Re: Remote Power Supply Connection

Ian Thompson-Bell wrote:
> 
> Trevor Wilson wrote:
> > "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
> > news:g16ked$1r7$1@[EMAIL PROTECTED]
> >> Trevor Wilson wrote:
> >>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
> >>> news:g13o17$10ph$1@[EMAIL PROTECTED]
> >>>> 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.
> >>> **How about: Not necessarily? Better?
> >>>
> >> Hardly.
> >>
> >>>>>  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.
> >>> **OK. It is not necessary to have rectifiers close to the
transformer. I
> >>> set up a test last night, with 2 Metres of cable, connected to a
> >>> transformer, thence to a rectifier, thence to an amplifier. An AM
radio
> >>> place VERY CLOSE to the cable picked up some radiation. Covering the
> >>> cable with an earthed sheild completely eliminated the noise.
> >>>
> >> And what current were you drawing from the rectified output?
> >
> > **4 Amps @[EMAIL PROTECTED]
 60 Volts.
> >
> >
> 
> That's a decent load. I am not completely convinced though. First an
> a.m. radio covers only a limited bandwidth from about 500KHz to 1MHz and
> I would expect fast rectifier spikes to produce spectrum well beyond
> that. Secondly, an earthed ****eld only eliminates the electric field.
> The magnetic field will see that as transparent. Have you tried it with
> an air band receiver?
> 
> Cheers
> 
> Ian

In one of my recent rude postings in reply to what Trevor Wilson said
about the issue,
I told him he had not considered magnetic induction of switching spikes.

Many amps suffer diode switching spikes causing a buzz at the output.

Someone here tried to use a Pereaux amp to power a 96dB sensitive old
Altec
bass driver and could not, because of output buzz.
I tested it at my place on my 90dB speakers and although the buzz was
clearly audible 300mm away
from speakers, and 4M its inaudible.

In tube amps buzz is a problem sometimes with poor design.

But keeping all the damn diodes and ac PSU bits off the audio chassis
and only having a DC supply brought in via cabling 
completely stops buzz pick up or magnetic induction.

Patrick Turner.