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Review and Measurements of Audio-gd NFB2 192 DAC

JohnYang1997

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I'm currently designing a headphone amplifier with negative fb of 300db at dc and 200db at 1k. That must be the best tool of worshiping god of negative feedback.
 

VintageFlanker

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When you see number of components in audio gd and the price and you compare with the price of toppings dx7s for exemple you see that topping should be much more cheaper.
Topping dx7s just four cheap op amp tpa1612 and 2 cheap headphone amps tpa6120
No research for design.
Audio gd nfb 11.38
Lot of components proprietary designs.
You said it all. You simply don't know what "design" means.

The difference between Topping and Audio-GD is called: Engineering.

One is bad designed with lot of components. The other properly engineered with few.
 
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JohnYang1997

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You said it all. You simply don't know what "design" means.

The difference between Topping and Audio-GD is call: engineering. One is bad designed with lot of components. The other properly engineered with few.
Don't argue with him. Let him design a dac without testing.
 

Krunok

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I was talking about your garden, not your pub.

Well, from what I remember most of the pubs in UK are older than your Declaration of Independence so there must be a bunch of fairries living in each of them! :D
 

LTig

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Wait a Second... If this stands for No Feedback design, then this DAC is freaking good!

This No Feedback Design stuff is utter BS. Except for maybe a few triode tubes the inherent gain of electronic components is so high that one must use negative feedback to get a working circuit in the first place.

I would expect that the output stage of almost any DAC chip uses negative feedback, so if negative feedback is the bottleneck for some magic sound features then they are already lost there, and no amount of No Feedback Design is able to restore them afterwards.
 

SIY

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I admit that I haven't tried a Croatian pub yet.
 

garbulky

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This No Feedback Design stuff is utter BS. Except for maybe a few triode tubes the inherent gain of electronic components is so high that one must use negative feedback to get a working circuit in the first place.

I would expect that the output stage of almost any DAC chip uses negative feedback, so if negative feedback is the bottleneck for some magic sound features then they are already lost there, and no amount of No Feedback Design is able to restore them afterwards.
If I'm gathering this right you are saying that no feedback dacs still must use negative feedback for the output stage and this is negates whatever advantage of no feedback in the dac? Could you elaborate more?
 

JohnYang1997

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If I'm gathering this right you are saying that no feedback dacs still must use negative feedback for the output stage and this is negates whatever advantage of no feedback in the dac? Could you elaborate more?
The so-called no negative feedback is local degeneration and can have some local feedback. Just no global feedback, which is the most effective feedback to decrease distortion. And just forget everything else, low distortion is low distortion. The waveform is the waveform. Anything without back up of measurements is bullshit.
 

Krunok

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I admit that I haven't tried a Croatian pub yet.

You haven't lost a lot as we don't have pub tradition here. But what I can recommend, if you ever get a chance to visit, are small, typically run by a family, restaurants that serve local food and wine. You may be pleasantly surprised there.. :)
 
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SIY

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You haven't lost a lot as we don't have pub tradition here. But what I can recommend, if you ever get a chance to visit, are small, typically run by a family, restaurants that serve local food and wine. You may be pleasantly surprised there.. :)

When I was working near Vienna, there were similar deals, Heurigen. Absolutely wonderful.
 

Krunok

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When I was working near Vienna, there were similar deals, Heurigen. Absolutely wonderful.

Exactly the same concept. Not so long ago we were in the same country Austro-Hungarian Empire, or "K und K monarchy" as it was popularly called, hence the similarities. In local dialect spoken here in Zagreb you can still find few hundreds of german origin words. :)
 

LTig

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If I'm gathering this right you are saying that no feedback dacs still must use negative feedback for the output stage and this is negates whatever advantage of no feedback in the dac?

Yes, this is what I expect as long as you use a ready made DAC chip. Even if its output stage is a simple emitter follower (what I strongly doubt) it uses 100% local negative feedback to get a gain of 1.

Could you elaborate more?

Sure. First we have to differ between the DAC as a complete audio unit and the DAC chip itsself. The DAC unit contains digital electronics before the DAC chip and analog electronics behind the DAC chip, which is fed by the analog outputs of the DAC chip.

Now, if the DAC chip uses negative feedback in its analog output stage and this somehow removes some magic parts of the sound quality I cannot see how the following analog stage without negative feedback could possibly restore these magic parts which had got lost in the DAC chip. It's always the weakest part of the chain which dictates the final sound quality.

Of course, when you think of how may amplifying stages with negative feedback the music signal passes before it is finally digitized there cannot be any magic sound quality left at all.
 

garbulky

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Yes, this is what I expect as long as you use a ready made DAC chip. Even if its output stage is a simple emitter follower (what I strongly doubt) it uses 100% local negative feedback to get a gain of 1.



Sure. First we have to differ between the DAC as a complete audio unit and the DAC chip itsself. The DAC unit contains digital electronics before the DAC chip and analog electronics behind the DAC chip, which is fed by the analog outputs of the DAC chip.

Now, if the DAC chip uses negative feedback in its analog output stage and this somehow removes some magic parts of the sound quality I cannot see how the following analog stage without negative feedback could possibly restore these magic parts which had got lost in the DAC chip. It's always the weakest part of the chain which dictates the final sound quality.

Of course, when you think of how may amplifying stages with negative feedback the music signal passes before it is finally digitized there cannot be any magic sound quality left at all.
This is very interesting. Thanks for the additional detail!
I didn't know there were different stages that have negative feedback in the dac. I have to confess I can't quite get the full picture because there is a lot of things you mentioned I don't know about (like global versus local negative feedback, a gain of 1, simple emitter follower, or the various amplifying stages present in a dac. If you or anybody wishes to talk about or link to that, I would appreciate it. Thanks
 

Krunok

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This is very interesting. Thanks for the additional detail!
I didn't know there were different stages that have negative feedback in the dac. I have to confess I can't quite get the full picture because there is a lot of things you mentioned I don't know about (like global versus local negative feedback, a gain of 1, simple emitter follower, or the various amplifying stages present in a dac. If you or anybody wishes to talk about or link to that, I would appreciate it. Thanks

In most DACs you will find a stage called I/V which amplifies the analog signal from the DAC chip and involves negative feedback. ;)
 

garbulky

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In most DACs you will find a stage called I/V which amplifies the analog signal from the DAC chip and involves negative feedback. ;)
Is this what they are talking about when they say "no feedback dac" ?
 

SIY

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Is this what they are talking about when they say "no feedback dac" ?

Sometimes they use an I/V converter if the DAC is current output. If the DAC is voltage output, the feedback is inside the DAC chip already. But you don't have to worry about it if you can't see it, apparently.

The "no feedback" thing is 50% pernicious superstition and 50% outright lie.
 

Krunok

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Sometimes they use an I/V converter if the DAC is current output. If the DAC is voltage output, the feedback is inside the DAC chip already. But you don't have to worry about it if you can't see it, apparently.

The "no feedback" thing is 50% pernicious superstition and 50% outright lie.

Exactly. Btw, my Topping D10 uses es9018k2m and uses opamp for I/V.
 

Krunok

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The "no feedback" thing is 50% pernicious superstition and 50% outright lie.

Btw, IIRC that story about negative feedback being a bad thing dates to 1970's or early 80s when there were some problem with amplifier oscilations. I think there was a guy (from Finnland?) who wrote an article about that but that problem has been rectified long ago.
 
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