Conference hips::uk_audioo

Sounds like you have some crosstalk or earth loop problems.

The soft background noise can be attributed to noise in the pre-amp and 
the power amp doing a nice job of making it louder!

As for the video,  are you using screened and earthed rca cables,  the best
type are the ones with earth straps that connect to a star earth on the back
of the pre-amp. This can make quite a difference....

Have you ensured that you have no earth loops,  ie. only one device in the
system provides the mains earth,  usually power amp or pre amp,  this
seems to quieten things down considerably.

In all audio,  you should strive for one "star" earth at the center of the
system,  I have experienced nasty noises with multiple earth connections.

_Richard

Richard,

When you say the star earth on the back of the pre-amp, do you mean the 
ground post next to the phono input ?  If so can you recommend a cable 
with an earth strap on it ?

Likewise with the mains earth.  All the items in the system are wired to 
3 pin 13 amp mains plugs with all three cores connected.  Should I 
remove the earth cores on all but the power amp ?

thanks,

Iain

Iain,

I can't remember any names of cables,  however they look like ordinary
RCA cables with a fly lead at each end,  the lead should be connected
to the earth post.

I believe the arrangement is that the outer braid is connected to the outer
of the phono plug and the fly lead,  in some extreme cases an extra braid
is placed around the signal braid for total sheilding.

However,  for earth loop problems,  I cannot quote this verbatim, but an
electronics engineer/audiophile friend informed me that you should always
concentrate on one signal earth per system.  This would not be so difficult
except for the fact that most RCA sockets are on the chassis,  and this is
connected to mains earth.  This can cause problems with earth not being
at the same potential throughout the system,  this causes audiable
nasties.

My solution was to ensure that each device in the system is securely 
connected together on the earth posts/chassis/rca connectors and then
only connect one mains earth on the power amp.

I am prepared for someone to pop up and correct this,  however it did make
a noticable difference to hiss and hum in the system.

Regards,

_Richard

    re .3
    "My solution was to ensure that each device in the system is securely 
    connected together on the earth posts/chassis/rca connectors and then
    only connect one mains earth on the power amp."
    
    This may remove the noise but can compromise safety; devices supplied
    with a 3-way power connection should always have all 3 connected.
    
    One answer is to ensure that all signal earths are only connected to
    mains earth at one point. This used to be at the record player, but
    since many don't have one these days that could be difficult! Chances
    are the preamp power earth and signal earth are not directly commoned, 
    so the preamp stud should be connected either to mains earth or - 
    preferably - a good low noise earth like a cold water pipe. This could
    bring lots of other benefits to the sound regardless of source.
    
    Another thing worth trying is to remove both of the shields on the
    interconnect, at the end connected to the device that is breaking
    through; this stops the device's "dirty" signal ground polluting the
    system's, but the interconnect is still adequately shielded. Or you can
    tie the signal earth in the breaking-through device back to
    the preamp stud.
    
    I had a similar problem to .0 when an old Technics tuner I had was 
    breaking through. Simply installing a good interconnect instead of the
    supplied el cheapo fixed the problem. I presume that the diode effect
    at rf of the lower quality copper/plugs/soldering was allowing rf gunge
    circulating in the tuner's signal earth to pollute the system's, whereas
    the better interconnect terminated the tuner's signal earth more
    effectively. Maybe this is where some perceived interconnect
    improvements originate, rather than their direct effect on the signal
    itself.
    
    Dave

Armed with these replies, tonight will find me yet again up to my neck 
in cables and the likes..

thanks,

Iain

Re: .4

I agree that disconnecting earth leads can be hazardous if appropriate precautions
are not taken,  however if you have some noise and it is reduced,  it is logical
to deduce that there is a problem with earth loops.

I decided to reduce this by ensuring that all chassis (ie. Mains earth) were
daisy chained from device to device and then only connected to the supply earth
via one plug.  I assume some of my old gear is not so scrupulous about audio 
screen/earth not being the same thing as mains earth.

I have also found that reversing live/neutral into some gear can make changes to
hum/noise,  although I always have a damn good look inside at the wiring before
changing things like that.

The problems with noise can vary between houses with PME earthing (neutral bonded
to earth locally) and conventional earth (neutral bonded to earth at substation), I
cannot help wonder what a floating earth of perhaps 100V or so above ground in a 
PME equipped house will do to audio gear,  even though the Faraday cage principal
makes it safe for use?

_Richard

The engineer for PJ Hifi came out last week to have a listen to my 
system.  He played about with it, and has come to the conclusion that 
the cause of most of the noise was the Rotel RC965 CD Player.  To 
demonstrate this, he played a cd, paused it and a whistling noise rang 
out from the speakers.

The player has now gone back Rotel.  In the mean time, PJ have lent me a 
Meridian 206 Player (secondhand �750).  Sneaky of them !

I'm very impressed with the improvement in the sound of the system.  Far 
more detail, better presentation of the music and at last I understand 
the word soundstage.

Tomorrow I'm picking up a 208 with built in preamp and remote.  This 
could be my next upgrade as it provides all the things I need from a CD 
and preamp in one package.

If only that Tax demand hadn't arrived yesterday, I would have bought 
the 206 on the spot.  Maybe later this year I can afford the 206 or 208 

Iain :(

Try and get your hands on a Meridian 207. It's similar to a 208, just uses older
technology. They can be picked up secondhand for less than 500 pounds.
You could always add a DAC later if desired.

GC