Residual Current Limiter for 70V and 100V audio line Amplifier.

[ontoaba]

I am thinking to applying residual current limiter at the amplifier output for 70Vline and 100Vline based amplifier, during safety issue and amplifier reliability.

I will start to design it if I think it is very useful.

Any suggestion or critics?

[ontoaba]

Residual Current may went through anything that giving current path to the ground instead of existing cable.

[sakis]

have i missed something ???i know that amplifiers like that are transformed coupled in the output ...so there in danger for human from that .... even if you put your fingers on it what makes the problem is the high frequency...not the voltage ...i think

also ....how can you make this while make shure that operates linear ????

[ontoaba]

The danger is the voltage.
The design is later, The problem is it useful or not needed. Because I have seen many of engineer in my country still using 70Vline when 100Vline with better efficiency is available and supported by both amplifier and loudspeaker. But the other side there many people says that proper isolator will fine, worrying is not needed.
Thanks.

[sakis]

i cannot understand you englidh ...sorry .... there is no need for any extra protection since any of this is transformer coupled

then again 100volt will be reached at peaks its not there all the time ...then again still there is no problem this cannot kill you

[ontoaba]

Of course not all of amplifier output is transformer coupled. Also not all of them rarely reaching its peak value, because sometimes high compressed signal is given to the amplifier.
I got from you that it is not needed when the output is transformer coupled. Also 100V cannot kill me.
Hmm. OK.

[sakis]

all existing amplifiers of the rate of 99% are transormer coupled

in 50-70-100 volt PA amplifiers either the power supply is made with a transformer plus the output is coupled with 100v transformer

in other pa amplifier may the output is not transformer coupled but the power supply is working with transformer and that makes it enough from a safety aspect

[ontoaba]

Yes, most of them using output transformer. And why they (the engineer) not using 100V and 70V is still the most used. If I ask them, they just say that it is dangerous.
May they just frightened by yellow shock warning, and then use another choice (70V).

[sakis]

no ...that is lack of knowledge ...the voltage of 100v can be reaced only at peaks it is not leathl even if you touch both of the wires that come out of the amplifier and also what scratches your hand is not the voltage but the high frequency ...

that is why in most of countries eventhough "100v" lines of sound go under the regulations of "low power" signals.... letus not forget that the use of these systems in hotels ,hospitals and other areas where a small amount of power while hundreds of speakers are connected to the same line is very common practice

if there was safety issues with signals like that be sure that in each country regulations and rules waxs going to be made by aythority to secure that

safe regards sakis

[ontoaba]

Thank sakis,
You right, the scratches is caused by high frequency. I remember my friend told me about body capacitance when I help him in his neural stimulator project. Human body will more capacitive at higher frequency, therefore the line will only scratching hand and not whole of body like 220V 50Hz do.