Audio Asylum Thread Printer
Get a view of an entire thread on one page
|For Sale Ads|
In Reply to: RE: 4N Pure Silver Dead Soft Wire Project posted by Duster on February 25, 2017 at 12:22:53
One of the enjoyable things about the design I'm shooting for is that it's not suitable for a commercial build, since it may be too delicate from a heavy duty POV. Like a number of DIY cable builds, it's not important that there is a level of fragility involved for my own use, not unlike the delicate nature of a turntable, and the responsibility of the end user to be extra-careful from a mechanical perspective. Good performance should not necessarily be limited by the danger of mishandling due to the thoughtlessness of a consumer electronics plug & play mentality vs. a DIY build for personal use. Folks must take care in the way they treat their own audio gear, in so many ways. So a DIY build can be as centered on performance as a designer wishes it to be, rather than compromise for the sake of a more robust commercial build for business purposes, which may sacrifice performance for the sake of avoiding customer returns.
In the case of using a very thin layer of PTFE Teflon tape vs. a more bulky cotton tubing as an insulator, I plan to use a single run of PTFE Teflon tape with a half-overlap that will effectively provide 2-layers of tape wrap for each wire, not even as much as the 4-5 wraps used for pipe sealing purposes as intended for PTFE Teflon tape. Even if an exposed gap very unlikely occurs at some point within the short 0.5 meter length, there will be 2-layers of tape around the opposing wire to provide the necessary insulation for a twisted pair. With so little dielectric mass, there should be minimal dielectric absorption involved in the matter, and it will allow the two opposing conductors to be very tightly twisted together without issue due to the material bulk of a fluffy cotton dielectric.
The primary goal of this DIY AES/EBU digital cable project is to allow two solid core conductors to be twisted tightly together, that do not require fillers that add dielectric mass in order to provide a structure that maintains a consistent geometry from end to end, since a medium gauge solid core wire with a minimal mass insulator can provide a very robust geometry vs. a thickly insulated stranded wire conductor tends to provide. This matter may also pertain to the bulky nature of cotton tubing, which is better implemented for analog interconnect cables and speaker wire rather than an AES/EBU digital cable application, IMO. Although the DIY build will not be measured to see if its number falls somewhere between the generous 110 ohm ± 20% (88-132 ohm) range for an AES/EBU digital cable application, in my experience of many that I've built perform much better than the 110 ohm commercial cables I've evaluated, and also tend to sound much better than 75 ohm digital coaxial cables if terminated with an audiophile-quality XLR connector vs. a pro audio XLR connector. Building the perfect twisted pair is the primary goal, in this case.
Hi. Where did you purchase the silver wire from ? Thanks.
For those in the US, Handmade Electronics sells bare 99.99 silver wire advertized as "soft annealed". I'll assume that this is just another term for "dead soft". It also costs a bit less, but more importantly domestic shipping will be quicker.
That's a good tip. I would have ordered the wire from Handmade Electronics if I was aware that they offered the product. It's also nice that they offer the wire in 1 foot increments, since I had to negotiate a 1.25 meter length with the Australian seller who offers the product per 1 meter increments, as I only require a 4 foot length for my DIY project. When divided in half, a pair of 2 foot wires per polarity when tightly twisted together results in an approximately 0.5 meter cable (about 20% less in length).
Duster, I'm wondering how you intend to get even close to the specified 110ohm characterisitc impedance?
Or do you agree with me that it's not important? (Although I'd argue that with a low resistance wire it actually *is* important, unlike a higher resistace conductor like, for example, carbon fibers)
btw, I find no mention of 20% tolerance in the AES3 spec. If the characteristic impedance mismatches the source or load impedances by any amount you will get reflections. Curious to know where this 20% tolerance figure comes from.
The following text taken from Allied Wire & Cable (see link below):
AES EBU specs for digital audio cable require a sampling rate from 32 KHz to 193 KHz, bandwidth from 4.096 MHz to 24.5 MHz, and an impedance of 110 ohms ± 20%. These are very broad specifications, allowing everything from 88 ohm cables to 132 ohm cables. However, standard analog audio cables have impedances ranging from 45 ohms to 70 ohms. There is a lot of room for difference between the AES EBU digital audio cable impedances and the standard analog audio range, which could cause jitter and signal reflection problems. Those problems could then lead to receiver bit errors. To avoid these issues, 100 ohm to 120 ohm twisted pair cables are recommended.
With such a broad 110 ohm ± 20% range specification, albeit with the vague notion of a tighter tolerance being recommended, I find the sonic benefit of my experiments outweigh the concern about conforming to AES/EBU specifications, which seem a bit arbitrary. The 75 ohm characteristic impedance tolerance of ±3 ohm is far more strict, including the strict rules of terminating RCA and BNC connectors for the purpose, which if not followed can cause impedance mismatches. Achieving an actual ±3 ohm tolerance for a typical 75 ohm S/PDIF digital cable build seems even less likely than achieving a broader 110 ohm ± 20% tolerance.
The following is a layman's perspective regarding my home-brew XLR digital cable builds for my own personal use:
While the 75 ohm characteristic impedance issue of an RCA connector or BNC connector termination involves a mechanical structure that maintains a precision relationship of the dielectric structure between the center conductor and the shield from end to end, an XLR connector has little to do with maintaining the dielectric structure of of a twisted pair. The termination of a balanced digital cable vs. a balanced analog cable is identical, with no particular termination method having to do with the mechanical structure of an XLR connector to cause a characteristic impedance mismatch. So a nominal 110 ohm characteristic impedance of a balanced digital cable seems to be unaffected by the structure an XLR connector.
As for the cable geometry, the key point of my AES/EBU digital cable design is to maintain a consistent and precision twist ratio, with the same loop area for each twist, without any gaps along the entire length of a twisted pair that will last the test of time. This is easy to do when a medium gauge solid core conductor with a low-mass dielectric is implemented for the task. My favorite wire being VH Audio's 21 AWG OCC solid core copper hookup wire with low-mass AirLok dielectric for the purpose. Not only does the wire sound great, it's also the easiest wire to tightly twist in a precision manner for noise cancellation purposes, and to firmly keep its shape without gaps. All the twisted pair needs is a simple outer wrap of heavy duty PTFE Teflon tape to help ensure that the tightly twisted solid core conductors keep a consistent geometry from end to end, without any gaps forming, and to provide an important level of cable resonance control.
A typical commercial AES/EBU digital cable design maintains a consistent geometry with the use of fillers (with added dielectric mass) that act as a former for a twisted pair to maintain a consistent geometry, which is especially needed for a typical pro audio stranded conductor with thick insulation, since that type of conductor does not easily keep its geometry within the moderate constraints of a typical cable jacket. So a typical AES/EBU digital cable design tends to need an opposing pair of rods or a bonding agent to keep the conductors evenly and firmly twisted together from end to end, whereas I find a medium gauge solid core conductor with low-mass insulation fulfills the need of a precision geometry that can be consistent from end to end without fillers for a balanced digital cable application. Furthermore, an audiophile-quality XLR connector is just as vital for audiophile performance rather than a typical pro audio XLR connector such as those from Neutrik and Switchcraft, which are unacceptable for an audiophile application, in my experience. The same applies to a pro audio 110 ohm AES/EBU digital cable such as those from Canare and Mogami. Finally, I break the pro audio rules by not using a ground conductor nor shielding for my AES/EBU digital cable builds, since they are unnecessary and degrade audiophile performance for a short 0.5 meter length home audio application, to my ear.
From an eBay seller in Australia. Most sellers offer 99.9% pure silver, while the Australian seller offers dead soft 99.99% pure silver in various gauges at a good price with an inexpensive shipping charge.
Post a Followup:
Post a Message!
This post is made possible by the generous support of people like you and our sponsors: