Fancy Mains Cables

In article ,
R. Mark Clayton wrote:
There is a slight argument for thicker cables, but a 4 Ohm speaker
outputing 100W will only be drawing 5A. Multi stranded cables are more
flexible, but even 1mm mains cable perfectly adequate.

Decent amps have a very low output impedance - of the order of 0.1 ohm or
so. This 'damps' the movement of the speaker - ie helps prevent it
overshooting while following the waveform. So it's not a good idea to
increase the loop resistance of speaker and cable by using too thin a
cable. In practice it also depends on the run.

--
*Strip mining prevents forest fires.

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

The message
from "Dave Plowman (News)" contains these words:

In article ,
R. Mark Clayton wrote:
There is a slight argument for thicker cables, but a 4 Ohm speaker
outputing 100W will only be drawing 5A. Multi stranded cables are more
flexible, but even 1mm mains cable perfectly adequate.

Decent amps have a very low output impedance - of the order of 0.1 ohm or
so. This 'damps' the movement of the speaker - ie helps prevent it
overshooting while following the waveform. So it's not a good idea to
increase the loop resistance of speaker and cable by using too thin a
cable. In practice it also depends on the run.

The advertised damping factor figures of 400 for such amps in the
Hi-Fi mags of 30 odd years back (the snake oil factor is far from new)
amused me since the only driver which had a significant 'in band'
resonance to be damped was usually just the bass (or 'woofer') and its
voice coil ohmic resistance (typically 90% of its impedance) was
effectively in series with the output impedance of the amp (usually
somewhere around the 0.1 to 0.01 ohm mark[1]).

Typical resonance impedances for an 8 ohm unit would be around the 32
ohm mark making the actual damping factor figure around the 4 mark,
almost regardless of whether the amp impedance was 0.0001 ohm or
somewhere around the 0.5 ohm mark. Yes, the low impedance of the amp did
help to improve damping of bass cone resonance, but nowhere near to the
extent implied by the advertising.

[1] The low impedance was acheived using negative voltage feedback (in
some transistor amp designs, massive amounts of such negative voltage
feedback were employed to not only flatten the frequncy response to a
ripple level less than 0.01db over the full band (from 10Hz or less
right up to 30KHz or higher) but also to bolster the 400 damping factor
claims.

For designs that predated power mosfet output devices, this was very
bad news, resulting in a form of distortion which, initially was only
identified as being the characteristic "Transistor Sound", eventually to
be identified as SID (Slew Induced Distortion). The problem was that the
devices were chosen on the basis of their low signal level frequency
response of a few hundred KHz rather than their high power (large
voltage swing) response which was typically less than a tenth of that.

Essentially the devices were producing an electronic analogue of the
mistracking distortion of a cheap pickup cartridge (or an expensive one
setup at too light a downforce) because they couldn't persuade the
output voltage to faithfully follow the demanded rate of change at mid
to full power levels. The massive amounts of negative feedback simply
aggravated the effects of SID.

The advent of mosfet power transistors to replace the old fashioned
bipolar devices largely cured this problem on account they shared the
same attribute of high power output capability into the MHz range that
the good old thermionic valve had been demonstrating for the past 40 odd
years or so.

In short, the Hi-Hi amp manufacturers had taken it for granted that the
bipolar power transistor of the day were basically solid state
equivilents to the thermionic devices used in the older valved designs
and had failed to fully test the resulting designs.

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

Dr Zoidberg wrote:
"Norman Wells" wrote in message
...
charles wrote:

I've just cancelled my subscription to BBC Music Magazine (after 17
yeas) when it ssid you should spend at least 25% of your hi-fi
budget on leads.

The James Randi Educational Foundation two or three years ago
offered a million dollar prize to anyone who could prove that
expensive speaker leads improved the sound quality. As far as I'm
aware, it was never won.


What price levels did they have in mind?
I can clearly hear the difference between 20p a metre cable and £3 a
metre cable but when you go much above this I'm not convinced at all
- especially by the wild claims of vast differences that are so often
made

Read more at:

http://gizmodo.com/gadgets/calling-b...ter-305549.php

and, I guess the links on that page. He was talking about exceedingly
high-priced cables, but against 'Monster' cables, whatever they are, and
whatever they cost, not presumably against a length of damp string..

Norman Wells wrote:
Dr Zoidberg wrote:
"Norman Wells" wrote in message
...
charles wrote:

I've just cancelled my subscription to BBC Music Magazine (after 17
yeas) when it ssid you should spend at least 25% of your hi-fi
budget on leads.

The James Randi Educational Foundation two or three years ago
offered a million dollar prize to anyone who could prove that
expensive speaker leads improved the sound quality. As far as I'm
aware, it was never won.


What price levels did they have in mind?
I can clearly hear the difference between 20p a metre cable and £3 a
metre cable but when you go much above this I'm not convinced at all
- especially by the wild claims of vast differences that are so often
made

Read more at:

http://gizmodo.com/gadgets/calling-b...ter-305549.php

and, I guess the links on that page. He was talking about exceedingly
high-priced cables, but against 'Monster' cables, whatever they are,
and whatever they cost, not presumably against a length of damp
string..

Actually, a bertter link for the whole story is:

http://gizmodo.com/315250/pear-cable...ch-for-answers

"Norman Wells" wrote in message ...
Dr Zoidberg wrote:
"Norman Wells" wrote in message
...
charles wrote:

I've just cancelled my subscription to BBC Music Magazine (after 17
yeas) when it ssid you should spend at least 25% of your hi-fi
budget on leads.

The James Randi Educational Foundation two or three years ago
offered a million dollar prize to anyone who could prove that
expensive speaker leads improved the sound quality. As far as I'm
aware, it was never won.


What price levels did they have in mind?
I can clearly hear the difference between 20p a metre cable and £3 a
metre cable but when you go much above this I'm not convinced at all
- especially by the wild claims of vast differences that are so often
made

Read more at:

http://gizmodo.com/gadgets/calling-b...ter-305549.php

and, I guess the links on that page. He was talking about exceedingly
high-priced cables, but against 'Monster' cables, whatever they are,

They are about £15 a metre - more than I'd spend but not totally ridiculous prices.
They'd show and improvement over cheap cable but I'd be sceptical of any big improvement over cables costing half that.

and whatever they cost, not presumably against a length of damp string..

I can see why he didn't get any claimants.


--
Alex

"I laugh in the face of danger , then I hide until it goes away"

"Norman Wells" wrote in message ...
Norman Wells wrote:
Dr Zoidberg wrote:
"Norman Wells" wrote in message
...
charles wrote:

I've just cancelled my subscription to BBC Music Magazine (after 17
yeas) when it ssid you should spend at least 25% of your hi-fi
budget on leads.

The James Randi Educational Foundation two or three years ago
offered a million dollar prize to anyone who could prove that
expensive speaker leads improved the sound quality. As far as I'm
aware, it was never won.


What price levels did they have in mind?
I can clearly hear the difference between 20p a metre cable and £3 a
metre cable but when you go much above this I'm not convinced at all
- especially by the wild claims of vast differences that are so often
made

Read more at:

http://gizmodo.com/gadgets/calling-b...ter-305549.php

and, I guess the links on that page. He was talking about exceedingly
high-priced cables, but against 'Monster' cables, whatever they are,
and whatever they cost, not presumably against a length of damp
string..

Actually, a bertter link for the whole story is:

http://gizmodo.com/315250/pear-cable...ch-for-answers


Indeed it is.
Thanks

--
Alex

"I laugh in the face of danger , then I hide until it goes away"

Ian wrote:

She insisted that no way could I distinguish mono from stereo from
another room, and she got up to go and check.

Guess who was right.

Since you said "Girlfriend" not "Ex-girlfriend" you obviously gave in...

Andy

"Clint Sharp" wrote in message
...
In message
, JPG
writes
How about some Shakti stones?

http://www.shakti-innovations.com/audiovideo.htm

Bloody hell, I'm having some of them for my car, they claim fitting them
knocked 33 tenths of a second off the 0-60 time!!!

Wonder if I fit two sets if it'd knock an extra 3.3 seconds off? I could
race against Bugatti Veyrons in my diesel Focus if they do...
Clint Sharp


If you nitrous oxide'ed your Diesel Focus it might?

Fifth Gear nitrous injected a 1.9 Diesel VW Golf
and it kept up with a Honda NRX!!

But the diesel Golf had to have a Auto gearbox,
as the torque produce would have wrecked the clutch!

AFAIK the fastest Diesel production saloon is the BMW 3 series
330 with a 3 litre v6 Y series engine?
I wonder what would happen if it was fitted with nitrous injection?

Steve Terry

On Mon, 11 May 2009 10:41:42 +0100, R. Mark Clayton
wrote:

Gold connectors Irrelevant for fixed used, where the connection is made
once and left connected. Some utility for professional use where equipment
is plugged and unplugged all the time - e.g. my Sony microphone has a gold
plated jack or a guitar lead.

Gold is quite soft and wears away reasonably easily at the thicknesses
they put on, so it is not suitable for repeated plugging and unplugging.
Frankly, for most things it is a complete and utter waste of the world's
gold reserves and should be banned.

Paul Ratcliffe wrote:
On Mon, 11 May 2009 10:41:42 +0100, R. Mark Clayton
wrote:

Gold connectors Irrelevant for fixed used, where the connection is made
once and left connected. Some utility for professional use where equipment
is plugged and unplugged all the time - e.g. my Sony microphone has a gold
plated jack or a guitar lead.

Gold is quite soft and wears away reasonably easily at the thicknesses
they put on, so it is not suitable for repeated plugging and unplugging.
Frankly, for most things it is a complete and utter waste of the world's
gold reserves and should be banned.

One of my childhood memories was Johnny Ball on 'Think of a Number' saying
that if you collected all the gold that had been mined, and lumped it
together, it would form a cube just 60 ft^3.

True or not ? (The programme was about 30 years ago)

--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk