> >> the forward current spikes which are significant.
> >
> > **No.
> >
> 
> Denial is not much of an argument.
> 
> >  With remote ac
> >> supplies these current spikes must pass through the cable and they
will
> >> cause serioes radiation. Any attempt to stop them happening will
simply
> >> stop the rectifiers from rectifying. That is why is is essential to
have
> >> the rectifiers close to the transformer.
> >
> > **No.
> >
> 
> Denial is not much of an argument.
> >>>>>>>>>> http://www.arcadvisor.com/faq/dc_direct_current_arc.html
> >>>>>>>>>>
> >>>>>> This clearly shows that at low currents (e.g HT currents) and
high
> >>>>>> voltages (e.g.HT voltages) dc arcing is very unlikely to occur.
> >>>> **Remind me: How much energy is able to be stored by large
(unstated
> >>>> values)
> >>>> capacitors?
> >>>>
> >>>> 0.5*C*V^2
> >>>>
> >>>> In a 100uF capacitor at 300V that's a mere 4.5 joules. Not worth
> >>>> worrying about.
> >>> **Points:
> >>>
> >>> * 4.5 joules is a substantial amount of energy.
> >> No it isn't. it is 4.5 watts for one second.
> >
> > **Yes, it is. It depends on how long it takes to charge/discharge
whatever
> > capacitance is on the other side of the connector. In 0.1 Sec, that is
45
> > Watts. In 0.01 sec, that is 450 watts. Certainly plenty of energy to
damage
> > surface treatment of most connectors. And, as I stated earlier, lots
of
> > builders use considerably more capacitance than 100uF and more than
300
> > Volts for their power amps. 1,000uF and 700 Volts is not unheard of.
And
> > THAT is a considerable amount of energy.
> >
> >> My small rotary hammer drill
> >>> is rated at 2.5 joules per strike and can pulverise bricks.
> >> And there you have hit the nail on the head. It is not the *amount*
of
> >> energy but the *rate* at which it is consumed that matters.
> >
> > **EXACTLY my point. 4.5 joules consumed in 10msec is a *lot* of energy
for
> > thinly plated connector to cope with.
> 
> No, 4.5 Joules consumed in 10mS is not a lot of energy, it is a lot of
> power.
> 
> Cheers
> 
> Ian

Ian, its difficult to argue with somebody who hasn't designed or built
any new amp for over 30 years,
and Trevor hasn't any experience designing remote PSU for tube amps.

Discharging dc from a capacitor rapidly to 0V through a contact point
such as a relay
or plug-socket connection can cause damage due to high sudden currents
causing high local heating.
Everyone knows this.
So when I make PSU to get dc supply across to a power amp I allow for 
possibilities for damage with incorrect use.

In some tube amps such as a VT100 ARC, there is well over 2,000uF at
+470V,
enough to blow the end off a screwdriver if it is used to shunt the
store of energy.
If there was a remote PSU, and one wanted to guard against cable plug
damage
due to a short in the amp B+ to 0V, one would place a fast blow fuse of
say 3 amps soldered into
the B+ line just before the output socket in the PSU.
Ordinary operation where perhaps only 250mA dc won't cause any troubles.

Getting dc power along a cable from a PSU chassis to an amp chassis
does not involve sudden current shocks if the gear is designed and used
right.
Leak and Quad did it routinely to get DC from a power amp PSU to a
preamp unit.

I never heard of any problems with such amps with dc transfer, yet Idiot
Wilson
maintains dc power transfer via cables is dumb, and no good.

I have designed and built and sold gear with DC in the cabling 
and never had any problem whatsoever.

Harold Leak and Peter Walker had 40dB more intelligence that Wilson on a
good day.

Wilson drifts around the subject like a drunken man asleep in a canoe.

There is NO point to his presence here at r.a.t except to waste
everyone's time.

He has NEVER offered anyone good advice on how to build better tube
amps.

Trevor is addicted to just sitting around and bull****ing.

Patrick Turner.