Cable design

I have several questions relating to cable design. First, though, I do not want any comments related to whether cables sound different-at all. I want to assume that there is a difference in the sound of different cables. My questions relate to the construction of cables and how the construction relates to the sound. My internet search hasn't revealed many sources to cover this but if you know one, that will work too. Right now I want to concentrate on interconnects between pre-amp and amp.

First, design: coaxial solid vs coaxial stranded vs twisted pair.
Second, material: copper vs silver vs silver coated copper
Third, electrical characteristics (as a function of the above): impedance, resistance, capacitance.
Fourth, insulation
Fifth, shielding vs non-shielded

This is interesting to me and the last thing I want is any argument about whether or not cables make a difference. If I get around to making my own ICs I would like to have some guidance. Thanks.
You need to add a Sixth: connectors.
Yes. Of course you are correct. And, how they attach to the wire. Solder or high pressure crimp. Thanks for adding that.
After a huge caveat of "not in every case," I can make the following comments regarding general characteristics of the items you list, based on my experience,with regards to interconnects;

Design: a twisted pair is generally superior sounding to a coaxial design - better focus. In addition, because a coaxial design has different wire and geometry characteristics for the positive and negative runs, it cannot be successfully used as a balanced connector.
With regards to twisted pairs, there are many ways to implement a twisted pair design by changing spacing, twists, shielding and more, and all those factors can affect the sound.
Other types of design include braided and spaced away pair (e.g., VH Audio Fine Silver IC's), as well as a sandwiched pair with flat conductors. Others have reported success with a spaced away pair in a flat orientation. I personally have had success with the VH Audio orientation where the two legs are wrapped around a core, and also some success with braided solid core wire.

With regards to materials, copper is generally considered warmer with better decay and body while silver is considered more detailed with more focus on attack, and is sometimes thought of as adding a harshness or edge to the sound although I am sure the Audio Note folks will disagree. I have a nice pair of silver interconnects and some nice silver speaker cables and, while I hear no harshness with either, I do believe the frequencies are sort of "tipped up" and that the presentation loses some body. Silver costs more. The only reason I can think of to use silver coated copper is for situations where you want corrosion resistance as it is often thought to be the worst of the options, although several well-known companies use it.

Interconnects should be low capacitance, speaker cables should be low inductance and resistance.

Opinions on insulation are all over the place. It used to be thought that teflon was tops, and most still think of it that way, but some believe teflon imparts a very slight unnaturalness to the sound compared to other materials such as polyethylene or especially natural materials such as cotton. Foamed teflon and foamed polyethylene are thought to be quite good. PVC is less used as a direct dielectric but is often used for jacket material. I personally like cotton or the foamed materials as a second choice. I have never heard silk although some, such as Duelund, use it.

I read a lot on these forums and following "common wisdom," many of my first ICs were unshielded. However, even though I have dedicated power lines, a high quality power conditioner for front end gear, and keep my wiring pretty tidy, I have since found that I prefer using shielded ICs so I now make everything that way using high quality tinned copper braid sleving, and I try to space that away a bit from the internal pair wires. Since I make mostly balanced cables lately, I spiral a ground wire outside the shield in the opposite direction of the twist on the internal wires.

I have had good success using high quality connectors from Furutech, for speaker cables, ICs and power cords, although I also like Oyaide for power cords.

To make your ICs, I would suggest starting out with the VH Audio fine silver wire recipe. You can use silver if you want but I would recommend using a high quality copper hook-up wire (VH Audio sells some OCC copper in their proprietary foamed teflon). Jupiter copper in cotton also sounds quite good in the 6/9s version. I like using 3/8ths inch diameter caulk backer for the core, or cotton rope if using cotton covered wire. If you are worried about corrosion of the copper in cotton wire, you can wrap a layer of teflon tape outside the wire to help reduce exposing the wire to oxygen and dampness. Connect the shield only to the source end and cover the whole thing in clean cut techflex. If making rca conductors I would use gold or rhodium Furutech connectors like the FP-108 or FP-110.

Please realize my comments are generalizations, in large part, and that changes in any part of the design, materials or implementation can affect the sound. Good luck.
Thank you for your detailed and thoughtful reply. I hope to have the time to begin experimenting. Cheers.
Seem like you and Davide256 have a common interest...See his post " Principles of audiophile cable construction? " Cheers!
How about solid core vs stranded cable?
Ditto on balanced cable if your system supports it. Some cable theory makes sense (to me anyway), and solid core pure copper is one of them, although I do have a silver solid core S/pdif cable (AQ Vdm 5). The best speaker cable I've owned is a set of (currently in my system) AQ Type 8 spiraled star quad perfect surface copper blah blah that sound fabulous, and seem like a bargain if you can find some in the "used" cable market.
I agree with you on the solid copper, Wolf.
I have always liked the sound of Harmonic Technology speaker cables for the money. In particular, the Pro 11 Plus described as,
"Pro-11 Plus is a one inch diameter cable using 19 strands of individually insulated 24ga. OCC copper filaments, resulting in a total of 11awg per conductor path. This design optimizes the ratio between surface area and core size, greatly reducing the 'skin' effect for high frequency detail and smoothness. The Single Crystal TM (OCC) construction and exceptionally high purity 6N copper allow this cable to make your system sound closer to live music!"
I believe the keys to their full, clear, dynamic sound are;
- OCC solid core copper conductors,
- multiple strands of individually insulated 24awg wire, and
- the use of foamed polyethylene insulation.
I am not sure I could consistently pick it out when listening, but I have found that, in general, I like cables with PE insulation, and particularly foamed PE insulation, better than similar cables using Teflon insulation, although the foamed teflon used by VH Audio sounds quite nice.

HT Pro 9 Plus/Reference, etc. provides a similar sound to the Pro 11 plus, but uses a variety of wires sized from 20 to 24 awg. HT went to this 20-24 awg range of wire sizes in their new Pro 11 Reference cables. I am not convinced the variety of sizes is better than the older version using only 24awg wires, and I own both Pro 9 plus with the range of sizes and Pro 11 plus.

I have taken apart both of the HT cables and the individual foamed polyethylene insulated wires are grouped and encased with a plastic material (I believe to be polypropylene), and then some elastic material inside of the larger diameter pvc outer casing. They look very similar to the construction of Neotech NES-3002 that you can see detailed on both VH Audio's and Sonic Craft's websites, except NES indicates the insulation on their cables is polypropylene, not PE. I have seen it speculated that Neotech directly makes (or used to make) cables for companies like HT and Acoustic Zen who would purchase the bulk cable, finish it off and sell it in the USA. The similarity in construction may support this.

I have made speaker cables that use individually isolated 6N 26awg solid core copper in cotton wires in a star quad geometry (16awg aggregate to MF/HF and 11awg aggregate to LF) and they also sound great. I recently put the HT cables back in my system and noticed a small increase in richness and body but the cotton insulated wires seem to be slightly more natural and neutral in the midrange. Both have great bass with depth and slam but the HT cables offer just a bit more body that is helpful to my current computer audio set-up.

I find it interesting how some quite successful companies NEVER specifically detail what is inside of their cables. Would you buy a car without looking under the hood? I admit being jaded about the whole cable thing, but fact is the cable industry in general has made a pile of money off of what amounts to wire, geometry, insulation materials and connectors. I certainly hear differences in cables, and I do use high quality wire (or bulk cable) and high quality connectors in my system, but I pay nowhere near the cost of a component for my wire.
I own 2 high performance German cars and if you look under the hood you can't see a damn thing. I also have paid relatively very little for my pile of cables as I find it much more fun to find clean used stuff. Besides, orphan cables need a nice home!
In MY experience, the connectors are the biggest factor in how the cable sounds. Only use shielded cable if you really need the protection against RFI. Shielding actually closes down the sound. Copper and silver (and gold, etc.) sound DIFFERENT....not necessarily better. The test is how it sounds in YOUR system.