Hi vdi_nenna
As you know, BOSOZ has a CL-60 from ground to the 3rd prong of the AC plug, not for current inrush on the xformer primary; so I don't think that the prior post is on-topic (though its the most common use of a CL-60)
My non-expert opinion is that a CL-30 or two would be OK here. In fact you could just omit them and use a wire as many people do. I think I used one in my 1st version but not in my 2nd version....but I forget.
On other threads this is a controversial saftey issue here at diyaudio.com. Think about it, if your chassis goes "live" do you want any built in resistance from the case to the 3rd prong ground?
This is why a few of people say not to use anything from ground to 3rd prong but many others say its no big deal and helps with ground loops. Others even put in a 10-200 ohm resistor instead of a thermister. whoa. I've seen a discussion of this before but I think it would be tough to locate it with the search engine.
Perhaps the "safe" thing to do would be to omit it and use a direct connection from gnd to 3rd prong, and see if you have any hummmmm. If you do try a CL-30 in series, if still there try the other one in series.
As you know, BOSOZ has a CL-60 from ground to the 3rd prong of the AC plug, not for current inrush on the xformer primary; so I don't think that the prior post is on-topic (though its the most common use of a CL-60)
My non-expert opinion is that a CL-30 or two would be OK here. In fact you could just omit them and use a wire as many people do. I think I used one in my 1st version but not in my 2nd version....but I forget.
On other threads this is a controversial saftey issue here at diyaudio.com. Think about it, if your chassis goes "live" do you want any built in resistance from the case to the 3rd prong ground?
This is why a few of people say not to use anything from ground to 3rd prong but many others say its no big deal and helps with ground loops. Others even put in a 10-200 ohm resistor instead of a thermister. whoa. I've seen a discussion of this before but I think it would be tough to locate it with the search engine.
Perhaps the "safe" thing to do would be to omit it and use a direct connection from gnd to 3rd prong, and see if you have any hummmmm. If you do try a CL-30 in series, if still there try the other one in series.
lgreen said:
Hmm . . . quite negative words.
Of course . . . i could misunderstand the question . . .
Anyhow, having the thermistor on the primary side of the bosoz is no harmful at all. I have it. Thanks to it, when I power on any one first of my pre or F1, I do not hear any "pop" noise. I am happy with the result.
If you just argue that it is no need, it would be your choice.
Babowana said:
Not intended to be negative at all. As I said the most common way of using one of these CL-60's is like you have done- inline with the primary though its not in Nelson's circuit diagram like this. Heck, I've got 2 of them there in series (with a delay circuit) to soft start mine too.
However, with all due respect, when someone asks about the cl-60 in the bosoz I take that to mean the cl-60 that appears in Nelson's bosoz schematic at the 3rd prong of the power connector.
steenoe said:
Sure, the thermistor on the primary side is something nice which we like to have (optional).
By the way, as you know . . .
We should foresee two failure scenarios in amplifiers. The first one is the short circuit. In this case, the fuse on the primary side will blow. The second one is the earth failure (its probability is very low, tho) of the circuit insulated by the chassis. This second failure might not blow the fuse, and with this second failure, if we touch the chassis, our hairs might shoot off in all direction. Just in case of this second failure, we need to connect the circuit ground to the earth of the wall power socket. Meanwhile, if we directly connect the circuit ground to the earth of the wall power socket, some polluted noises from the wall socket could invade the amp through the ground point. This is no good for the amp to be clean out of the noises. This is why the circuit ground is floated above the chassis connected to the wall socket, by a thermistor (or a resistor, or the diodes paralleled in opposite direction). I think that this thermistor is a must we should have.
Safety first!
vdi_nenna said:
Recently, we argued with an owner (of a ship) whether there is to be earth connection when the accommodation space is entirely insulated by wood. As the wood is non-conductive, we gave a conclusion that no earth connection of the wood wall is acceptable. If the entire wood case insulate clear of the internal circuit, the earth connection is considered as not necessary. Even if there is an earth fault inside of the amp, touching the wood by our hands is still safe.
I am not an EE. So, one of our electricians handled the above case.
The grounding of the inner circuit is still necessary, I think.
On a side note, Even if the entire wood encapsulated accomodation is considered entirely as an internal circuit, you will still have to ground it. The simple reason for that is that you will have penetrations as windows, piping, funnels and dorways (or even propeller shaft for smaller boats).
But it is true that there is no point in grounding the wood wall itself.
The circuitry must be protected from earth fault even if the cabinet is wood. Even though there is no safety hazard in touching the wood, you still have to consider handles, biinding posts, knobs etc. If touching the volume control gives you 120V or 240V shock, it is a sorry comfort that the wood is safe
And then there is the nasty noise.
Take care,
Ronald Pettersen - marine engineer
But it is true that there is no point in grounding the wood wall itself.
The circuitry must be protected from earth fault even if the cabinet is wood. Even though there is no safety hazard in touching the wood, you still have to consider handles, biinding posts, knobs etc. If touching the volume control gives you 120V or 240V shock, it is a sorry comfort that the wood is safe
And then there is the nasty noise.
Take care,
Ronald Pettersen - marine engineer
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