Flux FA-12 Review (headphone amplifier)

[Deleted member 26571]

Why does it have to be class A? You like the luxurious feeling of losing at least 50% of your power to heat the room?

A Class AB output stage has an unavoidable nonlinearity in the crossover region that can be minimized, but not eliminated, by choosing the proper bias current.

A Class A output stage, on the other hand, has much more constant gain and no nasty ripples in the center. In the figure below, trace "A" is the Class A output stage, and trace "B" is the optimally-biased Class B output stage. (Images courtesy of D. Self, "Audio Power Amplifier Design," Sixth Edition.)

Negative feedback substantially reduces but does not eliminate the crossover distortion. You need special tricks to achieve super-low distortion figures at high frequencies while avoiding instability. By certain objective standards, Class A is "better." For an amplifier required to produce no more than one or two Watts, the wasted power is inconsequential.

As always, your mileage may vary.

 

[JohnYang1997]

A Class AB output stage has an unavoidable nonlinearity in the crossover region that can be minimized, but not eliminated, by choosing the proper bias current.

View attachment 140768A Class A output stage, on the other hand, has much more constant gain and no nasty ripples in the center. In the figure below, trace "A" is the Class A output stage, and trace "B" is the optimally-biased Class B output stage. (Images courtesy of D. Self, "Audio Power Amplifier Design," Sixth Edition.)

View attachment 140769
Negative feedback substantially reduces but does not eliminate the crossover distortion. You need special tricks to achieve super-low distortion figures at high frequencies while avoiding instability. By certain objective standards, Class A is "better." For an amplifier required to produce no more than one or two Watts, the wasted power is inconsequential.

As always, your mileage may vary.

Reality of it is is that most "class A" amps are just class AB amplifier in Dougals Self's category.

Another thing is that ultimately what matters is the distortion in the end. Any feedback will introduce higher order harmonics. In a meaningful bandwidth of 20khz there's nothing special about crossover distortion. When enough feedback is added and when distortion is lower than -130dB with load, it's totally inaudible.

 

[Deleted member 26571]

Reality of it is is that most "class A" amps are just class AB amplifier in Dougals Self's category.

Another thing is that ultimately what matters is the distortion in the end. Any feedback will introduce higher order harmonics. In a meaningful bandwidth of 20khz there's nothing special about crossover distortion. When enough feedback is added and when distortion is lower than -130dB with load, it's totally inaudible.

I understand. I assume NFCA is something like nested differentiating feedback loops. That's what I meant by "special tricks." Everything is a tradeoff, but I can't argue with your results.

I like to build my own gear, so my priorities are a little different.

Edit: You might find this amusing. My HPA is about fifteen times the physical volume of an L30/E30. Makes less power, too, and more distortion. I'm very happy with this setup. Sounds extremely good.

 

[Iggnasty]

A Class AB output stage has an unavoidable nonlinearity in the crossover region that can be minimized, but not eliminated, by choosing the proper bias current.

View attachment 140768A Class A output stage, on the other hand, has much more constant gain and no nasty ripples in the center. In the figure below, trace "A" is the Class A output stage, and trace "B" is the optimally-biased Class B output stage. (Images courtesy of D. Self, "Audio Power Amplifier Design," Sixth Edition.)

View attachment 140769
Negative feedback substantially reduces but does not eliminate the crossover distortion. You need special tricks to achieve super-low distortion figures at high frequencies while avoiding instability. By certain objective standards, Class A is "better." For an amplifier required to produce no more than one or two Watts, the wasted power is inconsequential.

As always, your mileage may vary.[/QUO

I think I will be happy with my purchase

 

[Deleted member 26571]

I think I will be happy with my purchase

I think you will, too. It's beautifully designed and built, the performance is superb, and it's an example of wonderful old-school technology.

 

[Deleted member 26571]

Nice; but are you saying adjusting volume causes click and pops? My Bottleheqd DIY stepped volume control manages to avoid that somehow, so maybe it could be fixed here too

The FA-12 uses a six-section relay attenuator. Your Bottlehead stepped attenuator uses a rotary switch with shorting contacts. It's a completely different technology. Relay attenuators have certain advantages, but by nature they tend to make clicks and pops when changing levels. It's just the nature of the beast. Some implementations are better than others, so I read.

 

[Iggnasty]

The FA-12 uses a six-section relay attenuator. Your Bottlehead stepped attenuator uses a rotary switch with shorting contacts. It's a completely different technology. Relay attenuators have certain advantages, but by nature they tend to make clicks and pops when changing levels. It's just the nature of the beast. Some implementations are better than others, so I read.

I ordered the FA-22, I hope it has similar components…. I do agree with you, build quality alone…..

 

[Hemi]

This thread started after I sent my FA-12 to Amir. I had been impressed with its sound since the first time I turned it on and just wanted more people to know about this amp. I didn't care much how well it would measure, but I was glad to know that it turned out to be a well-engineered device. When I purchased the FA-12, I already had the Topping A90 and Schiit Jot2. The current situation is that I don't enjoy listening to them anymore. They both are great amps, but none of them can produce the sound stage the Flux does – it's larger in all the three dimensions. Sometimes, it makes me forget I have headphones on my head – thanks to a recently purchased Audeze LCD-XC. Before them, I enjoyed music with the MrSpeakers Ether CX, now I simply dive into the sea of sound and don't want to return to shore for hours.

My FA-12 is connected to the Yggy A2/U. I know it's not the most favorite DAC here, but it made want to sell my D90 and RME-2 DAC FS. Distortion-wise, they were among the ASR champions, but the timbre of some instruments seemed to sound a little bit unnatural to my ears – that's why I decided to give the Yggy a try. I would have been super happy to find out that the much cheaper DACs sound better or the same as the $2.5k piece of Schiit, so I could put that money back on my bank account and forget about the existence of expensive R-2R DACs forever, but that didn't happen. I do believe in scientific measurements and I've seen all those graphs with my own eyes, but my ears simply refuse to accept them, and I can't help it.

 

[Veri]

My FA-12 is connected to the Yggy A2/U. I know it's not the most favorite DAC here, but it made want to sell my D90 and RME-2 DAC FS. Distortion-wise, they were among the ASR champions, but the timbre of some instruments seemed to sound a little bit unnatural to my ears – that's why I decided to give the Yggy a try. I would have been super happy to find out that the much cheaper DACs sound better or the same as the $2.5k piece of Schiit, so I could put that money back on my bank account and forget about the existence of expensive R-2R DACs forever, but that didn't happen.

In a way that is funny to me because all of Schiit's "R2R" DACs use chips not even designed for audio but rather for instrumentation. They have objectively pointed out issues in both distortion, IMD, ... just overall not a top performer. They could actually tweak the chips to be more suitable for audio using de-glitching tech. But they choose not to and just use them as-is, with all flaws in tact.

So forgive me being sceptical about these specialised, non-audio Analog Devices chips somehow producing a "timbre" not found in IC chips actually purpose-made for audio. You're not hearing a more natural/real/timbre-precise sound. Do you think the people producing and mastering music are listening to these flawed distortion machines? How could one then think that the Yggy is more truthful? I think a proper volume matched controlled listening test would surprise you with the differences you now think are so clearly there.

https://www.stereophile.com/content/schiit-audio-yggdrasil-da-processor-measurements
"the overall shape of the reconstructed sinewave is good [...]but you can see significant errors at the signal's zero-crossing points"
"the Schiit clipped with signals higher than –10dBFS into the punishing 600-ohm load (fig.9). I then tested the Yggdrasil for intermodulation distortion with an equal mix of 19 and 20kHz tones (fig.10), and while the actual intermodulation products were between 90 and 100dB below the signal's peak level, the noise floor again looked ragged"
"It's difficult to sum up the Schiit Yggdrasil's measured behavior. While the processor's analog circuitry is superbly well designed, its digital circuitry appears to have problems with high-level, high-frequency tones, and with the LSBs of 24-bit data".

Yeah, what a great DAC...

 

[Hemi]

In a way that is funny to me because all of Schiit's "R2R" DACs use chips not even designed for audio but rather for instrumentation. They have objectively pointed out issues in both distortion, IMD, ... just overall not a top performer. They could actually tweak the chips to be more suitable for audio using de-glitching tech. But they choose not to and just use them as-is, with all flaws in tact.

So forgive me being sceptical about these specialised, non-audio Analog Devices chips somehow producing a "timbre" not found in IC chips actually purpose-made for audio. You're not hearing a more natural/real/timbre-precise sound. Do you think the people producing and mastering music are listening to these flawed distortion machines? How could one then think that the Yggy is more truthful? I think a proper volume matched controlled listening test would surprise you with the differences you now think are so clearly there.

https://www.stereophile.com/content/schiit-audio-yggdrasil-da-processor-measurements
"the overall shape of the reconstructed sinewave is good [...]but you can see significant errors at the signal's zero-crossing points"
"the Schiit clipped with signals higher than –10dBFS into the punishing 600-ohm load (fig.9). I then tested the Yggdrasil for intermodulation distortion with an equal mix of 19 and 20kHz tones (fig.10), and while the actual intermodulation products were between 90 and 100dB below the signal's peak level, the noise floor again looked ragged"
"It's difficult to sum up the Schiit Yggdrasil's measured behavior. While the processor's analog circuitry is superbly well designed, its digital circuitry appears to have problems with high-level, high-frequency tones, and with the LSBs of 24-bit data".

Yeah, what a great DAC...

I think there's nothing wrong with being skeptical. I'll take my turn now

Since I have the latest version of Yggy with the Unison USB module and newer firmware, is there a chance it would show better results than the older version reviewed on Stereophile?

As for the sound recording, sound engineers 30-40 years ago mastered music using audio analyzers that were not as advanced as the modern devices, but anyway, we enjoy this music. I don't have a degree in technical studies, but I think that minor signal imperfections the Yggy has simply dissolve in the noise floor of many records.

I was comparing the D90, RME-2 and Yggy for 4 months. It wasn't a proper volume matched controlled listening test, but I tried hard to make myself like the sound signature of the solid state DACs because they were much cheaper, smaller, and because of the metrics on this website. My ears and brain voted for Yggy almost every time I did those A-B listening sessions.

 

[Veri]

I think there's nothing wrong with being skeptical. I'll take my turn now

Since I have the latest version of Yggy with the Unison USB module and newer firmware, is there a chance it would show better results than the older version reviewed on Stereophile?

As for the sound recording, sound engineers 30-40 years ago mastered music using audio analyzers that were not as advanced as the modern devices, but anyway, we enjoy this music. I don't have a degree in technical studies, but I think that minor signal imperfections the Yggy has simply dissolve in the noise floor of many records.

I was comparing the D90, RME-2 and Yggy for 4 months. It wasn't a proper volume matched controlled listening test, but I tried hard to make myself like the sound signature of the solid state DACs because they were much cheaper, smaller, and because of the metrics on this website. My ears and brain voted for Yggy almost every time I did those A-B listening sessions.

-The digital (transport and jitter) part is probably improved a lot but the other issues are still there
-That is a fair point of course, good music is good music. But I'm very sceptical of these devices that somehow make good music.. 'more' good
-Of course if you love everything about the Yggy there is no harm done. In my personal experiences these feelings are terribly subjective though and sometimes you realise how much of it is fantasy.

Anyway, not attacking your experience in any way. I just find it curious why Schiit insists on making their multibit stuff the way they do. I wish I could find the post about de-glitching these industrial AD chips though, there was actual research done into it but it's probably a (relatively) huge cost to purpose-fit these chips rather than using parts explicitly made for audio in a plug-and-play manner.. but yeah people still believe tweaking and building around resistor ladders somehow make the sound better though. I've owned vintage DACs, auditioned soekris/holo audio DACs. I've not heard this magic. Sure it sounds good but why shell out so much end of off-topic from me!

 

[DeepSpace57]

When seen the measurements of Bifrost 2, you would think how noisy it is. In fact, there is no noise at all. Indeed it provides a bit euphonic sound, which makes me think a lot to buy it. I have never tried Yggy.
If i were in US, BF2 would be my DAC. I think Schitt should care of European customers too. No deny how musical its house sound is. I ve heard many amps including Singxer class a. No drum kick no buy from me!!! At Guardians of Asgards, many fail to sound precisely the kicks. @Hemi i just wonder how Flux Fa-12 performs at heavy metal music, especially drum kicks at 2:03 (Rise of the chaos wizard@Gloryhammer ) and at 0:58 to 1:20 (Twilight of thunder god@Amon Amarth). Is it meaty/thick/ presented-seperated well ?

 

[Veri]

When seen the measurements of Bifrost 2, you would think how noisy it is. In fact, there is no noise at all. Indeed it provides a bit euphonic sound, which makes me think a lot to buy it. I have never tried Yggy.
If i were in US, BF2 would be my DAC. I think Schitt should care of European customers too. No deny how musical its house sound is. I ve heard many amps including Singxer class a. No drum kick no buy from me!!! At Guardians of Asgards, many fail to sound precisely the kicks.

Wow. Erm, you sure drank the kool aid.

 

[windcaller]

-The digital (transport and jitter) part is probably improved a lot but the other issues are still there
-That is a fair point of course, good music is good music. But I'm very sceptical of these devices that somehow make good music.. 'more' good
-Of course if you love everything about the Yggy there is no harm done. In my personal experiences these feelings are terribly subjective though and sometimes you realise how much of it is fantasy.

I have been here long time as guest.. just got registered.

I think that explains why you care so much those 'measurement' only

Someone might call you lucky man as having golden ears So I think that is blessing, really!

 

[Veri]

I have been here long time as guest.. just got registered.

I think that explains why you care so much those 'measurement' only

Someone might call you lucky man as having golden ears

Well I don't know, when I audition some headphones or speakers regardless of price, the ones I "like" do correlate to the ones Amir measured as good performing, sticking close to targets like Harman, does that quantify as have good/gold ears? Although I did like the Ananda a lot.. which wasn't stellar on paper.
Once you know good audio it's just easy to discern sub-boosted "consumer" gear. Or badly clipping; terribly mastered music.
On the other hand, distortion in things like DACs tends to be orders of magnitude lower than the speakers/headphones. So having a hard time "appreciating" this performance boost. Also don't really hear what's "pleasing" about Class A or tubes, the transducer still sounds like the transducer to me. YMMV

 

[Snoopy]

So are the fluxlabs amps save to use? Or is it a potential death trap with the ground that is not connected?

 

[Jmm22]

So are the fluxlabs amps save to use? Or is it a potential death trap with the ground that is not connected?

Interested in this too. Was looking at the FA-10 for my HE, but may just go with a speaker amp that I can use for those and my desktop speakers.

Edit: apparently, you can request a ground power unit be installed when you order from Fluxlabs

 

[Hemi]

So are the fluxlabs amps save to use? Or is it a potential death trap with the ground that is not connected?

I still own the FA-12 Amir tested and I also purchased the Volot, their flagship headphone amp, last year, which has the ground switch. I've had zero issues with both units.