Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Sorting out Ground Loop problem with Modded Oppo

But your ok with hiring a thirdparty to muck around with high voltage that probably has no liability insurance if something did go wrong?

That's not anything against Gary, but a buyer should understand a bit about what he is experimenting with (even he hires someone else to do the work).

It was my understanding the PS mod was optional. But was in some of the "Bundle" deals.

The sale of device without an earth connection in most countries is illegal unless it is double insulated. Double insulated devices will be marked as "double insulated", Class II, or have the square within the square symbol.

The reason for this is that it is highly dangerous to use a device without the earth unless it was designed as such. A simple fault can cause any number of dangerous situations to arise. We are working with a device(s) that is(are) exhibiting fault conditions, as yet unknown. It may be a basic earth loop or it may be something else. We do not know.

Experimenting with electrics, including cutting earth pins (which in the UK would not work anyway due to the plug and socket design) should not IMHO be encouraged, unless done by someone who knows exactly what they are doing, no matter for how long.

I'm with Mr Meridian on this. If the original Oppo was double insulated, and Gary has introduced a mod that now requires a ground, the unit is no longer double insulated (and IMHO the original symbol or wording to signify double insulation should be obscured) then it should be used with a earth (ground in US speak) unless Gary either says that it is double insulated and should (IMHO) have used/supplied more appropriate two pin connectors. Otherwise the unit is faulty.

This isn't a nuclear reactor guys, geesh.

From my point of view once the device was electrically modified your taking chances of electrical faults ANYWAY !!!

I don't believe even Gary is qualified to say if it would still pass as "double insulated" and safe to run as it was (ungrounded) or not. Only a testing lab could say that.

I'm not saying to leave it ungrounded I'm saying to try it, to confirm if that is the problem FIRST. We may be pointing fingers to the Oppo ground for nothing.

If it does work you could ground the Oppo to the amp for safety reasons only. Or have it demodded. You need more info to proceed further IMHO. Would a demodded Oppo be 100% safe as original? Who knows.

I think suggestion of lifting ground on the AMP is worse because these are higher current units and WAS fully designed to be grounded where the Oppo was not (originally). So of the two I still it's better to go after the Oppo (after confirming it is the problem). Ungrounded Oppo would be the lesser of two evils.

Over grounding as suggested *IS* safe but IMHO band-aide-ish (for an audio purist point of view) and often does not eliminate hum completely but just reduces it. You can try that too if you the think the earth will stop from ungrounding the Oppo.

Markg doesn't understand all the risks and everyone has their own view on this. I'm extremely picky and was an electrician for 3 years before going to college for computer science. I don't blink an eye at opening the fuse panel. If you knew how bad so many electricians are in following rules you'd be a heck of lot more worried than an ungrounded DVD player. I wired my own pool and the inspector said I was one of VERY few people that did it 100% correctly. Neighbor had a licensed electrian do it and it never passed inspection. So I'm well aware of the risks here and would not suggest (trying it) if it was that dangerous. But don't try it while standing in a bath tub.

Lifting the ground for 5 minutes is no riskier than driving to work. You can respectfully disagree with that if you want. It's like not wearing a seat belt to the end of your driveway.

People have been lifting grounds on AMPs for years (ones that have no ground lift switch). The world hasn't ended yet. I've done it and I'm sure many here have done it in the past. Generally if I ever have had to do I dig deeper eventually to find the root cause, fix it then reground it. I have no lifted grounds at the moment and have not for quite some time.

And I'll bet at least one appliance if half the house holds have a missing ground. The world won't end if he tries it. But kiss all your loved ones today just in case.

One more thing. It's all about probabilities. What's the probability you get hit by car going to work to day. What's the probability a dna strand will mutate into cancer. What's the probability of being struck by lightning? What's the probability of getting hurt down hill skiing. What's the probability of not landing safely in a small airplane. What's the probability your feet are grounded and your ungrounded Oppo faults in the power supply and fuses a hot lead to the chassis, while your touching it?

Grounds, Seatbelts, Physicals, Airbags etc. reduce probabilities. I assure you the ungrounded Oppo has pretty low probability of hurting you in the big scheme of things.

Does ungrounding change the propability of hurting you, YES. But both probabilies are lower than things you are exposed to every day. Just stay in bed and you'll be safe. Well their is risks with that too.

And the Oppo will still be grounded even with power cord ground lifted through the 3 shielded RCA Cables to the 568.

If he isn't qualified to do that then he isn't much of an electronics guy. If the original Oppo was double insulated and was not compromised by the mod then I am sure that a half decent engineer would know if their mod was double insulated or not.

guys, the ground on my mods is for nothing more than a noise dump on the filtering, just remove the ground pin on a power cable to the Oppo, the Oppo is not a grounded component nor is it after my mods, but performance will be better with the ground connected because it is a noise dump(one of the uses of ground on gear)

however the problem lies elsewhere, not with the Oppo, well I shouldn't say problem because this is a easy fix via grounding corrections in the system, basically every component in the system has to be touching the same ground all at the same time, until that is fixed you will have hum going on

enough with the spook stories and hyperbole, jeez, any questions or help on how to fix grounding issues just ask lifting the ground on the amp is the best easiest fix, I have had to do it in 3 systems of mine at different locations, all with different gear, sometimes this is just how things have to be and it is not a big deal

-Gary

I generally agree with Gary here but I don't agree with ungrounding any amp.

Some amps are all metal, non double insulated with high voltage near the cage and are designed to be grounded. It won't blow up ungrounding it. I also agree folks do it all the time. But that does not make it right, or safe. I think it's less probable of something going wrong and potentially hurting someone to lift the ground on the Oppo instead (and loose the "noise dump" feature).And Gary agrees that's an option too.

If it still hums (lifting the Oppo ground) I personally think the issue is with the Oppo, but we won't know that until Mark tries it.

I disagree. We get products UL approved all the time. Any time we make an electrical change we can't decide if it's safe or not. It has to be reapproved. Gary could be a very competent electronics guy, but once the mod was done safety compliance is voided along with the warranty.

Not clear to me that markg has lifted the ground to see if it solves the hum problem, so all this speculation may be moot - at least in his case.

I have had the occassional hum problem that was not solved by lifting the ground, but most are. Particularly in complex, multi-component sytems ground-loop hums can be VERY difficult to erradicate. I had amps with a lifted ground for years without any problems, but then read about what could possibly happen and got all nervous about it.

My solution was to buy a few Ebtech Hum-X devices from amazon. Not cheap, but at $70, not too pricey either. Supposedly, the device isolates the ground but does not lift it, so you get the hum-elimination benefit without the shock potential - at least, that is what the device manufacturer claims. At the very least, every HT owner should have one sitting around as a diagnostic device because sooner or later we'll all get a hum problem (cripes, I sound like a shill for the product ....).