Thor, an all discrete Lateral FET Headphone Amplifier. - Page 12 - diyAudio
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Old 24th April 2012, 02:42 PM   #111
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Join Date: Oct 2004
Location: Denmark
Yesterday I finally finished my amp and took it home.

It sounded great at work, no hum or buzz.

So I hooked it up to the lineout out from the crappy integrated sound on my motherboard, turned the volume knob and there was silence. Then I reached about 10-11 o'clock on the volume knob and the hum started, increasing in intensity and then falling slightly towards the end of the volume knob, turning into a small background hissing type of sound. Great, sounds like I got a ground loop going.

Found my 6 year old crappy MP3 player and hooked it up and the hum or buzz was gone.

Today I hooked it up to a work laptop, same issue, hum and buzz. However, touching the case of my amp with one hand and the small metal hinges used on the laptop screen with my other hand cured it, once again there was silence. The hum and buzz was 100% gone, only thing left was a slight hiss from about 15 o'clock on the volume knob to max volume, most likely just the laptop putting out some noise.

Annoying as hell, but I'm just glad that it isn't my amp that is at fault.

Edit : Removing the laptop from the charger reduces the hum and buzz significantly, but it is still there. One hand on amp and one on laptop still works 100%. Annoying.

Edit#2 : If the latop is removed from the charger, it shouldn't be possible to get a ground loop. Hmm...

Edit#3 : Maybe I should just go ahead and buy that Cambridge Audio Dacmagic 100 DAC that I have been wanting for a few weeks now. It has a ground lift switch, problem solved. Or?

Last edited by Neutrality; 24th April 2012 at 03:04 PM.
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Old 24th April 2012, 05:33 PM   #112
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Found the issue.

The cabinet of my Headamp is grounded, the AC plug for the laptop charger does not have a ground pin. Pulled out the power plug from the wall socket with the cable and charger still attached to the laptop. Put one hand on my headamp cabinet and a finger on where the round pin should have been on the power plug and the hum was gone. There is still a hole there for a ground pin, just no pin.

This is great news as it not only explains why I have hum when using the work laptop I'm typing this on, but also why I have hum using the Headamp at home.

At work, my stationary work PC was grounded as well as my Headamp = No hum.

At home, my private stationay PC is not grounded and my Headamp wasn't either = Hum.

At school, my work laptop was not grounded but my Headamp was = Hum.

First thing I do when getting home is buying a decent power strip WITH ground.
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Old 24th April 2012, 06:21 PM   #113
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With that issue out of the way, lets talk about sound.

I'm limited by my low-end Sennheiser HD415 but I can still hear a clear improvement compared to driving them from my PC onboard soundcard.

It is a clear improvement in clarity and detail with the biggest change being the bass. The HD415 are known to have a bass that is a little loose or boomy. They are still tending to sound a little loose and boomy with the Thor headamp, but they subjectively sound like they go an octave lower than before and there is a lot more detail and slam in the bass now. Suddenly I hear a lot of little details in the bass that wasn't audible before.

What it is eaxctly that gives the improvement is not something I can 100% put a finger on, but it is probably a combination of the high 180mA bias setting+ability to deliver more current, as well as the almost 0-Ohm output impedance. It just gives a great deal of control over your headphones.

My next headphone(probably Beyerdynamic DT880/250) will be in a whole other league than the HD415 and I'm sure the Thor headamp will have no trouble living up to it.
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Old 24th April 2012, 07:32 PM   #114
Floric is offline Floric  Europe
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Quote:
My next headphone(probably Beyerdynamic DT880/250)
Very good choice, after some experiments, I ended there too. Try out the pro version, it sits a little tighter on the head, is a little cheaper (at least in Germany) and sounds a very little bit better than the hifi version - at least to my ears.

Regards

Flo

Last edited by Floric; 24th April 2012 at 07:33 PM. Reason: Typos, need to clean my keyboard
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Old 24th April 2012, 07:39 PM   #115
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Quote:
Originally Posted by Floric View Post
Very good choice, after some experiments, I ended there too. Try out the pro version, it sits a little tighter on the head, is a little cheaper (at least in Germany) and sounds a very little bit better than the hifi version - at least to my ears.

Regards

Flo
I have to find somewhere to listen to it first. Or maybe I'll buy it unheard , but it might still be several months off, gotta save up some money for it.

I'm not so sure I would want something that sit tight on the head. I'm not only after good sound but also good comfort and from what I have heard the hifi version of DT 880 are among the most comfotable headphones on the market.

I'll probably end up buying it from Germany, there is around EUR 60 to be saved compared to buying it here in Denmark.
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Old 24th April 2012, 07:44 PM   #116
Floric is offline Floric  Europe
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In fact its the same headphone with a comparable or the same comfort. The pro version is not very tight, just a little thighter. I like that in combination with those soft pads.

In some stores for musicians it's another 40€ cheaper then the hifi-version.
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Old 24th April 2012, 07:49 PM   #117
qusp is offline qusp  Australia
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the pro version is 600ohms too yeah?
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Old 24th April 2012, 07:56 PM   #118
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Originally Posted by qusp View Post
the pro version is 600ohms too yeah?
I think the Pro is only available in 250 Ohm while the hifi edition comes in 32, 250 or 600 Ohm versions.

Last edited by Neutrality; 24th April 2012 at 08:00 PM.
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Old 24th April 2012, 08:40 PM   #119
Floric is offline Floric  Europe
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Mine is 250, don't know about other ones.
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Old 24th April 2012, 09:00 PM   #120
qusp is offline qusp  Australia
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aha, well as far as I remember from doing recables there was zero difference between them, just loaded with different resistors across the drivers. so you could easily chance the 32ohm to the 600ohms
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