Biwiring with Nordost
 

"Eeyore" wrote in message
...


Trevor Wilson wrote:

"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:

* Use an amplifier which can deal with 2 Ohm (or better) load
impedances,
without Voltage drop or current limiting (no MOSFETs or valves, of
course).

MY mosfet amps will drive 2 ohms no trouble !

**That's what you think.

Do you know anything about them ?

**About the ones you use? Nothing.


Tell me about your objection to mosfets in this regard.

**I've never heard ANY MOSFET amp drive Quads adequately. Yours may well
be
different.

Is your objection to them based on any specific scientific principle is
what I
was trying to get at.

**Indeed. Several. MOSFETs:

* Exhibit much higher levels of distortion, at low bias currents, than
(modern) BJTs.
* Exhibit a negative tempco of gm. BJTs do not.
* Exhibit somewhat higher levels of distortion, at high bias currents, than
(modern) BJTs.


--
Trevor Wilson
www.rageaudio.com.au



--
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Biwiring with Nordost
 

"Eeyore" wrote in message
...


Trevor Wilson wrote:

"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:

Do some comparative listening with cable runs of around 10 Metres.
You'll hear a difference very easily.

To return to my earlier question.....

How much inductance do you think is audible ?

**Without nominating the length of the cables and the impedance of the
speakers, it is not possible to say.


I know it's not possible to give a blanket answer but how about in
terms of X dB @ X kHz ?

**Depends on the listener.

So, from your experience would you care to take a stab at a sensible
ball-park figure ?

**Depends on the listener.

You decline to offer any useful answer at all ?

**I provided the only possible answer.


--
Trevor Wilson
www.rageaudio.com.au



--
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Biwiring with Nordost
 

On 2007-01-09, Don Pearce wrote:
On Tue, 9 Jan 2007 20:26:51 +1100, "Trevor Wilson"
wrote:
**I never said it was audible. It is possible that it MAY be audible under
extreme conditions. It is certainly good engineering practice to ensure that
cable characteristics remain stable, regardless of load or drive conditions,
however.

The force is (mu0 * 2 * L)/(4 pi d) * I squared
Newtons per metre of wire.

L is the length of the wire
d is the separation

When the currents are in opposite directions, which they always are in
speaker wires, the force will tend to push the conductors apart.

In terms of what this could do to the sound, when a given geometry of
cable is pulled apart, there will be a tiny tendency for the
insulation to narrow as it is stretched. This will put more of the
electric field into the air, which will lower the effective dielectric
constant. This will speed up the signal. The result will be phase
distortion during peaks of the signal, which will result in
commensurate harmonic distortion.

The effects will be vanishingly small, and I would challenge anyone to
measure the effect in n audio context.

You can take the formula Don provides for force and combine it with
the formula for the inductance of the conductor pair and work out the
relative change of inductance from zero to a given current. So:

- for my particular 12-gauge 'speaker cable's dimensions

- in PVC (Young's Modulus of 0.1 GPa) as per my cable

- for a current of 5A (I have easy load, average sensitivity 'speakers)

the relative change of inductance is about 3.4 parts per billion [2].

I suspect the intermodulation products from that inductance change will
be well below the distortions from the drive units.

This relative inductance change is:
- proportional to the square of the current;
- inversely proportional to the dielectric's Young's Modulus [1]; and
- approximately inversely proportional to the square of the centre-to-centre
spacing of the conductors.

So smaller cables running higher currents may be more susceptible to
this effect. However I conclude that in my kit the effect is probably
negligible.

[1] e.g. PTFE (YM = 0.5 GPa) is 5 times stiffer than PVC

[2] formula on request if anyone wants to check

--
John Phillips

Biwiring with Nordost
 

Trevor Wilson wrote:

"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:

* Use an amplifier which can deal with 2 Ohm (or better) load
impedances,
without Voltage drop or current limiting (no MOSFETs or valves, of
course).

MY mosfet amps will drive 2 ohms no trouble !

**That's what you think.

Do you know anything about them ?

**About the ones you use? Nothing.


Tell me about your objection to mosfets in this regard.

**I've never heard ANY MOSFET amp drive Quads adequately. Yours may well
be different.

Is your objection to them based on any specific scientific principle is
what I was trying to get at.

**Indeed. Several. MOSFETs:

* Exhibit much higher levels of distortion, at low bias currents, than
(modern) BJTs.

Ok, I don't use them at low bias currents.


* Exhibit a negative tempco of gm. BJTs do not.

Is that a real problem ?


* Exhibit somewhat higher levels of distortion, at high bias currents, than
(modern) BJTs.

Gm related. Indeed. I use multiple devices in parallel with an attentant
increase in output stage gm.

Graham

Biwiring with Nordost
 

John Phillips wrote:

On 2007-01-09, Don Pearce wrote:
On Tue, 9 Jan 2007 20:26:51 +1100, "Trevor Wilson"
wrote:
**I never said it was audible. It is possible that it MAY be audible under
extreme conditions. It is certainly good engineering practice to ensure that
cable characteristics remain stable, regardless of load or drive conditions,
however.

The force is (mu0 * 2 * L)/(4 pi d) * I squared
Newtons per metre of wire.

L is the length of the wire
d is the separation

When the currents are in opposite directions, which they always are in
speaker wires, the force will tend to push the conductors apart.

In terms of what this could do to the sound, when a given geometry of
cable is pulled apart, there will be a tiny tendency for the
insulation to narrow as it is stretched. This will put more of the
electric field into the air, which will lower the effective dielectric
constant. This will speed up the signal. The result will be phase
distortion during peaks of the signal, which will result in
commensurate harmonic distortion.

The effects will be vanishingly small, and I would challenge anyone to
measure the effect in n audio context.

You can take the formula Don provides for force and combine it with
the formula for the inductance of the conductor pair and work out the
relative change of inductance from zero to a given current. So:

- for my particular 12-gauge 'speaker cable's dimensions

- in PVC (Young's Modulus of 0.1 GPa) as per my cable

- for a current of 5A (I have easy load, average sensitivity 'speakers)

the relative change of inductance is about 3.4 parts per billion [2].

That's -170 dB.


I suspect the intermodulation products from that inductance change will
be well below the distortions from the drive units.

This relative inductance change is:
- proportional to the square of the current;
- inversely proportional to the dielectric's Young's Modulus [1]; and
- approximately inversely proportional to the square of the centre-to-centre
spacing of the conductors.

So smaller cables running higher currents may be more susceptible to
this effect. However I conclude that in my kit the effect is probably
negligible.

That sounds like a safe conclusion.

Graham

Biwiring with Nordost
 

"Eeyore" wrote in message
...


Trevor Wilson wrote:

"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:
"Eeyore" wrote in message
Trevor Wilson wrote:

* Use an amplifier which can deal with 2 Ohm (or better) load
impedances,
without Voltage drop or current limiting (no MOSFETs or valves,
of
course).

MY mosfet amps will drive 2 ohms no trouble !

**That's what you think.

Do you know anything about them ?

**About the ones you use? Nothing.


Tell me about your objection to mosfets in this regard.

**I've never heard ANY MOSFET amp drive Quads adequately. Yours may
well
be different.

Is your objection to them based on any specific scientific principle is
what I was trying to get at.

**Indeed. Several. MOSFETs:

* Exhibit much higher levels of distortion, at low bias currents, than
(modern) BJTs.

Ok, I don't use them at low bias currents.

**Smart move. Of course, using BJTs eliminates that little inconvenience.
BJTs are MUCH better at low bias currents and slightly better at high bias
currents. Win - win.



* Exhibit a negative tempco of gm. BJTs do not.

Is that a real problem ?

**Sure. If you're using the MOSFETs within a feedback loop. Or outside one.
BJTs allow for external VI limiting, which, in turn, allows for ensuring the
limiting can be kept outside any feedback loops.



* Exhibit somewhat higher levels of distortion, at high bias currents,
than
(modern) BJTs.

Gm related. Indeed. I use multiple devices in parallel with an attentant
increase in output stage gm.

**Good stuff. Of course, BJTs are still better. And cheaper.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

Biwiring with Nordost
 

"John Phillips" wrote in message
...
On 2007-01-09, Don Pearce wrote:
On Tue, 9 Jan 2007 20:26:51 +1100, "Trevor Wilson"
wrote:
**I never said it was audible. It is possible that it MAY be audible
under
extreme conditions. It is certainly good engineering practice to ensure
that
cable characteristics remain stable, regardless of load or drive
conditions,
however.

The force is (mu0 * 2 * L)/(4 pi d) * I squared
Newtons per metre of wire.

L is the length of the wire
d is the separation

When the currents are in opposite directions, which they always are in
speaker wires, the force will tend to push the conductors apart.

In terms of what this could do to the sound, when a given geometry of
cable is pulled apart, there will be a tiny tendency for the
insulation to narrow as it is stretched. This will put more of the
electric field into the air, which will lower the effective dielectric
constant. This will speed up the signal. The result will be phase
distortion during peaks of the signal, which will result in
commensurate harmonic distortion.

The effects will be vanishingly small, and I would challenge anyone to
measure the effect in n audio context.

You can take the formula Don provides for force and combine it with
the formula for the inductance of the conductor pair and work out the
relative change of inductance from zero to a given current. So:

- for my particular 12-gauge 'speaker cable's dimensions

- in PVC (Young's Modulus of 0.1 GPa) as per my cable

- for a current of 5A (I have easy load, average sensitivity 'speakers)

the relative change of inductance is about 3.4 parts per billion [2].

I suspect the intermodulation products from that inductance change will
be well below the distortions from the drive units.

This relative inductance change is:
- proportional to the square of the current;
- inversely proportional to the dielectric's Young's Modulus [1]; and
- approximately inversely proportional to the square of the
centre-to-centre
spacing of the conductors.

So smaller cables running higher currents may be more susceptible to
this effect. However I conclude that in my kit the effect is probably
negligible.

**I concur.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

Biwiring with Nordost
 

"Laurence Payne" lpayne1NOSPAM@dslDOTpipexDOTcom wrote in message
...
On Tue, 9 Jan 2007 20:26:51 +1100, "Trevor Wilson"
wrote:

In any case, what's going to be audible about it ?

**I never said it was audible. It is possible that it MAY be audible under
extreme conditions. It is certainly good engineering practice to ensure
that
cable characteristics remain stable, regardless of load or drive
conditions,
however.

Is it good practice to massively over-engineer just so you can push
the price up?

**It is good practice to choose the correct product to do the job.
Regardless of cost.

BTW: There are far less costly ways of reducing inductance than using
Nordost. I've said so in the past and I'll say so again. Use RG213/U if you
want low inductance, low resistance and low cost.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

Biwiring with Nordost
 

"Eiron" wrote in message
...
Eeyore wrote:


Laurence Payne wrote:


"Trevor Wilson" wrote:


In any case, what's going to be audible about it ?

**I never said it was audible. It is possible that it MAY be audible
under
extreme conditions. It is certainly good engineering practice to ensure
that
cable characteristics remain stable, regardless of load or drive
conditions,
however.

Is it good practice to massively over-engineer just so you can push
the price up?

It's profitable to do that I'm sure.

It worked, for a while, for Trevor's favourite amp manufacturer.

**Nope. It worked for nearly 30 YEARS. That's hardly "for a while". It
worked, because the product was and still is audibly and measurably superior
to the competition. In any case, I prefer to call it 'a small pause in
production'. Let's see what occurs in 2007.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

Biwiring with Nordost
 

"Laurence Payne" lpayne1NOSPAM@dslDOTpipexDOTcom wrote in message
...
On Tue, 9 Jan 2007 13:39:20 +1100, "Trevor Wilson"
wrote:

Under the effects of EMF ????

**Indeed. Basic electrical theory. Two parallel conductors will move when
an
opposing current is passed through them.

Appreciably, in the context of speaker cables?

**As Mr Philips has recently posted, in the context of speaker cables, not
appreciably at all.

To what detrimental
effect on the sound?

**Capacitance and inductance will vary according to the signal applied.


--
Trevor Wilson
www.rageaudio.com.au



--
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