FX-Audio Tube 02 Pro Review (Headphone Amp)

[Saponetto]

Fine approach.

 

[JaMaSt]

If it were harmonics that would be reaching audible levels

It's not my thesis that the 2nd and 3rd order harmonics are audible - but rather that the power they consume by the amp affects all other frequencies across the spectrum - and this is what gives the tubes their tubbie-ness. Just a thought.....

 

[001]

Before you say, "but your test was not blind," I will remind you that neither are all the remarks about the sound being euphonic!

Of course not. This is Monti Czardas being euphonic. He's *really* good at it.

 

[solderdude]

It's not my thesis that the 2nd and 3rd order harmonics are audible - but rather that the power they consume by the amp affects all other frequencies across the spectrum - and this is what gives the tubes their tubbie-ness. Just a thought.....

They can't .. and the 'power' consumed by harmonics is 40dB or 60dB lower than the original signal (you would need an amp with shitloads of distortion for that)

To get an idea... assuming a headphone amp with 5mW average power draw (decently loud) the 'power' of the harmonics will be in the order of 10μW or so (max)

Also the harmonics won't be audible with tube amps because mostly they will be 2nd and 3rd mostly. All instruments/voices etc have harmonics that will be higher than what an amp will add.

The harmonics are not the problem with amps. That will not make anything sound better or worse. The biggest issue is inter-modulation distortion.
With harmonic distortion there will always also be inter-modulation (as soon as more than one sine wave is present which there always is).
These create frequencies that are not harmonically related and can fall outside of masking by music (with certain recordings) and these are never ' pleasant' nor 'increase sound quality'.

 

[GWolfman]

Sorry for the late reply, but I've been curious about this for a while now. Thanks!

 

[Snix]

Just got one at dirt cheap <50$.

Subjectively, tl;dr

As a headphone amp : 6/10 (-> AKG 701 Austria lot), kinda meh. Tubey distortion sth sth aside, it sounds muddy or adding 2 untransparent layers of veils at best.
As a preamp : 8/10 (SMSL D6 / Topping Dx7 Pro -> Tube 02 -> Aiyima A07 Pro / T9) it works well as a preamp (for the same price level amps, that is). 2 inputs, ok potentiometer. Didn't necessarily feel the significant tubey sound or anything (I'm an ASR heretic and having a separate tube setup)

All in all, imo, is it good for 50$? Kinda yeh as a preamp for a cheap an economy setup.
Would this make your system sound like heretic tube nirvana setup? No.

 

[GGroch]

Just got one at dirt cheap <50$.

I just got one on a similar deal. It looks nice, and its pretty versatile with dual line inputs and a gain switch (although the differences in gain are pretty small). Does not sound bad to me, and as Amir said, they did the faux tube glow pretty well.

On the topic of faux. This post says the GE Jan 5725 tubes are fake. Are all new GE 5725 tubes fake now? I find no discussion of the topic on the interwebs. They are certainly very common and cheap for a tube that hasn't been made in many decades. I think the story is that they are old new stock from defense department stockpiles. It is hard to believe they would have set aside all that many and I am sure that featuring US made tubes increases sales.

 

[Snix]

they did the faux tube glow pretty well.

Yeh,,,, nah, that's kinda turn me off quite a bit tbh

But it is indeed not a bad piece of electronics to throw in the system with 50$ budget, given if you need any of the functions it provides.

Also, I have a habit of throwing away the stock tubes of these kind of kits asap (especially seeing included "made in USA" tubes xD)
I swapped to Voskhod 6ZH1P-EV, so I didn't have privilege to enjoy the faux GE Jan 5725 just yet .

 

[GXAlan]

Are all new GE 5725 tubes fake now? I find no discussion of the topic on the interwebs. They are certainly very common and cheap for a tube that hasn't been made in many decades. I think the story is that they are old new stock from defense department stockpiles. It is hard to believe they would have set aside all that many and I am sure that featuring US made tubes increases sales.

Not the same tube, but there are stores like this which talk about having an inventory of 70,000

Pair GE 5654W vacuum tubes | Riverstone Audio

Closely matched pair (2 tubes) of vintage military-grade NOS JAN GE 5654W vacuum tubes. These carefully selected tubes can help bring out the best musical fidelity in amplifiers and pre-amps that utilize 6J1, 6AK5, 5654 and EF95 tubes.

www.riverstoneaudio.com

During WWII, the size of the military was unfathomably big by today’s standards and tubes powered everything…

Nonetheless, it’s pretty easy to spot suspicious 5725’s being sold. Tubes don’t need to be stored in climate controlled environments so the cardboard boxes should signs of deterioration. What you see is unreasonably clean looking boxes with unreasonably perfect labels at times…

 

[KaeliKoo]

I also picked up this unit at the $50 quite a few months ago, didn't really test or try it out much, too many toys...have never used it as a HP unit. I've noticed that putting in front of any of the 6 class D amps I have improves the soundstage quite a bit. Bass extension is certainly improved and has more punch. Totally subjective, working out nice tho

 

[dasdoing]

here is an intresting digital i/o "saturator": https://www.freqport.com/