100 Volt Audio, Band I or Band II?

BS 7671 itself tells us that the voltage limits relating to DC values are for "ripple-free" DC, and that that "ripple-free" is DC with no more than 10 % rms AC content. (See Guidance Note 5 for further information on where this comes from ... IEC 60479 series Effect of current on human beings and livestock.)

I would therefore agree that a 100 V audio line is Band II ... and that the protective provisions of BS 7671 apply for protection against electric shock (where automatic disconnection is not possible, or not appropriate, this would effectively mean Class II and electrical separation as being the viable options for protection against electric shock).

Treat as you would mains or at least 110V ;-)

However, you can use surprisingly thin wire as far as losses are concerned -  I have seen a whole campsite fed with a 70V system using telephone jumper pair, wired high and out of reach between trees.

100V audio is not generally at 100V ;-) Like audio watts, it relates to the peaks of the music or whatever. so do not expect to stick a meter on a 100V line and see 100V indicated. The shock risk is less when the volume is low.

In some ways it is better to think of it as 10watts per kilohm - the full audio peak power is only present when the drums go bang or whatever.

As an slight aside,  the effect of shocks at higher audio frequencies are slightly  different to 50Hz or DC, and slightly less dangerous.

Mike

Treat as you would mains or at least 110V ;-)

However, you can use surprisingly thin wire as far as losses are concerned -  I have seen a whole campsite fed with a 70V system using telephone jumper pair, wired high and out of reach between trees.

100V audio is not generally at 100V ;-) Like audio watts, it relates to the peaks of the music or whatever. so do not expect to stick a meter on a 100V line and see 100V indicated. The shock risk is less when the volume is low.

In some ways it is better to think of it as 10watts per kilohm - the full audio peak power is only present when the drums go bang or whatever.

As an slight aside,  the effect of shocks at higher audio frequencies are slightly  different to 50Hz or DC, and slightly less dangerous.

Mike