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Audio-GD NFB-12 - Page 128

post #1906 of 2247

you might be able to find the NFB-12 for just $20 or $30 more.  I highly recomend paying the extra $ for it

post #1907 of 2247
Quote:
Originally Posted by haejuk View Post

I think Scannon is probably on the right track.  I have found a nice amp for the D2000 on the used forum, but I am holding off on buying it because I am waiting to find a good dedicated DAC with the features I am looking for.  Any dedicated DAC suggestions with both USB and optical for around $150?

 

I've been thinking about it, and if you want to upgrade the dac and the amp then the nfb 12.1 might be the way to go.  Which amp were you looking at for the denons?  Because for $250 the nfb 12.1 does give you the features you want and, though I haven't heard it, has received great praise for its dac and amp.  It's just my opinion that the amp will not be a huge improvement over the e9, but please note that that is an assumption.

 

For $150 I am drawing a blank so far as dacs with optical and usb.  Similar blank at the $250 price point, unless you are willing to buy used.  My dac (nfb 3.1) has switchable inputs and is a dedicated dac that I could really only afford by buying used in addition to forgoing a new amp.  The DIY market is another place to look.

 

Audio-gd is a solid company.  There are deals to be had so far as dacs are concerned but if you decide to go with the 12.1 you're bound to be getting a quality product.

post #1908 of 2247

I actually decided to try something else, and if it doesn't work out sell it and go for the NFB-12.  I found a Meier Corda Arietta (old and discontinued, but seems to have a good reputation) on the used forum that should synergize very well with my Denons.  I also found a Hot Audio DAC WOW Dual that will allow me to switch between optical and usb.  I did stretch my budget by a little bit, but that just means that if I don't like it I can sell and have enough for the NFB-12 :p

post #1909 of 2247

I was bored a few days ago so I decided to take my NFB-12 apart.

 

It's impressive how easy it is to disassemble the unit. Only a few screws and everything slides right off. Well, almost. The ribbon cables inside are glued to the side of the case using what I guess is black hot melt glue. When I opened the case to change settings the first time, I mistook this glue for black epoxy. I'm glad it's not epoxy after all, because if it was, it would be impossible to take the board out of the case without a soldering iron.

 

I noticed a square of double-sided tape/foam on the board between the power inlet and the transformer. Being a bit too curious, I took it off. It's actually covering some jumpers used to change the unit voltage between 120v and 240v. My unit is set for 120v. I checked the pictures on Audio-gd's website and noticed that the unit pictured is 240v. So for anyone who would need to change the voltage settings of their NFB-12, here's a little montage I did : 

 

Voltage settings on the Audio-gd NFB-12. The configuration of these jumpers let you chose between 120v and 240v main voltage.

 

The settings are actually printed on the board, but it's not very clear. For 120v, you link the two pads aligned with the "110v" prints, same thing for both prints.. For 240v, you link the two pads aligned with the "220v" prints, and you let the other two pads open.

 

I then proceeded to cleaning the whole board with isopropyl alcohol and a fine brush. It's shocking how dirty the inside of the unit is. I actually had to clean it 3 times over before reaching an acceptable level of cleanness. The board seems to be covered with a sticky dust. I'm thinking it's dust that stuck to the soldering paste during the building process.

 

Here are some pictures of the underside of the board. Sorry for the crappy quality and the flash, I did the best I could with my phone's camera.

 

Underside of Audio-gd NFB-12 board.

Audio-gd NFB-12, underside of the circuit board.

 

Still being bored at this point, and having learned that the glue was not epoxy after all, I decided to replace the LED. I used an old, low intensity orange LED. No soldering was necessary, only a hot glue gun. I also decided to do something about the heat coming from the unit. Not that the NFB-12 is overly hot, it's just that I can't sleep at night knowing that there's a simple fix to lower the temperature inside the case : let it breathe. Studying the build, I noticed that the PCB sits high inside the case while leaving noticeable gaps around the walls. Using simple fluid mechanics, I concluded that I needed to drill holes at the lowest point and the highest points inside the case. The first step was to drill a series of 1/4" holes on a strait line along the middle of the unit, right trough the bottom of the case. Since heat is generated (or wasted, depending on your point of view) just about everywhere inside the unit, drilling holes bellow the circuit board and in the middle of it allow the heat from under the board to slip in the gap around it and go up, being replaced by cool air. This way, even the heat from the surface mounted components is dissipated. A lot of heat is also wasted out of the transformer and the PSU, dissipated by the multiple heat sinks on top of the board. All this heat goes up and out trough the gaps around the top cover. I placed washers between the cover and the case under every screw. This way there's a 1mm gap all around the case that allow warm air to flow out. PLEASE don't use metal washers if you plan on doing that!! I don't want to be responsible for a washer dropping inside your NFB-12 and shorting the hell out of everything it gets in contacts with. I used rubber washers, anything not conductive would do.

 

7e21f56b_NFB-12-Air-Holes.jpeg

Audio-gd NFB-12 with low intensity orange LED. Notice the cover is higher. I placed washers between it and the case to have a 1mm gap where air can flow.

 

The difference in temperature after this simple modification is impressive. Now the case is barely warm. I don't think it can even melt chocolate anymore. And it just looks more serious without the silly I'm-gonna-blind-you blue LED.

post #1910 of 2247

Thanks, KimLaroux!

Your solution of drilling the bottom of the case is simply brilliant!

Actually the impressive heat of NFB-12 worried me a bit in the beginning.

I've been reassured by Kingwa about its harmless.

Actually I found that most of the heat is generated by the voltage regulators beside the the transformer (about 50-55° C).

Moreover, when you use the USB input, the temperature is higher than when you use the S/PDIF or opt inputs.

And the use of the headphones doesn't raise the temperarure as much as I expected.

 

post #1911 of 2247
Quote:
Originally Posted by AF115 View Post

Thanks, KimLaroux!

Your solution of drilling the bottom of the case is simply brilliant!

Actually the impressive heat of NFB-12 worried me a bit in the beginning.

I've been reassured by Kingwa about its harmless.

Actually I found that most of the heat is generated by the voltage regulators beside the the transformer (about 50-55° C).

Moreover, when you use the USB input, the temperature is higher than when you use the S/PDIF or opt inputs.

And the use of the headphones doesn't raise the temperarure as much as I expected.

 


It's class A, so the louder you play the LESS heat is released.  :-)

post #1912 of 2247

Is that true?

 

Class A amplifiers release more heat when playing at lower volumes?

 

Because that would explain alot
 

Quote:
Originally Posted by mrspeakers View Post


It's class A, so the louder you play the LESS heat is released.  :-)



 

post #1913 of 2247
Quote:
Originally Posted by mac336 View Post

Is that true?

 

Class A amplifiers release more heat when playing at lower volumes?

 

Because that would explain alot


Class A amps run at CONTINUOUS full power, always.  If you're not putting that power to work, it's wasted as heat.  No/low music, more heat.  More music power less heat.

post #1914 of 2247

How would the NFB perform if I were to use it solely as a DAC; I would be using a tube amp such as a lyr or bottlehead as the amp

post #1915 of 2247
Quote:
Originally Posted by mac336 View Post

How would the NFB perform if I were to use it solely as a DAC; I would be using a tube amp such as a lyr or bottlehead as the amp


I use it that way too with my Crack and EF5 - sounds very good to me and you can play around with the 9 digital filters
post #1916 of 2247

How exactly do the filters alter the sound?

 

Mine doesnt have the switches So I would have to open it up and mess with it.

post #1917 of 2247
Quote:
Originally Posted by mac336 View Post

How exactly do the filters alter the sound?

 

Mine doesnt have the switches So I would have to open it up and mess with it.


Detail/clarity, warmth, etc.  Best to make sure yours have the switches internally (it will if it's a new shipment) - the early ones didn't have the ability to change the digital filters.  

 

post #1918 of 2247

I have the version with the filters selectable with jumpers. I tried all the filters while the unit was on and playing, but I seriously could not spot any difference. Do I have to restart the unit for the filters to get applied? Or restart playback?

 

From the pictures I concluded that the 12.1 had the filter switches connected directly to the filter headers. So changing jumper positions on the 12 should be the same thing as flipping the switches on the 12.1... and audio-gd's website says the 12.1 does not need to be shut down to change the filters. 

 

So am I doing something wrong, or is the difference between the filters that subtle?

post #1919 of 2247
Quote:
Originally Posted by KimLaroux View Post

I have the version with the filters selectable with jumpers. I tried all the filters while the unit was on and playing, but I seriously could not spot any difference. Do I have to restart the unit for the filters to get applied? Or restart playback?

 

From the pictures I concluded that the 12.1 had the filter switches connected directly to the filter headers. So changing jumper positions on the 12 should be the same thing as flipping the switches on the 12.1... and audio-gd's website says the 12.1 does not need to be shut down to change the filters. 

 

So am I doing something wrong, or is the difference between the filters that subtle?


I always power mine down because I was afraid of shorting something by accident, but you're right - if you can change filters with front switches on 12.1, you should be able to with jumpers internally.

 

I didn't try them all, but the difference between the default (2x brickwall, I think) and 8x min phase apodising wasn't subtle to me.  This was with DT880/600's - which are fairly detailed cans. 

 

post #1920 of 2247
Quote:
Originally Posted by captouch View Post


I always power mine down because I was afraid of shorting something by accident, but you're right - if you can change filters with front switches on 12.1, you should be able to with jumpers internally.

 

I didn't try them all, but the difference between the default (2x brickwall, I think) and 8x min phase apodising wasn't subtle to me.  This was with DT880/600's - which are fairly detailed cans. 

 


How did the filters affect the sound?

 

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