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Discussion Starter · #1 ·
I have just bought some secondhand Rotel RB-991 power amps, sounds fantastic, until I switch on my Davis Cinema One :(


Whenever the lamp in the projector is on, I get a buzzing from the tweeters in all of my speakers :(


If the projector is in standby, with the fans running, no buzzing at all, just when the lamp is on does the buzzing start.


The Davis is injecting noise into the mains, that the Rotels pick up.


Has anyone heard of this before?


Can anyone suggest a filter to catch the noise before it gets to my power amps ?


I have a good clean mains supply installed, just for the AV , with an earth spike adjacent the sockets the Amps are plugged into.



Help !


Mark.
 

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Hi Mark


All I can think of is something like a Belkin filter - Argos do them and with their 16 day no quible money back thingy, you've nothing to lose..


Gary
 

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Discussion Starter · #3 ·
Hello Gary,


I tried a few products from Russ Andrews.

The £40 plug in 'silencer' cured it.


I have since made my own filters, following advice on the tweaking forum here, with great results.



Mark.
 

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JVC NX7 Projector, Draper 132" (2.35:1) Techvision XT 1300x, Panasonic DP-UB420, Zidoo Z9x, Zappit
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Mark,

By any chance do you have a cable-tv feed hooked up to the Davis? If so, disconnect that cable and see if the noise persists. A few years back I had a similar problem, though with a Lexicon DC-1 processor. A Mondial ground hum isolator cured the problem.


Another option is to try to isolate your Davis from the other components by putting it on a different electrical circuit. As an experiment, try running a long extension cable from another circuit in your home to the Davis and see if you get the same "hum" problem.


Also, how physically close to the Davis are your power amps and processors?

Good Luck,

John G
 

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Hello,


I can confirm what John G. wrote. I had the same problem with a few clients of me and each time it was solved by putting the projector on another electrical circuit or, disconnect the "ground" (I hope this is correct in English) for the projector, so you only have the + and - connected. This also solved the problem. I had the same problem also with a SIM2.


Greetings from Belgium,


Marc Bosmans

HomeCinema Center
www.adynco.com
 

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Discussion Starter · #6 ·
Hello,


The Davis DLP is about 25 feet from my AV amps.


The noise was almost cured by disconnecting the s-video cable from my Sony 7700 DVD player (not that this is used now - HTPC for DVD)


Must have been an earth loop somehow.


Plugging the Davis into a different mains circuit cured the rest of the noise I could hear through the tweeters.


I hired an Audioprism noise sniffer from Russ Andrews over here in England.


The noise sniffer is a marvellous gadget to listen to the noise on the mains cables.


The Davis PSU is VERY electrically noisy, closely followed by my Rotel RB-991 power amps.


I am sure that many switched mode PSU's pollute the mains badly, so am not knocking the Davis or the Rotels.


Using the 'Silencer' Plug in filter beside the projector, reduced the noise on the mains a lot, but not completely.


I cannot now hear any buzzing from my tweeters, so I am happy :)


There is still noise on my mains supply, but not enough that it can be noticed through my amps and speakers.


I am now trying various DIY designs of mains filters.


Thanks for the help,


Mark.
 

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Hi Mark,


Glad you had a positive result. :)


A question for you - I'm pretty happy with my DLS8, but want to tweak a bit (I'm bored :) ). Do you use a lens filter on your Davis? I can't see anything wrong with my image, but wondered if a filter makes much difference.


What about blacking out the clear section of the colour wheel? Do these mods make any real improvement?


Cheers.


Gary.
 

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Discussion Starter · #8 ·
Hello Gary,


I have not got round to trying any Davis tweaking yet.


Not sure that I have enough lumens spare to try a filter.


I have just made a big RGBHV cable with RG6 SDV cable, and made an EVC to BNC breakout adapter, as fitting BNC's to a Cinema one looked a little risky. Hopefully the RG6 will be an improvement on a VGA cable and EVC adapter, and is a good move for the next projector upgrade.


I am generally happy with the Cinema one, DVD looks great with Theatertek, could do with more pixels of course.


Will make do until I can afford a Dila or the hitachi or whatever.


I would be tempted to buy an XGA Davis if I found one cheapish,



Mark.
 

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If you want to tweak, try DavisTuner! See my sig. For me, a different gamma curve brought out a lot of shadow details.



Mike
 
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