Noisey theater bypass in ET3SE

[medward0]

Posting this to help others who may be losing their minds as I have been over the bypass buzzing.

For TV and movies, I've been running the HT front channels through the CJ pre theater bypass circuit (unity gain, they call it) and on to my main amp. In this setup, I use the HT pre/pro for volume control.

When using the bypass, I was getting what sounded like a ground loop buzz and I've been wracking my brain to figure it out. Was it the pre/pro? The cable runs? ....

So, this last weekend, I took everything apart and hooked up one piece at a time, etc. (one side benefit was that I cleaned all the connections/connectors) and redressed all the cables. Kinda fun, really, in an OCD-kinda way.

Well, the buzzing in the bypass circuit has nothing to do with the HT set up. Even with no inputs when I switch the pre to bypass, it makes an awful buzz...why would it buzz loudly if there is no input to the bypass? With an input (I tried several sources), the buzzing isn't as loud, but it is still there.

Change from theatre bypass back to "source" and buzz goes away...silence.

So, for now, I'm just running the TV/theatre through an aux input on the pre and it is quiet, quiet, quiet. This has some disadvantages, but at least it is finally quiet and I can enjoy the silence.

[pstrisik]

If you have cable service, try disconnecting the cable from the cable box. It solved a hum problem for me, even though some of my troubleshooting indicated something else. It was more of a universal hum though.

[Joe Appierto]

If it is your cable box, try an isolation transformer. I had a 60 cycle hum coming through my system because of it and once the transformer was inserted into the cable feed, it completely disappeared with no degradation of the cable's audio/video signal as far as I could tell.

I used this one Amazon.com: TII 220 Ground Loop Isolator for Cable TV applications: Car Electronics (http://www.amazon.com/TII-220-Ground-Isolator-applications/dp/B0070Q6URO/ref=sr_1_107?ie=UTF8&qid=1383132677&sr=8-107&keywords=isolation+transformer) and for $21 it was well worth it.

[pstrisik]

If it is your cable box, try an isolation transformer. I had a 60 cycle hum coming through my system because of it and once the transformer was inserted into the cable feed, it completely disappeared with no degradation of the cable's audio/video signal as far as I could tell.

I used this one Amazon.com: TII 220 Ground Loop Isolator for Cable TV applications: Car Electronics (http://www.amazon.com/TII-220-Ground-Isolator-applications/dp/B0070Q6URO/ref=sr_1_107?ie=UTF8&qid=1383132677&sr=8-107&keywords=isolation+transformer) and for $21 it was well worth it.

Agreed. I used the Jensen Transformers equivalent. It was more expensive, but it was the one most talked about and I wanted to nip it on the first try. That it did.

[medward0]

Thanks, guys. I do have an isolation transformer device for the cable box and it didn't help the issue at all in my case. Even unplugging the cable box and disconnecting the cable coax outside of the house had no effect.

My take is that there is an issue with the pre bypass circuit as there is a buzz if the bypass is selected even if no input and the cable box and coax are off/disconnected.

My solution, as it were, is to just not use the bypass circuit and use another input on the pre for the output from the pre/pro. Not happy that this is the case and I'm not certain what the issue with the pre is.

Sigh...I love my the sound from my CJ gear, but it has been so hard to find quiet enough tubes and now the theatre bypass circuit buzzing and I have to use a cheater plug to keep my amp from humming too. Reminds me of my 20 year old Land Rover: it is a pain sometimes, but I put up with it and love it because of what it does.

[rocky500]

I have 3 amps here I was switching between with my ET3SE.
One amp has the similar problem as you describe while the other 2 are ok.
The one in question has the highest gain of 35dB. I have ordered some attenuators to try between the Pre and amp as I suspect it is a gain issue.
Here is a recording of the problem as I switch between Bypass on and off.
Playing: R05_0005.MP3 - picosong (http://picosong.com/kWDk)

ADDED: Just recieved 2 RothWell In-line 10dB attenuators today and put them in and the problem is now gone!
Put between the CJ Pre and the amp. Has given me a better control of the volume as well.
Quieter background and now switching to HT Bypass works well, no more buzzing.