?? OK to daisy-chain power conditioners?

[Sambob2]

I read that you have tried disconnecting every conceivable combination of interconnects and power cables.

If you are plugging all power connections into different branches of outlets, ie different circuits, in your case 15 amp and 20 amp, you have the potential for ground loops. Even if they are the same amperage, 15A and 15A, or 20A and 20A the key here is different branches. I think most of us know that.

All equipment must be connected to the same ground point. Regardless of how long the ground wire has to be, they all must converge and connect at the same point or line. I think most of us know that as well.

Something I read, (several years ago) I believe it was on the Paramax website or technical data sheet which came with my Paramax line filter/isolater.
If you have equipment hooked up to two different branches of outlets and listening to each individually has no hum, that is each system is isolated and there are no interconnects between those two systems, you should be ok. However, if you are connecting your A/V system audio line outputs to your stereo system line inputs on a differnet branch of AC power, the potential for a ground loop can be possible. The key here is that you are connecting one system to another using two different branches of outlets, but connected thru the interconnects. This can create a ground loop as well.

Similarly, I've read that this is true for lightening protection/isolation as well. In other words, if one sytem is on a surge (lightening) protector and the other on another branch is not, yet both systems are connected by interconnects, both systems are liable for lightening damage thru the interconnect.

I can't tell from your posts wether or not you completely isolated your A/V from your audio system interconnects, but you may want to go over this again. The other choice is to do what you said, completely, and I mean completely disconnect everything and start to plug things in one at a time until one system is up and running without hum. Keep connecting equipment until the hum shows itself and try connecting that system to the original systems power source. You'll also need to connect the ground to the original systems ground point too.

Last point, could you have broken one of the shields on an interconnect cable? Or worse, could you have compromised the shield connection on one of the cables slightly?

 

[sleepysurf]

I currently have everything running off my sole (duplex) 20A dedicated liine (not using any of my six 15A outlets). That step eliminated 50% of the hum, but what's left is still clearly audible. I have tried a bare-bones setup with NO sources plugged in, i.e. Preamp > Amp > Summits = NO noise. However, if I plug in any source, I get varying degrees of hum. Squeezebox 2 direct to CT5 adds just a little hum. Squeezebox to Benchmark, and then to CT5 adds a bit more. Oppo direct to CT5 yields moderate hum, and Oppo (with HDMI connection to Denon 3808 and HDTV) is the worst. I have also tested with ALL OTHER GEAR unplugged (even unplugged my Summits, and let the panels run on residual power!), with no improvement. I've also swapped out multiple interconnects (likewise thinking I could have a broken shield connection). FYI, the Oppo player does NOT have a grounded 3-prong cord, so I even tried externally grounding via a wire from a chassis screw on the Oppo to my Belkin PF60 external ground tap (as suggested by Oppo Support), but no luck with that either. Only thing I haven't tried yet is eliminating my Belkin PF60 conditioner/surge protector altogether, and I will do that ASAP (will have to substitute with the Monster HTS 3500 in order to have the minimum 5-6 outlets I need).

 

[Hocky]

Have you tried a different preamp? Maybe that is where the problem is.

 

[sleepysurf]

Finally... making some progress!

"Cheater plug" on the Benchmark eliminates 25% of hum, and disconnecting the Oppo analog out to the CT5 eliminates the other 25%!!! Looks like it's indeed a "multifactorial" problem. That explains why the Squeezebox alone into the CT5 is the quietest of all!

I can live without the Oppo analog out (used only for SACD playback), but really need the outboard DAC. I tried another power cord with the Benchmark, but still get hum unless I use the "cheater", which confirms I still, somehow, have a ground loop.

Right now, with the Squeezebox coax digital (and Oppo Toslink) into the ungrounded Benchmark, it's dead quiet!! However, once I connect my Denon (pre-outs) to the CT5 Home Theater inputs-- back to maximum hum : (

BTW, the "cheater" on the CT5 does NOT eliminate the hum, so I think the problem components are clearly "upstream."

Now what??

 

[sleepysurf]

Have you tried a different preamp? Maybe that is where the problem is.

MY Modwright SWL 9.0 also suffered from some hum, but it was barely perceptible from my listening position, so I ignored it. I will swap it back in, and see if the same sources are still at fault.

The CT5 is actually a MUCH more "transparent" preamp than the Modwright, with such a low noise floor, that any background noise (including recorded hiss) is much more audible. It's clearly very "sensitive" to extraneous noise, whether it be ground loop, or RFI (and, in fact, the manual states that it's design uses minimal RFI filtering), but I don't (at this point) think the preamp is the problem (especially now that I found a way to get a purely silent background).

 

[sleepysurf]

Almost got it solved! It appears the hum is actually coming from my C-J Premier 350 amp (not the CT-5)! The only single intervention that completely eliminates the hum is using a cheater plug on the Premier 350 amp. With that in place, NONE of my audio or video sources creates any hum whatsoever! Placing a cheater on the CT-5 has no effect, however placing cheaters on both my Benchmark and Oppo also eliminates it).

Fellow MLOC member Craig stopped by today, with his Entech Wideband Powerline & EMI Noise Analyzer (very cool device!). We checked both my dedicated 20A line, and adjacent 15A lines in my Family/Listening room, and they are all fairly noisy compared to some other outlets elsewhere. I don't know if that's an issue with my overall home electrical wiring, or breaker panel, and might need to get an electrician to investigate further.

Regardless, it seems the Premier 350 amp is somehow picking up and amplifying this noise. I left a message for C-J Service to call me back to discuss further. In the meantime, I'll (temporarily) use the cheater, and happily switch from "investigator" mode back to "listening" mode!

 

[Brad225]

Glad to hear things are quiet again.

 

[sleepysurf]

I talked to Ed at C-J, and he told me that elusive "ground loops" can still occur if multiple grounded components are all plugged into a single circuit, and that eliminating one (sometimes more) of the multiple grounds (as I discovered) can usually solve the problem. He checked with his Tech, and reassured me it's perfectly safe to keep using the "cheater plug" on the amp, as long as I have the grounded CT-5 (or another grounded component) connected to it. Problem now officially solved! Thanks to all who publicly (and privately) helped me with this!

Finally, time to kick back and do some listening! I'm actually hosting our local listening society meeting on 4/17, and will report back on everybody's impressions of the CT-5!

 

[Audioseduction]

Alan, sure glad you resolved your hum issue before the TBLS meeting on Saturday. You know me; I’m a very critical listener. :music:

 

[Bruce Weiland]

Hi Alan,

I just ran across this thread. I have been dealing with an intermittent PS issue in one of my Prodigy and was looking for any thread the discussed the DEC (dynamic expansion circuit) in the crossover. That's how I got here.

Had I been on this thread earlier I would have made the "radical" recommendation to lift all but ONE of the grounds. Since you have come to ground lifting on your own, and gotten some "blessing" from CJ, my recommendation will not be so radical.

Another ML (non forum member) and I have been experimenting with lifted grounds over the past few years with "amazing" improvements in our systems performance.

As an aside, daisy chaining AC conditioners will create some decrease in the systems potential maximum dynamics, but it can be rather subtle and other audible benefits (sweeter midrange, less grain) can far out weigh the subtle dynamics loss. One has to experiment with this for the best result.

Back to your issue. LIFT ALL GROUNDS BUT ONE. :devil: In most systems having the preamp grounded sounds the best. In mine it ended up being the DAC.

If you use a simple EMF "sniffer" for one piece of equipment at a time and turn the plug over using a cheater with the ground broken off and the piece of equipment not connected to anything (ie - preamp plugged into wall and turned on with absolutely no interconnects attached) you may find that some chassis's have less EMF radiation with the plug "up side down". In most cases the least EMF (which generally means the least residual current on the chassis, so this can be done with a VOM) will give you the best sound.

Once you have completed that orientation. Use a ground on JUST the preamp and see how it sounds. Now add a ground on some other piece that has not caused an audible ground loop before and see what happens. I believe it will not sound as good to you, even though there is NO hum. The image will claps some, it won't be as sweet, there will be less subtle inner detail.

This applies to your ML too. Just ground one speaker and the pre and see if that makes the system less enjoyable than with only the pre grounded, even though you do not hear a hum.

OK. Now lets get crazy. You have something like a star ground (I say something like) for your system now. BUT you still have two ground paths between each piece of equipment, the left and right shields.

Lift just one shield. :devil: You don't have to destroy you interconnects. Many highend pieces of equipment do not have the shield portion of the RCA grounded to the chassis. Open the case, get out your soldering iron and desolder the ground connection on one channel. Make it the same channel for every piece you do this with, so it is easy to remember. You can do this on every other piece and get the effect. Sometimes the improvement is subtle, somethings it will blow you away. It is system dependent.

DO NOT TURN THE SYSTEM ON UNTIL ALL THE "GROUNDED" INTERCONNECTS ARE CONNECTED. You could produce a large, terrible sounding transient that would take out any number of pieces down stream, mainly amp and or speakers.

Once you have settled on what piece will be grounded, get rid of the cheaters (additional contacts in the AC decreasing ultimate system performance). Either remove the ground pin from the plug or open the case and desolder the ground connection there.

Have fun. I believe that you will be amazed at the sonic improvement in you system and wonder what you were missing as you went through the upgrade process. :rocker:

Back in the 70's and early 80's, before UL saved us from ourselves , ALL our equipment only had two prong plugs.

Please let us know what you find/hear.

Anyone else want to try this?

Bruce

 

[sleepysurf]

... Had I been on this thread earlier I would have made the "radical" recommendation to lift all but ONE of the grounds. Since you have come to ground lifting on your own, and gotten some "blessing" from CJ, my recommendation will not be so radical.

Another ML (non forum member) and I have been experimenting with lifted grounds over the past few years with "amazing" improvements in our systems performance.


Back to your issue. LIFT ALL GROUNDS BUT ONE. :devil: In most systems having the preamp grounded sounds the best. In mine it ended up being the DAC...

Thanks for the tips Bruce... better late than never! Good to know that you and Ed (at C-J) are in full agreement on this. I'll try the "rotated ground" tweak with my DAC and see what happens.

As for disconnecting the RCA grounds on one channel of all components, I'm going to pass on that! Just a little too surgical for my taste! Anybody else here try that?

 

[sleepysurf]

Hmmm. I'm just setting up for our local listening session tomorrow, so all my video gear is disconnected for now. Just tried the "cheater" on the DAC only (Pre and Amp now both grounded), and still have dead silence! On first blush, vocals and decay of notes actually sound "cleaner and crisper" vs. when the Amp was ungrounded, so I think you're onto something! I'll add this "experiment" to our listening comparison tomorrow (if we have time).

 

[Bruce Weiland]

Alan,

I just want to make sure.

When you speak of rotating ground, you do mean, only one piece grounded at a time, right?

I understand you hesitance on the surgery.

Have fun with the listening group. I look forward to hearing about the results.

Bruce