terminating audio lines like RF

[dufus]

Archived from groups: rec.audio.pro (More info?)

http/www.borbelyaudio.com/kit_upgrades_term.asp

Is this total hooey, or what? I thought at audio frequencies these
effects are very small, and completely imperceptible. The longest mic
cable I ever use is 100 ft. But no mic will happily drive 150 ohms.
For line levels, the lower Z that any output stage must drive with
this approach definitely has distortion and voltage swing drawbacks,
versus the 10k input Z of a bridging input. What do y'all think?

Dufus

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

Despite my being an audiophile that hears differences between cables, capacitors, and various
other aspects of neurotic audio tweakdom, this particular one is s load of dingo's kidneys.
Aside from your correct point that reflection effects in cables are either totally
insignificant or non-existent below radio frequencies, there aren't many preamps that would be
happy driving the low Z loads this guy is talking about. A handful of preamps, such as tube
hybrid preamps with high current mosfet source followers, might sound better into such a low Z
load, but merely by virtue of pushing the preamp's output stage into higher current operation
for a given volume level, where the performance might be more linear. Perhaps this guy has
heard such an effect & has drawn the wrong conclusion about the cause.

--
Stephen Sank, Owner & Ribbon Mic Restorer
Talking Dog Transducer Company
http/stephensank.com
5517 Carmelita Drive N.E.
Albuquerque, New Mexico [87111]
505-332-0336
Auth. Nakamichi & McIntosh servicer
Payments preferred through Paypal.com
"dufus" <seanbroderick20003@yahoo.com> wrote in message
news:9da972e8.0411200442.1437f1cc@posting.google.com...
> http/www.borbelyaudio.com/kit_upgrades_term.asp
>
> Is this total hooey, or what? I thought at audio frequencies these
> effects are very small, and completely imperceptible. The longest mic
> cable I ever use is 100 ft. But no mic will happily drive 150 ohms.
> For line levels, the lower Z that any output stage must drive with
> this approach definitely has distortion and voltage swing drawbacks,
> versus the 10k input Z of a bridging input. What do y'all think?
>
> Dufus

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"dufus" <seanbroderick20003@yahoo.com> wrote in message
news:9da972e8.0411200442.1437f1cc@posting.google.com
> http/www.borbelyaudio.com/kit_upgrades_term.asp
>
> Is this total hooey, or what?

Total hooey.

I presume that Borbley didn't get the standard EE lecture about transmission
lines that starts out by saying that a cable has to be some fraction
(usually at least 1/8 probably far more) of a wavelength at the highest
frequency of interest, to be thought of as a transmission line.
That's a little more than a mile at 20 KHz.

If we lift our sights to SACD-like 100 KHz, we're still talking over 1,000
feet before a cable could in our wildest imaginings be thought of as a
transmission line.

>I thought at audio frequencies these effects are very small, and
>completely imperceptible.

This would be orthodox thinking. However, in a sighted evaluation I might be
cable to convince you that you were hearing something.


> The longest mic cable I ever use is 100 ft.

My longest snake is 150 feet and I regularly plug 20-50 feet of mic cable
into it. That's a room that is about 80 feet deep. In a big room this could
double.

>But no mic will happily drive 150 ohms.

Depends what you call happy.

> For line levels, the lower Z that any output stage must drive with
> this approach definitely has distortion and voltage swing drawbacks,
> versus the 10k input Z of a bridging input.

There are some pretty robust line drive output stages out there. Many will
drive their building-out resistors (i.e., an external short circuit) to +4
without clipping. They wont' do +22 cleanly, of course. Nonlinear
distortion will rise but still remain way below 0.05%.

> What do y'all think?

Borbly has spent too much time reading the pseudoscience in some of the
ragazines that publish his construction projects. He seems to believe
everything they say.

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

In article <9da972e8.0411200442.1437f1cc@posting.google.com> seanbroderick20003@yahoo.com writes:

> Is this total hooey, or what?

Yup. Someone has a good imagination.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" wrote ...
>
> seanbroderick writes:
>> Is this total hooey, or what?
>
> Yup. Someone has a good imagination.

Boberly had some good construction articles in the early
days of The Audio Amateur magazine. Kinda strange to
see such wacko stuff out of him how.

 

[mark]

Archived from groups: rec.audio.pro (More info?)

> >
> > Is this total hooey, or what? I thought at audio frequencies these
> > effects are very small, and completely imperceptible. The longest mic
> > cable I ever use is 100 ft. But no mic will happily drive 150 ohms.
> > For line levels, the lower Z that any output stage must drive with
> > this approach definitely has distortion and voltage swing drawbacks,
> > versus the 10k input Z of a bridging input. What do y'all think?
> >
> > Dufus

It's bunk.

For the example they gave, the driving side of the cable was
terminated. THe reflection would bounce back from the load and be
absorbed back into the pre-amp source Z. The load side would still
have a perfect signal even if it were an RF signal. There is only a
problem if the signal is re-reflected back toward the load. At
audio wavelengths, the cable would have to be very long to create a
problem.

What can be a problem, if the source cannot drive the capactiance of a
mismatched cable, the high end may be rolled off.

Mark

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:10pvb64f95e7kbf@corp.supernews.com
> "Mike Rivers" wrote ...
>>
>> seanbroderick writes:
>>> Is this total hooey, or what?
>>
>> Yup. Someone has a good imagination.
>
> Boberly had some good construction articles in the early
> days of The Audio Amateur magazine. Kinda strange to
> see such wacko stuff out of him how.

TAA has a long history of flirting with pseudo-science.

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1100962756k@trad...
>
> In article <9da972e8.0411200442.1437f1cc@posting.google.com>
seanbroderick20003@yahoo.com writes:
>
> > Is this total hooey, or what?
>
> Yup. Someone has a good imagination.

Thing is, Erno Borbely is a pretty well-respected engineer with some good
designs in his background, notably the Hafler DH-200 power amplifier (maybe
the DH-101 preamp too -- it's his style of circuit). And he's designed some
line output stages capable of hefty outputs, on the order of +24dBu into 100
ohms. I always wondered why; now I guess I know.

For home use this is indeed total hooey. I can conceive of circumstances,
though, where it might matter, notably the wiring of a large broadcast
facility that covers a square block or two, or perhaps a major convention
center. At somewhere like McCormick Place, for example, I can see needing to
take transmission line theory into consideration, and amplifiers like
Borbely's, set up for 50 ohms out and in, might be just the ticket. Of
course, most of us don't live in McCormick Place. Maybe he's been doing
contract wiring for Deutsche Rundfunk, and got carried away.

Peace,
Paul

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger" <arnyk@hotpop.com>
wrote:

>> http/www.borbelyaudio.com/kit_upgrades_term.asp
>>
>> Is this total hooey, or what?
>
>Total hooey.

Are Borbely's resistor values correct for the balanced line?

Chris Hornbeck

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

"Chris Hornbeck" <chrishornbeckremovethis@att.net> wrote in message
news:icevp0hi3rkms6rskjeagrgkqjocrq20rf@4ax.com...
> On Sat, 20 Nov 2004 13:02:00 -0500, "Arny Krueger" <arnyk@hotpop.com>
> wrote:
>
>>> http/www.borbelyaudio.com/kit_upgrades_term.asp
>>>
>>> Is this total hooey, or what?
>>
>>Total hooey.
>
> Are Borbely's resistor values correct for the balanced line?

Depends on the characteristic impedance of the balanced line?

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

On Sat, 20 Nov 2004 16:04:57 -0800, "Richard Crowley"
<rcrowley7@xprt.net> wrote:

>> Are Borbely's resistor values correct for the balanced line?
>
>Depends on the characteristic impedance of the balanced line?

He specifies "110 ohm" cable and 110 ohm build-out and load
resistors. I guess my question goes to the cable's spec method.

Chris Hornbeck