New Pre-Amp Coming Soon!

Drenis

I was out of town all weekend so didn't get any time to tinker. However, I have a bloody ground hum now in my system. What's causing it I haven't the foggiest idea. Tonight will be the first time I get to try and figure out what's causing the hum. There has never been a ground loop hum.

So far I'm thinking it's my AVR or DAC of all things. Everything is plugged into my Furman line conditioner. Removing the IC's from the AVR to my Pre immediately removes the hum. If I use the HT Bypass from the AVR, the hum is full blown loud. If I run the IC's from the AVR into any input, the hum is there (Turn AVR volume up to induce gain for the pre-outs to the pre-amp), then the hum ONLY gets louder as you increase the volume on the pre-amp.

The only components plugged into the same bank as the pre-amp are the AVR, DAC and my Squeezebox Touch. My gaming consoles and cable box are on another bank.

Should be an interesting evening trying to figure this one out...

chumlie

Never mentioned a hum in your last post. What changed ?

tonyb

Drenis, since the hum appeared after the addition of the pre, it's either the cables your using, or you have too many grounds going into the furman. The cheapest solution is to stop by any hardware store, Walmart, etc, and pick up a cheater plug. A plug that coverts a standard 3 prong plug to 2 prong. Try it first on the pre, or on the receiver. Cost you 2 bucks. You won't harm anything by doing this and it's the easiest,cheapest place to start.

Drenis

chumlie wrote: »

Never mentioned a hum in your last post. What changed ?

I just never mentioned it cause I hadn't done any troubleshooting. I had very little time before I had to head out of town. The hum began when I first setup the HT bypass.

tonyb wrote: »

Drenis, since the hum appeared after the addition of the pre, it's either the cables your using, or you have too many grounds going into the furman. The cheapest solution is to stop by any hardware store, Walmart, etc, and pick up a cheater plug. A plug that coverts a standard 3 prong plug to 2 prong. Try it first on the pre, or on the receiver. Cost you 2 bucks. You won't harm anything by doing this and it's the easiest,cheapest place to start.

I swapped the cables going from the AVR to the Pre and that changed nothing. All IC's are MIT EXP 1's from DAC->Pre->Amp. I can't recall if it's the DAC or the AVR that is only a 2 prong setup. My house had the electrical re-wired recently so it should be a true ground.

Tonight I'll start unplugging components from the back of the Furman until it quits.

Drenis

So I've been doing a little reading in anticipation to tinker when I get home. I came across the 2100 owners thread over @ AVS and someone posted something similar to my scenario where it was the cable box causing the hum. Once the coax was disconnected all was fine.

http://www.avsforum.com/avs-vb/showthread.php?p=18727476#post18727476

Now I have my coax for my cable running through my Furman as well so the line is protected and filtered. While I logically think it can't be the coax I wonder if it might be. I also have HDMI AND component video/audio running from the AVR to the TV. A couple switching power supplies for the Squeezebox, Wii and external HDD for the cable box.

The 2100 manual also states to run the amp and pre on the same circuit. I run the amp on its dedicated amp circuit with the Furman (See picture in link for layout of Furman - http://www.furmansound.com/new/images/highres/ELITE-15PFi-rear.jpg). So that first bank, ONLY my Carver is plugged into that which is 2 prong. The pre along with 3 other components take up the next bank and the last bank is full as well.

Regardless of this post, until I tinker later, nothing will get accomplished. But everything was setup for a flawless user experience. This hum means something will have to go and that might mess up the layout. I HATE that...

Drenis

Alright, someone may have some advice with the following information on what I can do next.

I traced the hum back to the AVR. Once I unplugged the HDMI cable coming from the cable box, it stopped. I shook my head and began to unscrew the coax. Bingo. I began to scratch my head because the cable runs through my power conditioner (Furman Elite 15-PF i) which eliminates this hum. So I ran direct and bypassed the Furman and the hum stays present once the coax is attached to the cable box.

Now I'm at a loss for what may cause this as it was ONLY introduced once I introduced the pre into my rig. There has never been a hum before due to grounding. It worked fine. So I'm a bit frustrated at the moment. Where is the hum coming from? The cable is split once it enters the house and as such, one cable feeds the TV and the other over to my computer where the modem and router are. For fun I disconnected my RJ-45 run from the router to my SQBT to eliminate any possibility and that did nothing. I really don't think that split cable run would have any effect.

It seems that the only way to kill the ground hum is to pull the plug for the pre-amp. I tried running different combinations of gear on the same power banks.

I'm not sure what to do next. I've never been faced with this situation before. Fact is I need sound from the television to come out this rig. So something has to work... who knew HDMI carries a ground signal which passes a hum

Drenis

I must say... anyone on the fence about jumping into separates, do it now.

Just wow. I thoroughly enjoyed the last 4 hours.

FTGV

Drenis wrote: »

.

I'm not sure what to do next.

http://www.cs1.net/products/jensen_transformers/VRD-1FF.htm

tonyb

Really my good man, try the cheater plug first, 80% of the time thats all you need.

Drenis

FTGV wrote: »

http://www.cs1.net/products/jensen_transformers/VRD-1FF.htm

Thanks for the link.

tonyb wrote: »

Really my good man, try the cheater plug first, 80% of the time thats all you need.

Isn't that just putting a bandaid on the problem though?

So I'm assuming that by the pre not being 2 prong, it is the chain for the loop. My DAC is 3 prong and it produced no hum.

I'm going to pick up a cheater plug tomorrow though and use it on the pre.

FTGV

While the cheater plug may work that third prong is there for a reason,to provide a safety ground.For that reason IMO it is better to look to a better permanent solution than just defeating it.The link was just one known effective example of CATV isolation transformer .A search of the net I'm sure should result in other less expensive alternatives.

Drenis

FTGV wrote: »

While the cheater plug may work that third prong is there for a reason,to provide a safety ground.For that reason IMO it is better to look to a better permanent solution than just defeating it.The link was just one known effective example of CATV isolation transformer .A search of the net I'm sure should result in other less expensive alternatives.

I know the importance. That's why I don't want to permanently use a plug.

This was also suggested but between what you suggested and this. Only yours is rated to work with Digital TV setups. Still looking at a rough $40-$50 difference without factoring in proper costs for tax and shipping. This pre is no longer a good deal now. :razz:

I'm thinking of going a different direction with my configuration and removing the AVR completely out of the picture.

heiney9

Why not just re-route the cable box and NOT have it go thru the Furman? Unless I read your explanation wrong it's the cable box that is the issue when the AVR is plugged in??? Or do I have that wrong?

Drenis

heiney9 wrote: »

Why not just re-route the cable box and NOT have it go thru the Furman? Unless I read your explanation wrong it's the cable box that is the issue when the AVR is plugged in??? Or do I have that wrong?

I did remove the cable from the Furman when I found the issue and plugged it directly into the cable box bypassing the surge protection and filtering of the Furman.

Edit: I think what I will do is run all my sources (CATV, gaming consoles...) through the TV inputs (PITA if you have a Sharp Quattron) and rid the AVR. Run analog out from the TV to the Pre. This also might induce hum. If it does then I'll have to spring for one of those filters... although that leads me to think that something is improperly connected whether from the cable company or it not being grounded in my house (really unsure though - I'll ask a electrician who is a friend of mine).

Or replace the AVR with a soundbar and cease connecting the two systems together which will eliminate the hum.

heiney9

Not so much improperly connected, but maybe just not compatible. Wiring sytems together that include, TV, HDMI, CATV, COAX and a combo of 2 and 3 pronged plugs as well as game systems thrown in the mix can be frustrating sometimes. That's a lot of connection and cables doing carrying a lot of different signals.

H9

Drenis

heiney9 wrote: »

Not so much improperly connected, but maybe just not compatible. Wiring sytems together that include, TV, HDMI, CATV, COAX and a combo of 2 and 3 pronged plugs as well as game systems thrown in the mix can be frustrating sometimes. That's a lot of connection and cables doing carrying a lot of different signals.

H9

You're exactly right. With the pre being 3 prong, that's all that was needed to complete the loop. when when I joined the analog side of those connections to the pre.

Time to reorganize and the other half will just have to make do. The pre stays. Music is fantastic. I've never heard the A9's sound SO good compared to when I first bought them. I can;t comprehend what xover upgrades will bring as it's the only thing left to do; mod the speakers.

heiney9

Glad you are enjoying it and glad you took the advice and tried seperates for yourself. IIRC, you weren't convinced it would make such a positive improvement.

Enjoy!

H9

Drenis

heiney9 wrote: »

Glad you are enjoying it and glad you took the advice and tried seperates for yourself. IIRC, you weren't convinced it would make such a positive improvement.

Enjoy!

H9

You are spot on. See post #38. :razz: I really don't think I could take a step back now.

dudeinaroom

Awesome find. What are you doing with the amp? I'd use it top power center(s) or surrounds, but that's me.

Drenis

dudeinaroom wrote: »

Awesome find. What are you doing with the amp? I'd use it top power center(s) or surrounds, but that's me.

I'm going to sell it as I have no use for it. I am spending some time getting a feel for the sound currently then I'll swap the Carver out for the 2125 for a listening session.

Who knows, maybe I'll like the Parasound amp more. :razz:

tonyb

Blame your hum on Detroit. :cheesygrin:

http://www.foxnews.com/world/2012/05/01/canadians-make-racket-about-mysterious-hum-coming-from-us-side-border/?test=latestnews

Apparently, Canadians want to put a big cheater plug on Detroit. Just an amuseing side note, given your from north of the border.

Drenis

tonyb wrote: »

Blame your hum on Detroit. :cheesygrin:

http://www.foxnews.com/world/2012/05/01/canadians-make-racket-about-mysterious-hum-coming-from-us-side-border/?test=latestnews

Apparently, Canadians want to put a big cheater plug on Detroit. Just an amuseing side note, given your from north of the border.

Hah... I had a good chuckle at that, thanks.