Tripp Lite Isolation Transformer

[Jason Coleman]

With so many people experiencing this "hum," I'd find it kind of hard to believe that we all have defective units. Like I said, I unplugged everything from my system except for the speakers, disconnected my cable, changed outlets (20-amp dedicated and otherwise), etc. I really tore the whole thing apart. Now I've added a TrippLite Isobar and it hasn't made any difference either. BTW, wouldn't a ground loop hum have presented itself before I bi-amped? I could turn my 3805 up to +18dB and put my ear right on the speaker and it was absolutely and totally silent. That was before any kind of decent surge protection and with all of my equipment hooked up and cables running every which way (but loose!).

Is there something else that you'd suggest?

Jason

 

[Hannahman]

I agree with Jason.

In fact, tonight I purchased new shielded Monster M Series cables for my interconnects to biamp the 3805 to the VDP inputs.

I spent another $58.00 for the cables and I still have speaker hum. I am throwing tons of money at the problem with no results.... Thanks god I can return this stuff.....

Any other suggestions....

 

[keenan]

Is there something else that you'd suggest?

Jason

If I understand correctly you are doing this bi-amping by connecting a Zone 2 set of preouts back into another input on the 3805. I have no idea if this will work or if it even makes electrical sense but, have you tried using an interconnect with the shield/ground disconnected or lifted on one end of the cable? It sounds like the ground loop is being created when connecting the outputs to the inputs. It's worth a try although it may be a waste of time.

Good Luck,

Jim

 

[Jason Coleman]

Jim-

This may sound noobish, but how would I go about disconnecting/disabling the ground on an interconnect?

Thanks,

Jason

 

[djoxygen]

I went back through this whole thread and can't find any specifics on the wiring of your setup, Jason, or yours, Hannahman. If, as keenan guesses, you're using a zone 2 out, or any other out on your receiver, as a 2nd source for the same set of speakers, that's probably the wrong way to go about it, and is probably the source of the hum.

The correct way to bi-amp is taking one L/R set of line-outs from your receiver/pre-pro, splitting it into 2 frequency ranges with a cross-over (giving you L-hi, L-lo, R-hi, and R-lo), amplifying each of these (usually 2 stero amps) to the two sets of terminals on each speaker.

Before you go cutting any grounds, please post details of your setup and lets see if we can figure out any obvious culprits first.

 

[Hannahman]

Thanks for the assistance... I have tried to detail my setup below:

From the wall Outlet:

Tripp Lite Isolation Transformer 1000 Watts. My Monster Power Conditioner 3600 is plugged into the Tripp Lite. The following components are plugged into the Monster at the corresponding outlets based on Digital Filtering etc.

Sony 61" LCD
Panasonic DVD
Tivo Series 2
HD Tivo
Velodyne Sub
Denon 3805
Techincs MultiDisc CD Player

I am using Klipsch reference series speakers in 5.1 surround. Speaker wire is Monster Z series shielded or sheilded 12 Gauge in the attic for the rears. The 2 main left and right speakers have dual inputs to separate the input sources.

All of the components are hooked up via Digital Optical Cable except the Series 2 Tivo and my Ipod docking station.

The 3805 is biamped from Zone 2 pre outs to the unused Video Disc Player inputs. ( I installed $50 shielded Monster Cables for this) Still have hum...

The HD Tivo has 2 RG6 cables running to it to allow me to watch and record at the same time.

I also have an off the air antenna connect to the HD Tivo to get my locals in Hi-Def. This has a Radio Shack Amplifier to help boost the signal over the long cable run through the attic.

I also have some fluctuation in incoming power voltage that ranges from 112 to 123 The isolation transormer helped with boosting this to 125 before turing on my equipment, even though it is only supposed to relieve line noise etc.... Go figure...

This is about it....Let me know your thoughts or suggestions. Thanks

 

[djoxygen]

The 3805 is biamped from Zone 2 pre outs to the unused Video Disc Player inputs.

So your goal is to use 2 extra channels of the 7ch amp in the Denon as the 2nd "stereo" amp in your L/R mains?

How are you accomplishing the cross-over part of the bi-amp setup? Are there high and low pass filters in the 3805? Can you route the VDP inputs to a set of amp channels independently of the rest of the 5.1 signal flow/processing?

Without knowing how the Denon is wired internally, or knowing much about the setup controls available to you, I'm not sure if or how well this will work, but looping its output back to its own input might be the cause of the ground loop.

 

[keenan]

Jim-

This may sound noobish, but how would I go about disconnecting/disabling the ground on an interconnect?

Thanks,

Jason

Like I said, I'm not sure it will work but unscrew or disconnect the plug on the end of the IC. You should have a wire screwed or attached in some manner to the ground or shield part of the plug and one attached to the signal or center conductor of the plug. Disconnect the shield/ground wire from the plug so only the signal or center conductor is connected to the plug. You only need to do it on one end of the cable. If you have some inexpensive spares around try it on those first.

Plug it back into the input jack on the receiver and see what happens. I would have your volume set low when you first turn it back on. I have read about this procedure before somewhere when they were trying to eliminate a ground loop hum.

I would try it for you but I am not bi-amping in the manner you are.

Jim

 

[keenan]

I went back through this whole thread and can't find any specifics on the wiring of your setup, Jason, or yours, Hannahman. If, as keenan guesses, you're using a zone 2 out, or any other out on your receiver, as a 2nd source for the same set of speakers, that's probably the wrong way to go about it, and is probably the source of the hum.

The correct way to bi-amp is taking one L/R set of line-outs from your receiver/pre-pro, splitting it into 2 frequency ranges with a cross-over (giving you L-hi, L-lo, R-hi, and R-lo), amplifying each of these (usually 2 stero amps) to the two sets of terminals on each speaker.

Before you go cutting any grounds, please post details of your setup and lets see if we can figure out any obvious culprits first.

They are passive bi-amping the full frequency and letting the speakers crossovers do the high low split. No, it's not the best way to do it but evidently with this receiver it's possible without the need for external amplifiers.

Although, if it can't be done without inducing hum in the signal then I would consider the procedure of no value.

Jim

 

[cstanley]

back to the original subject of isolation transformers a
suggestion would be to try a balanced power unit as opposed
to just a line conditioner or a isolation transformer...

http://www.equitech.com/products/products.html

balanced power is fairly new (only code since 96 i believe)
and basically it invovles putting voltage 180 degrees out
of phase, so instead of the 2 AC wires being 0V & +120v
they are -60v & +60v.

i have put 2 of these in a studio i've helped setup, it did lower noise
floor about 8-10db (if you think you have grounding problems we
had about 60 pieces of audio gear all going to a 512 point
tt patchbay on a 20 year old console). one went on the 24 track 2"
and the other was for all the outboard gear, console, etc.

they are not cheap, you can get it in any size from 5 amps to
70 amps, and it does work.

-carl

 

[djoxygen]

OK, I think I've finally caught up to everyone on the 3805 thing. Another person posting questions about the same stunt in a different thread (but trying it without bi-amp-able speakers) mentioned Clint's review, which I hadn't previously read.

I'd have to guess that if most of you trying the trick are hearing the hum, then it's probably not going to work right off the bat. If running in a normal configuration manifests no hum, then somehow the Denon's internal wiring is allowing the loop from Pre-out to Input to Zone2 to have a multi-path ground. The only chance you have to get rid of it is to try to lift the ground on one end of the cables used for the loop, as described by keenan.

All the isolation transformers, power conditioning, and balanced power supplies in the world aren't going to fix this one.

Let us know when you try it.

 

[djoxygen]

they are not cheap, you can get it in any size from 5 amps to 70 amps, and it does work.

someday... someday... <dreamy, far-away look in eyes>

Seriously, though. I've read (not just mfr claims) that in a properly wired pro studio that 8-ish dB drops in noise floor are common when moving to balanced power. I'm not sure the benefit would be as great in a home theater since there's far fewer pieces of gear adding to the noise level.

Speaking very generally, bal power won't fix anything that's broken, so ground loops aren't magically going to go away. But once everything else is done and done well, bal power can give you that extra nothing when you're running with the throttle wide open.

One thing I've never been entirely clear on - maybe you can answer, Carl: Does balanced power in and of itself also provide line conditioning, or will noise on the source A/C line be reflected post-transformer in the balanced lines. (I think some of the bal power supplies provide conditioning and surge suppresion as well.)

 

[Jason Coleman]

Thanks Jim and DJOxygen-

So this is beyond bizarre. Jim, I did disconnect the ground from one end of each cable and the hum did go away. Then, I reconnected it just to make sure that it was indeed the culprit and the hum is still gone. I tried several sources and maxxed out the volume and there's the sweet silence that I was used to...until I hit play. The bi-amping, regardless of whether considered a stunt or simply resourceful, is a process so simple and inexpensive and with such absolutely excellent results that it's simply the bomb. I've got ADP-470's to pick up before I can get an amp for my 3805, and I've only got room for a 5.1 setup, so the bi-amp is a no-brainer for now.

I'll keep checking, but hopefully this magical disappearance is permanent!

Jason

 

[keenan]

Thanks Jim and DJOxygen-

So this is beyond bizarre. Jim, I did disconnect the ground from one end of each cable and the hum did go away. Then, I reconnected it just to make sure that it was indeed the culprit and the hum is still gone. I tried several sources and maxxed out the volume and there's the sweet silence that I was used to...until I hit play. The bi-amping, regardless of whether considered a stunt or simply resourceful, is a process so simple and inexpensive and with such absolutely excellent results that it's simply the bomb. I've got ADP-470's to pick up before I can get an amp for my 3805, and I've only got room for a 5.1 setup, so the bi-amp is a no-brainer for now.

I'll keep checking, but hopefully this magical disappearance is permanent!

Jason

So it did work? No hum now? When you hooked it back up to verify did you make a good connection? Did you try a different standard wired cable? If so, I have no explanation for why you have no hum either way now. But since that was the desired result, congratulations, expect my bill in the mail

Jim

 

[keenan]

someday... someday... <dreamy, far-away look in eyes>

One thing I've never been entirely clear on - maybe you can answer, Carl: Does balanced power in and of itself also provide line conditioning, or will noise on the source A/C line be reflected post-transformer in the balanced lines. (I think some of the bal power supplies provide conditioning and surge suppresion as well.)

BP is one of the things I have been looking at also. I think ultimately I will just try one that can be returned and see how it looks/sounds as every setup will be different and produce different results. It may do nothing or it may do a lot.

Jim

 

[djoxygen]

That does seem odd that it still works (assuming your reconnected ground is a solid cxn).

Speculations:

1 - Orig cable was faulty and grounding out internally
2 - Cable was incorrectly in contact with the frame of the Denon at one of the jacks
3 - One of the jacks inside the Denon wasn't 100% solid and was grounding out inside the chassis
4 - The prevailing winds were from the South when you first tried it and are now blowing from the West >:-D

Please try a set of unaltered cables and let us know what you find.

Now that you've (hopefully) got it resolved, you should find out the specs on the passive crossover in your speakers, get an active crossover set to the same freq and slope, and find out the joys of true bi-amping!

 

[keenan]

Now that you've (hopefully) got it resolved, you should find out the specs on the passive crossover in your speakers, get an active crossover set to the same freq and slope, and find out the joys of true bi-amping!

Have any recommendations for actives? Shouldn't the passive cxs in the speakers be disconnected if possible? Doesn't leaving them in the signal path cause phase problems or other sordid nasties?

Jim

 

[cstanley]

i know the equitech have surge protectors on them, i think the
line conditioning is inherent in the balanced power.

remember if you do have balanced power not to plug any lights
(UV, incandecent) into the balanced power or a nasty hum will
show up. you also need a real ground for the buildings AC (2 8 ft
copper pipes in earth).

you are probably right about not getting a 8db drop in noise floor
in a home environment. my noise floor right now is my tivo's
hard drive...

-carl

someday... someday... <dreamy, far-away look in eyes>

Seriously, though. I've read (not just mfr claims) that in a properly wired pro studio that 8-ish dB drops in noise floor are common when moving to balanced power. I'm not sure the benefit would be as great in a home theater since there's far fewer pieces of gear adding to the noise level.

Speaking very generally, bal power won't fix anything that's broken, so ground loops aren't magically going to go away. But once everything else is done and done well, bal power can give you that extra nothing when you're running with the throttle wide open.

One thing I've never been entirely clear on - maybe you can answer, Carl: Does balanced power in and of itself also provide line conditioning, or will noise on the source A/C line be reflected post-transformer in the balanced lines. (I think some of the bal power supplies provide conditioning and surge suppresion as well.)

 

[djoxygen]

Have any recommendations for actives? Shouldn't the passive cxs in the speakers be disconnected if possible? Doesn't leaving them in the signal path cause phase problems or other sordid nasties?

I don't even know if any of the HT mfrs make x-overs. I only know the pro stuff. Behringer (not recommended) at the low end, dBx and Rane (decent) in the middle, and Ashly (very nice) toward the top. I'm pretty sure all these have balanced ins and outs, though, so you'll at least have to do some cable adapting from RCA to 1/4" or XLR. Ideally you'd use a transformer like the Aphex 124A to step up to +4 Bal and back down to -10 RCA.

Now the snag: You want to send one L/R pair out and return 2 pairs. Can the Denon route 2 extra internal paths the way you've done the 1 with Zone2?

As far a disabling the internal passives, that's a good question. Pro speakers don't usually have those jumpers on the outside, and with 1/4" jacks, they can have mechanical switches internally break connections when cables are plugged in. Might want to ring up Klipsch asking about the correct way to do this - I don't want to speculate on how their speakers are wired.

 

[Hannahman]

The struggle to eliminate hum continues.......


I also modified my audio cables like Jason and left the center of the cable intact. No luck... the slight buzz continues...

Jason, how did you modify your cables. Were they a pair of Monster Cables?

I bought a pair that allows me access by unscrewing the cover. I snipped the connection on the side of the connector. I did this on both cables but I only did it on 1 side of each cable. Did you do this to all ends of the cables?

Any thoughts????