Phil Allison wrote:

"Nick Gorham"

** How about a lumpy join in the drive belt ?



If that was the case, I would expect the noise to be when the lump passes
over the pully, which would be less that 33.3 or 45.




** How is that so ????????

No matter what size the belt is, it only traverses the motor pully once per
table revolution.

Think it through .......

Even Homer nods....

--
Eiron

No good deed ever goes unpunished.

On Tue, 29 Aug 2006 20:24:30 +1000, "Phil Allison"
wrote:

If that was the case, I would expect the noise to be when the lump passes
over the pully, which would be less that 33.3 or 45.



** How is that so ????????

No matter what size the belt is, it only traverses the motor pully once per
table revolution.

Think it through .......

Only if the motor pulley is zero size, at zero distance from the
platter :-)

"Phil Allison" wrote in message
...

"Nick Gorham"


** How about a lumpy join in the drive belt ?



If that was the case, I would expect the noise to be when the lump passes
over the pully, which would be less that 33.3 or 45.



** How is that so ????????

No matter what size the belt is, it only traverses the motor pully once
per table revolution.

Think it through .......




....... Phil

If the belt has a length of 500mm and the platter pulley is approx 80mm
diameter (circumference of 250mm approx) a point on the belt would go around
the pulleys once for every two revolutions of the platter pulley. If the
belt length is as close as possible to the circumference of the platter
pulley a point on the belt will go around the platter pulley once for each 1
and a bit revolutions of the platter pulley.

Phil Allison wrote:
"Nick Gorham"

** How about a lumpy join in the drive belt ?



If that was the case, I would expect the noise to be when the lump passes
over the pully, which would be less that 33.3 or 45.




** How is that so ????????

No matter what size the belt is, it only traverses the motor pully once per
table revolution.

Think it through .......




....... Phil



I did think it through before posting. I would guess you didn't, and so
you were wrong. Note that I said less than, not a lot less than, just
less than.

--
Nick

On 2006-08-29, Eiron wrote:
lordy wrote:

Done. I've re-recorded the clip, and added another clip from another
vinyl source for good measure.

http://lordy.org.uk/noise.html


Note that the very low frequency repeats 33.3 times per minute on the LP
and 45 times a minute on the 45. Could be a dodgy bearing or two duff discs.

There may well be no earth anywhere, which is just as likely to cause mains hum
as two earths. You may need to add an earth.

I'm assuming from that reply the noisiest frequency (hum), is 50Hz for both from that
reply, and that's why you are still suspicious of earthing issues?

FWIW I took it downstairs and hooked up to my amp (Cambridge Audio A500)
and the hum is still there!

Lordy

On Tue, 29 Aug 2006 11:35:21 GMT, lordy wrote:

On 2006-08-29, Eiron wrote:
lordy wrote:

Done. I've re-recorded the clip, and added another clip from another
vinyl source for good measure.

http://lordy.org.uk/noise.html


Note that the very low frequency repeats 33.3 times per minute on the LP
and 45 times a minute on the 45. Could be a dodgy bearing or two duff discs.

There may well be no earth anywhere, which is just as likely to cause mains hum
as two earths. You may need to add an earth.

I'm assuming from that reply the noisiest frequency (hum), is 50Hz for both from that
reply, and that's why you are still suspicious of earthing issues?

FWIW I took it downstairs and hooked up to my amp (Cambridge Audio A500)
and the hum is still there!

Lordy


Of the three main bits of kit - computer, preamp and deck, which of
them are actually grounded through their own mains lead? There is
plainly a ground loop to be eliminated here.

d

--
Pearce Consulting
http://www.pearce.uk.com

On 2006-08-29, Don Pearce wrote:
On Tue, 29 Aug 2006 11:35:21 GMT, lordy wrote:

On 2006-08-29, Eiron wrote:
lordy wrote:

http://lordy.org.uk/noise.html

Of the three main bits of kit - computer, preamp and deck, which of
them are actually grounded through their own mains lead? There is
plainly a ground loop to be eliminated here.

The amp has a similar 3 prong kettle lead as the PC. I'm assuming its
grounded correctly internally.

The screw on the back of the PC is connected to the PSU so I would hope
that was grounded too.

The Preamp did not have a ground, but I was only using that for my PC,
not for the amp chich has an internal phono stage.

Is it likely the deck is faulty?

The wiring on the factory fitted cart looks correct also.

Lordy

On 2006-08-29, lordy wrote:
On 2006-08-29, Don Pearce wrote:
On Tue, 29 Aug 2006 11:35:21 GMT, lordy wrote:

On 2006-08-29, Eiron wrote:
lordy wrote:

http://lordy.org.uk/noise.html

Of the three main bits of kit - computer, preamp and deck, which of
them are actually grounded through their own mains lead? There is
plainly a ground loop to be eliminated here.

Just for clarity, problem occurs on main amp as well as when connected
to my PC.

The amp has a similar 3 prong kettle lead as the PC. I'm assuming its
grounded correctly internally.

The screw on the back of the PC is connected to the PSU so I would hope
that was grounded too.

The Preamp did not have a ground, but I was only using that for my PC,
not for the amp chich has an internal phono stage.

Is it likely the deck is faulty?

The wiring on the factory fitted cart looks correct also.

Lordy

lordy wrote:
On 2006-08-29, Eiron wrote:
lordy wrote:

Done. I've re-recorded the clip, and added another clip from another
vinyl source for good measure.

http://lordy.org.uk/noise.html

Note that the very low frequency repeats 33.3 times per minute on the LP
and 45 times a minute on the 45. Could be a dodgy bearing or two duff discs.

There may well be no earth anywhere, which is just as likely to cause mains hum
as two earths. You may need to add an earth.

I'm assuming from that reply the noisiest frequency (hum), is 50Hz for both from that
reply, and that's why you are still suspicious of earthing issues?

FWIW I took it downstairs and hooked up to my amp (Cambridge Audio A500)
and the hum is still there!

Lordy

Just FYI (I gather you've sorted this now) I had problems with
mechanical noise (not audible through the speakers) from my RPM9. It
turned out that the platter was rubbing against the plinth beecause the
main bearing was incorrectly adjusted. Easily fixed (even though it took
Project's agents two attempts), but I've just noticed it's slipped
again, so it's out with the spanners ;-)

In article ,
lordy wrote:
Strange - it's mainly hum which would suggest a ground problem,
although it would be nice if the clip included a bit before the stylus
was lowered.

Done. I've re-recorded the clip, and added another clip from another
vinyl source for good measure.

http://lordy.org.uk/noise.html

I noticed something a bit odd, the hum
only appears when the needle finds the groove. When its skirting around
outside of the groove there is no noise.

I'm totally lost as to why the hum should only start when the stylus
actually hits a groove.

I look forward with interest to the theories. ;-)

--
*There's no place like www.home.com *

Dave Plowman London SW
To e-mail, change noise into sound.