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Author Topic: Thicker Wire = Better Sound?  (Read 1072 times)

klaus

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Thicker Wire = Better Sound?
« on: May 22, 2020, 04:54:23 pm »

I no longer post or respond to discussions (or allow them here) where people question the fact that audio cables between audio components contribute a sound. I know from decades of experience that different construction of cables  connecting between condenser mics, power supplies and mic pre's will have a more or less significant influence on the sound. 

What can and should be discussed are factors that may contribute to a cable's transmission properties, especially when they can be scientifically explained.

Below I am copying a stimulating opinion about the topic. The writer, a respected audio professional, believes there is an advantage to terminating seven-conductor tube mic cables, historically and still manufactured for companies like Neumann, Schoeps, Brauner, Bock etc. differently than was customarily prescribed by the German broadcast system, Neumann, and others in the tube mic era: Back then, ground and heater were terminated to the two thicker conductors, and the thinner conductors to audio (+), audio (-), B+, and variable polarization voltage.

Here is the poster's theory why we should try it differently (unedited):

I figured someone would challenge me on this, historically I always did it the way you do as well, but here is my argument for using the thick wires for signal:

1.  The audio output is a low Z system, the DCR (DC resistance. KH) of a mic output transformer is typically 30-50ohms from my experience measuring them.  So at low frequency, having low Z on the audio lines is especially important.

2.  The thinner wires are not spec'd in their data book as a "gauge", but by rough calculation they should be able to handle a  minimum of 2.5A, upwards of 4A.  For the filament I double 2 because there are extra.  For an AC701, I should have at least 5A/0.1A = 50x over rating.  So there is ample current carrying capability in the thin wires, especially if I double an unused one for the filament.

3.  b+ at most carries 40-50mA in a U47, other than that its typically a few mA, so the thin wire easily handles both situations.  For the U47 I double up the b+ with 2 wires.

4.  Ground current is not separate, so audio and filament grounds are carried in the shields (most mics).  Ideally you would want the filament ground separate, and run through heavy wire also.  But this is not the way most mics operate.

5.  This scheme favors the audio, considering it the most important signal, and provides the lower Z between the transformer and the output jack on the supply.  The thick wires are 252 x 0.05mm stranded, the thinner wire 72 x 0.05.  So there are more strands = more surface area i.e. less skin effect, the higher the frequency, signals penetrate less into a conductor.  Dc flows through an entire conductor, RF only on the surface. 

I welcome your thoughts.  I have only been doing this for about a year, but have thought about it for a long time.  I kept asking myself, which more more important, the DC power or the audio signal out.  If the wires are more than capable of handling the DC, then why not give the audio a better signal path?  Eventually I decided to do it, and take whatever heat came along with that decision.

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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

RadarDoug2

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Re: Thicker Wire = Better Sound?
« Reply #1 on: May 22, 2020, 05:02:26 pm »

His whole theory is incorrect. While the output transformer is low Z, it will typically feed a bridging load. The filament draws the most current in the microphone, and so voltage drop on the cable will be the most significant. The thick wires should be used for the filament supply.
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klaus

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Re: Thicker Wire = Better Sound?
« Reply #2 on: May 22, 2020, 08:37:15 pm »

His whole theory is incorrect. While the output transformer is low Z, it will typically feed a bridging load.

Could not find a definition for "bridging load" anywhere. Did you mean the common 1:5 ratio of mic output to pre-input impedance?
Please explain in simple language what you mean, and how the theory of using thicker wire gauges for a balanced audio signal yielding better audio is incorrect.
Thanks.
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Klaus Heyne
German Masterworks®
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RadarDoug2

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Re: Thicker Wire = Better Sound?
« Reply #3 on: May 23, 2020, 02:44:12 am »

A bridging load is typically at least ten times the driver output impedance. In line level signals, a 600 ohm output drive (which could be 100 ohms source impedance) with a load of 10,000 ohms would be typical. Most mike preamps are arranged to supply a 1K load to a 200 ohm microphone, so not completely bridging.
With regard to using the thin wires for filaments. Most 6.3 volt heaters in small tubes draw 300 mA. While this is not a huge current, the idea of using the thin wires when you can use the thick ones is not good engineering. Perhaps someone from Neumann can chime in? They designed the product and specified the cable. They used the thick wires for filament based on good engineering practice.
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RuudNL

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Re: Thicker Wire = Better Sound?
« Reply #4 on: May 23, 2020, 09:15:33 am »

As far as I know, 'skin effect' isn't of any importance for audio frequencies.
It only plays a role at frequencies in the MHz. range.
Also 'characteristic impedance' can be neglected for audio, unless your microphone cables are longer than 15000 meters...
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afterlifestudios

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Re: Thicker Wire = Better Sound?
« Reply #5 on: May 23, 2020, 12:14:08 pm »

Does capacitance also come into play when using thicker wire?  I know lower capacitance is favourable in high impedance situations (guitar pickup to amp) and as you increase the diameter of the conductor, the capacitance goes up.  But I don’t know if capacitance has much effect on audio frequencies in low impedance situations like microphone to mic pre.
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klaus

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Re: Thicker Wire = Better Sound?
« Reply #6 on: May 26, 2020, 05:42:26 pm »

The writer of the OP added the following:

"Think about it this way:

If you had to run a balanced audio signal through (Gotham cable) GAC-7, and there were no other signals, what wires would you choose?
I would choose the heavier gauge because of the higher strand count, lower Z, and durability.

Now take each signal:

B+ = <10mA usually, no need for heavy gauge

Pattern Voltage: <5mA, no need for heavy gauge.

Negative Grid bias: <5mA, no need for heavy gauge.

Filament: 0.1-.2A:
First look at the wire: Thin wire in GAC-7 = 0.14mm^2

According to standard wire gauges: (https://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_AWG_wire_sizes)

(...) All the reading I have done says the capacity has to do with cross-sectional area at DC, as frequency goes up, the strand performs better than solid.  The chart I initially reference use the numbers 2.2A for 26ga, 3.5A for 24ga.
This equates to roughly 25 gauge (not listed), so looking at the numbers and taking worst case (26 gauge at 60 deg C), that would be 1.3A. 

Double that = 2.6A, compute over-rating for common tube filaments:
AC701 i=0.1A over-rating = 2.6/.1= x26

6072 i=0.15A over-rating = 2.6/.15= x17.3

6267 i=0.2A over-rating = 2.6/.2= x13

The actual over-ratings for the thin wires in GAC-7 will be higher than these.
Any tube that uses more current than 0.2A like an EF14 I wouldn't do this way.  Given the U67 only needs 4 inner conductors, you can triple the wire.



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Klaus Heyne
German Masterworks®
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