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Static/Hum in Little Dot MK III

post #1 of 8
11/17/10 at 12:17pm
Thread Starter 

Hi,

I'm new to Head-Fi.org and have been viewing these forums for almost a month now. I finally decided on Beyerdynamic DT-990/600's (just received them last week). Also, I pulled the trigger on the LD MK III yesterday.  I'm definitely amazed at the sound quality and I thank Penchum for the wonderful review.  The problem I'm having is that I hear a low humming noise at around 11'oclock on the volume dial and it gets louder as I increase the volume.  My source is an Auzentech Forte soundcard's front line out (that green 1/4" connector from the D-Sub dongle) to the Little Dot with the cable that was included.  So far, i'm loving the sound i'm hearing from it, but the hum at increased volumes is irritating. 

I heard a solution is a ground loop isolator or a cheat plug... but i'm unsure which would work in my situation and not give me diminished sound quality or become a fire hazard.

 

Any help is greatly appreciated. 

 

Thanks in advance.


Edited by Zudeo - 11/17/10 at 12:31pm
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Gear mentioned in this thread:

Beyerdynamic DT 990 - 600 Ohm
post #2 of 8
11/17/10 at 1:14pm
Thread Starter 

bump.

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post #3 of 8
11/18/10 at 7:22am

I don't know if this will help but i've had my MKIII for 2 yrs now and a couple of things that have given me static/hums: phones being nearby, computer hardware, and also once my cat puked under the amp and some of it got wet.. :P Something that might help you is using an optical output instead of the 3.5mm jack.

 

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post #4 of 8
11/18/10 at 8:08am
I used to own the same amp and headphones as you. The static was solved when i got a ground loop isolator. Hope it helps u
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post #5 of 8
11/19/10 at 8:24pm

I had hum on my LDMKiii twice:

 

1) One of the stock driver tubes was bad. If I flipped the unit on its side the hum went away. Took quite awhile to figure that one out. In this case, even though only 1 tube was bad, the hum was in both channels.

 

2) I had changed the jumpers to put in some Mullard 8161's (now permanently installed BTW). BUT I hadn't put one of the jumpers on squarely. In this case the hum + static was in only 1 channel.

 

I haven't had ground loop hum, but that's an enemy I'm well experienced with so I'm pretty careful with grounding. 

 

My LDMKiii is now set on highest gain,10, and only self-noise I get is a tiny bit of hiss with nothing playing going past 2 o'clock or so. If all is well you really shouldn't have any self-noise.

 

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post #6 of 8
12/29/10 at 6:36pm
Thread Starter 

Thank you all for replying.  As i'm pretty new here, I didn't expect anyone would reply.. unfortunately I haven't checked back in this thread since the last 'bump' until today.  I really appreciate it though.  

As for the source of the hissing it seems as though it's from my Auzentech Forte card.  Between that and my Zalman Mic, I have to Restore Defaults on whatever Sound Mode i'm on in the Auzentech Control Panel.  In the new year i'm going to pull the cord on a Little Dot DAC_1.  I've heard it's definately better than the Auzentech DAC so i'm definately looking forward to it.

 

I've also been curious about Tube Rolling.  I've heard that the Mullards are capable of more bass as I don't feel that the 990's deliver as much upper bass as i'd hoped.  Anyways, i'm sure that's for a different thread.  

Thanks again.

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post #7 of 8
12/29/10 at 7:05pm

Hello, I had the same problem. I believe the grounding issue is tied to the front right screw on the chassis (you can verify this by touching the screw and the case at the same time - try it with all of them). I ended up fixing the problem by adjusting the screw a little until it vanished.

 

Mine was very loud though - almost as loud as the signal.

 

I used big shield mullard M8100s.


Edited by MrGreen - 12/29/10 at 7:07pm
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post #8 of 8
1/5/11 at 8:26pm
Thread Starter 

Thank you :-) 

One question though, what are "big shield" tubes? I've been looking to do some tube rolling and eBay has some rediculous prices for them.  I've been thinking about M8161's, M8100's or M8083's but I have no clue why people prefer "big/large shield" tubes vs. "small" ones?


Also, where do you get your tubes from?

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Gear mentioned in this thread:

Beyerdynamic DT 990 - 600 Ohm
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