Flux FA-12 Review (headphone amplifier)

[LTig]

Company advertises bandwidth up to 1 Mhz. I don't test that high but the unit has very wide bandwidth:
View attachment 115160

I wonder about the slight rise starting 30 kHz. This is quite strange for a solid state device. Could this stem from a resonance higher up and might this lead to instability under specific conditions?

 

[amirm]

@amirm I noticed the output isn't 4VAC, it's >4.2V. Doesn't this possibly provide an unfair advantage on the SINAD measurement? Granted, some improve, some diminish, with higher output. Normally it's much close to or exactly at 4V.

The steps on its attenuator are too coarse so I could not get 4 volts. One notch lower resulted in 3.5 volts or so. So I decided to give it slight advantage with 4.2 volt.

 

[amirm]

I wonder about the slight rise starting 30 kHz. This is quite strange for a solid state device. Could this stem from a resonance higher up and might this lead to instability under specific conditions?

I noticed that too. It may have that issue.

 

[Noob]

I am also an audio technician and a graduated electrical engineer. I haven't been "misinformed", but you did not reply to my question. Let's say audio glossary may vary slightly depending on what we are talking about, but that's not really the point. A warm headphone or speaker, very linked to the frequency response, elevated in the upper bass/low mid region. Can you make this guitar warmer? well kinda let's agree with "frequency content" rather than frequency response and yes harmonic distortion change the frequency content and adding a bit of tasteful distortion may somewhat, but it's a stretch, make the tone sound warmer (or less bright), but come on, you know full well that if a guitarist ask you to make his guitar warmer... You reach to your EQ first, please...In all cases, it don't mean make my guitar more distorted. Now, we are talking of an amp with a THD at 82 dB below signal, with no indication that it's frequency dependant. I am not saying that it's not audible, it could be, but this indication alone is certainly not something that can tell us that it is aimed at molding the tonal signature.Or that it's a "trick to maximise distortion while minimizing noise". It is hifi, with a distortion level lower than anything from 30 years ago, and much much lower than the typical tube colorful amps That's why I asked if you heard it.... Last thing, first time in my 20 years carreer that I hear reverberation is saturation...

Ok, seems I missed your point.

I still don't really know what your point is. One amp measures better, but you believe the one that measures worse is actually the better amp or at least the better purchase value. I asked why. I still have not received an answer.

And I am surprised you don't consider effects like reverb in the category of saturation. It's one of the most common techniques used both live and in studio to create tonal saturation on both vocals and instruments. In fact, for drums in particular, I don't think I have heard of any other technique used more frequently than a nice plate reverb to make drums sound larger and fuller.

That you have gone 20 years in the business without even coming across the mere concept is rather shocking to me.

I have learned something new today.

 

[PeteL]

Ok, seems I missed your point.

I still don't really know what your point is. One amp measures better, but you believe the one that measures worse is actually the better amp or at least the better purchase value. I asked why. I still have not received an answer.

And I am surprised you don't consider effects like reverb in the category of saturation. It's one of the most common techniques used both live and in studio to create tonal saturation on both vocals and instruments. In fact, for drums in particular, I don't think I have heard of any other technique used more frequently than a nice plate reverb to make drums sound larger and fuller.

That you have gone 20 years in the business without even coming across the mere concept is rather shocking to me.

I have learned something new today.

I am not the one that said the one that measure worse is the better amp. I just wanted to know why you said it was warmer that's all. I use reverb all the time, to create depth, a spatial image, a 3 dimensional stage. Reverb is simply has you said, the decay. And is also a natural physical characteristic of a room or space. Saturation is clipping, more likely if we talk of it as something positive, analog soft clipping or tape saturation, but basically if it saturates, you're in the red. I don't know other usage for the term.

Edit: But I will give you this one, yes sometime, subtle tube or tape saturation maybe referred to as adding "warmth" I kinda get where you were going with this, and yes also somehow reverb can, but that's more of a stretch make a performance less dry, more smooth so maybe, warm is not totally unheard in this context, but I wouldn't use it, I use wet or big...

 

[Hemi]

Safety ground from mains is left disconnected on the IEC jack! Why or why? They have nice crimping on the other two terminals. They should have finished the job with proper grounding of the third terminal.

I reached out to Flux with a question regarding the FA-12 being not grounded, and was told that the safety ground can be installed upon request when you order your amp. All their devices have double or triple insulation, but they still highly recommend to properly ground the source device. Their more expensive units have a switch that disconnects the ground.

 

[restorer-john]

I reached out to Flux with a question regarding the FA-12 being not grounded, and was told that the safety ground can be installed upon request when you order your amp. All their devices have double or triple insulation, but they still highly recommend to properly ground the source device. Their more expensive units have a switch that disconnects the ground.

It is my understanding that if a 3 pin IEC chassis fitting is present, the device MUST be chassis earthed or it is not a compliant product for sale.

A double insulated and unearthed product using an IEC style socket should use a two pin (C17/C18) fitment instead:

The interior shots of the product do not show double or triple insulation. In fact there appears to be no insulation on the fuse holder, in rush resistor, or underneath the mains PCB to the chassis. There should be a layer of elephant-hide under the PCB. It would not even qualify for single insulation with an earth IMO.

 

[Hemi]

The guys at Flux seem to be very responsive. I believe if someone more knowledgeable (I'm only a graphic designer ) in this subject asks them about how they managed to isolate the internals, they will explain that from a technical perspective.
Here's their FB page https://www.facebook.com/fluxlabacoustics

 

[Noob]

I am not the one that said the one that measure worse is the better amp. I just wanted to know why you said it was warmer that's all. I use reverb all the time, to create depth, a spatial image, a 3 dimensional stage. Reverb is simply has you said, the decay. And is also a natural physical characteristic of a room or space. Saturation is clipping, more likely if we talk of it as something positive, analog soft clipping or tape saturation, but basically if it saturates, you're in the red. I don't know other usage for the term.

Edit: But I will give you this one, yes sometime, subtle tube or tape saturation maybe referred to as adding "warmth" I kinda get where you were going with this, and yes also somehow reverb can, but that's more of a stretch make a performance less dry, more smooth so maybe, warm is not totally unheard in this context, but I wouldn't use it, I use wet or big...

I see where the confusion initiated. I got usernames confused. You were indeed not the one who said the FA-10 is better.

And I agree "wet" and "big" are the more typical terms used when talking about effects. But effects can effect a song or instrument in more ways than one. Like I can have reverb with a very "big" and "wet" sound but still most of the tonal character in the highs and it would be adding a bit of coolness or airyness or sparkle along with the bigness and wetness. (lol this is hilarious to talk about. The terms just feel so silly when written out.)
And I could have another reverb that doesn't extend the highs as much but rather extends more of the lower mids, and being equally big or wet can add warmth.

I hope that explains better how I was thinking of the term.

 

[Francis Vaughan]

It is my understanding that if a 3 pin IEC chassis fitting is present, the device MUST be chassis earthed or it is not a compliant product for sale.

Indeed, this is my understanding as well.
Compliance and safety standards seem to have vanished in the new internet age of on-line purchasing. There is nobody carrying the can for responsibility when a dangerous, non-compliant, item is imported. So we are seeing no end of lethal devices for sale. Just grab a couple of Big Clive's You Tube video's to see the grimly hilarious death dealing merchandise he tears down.

As much as one has some sympathy for a small cottage industry HiFi equipment vendor, and the costs of getting the needed certifications, not even bothering to design the thing to be compliant in the first place is inexcusable. This amp would not pass safety specifications in just about every market on the planet. But selling it on-line avoids difficult questions, at least for now. At least until the first fatality. Optional installation of a ground cheating switch is even more insane. Getting hum free amplifiers to work is not exactly a new science. Just careful layout and an understanding of how the various forms of interference work is needed. Potentially lethal workarounds are again, inexcusable.

The criteria for double insulated design are well documented, and not really all that onerous. But a bit of paint or anodising does not count.

Amir has taken other less than safe build quality devices to task for arguably lesser flaws. This amp is lovely in its execution, all the way up to manifest breach of well understood safety design guidance. They can and should fix this. And do so in a manner that would place them on a path to gain proper safety certification. It may not be the place for ASR to beat the drum on this, but IMHO, someone should. Manifest failings in safety design should be called out, and again, IMHO only, disqualify the device from recommendation.

 

[Hemi]

It is my understanding that if a 3 pin IEC chassis fitting is present, the device MUST be chassis earthed or it is not a compliant product for sale.

A double insulated and unearthed product using an IEC style socket should use a two pin (C17/C18) fitment instead:
View attachment 115295

The interior shots of the product do not show double or triple insulation. In fact there appears to be no insulation on the fuse holder, in rush resistor, or underneath the mains PCB to the chassis. There should be a layer of elephant-hide under the PCB. It would not even qualify for single insulation with an earth IMO.

According to this rule, the Esoteric from Teac is a non-compliant product too.

 

[Francis Vaughan]

According to this rule, the Esoteric from Teac is a non-compliant product too.

Yup. I had a look at the Esoteric web site. Every device for which there was an internals picture was the same. Yet the manual claimed CE compliance for the European model. I wonder if the pictures are of a generic working, but not certified in any market, version. It would be very interesting to get an internals shot from a commercially sourced item, and not a publicity shot (which are often also pre-production.)

 

[PeteL]

Indeed, this is my understanding as well.
Compliance and safety standards seem to have vanished in the new internet age of on-line purchasing. There is nobody carrying the can for responsibility when a dangerous, non-compliant, item is imported. So we are seeing no end of lethal devices for sale. Just grab a couple of Big Clive's You Tube video's to see the grimly hilarious death dealing merchandise he tears down.

As much as one has some sympathy for a small cottage industry HiFi equipment vendor, and the costs of getting the needed certifications, not even bothering to design the thing to be compliant in the first place is inexcusable. This amp would not pass safety specifications in just about every market on the planet. But selling it on-line avoids difficult questions, at least for now. At least until the first fatality. Optional installation of a ground cheating switch is even more insane. Getting hum free amplifiers to work is not exactly a new science. Just careful layout and an understanding of how the various forms of interference work is needed. Potentially lethal workarounds are again, inexcusable.

The criteria for double insulated design are well documented, and not really all that onerous. But a bit of paint or anodising does not count.

Amir has taken other less than safe build quality devices to task for arguably lesser flaws. This amp is lovely in its execution, all the way up to manifest breach of well understood safety design guidance. They can and should fix this. And do so in a manner that would place them on a path to gain proper safety certification. It may not be the place for ASR to beat the drum on this, but IMHO, someone should. Manifest failings in safety design should be called out, and again, IMHO only, disqualify the device from recommendation.

I agree with everything you said about safety. But as a side note, yes making hum free amplifier is not a new science, but it evolved quite a bit and the how to vary much according to eras, and even from manufacturers from modern days. A hum free amplifier is easy, a hum free "system", unfortunately, not always. A good example is Starting in 2005 with updates as lately of The audio engineering society took a good shot at trying to standardize practice for audio grounding, and the good old star grounding sheme is pretty much gone. Take a look at AES 48 paper if you may:
https://www.aes.org/publications/standards/search.cfm?docID=44

But it's only specifics issue to audio, it doesn't cover the full electrical methods, and it's not about safety, It's an example. You have to recoup different paper to figure what's the "right" way.

Bottom line, not everybody does the same thing.

I am not sure what's the solution to this but yes, double insulated (whatever that is) unearthed designs, is easier.
In the mean time, all the touring sound technicians I know have a few of these in their gig bags, and they are being used more often than we'd think. Not that it's the right thing to do, not that we wouldn't prefer not to, but it's still to this day, unfortunately, a necessity.

 

[sarumbear]

To my knowledge, Germany follows the same CE regulations than the rest of the European Union. This amp is for the European market. Metal chassis, no earth pins, 230V

View attachment 115215

You can self certify CE mark. It’s not a 3rd party test. The seller simply relinquish their defence of a possible litigation.

 

[PeteL]

You can self certify CE mark. It’s not a 3rd party test. The seller simply relinquish their defence of a possible litigation.

Yes, you can self certify, but you still have to deposit the documentation, extensive documentation, that demonstrates that you comply. Self declaration don't mean you can slap the logo on anything.

 

[sarumbear]

Yes, you can self certify, but you still have to deposit the documentation, extensive documentation, that demonstrates that you comply. Self declaration don't mean you can slap the logo on anything.

As a person who self certified half a dozen (video) equipment I can assure you it’s no big deal. CE mark simply indicates that the product may be sold freely in any part of the European Economic Area, regardless of its country of origin. Whoever signed the forms takes responsibility that product is compliant with relevant regulations. It’s NOT a certification.

 

[PeteL]

As a person who self certified half a dozen (video) equipment I can assure you it’s no big deal. It simply indicates that the product may be sold freely in any part of the European Economic Area, regardless of its country of origin. Whoever signed the forms takes responsibility that product is compliant with relevant regulations. It’s NOT a certification.]

Didn't you have to obtain the ROHS certificates for all the parts in your product? Just this part, and it's far from all, is hell, getting all the part manufacturers to cooperate. Personally I was buried in work for this, I don't get how it would be different in the video industry.

 

[sarumbear]

Didn't you have to obtain the ROHS certificates for all the parts in your product? Just this part, and it's far from all, is hell, getting all the part manufacturers to cooperate. Personally I was buried in work for this, I don't get how it would be different in the video industry.

It’s a lot of paperwork, I agree but manufacturing involves paperwork, lots of it. It has been like that for decades. If you decide to manufacture and decide to sell globally, you should accept the burden. OR, risk the consequences and self certify. As you know, there’s no registry for CE marks.

 

[amirm]

I wonder if the pictures are of a generic working, but not certified in any market, version.

Seems to be the case. I searched and found this picture by an owner:

We clearly see a ground terminal together with ferrite cores they added to pass emissions tests.

Still strange to see soldered terminals on the IEC jack though. Standard is spade terminals.

 

[amirm]

Is this the same product pictured earlier on with the red PCBs?

It looks pretty close to it. This is the N-05 streamer. https://forum.polkaudio.com/discussion/186675/esoteric-n-05