Which cables cause issues for high bandwidth amps?

As in, blow them up? I recently bought a McCormack amp and blew it up when using Goertz Alpha Core MI-2 cables. I am about to get the amp back from being repaired, and I want to make fricken sure that I don't repeat the episode. Now, I do have a feeling that there was something wrong with that amp in the first place, but I still want to be very careful.

I now know that using the Goertz was a no-no, but I am told there may be other brands of cables with the same concerns. I have been advised to stay away from "flat" cables for the McCormack. Is this true, or an over-generalization?

I am looking for moderate price options, if anybody has experience with cables that sounded great with McCormack amps. Thanks a bunch!
First I'd like to make sure that you've connected your cables correctly and did not short on neither end amp or speaker.
If you're certain that it realy happened with Goertz, I'm not surprised. I heard that happening with several more brands and they're not cheap at all. Some of manufacturers place wrong color code and that causes problem to fry the amp. Any cable you purchase test for continuity between each color code before connecting to the amp. Test color code and shorts between positive and negative runs on your Goertz cable and maybe you'll be able to claim back funds for amp repair. Please be noted that there are lots of replicas sold on chinese sites of Siltech, Transparet, Harmonic Tech, pricey AudioQuest models... The more expencive cable, the more chances for you to get fake that could have issues.
Among high-performance cables I would choose VanDenHul. They'll be able to provide you with speaker cable that BEST matches your amp. IMHO they have best quality control and customer service. You can even build your own cable by choosing gauge, per-unit impedance parameters and length. They have all technical charts available for your convenience.
Cables having ultra-high capacitance are the ones that can cause the problem you experienced, if they are used without a properly configured Zobel Network. I believe Goertz can supply those networks, for use with their cables.

What "ultra-high" means, in terms of capacitance per foot, depends on the length of the cable, since the total capacitance of the cable is proportional to length. Following are what IMO are some rough ballpark guidelines for typical cable lengths, which are NOT based on any kind of precise analysis.

For typical lengths, I would start to become concerned if capacitance gets into the area of perhaps 600 to 1000 picofarads (pf) per foot or more, which equals 0.6 to 1 nanofarad (nf) per foot. Your MI-2's are 6000 pf/foot!!

For typical lengths I would not expect capacitances below perhaps 300 or 400 pf/foot to be a problem with nearly all amplifiers.

I would be increasingly cautious if the amplifier is one of those few having bandwidths in the megahertz region.

Regarding flat cables, yes, some of them have very high capacitance, but some do not. The Nordost's, for example, have extremely low capacitance, on the order of 10 pf/foot.

The great majority of speaker cables do not have ultra-high capacitance.

-- Al
Thanks for the replies!

First, I am confident the cables were hooked up correctly. Also, I am now using the exact same set of cables with a Yamaha receiver and Monitor audio speakers and everything has been working fine for months, and the sound is pretty good.

Second, I want to see if I understand correctly that the spec that is the culprit in inducing these oscillation problems in amps is capacitance? And that as long as I keep that spec under 300-400 pf/foot, I am OK? Or, are there any other cable specifications that would ruin an amp?
Oh, also, the guys who are repairing my McCormack amp are discouraging the use of the Goertz cables, EVEN WITH the use of the Zobels across the terminals.
I want to see if I understand correctly that the spec that is the culprit in inducing these oscillation problems in amps is capacitance?
And that as long as I keep that spec under 300-400 pf/foot, I am OK?
For typical lengths, say up to 12 feet or so, I would be confident of that. As I indicated, I am not basing that on any precise analysis, and a precise analysis would be dependent on the design of the particular amplifier. But I believe I am erring in the direction of being cautious, and so chances are that values that are somewhat higher than that would be ok too, at least in most cases.
Are there any other cable specifications that would ruin an amp?
No, I can't envision any other way in which a speaker cable could harm an amp, assuming of course that it does not have a short between the two conductors as the result of a defect.

-- Al
I just don't get how one can get such huge per-unit capacitance in the cable and for what purpose?? There's also no specific disclaimer not to use with high-bandwidth amps... Who's supposed to be accountable for this kind of situation?
My H/K Signature 2.1 amp did NOT like my Goertz MI-2 cables until I installed a Zoebel network across the terminals of the speakers. However, my Gallo 3.1/Butler amp combo seems to have no problem with it. Apparently the MI-2s with certain speaker/amp combos will cause the amp to go into oscillation...

Correction: I misread the Goertz datasheet. The capacitance of the MI-2 is 950 pf/ft, which is still very high of course.

Marakanetz, the high capacitance is a side effect of their approach to achieving their primary design goals, which were ultra-low inductance and ultra-low Characteristic Impedance.

Whether the ultra-low inductance is overkill or not, and whether the ultra-low characteristic impedance is likely to provide any benefit, are debatable and most likely system dependent, IMO.

-- Al
Man, I would not even THINK of using the same cables when you get your amp back! 12ga stranded will work fine IMO.
Thanks for all the replies. My cable length for this setup is 8-10 feet.

I do have on hand a set of old 12 ga Esoteric Ultra Cable Premier OFHC that I can use for the LF terminals and a set of Morrow Audio SP2 that I can use for the HF terminals. The Goertz cables ended up being used because I was trying out the McCormack amp in the bedroom system, which is where the Goertz cables were located.
When I was having my Odyssey amp built, the designer warned me to stay away from the flat cables. He told me it would cause the amp to go into oscillation. I was using MIT cables at the time and have switched to Groneberg now.
Ive used Goertz mi-3 cables with my McCormack DNA-2 for years first with Theil cs6 and now Dynaudio c1. No problems. I did put the zobel across the second set of output terminals on the amp. it seemed easier.