Ungrounding an Amp--Any Danger?

Your preamp should be the only grounded component to achieve the lowest noise floor. The other components drain to ground through the interconnects, to the preamp, and then through the preamp's grounded power cord.

Danger will then be present if you either

A.) Unplug the preamp from the wall, or
B.) Remove the interconnects between a (ungrounded) component and the (grounded) preamp, or
c.) Both

If you use a cheater plug(s) on a component(s) to eliminate hum (ground loops) just make sure the component has a path to ground -- usually through the ICs and the preamp. If you need to rearrange your stuff, just turn it all off AND unplug it first (which you should do anyway!)

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Zaikesman, re the van den Hul "screened" (shielded) coaxial products: There are only two unbalanced cables which are spec'd. for audio signal transfer, and both of them use vdH's proprietary non-metallic "Linear Structured Carbon" as the shield. Since it's carbon (non metallic) it's not affected by EMI (hum) and does a pretty good job soaking up RFI.

But as I said in my earlier post (I should have listed it I suppose) this product is definitely a hybrid. Most of vdH's audio cables do use balanced (shotgun) conductors in fact. You can see them all at:

http://www.vandenhul.com/cable/c-cab-ty.htm#12

Joe, I'm not sure you're right about grounding thru the amp. Yes it will provide a single ground path, but I understood that "star grounding" is when each component (or each device on a circuit board or chassis) has it's OWN shortest path to the ground point -- thus making the preamp the preferable compoinent to ground, and not the amp.

One thing a lot of people forget to do when using the preamp as the center of the "star", is to make sure ALL directional arrows (if present on the interconnects,) point to the preamp. This insures that all shielding inside the ICs will be connected to ground at the preamp. This isn't 100% true 100% of the time, but MOST cable manufacturers point the arrowheads to the end of the interconnect where they've connected the shield (the other end is not connected). The reason for all the BS about pointing the arrows in the "direction of signal flow" is so the manufacturers can get you to do the right thing without going into an explanation that might be over the head of most consumers.

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Bob, I'm afraid you are incorrect about "unbalanced" ICs. First of all, the correct terminology is "single-ended" ICs. Some single-ended ICs have a coaxial configuration, where the shield is indeed used for a signal carrier, but they are usually only found today in 75 ohm coaxial FM and TV cable and in some 110 ohm digital interconnect. They are no longer used for audio signal IC, except in those cheap RCA patch cords which are packed with inexpensive gear to get the consumer "up and running" -- and they don't have arrows on them.

The audio ICs I was referring to are known as "shotgun" interconnects, and were the original Bruce Brisson design which put Monster Cable on the map. Bruce left Monster early on to start MIT, which he still owns. The shotgun design is a single-ended interconnect (which means one ground conductor and one hot conductor), but there are TWO identical (double-barreled?) signal conductors surrounded by a ("floating") shield which is only connected at one end and therefore cannot carry any signal or current. The conventional (though not universal) indication for the end at which the shield is connected to the ground ring of the RCA, is an arrow which points to that end. This configuration applies to the majority of decent conventional audio cables today, from the cheapest Audioquest, Straightwire, Monster, XLO, Cardas, etc., to expensive (and even unconventional) designs like Magnan, Purist, Transparent, and Siltech. Two of the well-known brands that represent exceptions to the shotgun design (and only in certain models now) are Nordost (flat conductors) and Kimber (braided conductors). Using the old single-conductor-and-braid/shield design for audio signals anymore is just asking for "hum trouble."

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Also, a word about "shielded" power cords. Manufacturer supplied power cords, if they are shielded (and most aren't) must have the shield connected at both the AC plug end and the equipment (or IEC plug) end. That is a UL underwriting requirement. Good for your power saw, bad for your audio -- instant ground loop!! So, if you feel your equipment might benefit from a shielded power cord, get an aftermarket one with a floating shield and no UL rating.

One place I absolutely recommend using a (floating) shield power cord is the DAC, CDP, or DVD. These devices tend to broadcast digital RFI from their power cords unless they are adequately shielded. They also pump digital RFI into the electric lines, so put them on their own circuit, or use a power conditioner which has a couple of outlets with digital filters specifically for this purpose.

Bob and bigtee, we are wandering far from Mr. Socprof's thread, so let's not do that.

I'd be happy to continue this discussion either privately (you can email me) or, if either one of you would like to start a thread on the subject of balanced versus single-ended interconnect design, and their susceptibility to EMI/RFI contamination. That is not the subject of Mr. Socprof's inquiry.

Neil

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Bigtee: So??

Skippack, let me answer your (very reasonable) question which is in the spirit of this thread: The signal ground lift switch is used to lift (disconnect or separate) the signal ground return leg in the amp's audio circuit(s) from the metal chassis (which still remains connected to the ground prong of the AC plug. Bryston has done this for years (do you have a Bryston?) This means that your non-shotgun coaxial single-ended interconnect is less likely to become part of a ground loop and pick up hum, while at the same time you are still personally pretty well protected from most shock hazards, even if you're dumb enough to remove your interconnects without turning off or unplugging your amp (just don't touch anything inside because under those conditions, it will take literally hours for the power capacitors to discharge!!)

When the manufacturer provides them, you always see these switches on amps but never on preamps or other components. That's because manufacturers expect you'll always want to ground the preamp to make it the center of a proper "star grounding" layout.

If you are using balanced interconnects between your amp and preamp, meaning the kind with an XLR connector and three signal conductors (plus, minus and ground) with a (optional) shield, then it's not necessary to "lift" the signal ground at the amp or use a cheater on its AC plug because any noise generated in, or picked up by the signal conductors will be self-cancelling.