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Audio-GD NFB-12 - Page 145

post #2161 of 2247

I have NFB11.32 and let it on, runing music for 48 hours, and nothing happened. Yes, it is hot.

 

NFB11.32 is in burning-in period, so I let it to play during night, and during day.

 

And to listen to it for 2 days, I don't see anything wrong with it... for example, man can be ill and need to be at home... can happen.

post #2162 of 2247

I've had mine on for months now. And no problems. You guys with overheating problems had bad luck.

post #2163 of 2247

Is anybody pairing another amp or dac with their NFB 12? Is it worth it?

 

I'll be using it primarily with Mad Dogs.

post #2164 of 2247

I have an hybrid tube amplifier that I sometimes use with the NFB-12. Most of the time though I use my headphones directly from the NFB-12. In my opinion, it has plenty of power on it's own to drive just about anything.

 

Besides, using another amplifier with the NFB-12 seems silly. The RCA outputs are connected to the output of the amplifier, so connecting them to another amp is essentially amplifying an amplified signal. The signal is not cleaner out of the RCA than out of the headphone jack, so there really isn't much gain in using another amplifier. In fact, it can only be worse. Making the audio signal go trough yet another amplifier cannot make the signal cleaner than it is, or give you more resolution. The external amplifier will add it's own noise and distortion to the signal. It will not replace the noise and distortion of the NFB-12's amplifier, because the signal still goes trough the NFB-12's amplifier.

 

Just thinking about it gives me a headache... lol.

 

I mean if you want to use a cleaner amplifier than what the NFB-12 already has, then you should get a cleaner DAC too. Something simple, with very little processing. And normal line-level voltages... 

post #2165 of 2247
When you plug in another amp to the dac out does it not bypass the internal amp? Can't you set it to variable or fixed?


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post #2166 of 2247
Quote:
Originally Posted by HeatFan12 View Post

When you plug in another amp to the dac out does it not bypass the internal amp? Can't you set it to variable or fixed?

 

No, it does not bypass the internal amplifier. I dissasembled my NFB-12 many times and studied the circuit. There's a wire going from the RCA connector to the front of the unit. It's connected to a relay that switches between the headphone out and the RCA. The other end of the relay is connected to the output of the internal amplifier. For the curious, this is the relay right next to the headphone socket.

 

When you toggle the HP/Variable/Fixed switch, you're just switching the relay that changes the output of the amplifier. In "fixed" mode, this relay stays in the same state as in "variable", sending the output to the RCA. "Fixed" triggers a second relay that bypasses the volume knob. It fixes the output volume at 50% trough a pair of resistors. This relay is placed right behind the volume knob. Electrically, it's half-way trough the amplifier.

 

There'a another pair of relays installed between the DAC chips and the amplifier that changes the "gain" of the amplifier. It's simply a set of different values resistor that attenuate the signal (it's a current signal) before it gets to the amplifier.

 

You probably noticed yourself that the High and Low gain setting also affects the level of the RCA output... what did you make of that?

 

I can't help but find the use of so many relays a dirty way to add features. I mean, the signal goes trough 3 relays! Relays are mechanical things, and they do fail. If only one of the 4 relays failed, your unit will be stuck with in the configuration the relay failed in.

 

But what's even more ridiculous is this quote from the FUN's description:

 

The FUN will come in a 100-127V version and a 220-240 version, depending on the geographical location and customers choice. The reason we don't make it with a selectable voltage is that 1: We are afraid if customers choose the wrong voltage, they will wreck their unit, and 2: While in low quality audio equipment, you can't hear the effect on the sound quality of using a selectable voltage switch, in hi-quality gear, which includes the FUN, the deterimental effects of using a voltage selection switch will be audible, not to mention the positive effects of a better power cable.

 

There's an obvious lack of integrity here. Audio-gd seems to believe a switch on a main's power line will affect sound quality. They also claim "better" power cables have "positive effects". But still they place 4 relays inside the audio signal path of the NFB-12. Ridiculous nonsense.

 

The cross-talk between the channels of the NFB-12 is remarkably higher than my DIY'ed tube hybrid, which has none. I'm totally blaming this on the overuse of relays.

post #2167 of 2247
Quote:
Originally Posted by anoxy View Post

Is anybody pairing another amp or dac with their NFB 12? Is it worth it?

 

I'll be using it primarily with Mad Dogs.

 

I use mine quite a lot with my LD MKIV.  I have noted what KimLaroux says above (and totally agree with him re crosstalk) ........ but what can I say ....... I like the sound of the NFB-12 and LD MKIV combo wink.gif

post #2168 of 2247

Mine is literally on 24 hours a day for maybe a week at a time. I only turn it off when I transport it or I'm away from home for more than 48 hours. It gets warm at best, it just sits on my desk.

 

Am I silly thinking of running this thing out to a Schiit Mjolnir? I'm feeling too stingy to buy a Gungnir and I've always been supersticious about spending serious money on a DAC.

 

Also should I be messing around with the filters? I feel like I should be getting more bass out of my LCD-2's =/

post #2169 of 2247
Great info. Thanks KimL.
post #2170 of 2247
Quote:
Originally Posted by KimLaroux View Post

 

No, it does not bypass the internal amplifier. I dissasembled my NFB-12 many times and studied the circuit. There's a wire going from the RCA connector to the front of the unit. It's connected to a relay that switches between the headphone out and the RCA. The other end of the relay is connected to the output of the internal amplifier. For the curious, this is the relay right next to the headphone socket.

 

When you toggle the HP/Variable/Fixed switch, you're just switching the relay that changes the output of the amplifier. In "fixed" mode, this relay stays in the same state as in "variable", sending the output to the RCA. "Fixed" triggers a second relay that bypasses the volume knob. It fixes the output volume at 50% trough a pair of resistors. This relay is placed right behind the volume knob. Electrically, it's half-way trough the amplifier.

 

There'a another pair of relays installed between the DAC chips and the amplifier that changes the "gain" of the amplifier. It's simply a set of different values resistor that attenuate the signal (it's a current signal) before it gets to the amplifier.

 

You probably noticed yourself that the High and Low gain setting also affects the level of the RCA output... what did you make of that?

 

I can't help but find the use of so many relays a dirty way to add features. I mean, the signal goes trough 3 relays! Relays are mechanical things, and they do fail. If only one of the 4 relays failed, your unit will be stuck with in the configuration the relay failed in.

 

But what's even more ridiculous is this quote from the FUN's description:

 

 

There's an obvious lack of integrity here. Audio-gd seems to believe a switch on a main's power line will affect sound quality. They also claim "better" power cables have "positive effects". But still they place 4 relays inside the audio signal path of the NFB-12. Ridiculous nonsense.

 

The cross-talk between the channels of the NFB-12 is remarkably higher than my DIY'ed tube hybrid, which has none. I'm totally blaming this on the overuse of relays.

Is this verified that the amp is not bypassed.....Not saying you are not correct, just looking for other sources. If so, it kinda bums me out. I have a NFB-12 that can run forever and not overheat, but I have been thinking of using another HP Amp to use with the 12's DAC.

 

Oh well......


Edited by dwinnert - 1/4/13 at 9:48am
post #2171 of 2247

Can somebody tell me what the difference between the HP and DAC options are on the NFB 12.1? Switching it doesn't seem to make any difference...I know, sorry for the dumb question :3

post #2172 of 2247
Quote:
Originally Posted by anoxy View Post

Can somebody tell me what the difference between the HP and DAC options are on the NFB 12.1? Switching it doesn't seem to make any difference...I know, sorry for the dumb question :3

 

It's supposed to switch between the 1/4" jack at the front and the RCA connectors at the back.

 

Do you have anything connected trough the RCA? Does it work?

post #2173 of 2247

Nope, nothing connected via RCA, just Optical to my iMac.

post #2174 of 2247
Quote:
Originally Posted by anoxy View Post

Nope, nothing connected via RCA, just Optical to my iMac.

 

Optical is a digital input, which is unrelated to the problem.

 

So if I understand correctly, you have signal out of the 1/4" jack, no matter the position of the Output switch?

 

If this is the case, then you have a defective unit. You should have no signal out of the RCA, since the selection is done using a relay and a relay cannot be in two states at the same time.

 

It could be as simple as a broken wire or solder joint. It could be a dead relay. Or a defective switch. In any case, anyone who knows their way around a circuit board will have no problem debugging and fixing it. It's a very simple circuit.

 

But then if you don't need the RCA, you don't really need to get it fixed. Performances should not be affected by such a problem. 

post #2175 of 2247

Even though I'm in fixed mode, the volume pot still affects the volume. Does this happen to anyone else?

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