Review and Measurements of Audio-gd NFB28.28 DAC and Headphone Amp

[BurritoJustice]

Mm but that doesn't have XLR pre outs. The ADI-2 DAC does, and XLR pre is more important than balanced headphone out. Is there anything else? I'm strongly thinking I'll compromise and go for the ADI-2 DAC.

The single ended output on the DAC is enough for almost literally anything. I use balanced output (on the Pro or the 789) exclusively with the HE6se, but they are literally orders of magnitude harder to drive than any other headphone you'll ever buy. (53ohm 77dB/mW)

For example the HE560 (43ohm, 90dB) can easily be driven to painful levels.

 

[concorde]

@BurritoJustice I see. It's just I paid extra for my Fostex TH900 to come with a balanced cable. Not the end of the world to not use it.

The "Pro"? Does that mean the ADI-2 Pro? That doesn't seem to have a balanced HP output either. Do you use the rear XLR's?

 

[BurritoJustice]

@BurritoJustice I see. It's just I paid extra for my Fostex TH900 to come with a balanced cable. Not the end of the world to not use it.

The "Pro"? Does that mean the ADI-2 Pro? That doesn't seem to have a balanced HP output either. Do you use the rear XLR's?

The Pro line has two identical headphone amps, so with a custom adapter (can be found online for reasonably cheap, or just DIY) you can run in balanced mode for twice the voltage, output impedance, I believe twice? the amperage, and a minor increase in SNR.

It should be noted that there isn't an implicit benefit to running your headphones balanced, as headphones are naturally balanced (no ground) you are really just driving them deferentially (the difference between two inverse signals creates the voltage across the driver). To the headphones (mechanically), this is identical. This of course doesn't account for specific devices where implementation can show marked gains.

Funnily enough the most significant benefits to "balanced" phone configurations are the improved connector (TRS is a mess compared to XLR4, for various reasons), and the reduce in crosstalk and noise from having separate grounds. As a fun fact, the Benchmark HPA4, though marketed as a balanced amp, is actually run single ended (as opposed to differentially, L-L+) with independent grounds in the XLR4 connector. It is also likely the best measuring amp out right now, given how even stripped back versions can be so potent.


E: I've also now realised I've got quite far off topic, sorry for that

 

[andreasmaaan]

Can you limit the voltage on the rear XLR's to 1.4Vrms (line level)? (My power amp has a sensitivity of 1.4V so I don't want to exceed this when adjusting the volume.)

The line out gain on the Adi-2 DAC can be set at different levels. Finer adjustments can then be made with the volume control on the front. If you fix the gain at +7dBu, that corresponds to about 1.7 V RMS, which should be about right for your power amp.

What if I want to add a subwoofer as well as XLR out going to speakers? How do you keep the volume going up evenly for the speakers + sub? And how would I avoid exceeding 1.4V if there are two outputs going at the same time? Can I split the power evenly (to sub and to power amp)?

I wouldn’t worry too much about the line level exceeding 1.4 V imo. You should leave a little headroom anyway so that you can turn the volume up adequately with quieter recordings.

Re the sub, which sub or sub amp will you be using?

 

[concorde]

@BurritoJustice If you can do that on the Pro can't I use an XLR adapter on the ADI-2 DAC for the TH900? Thanks for your write up

 

[BurritoJustice]

@BurritoJustice If you can do that on the Pro can't I use an XLR adapter on the ADI-2 DAC for the TH900? Thanks for your write up

Yes, you cannot use your headphones balanced with the ADI-2 DAC. My main point is that you don't need to. The single ended output is easily enough to power almost anything, and you don't get much other than output power through a balanced connection.

If you must upgrade to a balanced headphone amp, there are two good options from there. Getting a 789 for use with the DAC, or going up to the pro for the balanced headphones. The Pro is more compact and convenient (and it can do two separate lines out which is useful for a sub), and the 789 has more power and setup versatility (and is a better measuring amp, though their levels of distortion are already below the DAC so the difference is academic).

 

[concorde]

@BurritoJustice Ok. I just wanted balanced as an experiment, due to the noise cancellation, but I can live without it.

The Pro FS and ADI-2 DAC both have 1x Balanced and 1x Unbalanced pre-outs. On the ADI-2 DAC can you only use one of these options at a time, but on the Pro FS you can use both?

If this is the case is there any way I can use a sub with the ADI-2 DAC? Like if I had a sub that can pass XLR, or an XLR splitter or something?

If not - you can use both lines out at the same time on the ADI-2 DAC (XLR to speaker amp ; RCA to sub) - I'm guessing the RCA will be slightly lacking in power compared to the XLR at any time? So I could correct this by increasing sub volume; or can I do it in the DAC settings?

Can the ADI-2 DAC supply enough power to feed both my Crown amp and a sub (I'm assuming that would be 2.8Vrms)?

 

[andreasmaaan]

@andreasmaaan Ok that sounds great. Sub:
Possibly a Rythmik like this: ( http://www.rythmikaudio.com/FV15HP_features.html )
Or a JBL passive like this ( https://jblsynthesis.com/productdetail/s2s-ex.html ) with a second Crown Drivecore amp ( https://www.crownaudio.com/en/products/xls-1502 ). (I also use that exact amp with my speakers.)
Or something else.

The JBL route is probably too expensive though.

If the sub amp has its own gain control (whether part of an active sub or a separate amp), I think you’d be fine outputting the mains via XLR and the sub(s) via RCA from the Adi-2 (or vice-versa).

However, you won’t have separate control over EQ/filters for each output, so you won’t for example be able to high pass the signal to your mains, or EQ the sub(s) without doing the same to your mains. For this reason, if you’re set on using the Adi-2 DAC, i’d recommend an active sub with its own filters (like the Rhythmik), with just one stereo output from the DAC to the sub and then a high-pass filtered output from the sub to speakers.

If you want to output separately to sub and mains and control EQ and filters from the DAC, I’d recommend an active DSP unit with analogue outputs instead of the Adi-2. The MiniDSP SHD might be overkill, but is in the same league (almost) as the Adi-2 in terms of performance (see Amir’s measurements). Other cheaper options should also be audibly transparent. There are members here with more experience with a variety of these units than I have..

 

[concorde]

@andreasmaaan Thanks, very useful info. By the way the Crown amp I use can do low pass / high pass I believe

 

[trl]

http://www.hdfever.fr/2014/07/10/test-oppo-ha-1/#postTabs_ul_51675
https://hometheaterhifi.com/reviews/headphone-amplifier/oppo-ha-1-headphone-amplifier-review/
https://reference-audio-analyzer.pro/en/report/dac/oppo-ha-1.php

Seems a powerful and very low-noise headamp. Few skirts might be seen on measurements around the fundamental, but nothing to worry about. It would be nice to see that toroid shielded and to get rid of the 50/60Hz hum, but at -120dB you'll probably not notice, even with sensitive IEMs.

Some headfier said smoothing about too much heat generated, but this is normal for a Class-A operating amplifier. If inside a 25C room, after intensive listening (>2 hours at moderate-to-high levels with planars) the heat on top of the case is not over 45C then we're fine. As an example: my Matrix HPA-3B was able to rich 50C on top under the above conditions, so...that's pretty high I'd say.

Same black PCB, like the Audio GD, just a better layout (with more air and space between components), not using the same cheap heatsinks, and really good capacitors.

If you find it at a bargain, you might want to listen to it and...maybe you'll get it, it's all about the final price after all.

 

[Figuy1017]

Hum... That's devastating. I owned some AGD products these last two years: DAC 19, NFB 28.38 and R2R-11. I kept none of them (though I have to admit I really liked the warmish "tube" sound of R2R-11). Now, I'm running with an ADI-2 DAC and it's like I just discovered what a clean and neutral sound is.

My experience, in addition to these measurements make things clearer : I will never buy any unit from them again.

I got sucked into subjective measurements of several devices. Owned two versions of the dac19 a MHDT Orchid and. Sh Jot. The Orchid was supposed to be a upgrade to the 19 well it wasnt. Sold it. after seeing terrible measurements for other audio gd I sold my dac19 10th anniversary. as well. The Jot was terrible it had a very 2d sound I found grating. I decided list to subjective reviews was going to break me so decided I need facts not peoples opinion. I’ve been a lot happier and have bought and sold a whole lot less since those days to say the least

 

[Jimster480]

I got sucked into subjective measurements of several devices. Owned two versions of the dac19 a MHDT Orchid and. Sh Jot. The Orchid was supposed to be a upgrade to the 19 well it wasnt. Sold it. after seeing terrible measurements for other audio gd I sold my dac19 10th anniversary. as well. The Jot was terrible it had a very 2d sound I found grating. I decided list to subjective reviews was going to break me so decided I need facts not peoples opinion. I’ve been a lot happier and have bought and sold a whole lot less since those days to say the least

I totally agree. Once I got a high sinad device; I've just kept it for years now.
I've only accumulated the thx 789 and now a geshelli archel2 pro over 2 years. I sold everything else I had and I am just happy with what I have.