Is there an optimal interconnect lenght?

The shortest is the best.

Remember: The longer the 'connection' the higher the resistance and the bigger the possibility that the cable will turn into a 'nasty' microphone. Yes- a microphone!

Cables don't "work" - their job is to transfer electrons between the components more or less perfectly. The longer the more difficult it is for the electrons to travel.
Different dielectrics & electron-carriers (copper, silver, carbon) may cause that cables sound different from eachother.

Best regards,
Dewald

Well, I am going to take the contrarian point of view.
I think the optimal length of I.C. cable is 1 meter.
(However, from a sonic standpoint, there certainly is nothing wrong with a half meter cable, unlike what your friend may have said!)

Another audiophile friend of mine passed on this same advice to me. "Never buy a 0.5 meter (20 inch) I.C."

His reasoning, and I agree, for the most part, is that there may come a time when due to system changes (and face it, we audiophiles are ALWAYS making system changes!), or changes to your rack, or how you position your equipment on your rack, you'll separate out the pieces of equipment you need to connect, and with only 20 inches of cable, you'll possibly run short. With 39 inches, you'll rarely encounter this problem, (Although, if you have a fair number of source components, like I do, you might. I have 5 input devices all going into my preamp. Obviously, 0.5 meter cables would not work for more than two of them.)

The cost of going from a half meter to a meter is not that great, IMHO. By having a bit more cable, you'll be able to separate your cables and keep proper distance between them. Plus by having all your cables at 1 meter, you'll be able to upgrade your cables and push your older (and usually more obsolete cables), to your lessor used components.

Anyway, my two cents worth!

I agree practically with Kurt. There are times when you can't even cross
from the right side to the left side of two components that may have a
little height, or differing depth with a .5M even atop each other. The
broadest market for resale will be 1M (tied in there). Though, oddly the manufacturer may actually have designed it around a length other than the shorter. and there may be very subtle differences between that length and the half meter, if your system can detect that is an 'if" or "myth" in cases where longer is a tone control.

The optimal length for interconnects is determined by a lot variables. Ideally the inteconnects will be just long enough to connect components (duh) wiht just a little extra room so as not to strain the actual connections. The proper length may be detemined by a few different variables, such as allowing components to be far away from each other so that they don't interfere with each other and at the same time not being so far from each other that the interconnect becomes so long that it strains the source component. The interconnect should be of appropriate length so that cable "dressing" is best addressed without becoming part of the problem. Of course amplifiers may dictate interconnect distances. Some instances are best served by long interconnects and short speaker cables other instances may be better served with short interconnects and long speaker cables. Passive pre-amps tend to work better with short interconnects. Balanced interconnects allow for greater lengths with less compromise due to the extra length. And things like capaciatance and shielding of the particular cables and the output and input of the components attached may vary the needs. Then there is the matter of resale value. Yes there is an optimal length, but, it varies not only from system to system but from cable to cable, component to component and every combination there in. Even different environments may have an effect on appropriate interconnect length.

From an electrical standpoint, shorter is better, but keep in mind that many cable manufacturers voice their cables to sound best in the most common length, which is 1 meter.
Of course, if you have a particular model in mind, perhaps the dealer would be willing to let you audition two different lengths to determine which works best in your system.