hiss using preouts on denon 3801?

Discussion in 'Archived Threads 2001-2004' started by Chriss M, Mar 2, 2002.

  1. Chriss M

    Chriss M Second Unit

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    i recently added an Anthem MCA-3 power amp to go along with my denon 3801, and i've since noticed a slight increase in hiss from my speakers. The hiss is not audible from more than a foot or so away from the speaker, but it is definitely a bit louder than when i was using the denon's amplifiers.

    At first i thought it was the anthem amp which was adding the additional hiss, but if i leave the amp powered on with the 3801 off, the speakers are almost dead silent. I have to put my ear directly to the tweeter and even only then can i BARELY hear any noise. However once the 3801 powers up the hiss returns.

    I realize that there will always be some amount of noise but im just curious as to why the hiss has increased from before adding the amp. Is it simply that using the preouts on the 3801 adds more noise than the "internal" wiring?
     
  2. Chriss M

    Chriss M Second Unit

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    not even a pity reply ? [​IMG] [​IMG]
     
  3. Alexis

    Alexis Stunt Coordinator

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    what kind of interconnects do you have?

    It could be the Anthem is more sensitive to line noise if you don't have a line conditioner, probably not since you don't get a hiss with the denon turned off.
     
  4. Steven Simon

    Steven Simon Producer

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    Unplug your cable connection or SAT from the wall and see if the hum goes away. If it does, you have a ground loop issue. If it goes away, check back in here, and we'll talk about remedies....
     
  5. MatthewJ S

    MatthewJ S Supporting Actor

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    Yes, I believe (although I'm often shunned for stating)that there is ussually very little quality put into the pre-out stages of most receivers ...meaning that ,yes, the pre-out section is often used as a "feature" for curb appeal and that what most rcvr mnfgr's spend on the components of a pre-out stage is something slightly greater than zero...so ,indeed ,you may be hearing noise or loosing quality in SOME/MANY rcvrs buy using their pre-out stage...this being said,I love outboard amps additional current,quality,etc...but if a rcvr spent put as much into building a quality pre-out section(which statistically will be used by very few) then we would see their prices rise to something approaching(poss. exceeding[?]) the price of pre-amps!

    just my 3 cents
     
  6. Chriss M

    Chriss M Second Unit

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    Steven -
    I'm pretty sure this isnt a ground loop issue, since the sound isn't a humming noise. It's really just a faint hiss. On another note though, i do have a ground loop problem with my subwoofer amp due to the CATV, which is currently being solved with a cheater plug. Would one of those ground loop isolator boxes they sell at parts express for $10 take care of this?
    Matthew -
    That's what i was afraid of. I was hoping to be able to get by with the 3801 for a while, but this is making want to buy a dedicated pre/pro now....which also means i will need another 2 channels of amplification [​IMG]
     
  7. Sankar

    Sankar Second Unit

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  8. Chriss M

    Chriss M Second Unit

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    Sankar, I'll give that a try when i get home.

    In the meantime, any other experiences with using a similar receiver as a pre/pro ?
     
  9. Sankar

    Sankar Second Unit

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    Well, yes! I use my 3801 as a pre!

    The fronts are driven by an AT1504 (in bridged mode) and the center and 4 surrounds go through an AT1505. I have not noticed any hiss as such (though a very very slight ground loop hum does exist even after I put in a dedicated 20A circuit, new ground rod, Monster 2500 etc .. but the hum is not detectable from 3 inches away, so I'm not losing any more sleep over it) .. which is why I inquired about the cabling etc. Actually, I even have the signal from the 3801 go through an AudioControl Rialto equalizer .. and still no hiss to talk about ...

    Another thing you could try is to leave the speakers on the Anthem (as they are currently) and disconnect the cable at the Denon end (not at the Anthem end, which you probably did and verified that there is no hiss) .. is the hiss there (if so, it may be induced by the cable). Also, remove ALL inputs to the 3801 and ground the body of the Anthem to the Denon .. any reduction in hiss? Unfortunately, I suspect that like the dreaded ground loop hum, eliminating hiss may also take some work ..
     
  10. Chriss M

    Chriss M Second Unit

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    i didnt have too much time to play last night, but i did get to try removing the interconnects. It seems that if i unplug the interconnect between the amp and the 3801 from either end the hiss stops, or at least is reduced to a nearly inaudible level. Im not quite sure what this means exactly but it does seem to continue to point to the 3801 as the source of the problem.

    Tonight i will pull the amp and the 3801 from the rack and disconnect everything. I'll connect one speaker and one interconnect and see if the hiss remains.
     
  11. Sankar

    Sankar Second Unit

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    Yes, that does point to the 3801 (or "earlier" in the chain). Before you pull out everything, you may wish to (you may have already tried some of these)
    • Check if the hiss is present no matter what input is selected on the 3801 e.g. try an unconnected input like VCR2 or something. Also try to use the "Direct" mode since that bypasses all tone control circuitry etc in the 3801.
    • Does the hiss persist if you disconnect all inputs to the 3801? (this includes audio and video inputs) [/list=a]



      If the hiss goes away in either case, then the problem may not lie with the 3801.



      If it persists even with all inputs disconnected, then try shorting the grounds (i.e. input ground on the 3801, output ground on the 3801, amp body, etc .. when I was tracking my ground loop, I had a wire connected to one end and kept touching the various points to see if there were any changes) directly to see if that impacts the hiss. This is usually easier if there are 2 people involved -- one with his/her ear to the speaker and the other with the wire.



      As a final test (with all else disconnected), short the appropriate inputs .. i.e. at the appropriate input stage on the 3801, short the center pin of the rca jack to its shield (ground) .. this will put a 0V signal effectively, and any remaining hiss must be due to the 3801.
     
  12. Chriss M

    Chriss M Second Unit

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    Thanks Sankar, i will try all of those things tonight.

    Regarding the inputs...the noise seems to stay the same regardless of the selected input. There are 3 things ive noticed that cause the hiss to stop - turning the 3801 off, selecting and forcing a digital input source (auto mode off to keep it from reverting to analog), or turning the volume one click past "-60" where it reads "--".
     
  13. Sankar

    Sankar Second Unit

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    Turning the vol control to "--" effectively disconnects all inputs.

    The fact that using a digital input eliminates the hiss is good news. That suggests that its probably not the internal circuitry that's causing the hiss. I have a suspicion that removing all inputs will eliminate the hiss .. then you can add them one by one to find the culprit.
     
  14. Chriss M

    Chriss M Second Unit

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    well i finally had some time to play around with this. I ended up pulling the 3801 and the amp from the rack and plugging them in in another location, away from everything else. Hooked up only 1 interconnect and 1 speaker, and still heard the hiss. So i guess i must have a "noisy" 3801 [​IMG] is this something that can be brought in and repaired under warranty?
     
  15. Sankar

    Sankar Second Unit

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    I presume that you bought this from a Denon authorized dealer? If so, you should be able to take it to any Denon repair center and have them check it out.
     
  16. Chriss M

    Chriss M Second Unit

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    i think the Denon is the ONLY component i own that i DID purchase from an authorized dealer [​IMG] I see if i can bring it to a repair center this week. Thanks again for all the help.
     
  17. Sankar

    Sankar Second Unit

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    Cool! Same for me -- my 3801 is the only item in my HT that was bought from an authorized dealer!

    Let us know how it all turns out...
     

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