[GoneToPlaid]

I recently received this FX-AUDIO Tube-02 Pro from Amazon. It is advertised as being a class A tube amplifier. I do believe that it is. This tube amp's motherboard is the 2021-09-07 version 1.1. This headphone amp comes with GE JAN 5725W tubes. The FX-AUDIO website and the Amazon listing for this amp state that only 6J1 and 6J2 tubes are additionally compatible. I measured both the voltages and the resistance between all seven of the tube socket pins. It turns out that, at least for this amp's version 1.1 motherboard, any EF95 tube can be installed in the FX-AUDIO Tube-02. This has indeed proven to be true since I presently am using Voskhod Rocket 6ZH1P-EV tubes in this amplifier since tube pins 2 and 7 are connected to eliminate the military use of the sharp cutoff feature of the 5725W or equivalent tubes such that the stock 5725W tubes essentially become 5654W tubes in audio operation. Additionally, pins 5 and 6 for the tubes are also connected. I totally love the very clear tube sound since the even order harmonics from the tubes are strong in comparison to the odd order harmonics, and since all harmonics also properly and rapidly decay with increasing frequency. This is just the sort of thing which one desires for a warm yet clear tube sound. The Tube-02 Pro has extremely good signal to noise ratio. Notably, the Tube-02 Pro also does not contain any IC op amps. The output stage is driven by transistors.

I am totally new here. I am hesitant to write my first product review which would include product photos and internal product photos. I hope that someone else evaluates the FX-AUDIO Tube-02 Pro and creates a review for it.

 

[bithloman]

I recently received this FX-AUDIO Tube-02 Pro from Amazon. It is advertised as being a class A tube amplifier. I do believe that it is. This tube amp's motherboard is the 2021-09-07 version 1.1. This headphone amp comes with GE JAN 5725W tubes. The FX-AUDIO website and the Amazon listing for this amp state that only 6J1 and 6J2 tubes are additionally compatible. I measured both the voltages and the resistance between all seven of the tube socket pins. It turns out that, at least for this amp's version 1.1 motherboard, any EF95 tube can be installed in the FX-AUDIO Tube-02. This has indeed proven to be true since I presently am using Voskhod Rocket 6ZH1P-EV tubes in this amplifier since tube pins 2 and 7 are connected to eliminate the military use of the sharp cutoff feature of the 5725W or equivalent tubes such that the stock 5725W tubes essentially become 5654W tubes in audio operation. Additionally, pins 5 and 6 for the tubes are also connected. I totally love the very clear tube sound since the even order harmonics from the tubes are strong in comparison to the odd order harmonics, and since all harmonics also properly and rapidly decay with increasing frequency. This is just the sort of thing which one desires for a warm yet clear tube sound. The Tube-02 Pro has extremely good signal to noise ratio. Notably, the Tube-02 Pro also does not contain any IC op amps. The output stage is driven by transistors.

I am totally new here. I am hesitant to write my first product review which would include product photos and internal product photos. I hope that someone else evaluates the FX-AUDIO Tube-02 Pro and creates a review for it.

just saw audio science reviews measurements on this unit and it seems great and engineered well. are you saying you can interchange any 5725 types of tubes like other pre amps? or is there precautions needed in tube choice? normally many different kinds are compatible without damage. is this not true here? thanks where did you buy this i only see it from china.

 

[GoneToPlaid]

just saw audio science reviews measurements on this unit and it seems great and engineered well. are you saying you can interchange any 5725 types of tubes like other pre amps? or is there precautions needed in tube choice? normally many different kinds are compatible without damage. is this not true here? thanks where did you buy this i only see it from china.

 

[GoneToPlaid]

The 5725 tube direct equivalents are 6AS6W and 6187 tubes. FX-AUDIO says that the 5725 tubes can be replaced with Chinese 6J1 or 6J2 tubes, and that other models are temporarily incompatible. Yet as I mentioned and at least for the version 1.1 motherboards, theoretically any EF95 tube can be used since the motherboard does tie together pins 2 and 7 of each tube. Pin 7, when not tied to pin 2, operates grid 3 as a suppressor grid in order to control the sharp RF cutoff feature of the 5725 tube. Attached is a PDF I made about the Tube-02 Pro tube connections and the measured voltages. Since each tube's pin 2 is connected to pin 7, this effectively negates the 5725 tube's sharp RF cutoff feature. I mentioned that theoretically any EF95 tube can be used in the Tube-02 Pro. I have used GE JAN 5654W tubes and Voskhod 6J1P-EB (6ZH1P-EV) tubes in this preamplifier. Presently I am using the Voskhod tubes.

 

[GoneToPlaid]

Attached are photos of my Tube-02 Pro's circuit board. The circuit board is heavily lacquered, making it hard to see a lot of the circuit board's traces. Note that FX-AUDIO has scraped off the markings on the tops a couple of ICs and off of the tops (non heat sink side) of the output transistors. This is the first time that I have seen FX-AUDIO do this, although admittedly I have only seen closeup circuit board photos for less than a dozen of their products. Perhaps FX-AUDIO is trying to prevent their competitors from quickly duplicating their design? You will also note that FX-AUDIO is using SMD barrel resistors, which have better power handling than flat SMD surface mount resistors, for their "Class A" output stage in order to strongly drive the headphone output jacks. The six large blue film caps are Epcos 3.3 uF 63 volt. The two smaller blue film caps are Epcos 1.1 uF 100 volt. The tubes are operated at +/- 11.7 volts since they are only used for signal processing and not for amplification. Unlike the FX-AUDIO Tube-03 MKII which has dangerous internal operating voltages (+99 volts going to the tube plate and grid 2) when powered on, this Tube-02 Pro merely has +11.7 volts or -11.7 volts going to the tube cathodes, plates, and grids 2 and 3 when powered on. The Tube-02 Pro powers the tube heaters at only 5.4 volts instead of at the nominal 6.3 volts. This is because the tubes are only being used to process signal instead of being used for signal amplification. These low tube voltages strongly imply that the installed tubes should last much longer than the rated nominal lifespan (5000 hours) of the tubes.

 

[GoneToPlaid]

I have been using my Tube-02 Pro for quite a while now, and I love the sound. One nice thing about using tubes for signal processing is that the tubes help to kill the BA timbre of earphones which have balanced armature drivers. One thing which I did not mention in my above review is that, since this is a hybrid tube headphone preamp, you do need to be careful about how much RCA line-in signal voltage you feed to this tube preamp. If connected directly to your computer's motherboard or sound card line out jack, set the maximum volume in Windows to no more than 75% of full volume or perhaps a bit lower at 70%. Why? Because too high of a sound signal (in terms of voltage swing) from the sound source going into the Tube-02 Pro's RCA inputs can cause strong distortion in the built-in digital op amp stages in the Tube-02 Pro. In other words, limit the RCA input signal voltage and instead use the Tube-02 Pro's volume knob for volume control.

Another note: The Tube-02 Pro does use relays and does detect when anything is plugged into its headphone output jacks. It does this in order to protect the headphones from any really loud and potentially damaging "thumps" which would be heard when plugging in the headphones. If you use an adapter cable to adapt your headphones or IEMs for use with the Tube-02 Pro, make sure that you first plug in your headphones or IEMs into the adapter cable, and then plug in the adapter cable into the Tube-02 Pro. Following this procedure will avoid any audible and potentially damaging "thumps" which could damage your headphones or IEMs.

 

[cpu235]

I got it used from a friend for a low price and I think it is an okay unit if you are chasing tube sound. It pairs well with high-independence headphones since some low-independence iems I used with the amp have noise when the volume knob is over 50%. The frontplate design looks pretty terrible though, I wish they kept the normal FX Audio design instead of this since I think the build quality was actually not bad.

 

[cpu235]

I got it used from a friend for a low price and I think it is an okay unit if you are chasing tube sound. It pairs well with high-independence headphones since some low-independence iems I used with the amp have noise when the volume knob is over 50%. The frontplate design looks pretty terrible though, I wish they kept the normal FX Audio design instead of this since I think the build quality was actually not bad.

After resoldering some connectors the static noise drastically decreases, there are some cold solders out of the factory on the board which created the static noise on my amp.

 

[cpu235]

I purchased the Voskhod Rocket 6ZH1P-EV recently and tried it with the amp, and it sounds way better than stock, no wonder people raved about this tube, it sounds warmer and wider without losing details, and reduced the sharpness/ 6k peak on my HD700. Thanks for the recommendation @GoneToPlaid

 

[Rogyupii]

I recently received this FX-AUDIO Tube-02 Pro from Amazon. It is advertised as being a class A tube amplifier. I do believe that it is. This tube amp's motherboard is the 2021-09-07 version 1.1. This headphone amp comes with GE JAN 5725W tubes. The FX-AUDIO website and the Amazon listing for this amp state that only 6J1 and 6J2 tubes are additionally compatible. I measured both the voltages and the resistance between all seven of the tube socket pins. It turns out that, at least for this amp's version 1.1 motherboard, any EF95 tube can be installed in the FX-AUDIO Tube-02. This has indeed proven to be true since I presently am using Voskhod Rocket 6ZH1P-EV tubes in this amplifier since tube pins 2 and 7 are connected to eliminate the military use of the sharp cutoff feature of the 5725W or equivalent tubes such that the stock 5725W tubes essentially become 5654W tubes in audio operation. Additionally, pins 5 and 6 for the tubes are also connected. I totally love the very clear tube sound since the even order harmonics from the tubes are strong in comparison to the odd order harmonics, and since all harmonics also properly and rapidly decay with increasing frequency. This is just the sort of thing which one desires for a warm yet clear tube sound. The Tube-02 Pro has extremely good signal to noise ratio. Notably, the Tube-02 Pro also does not contain any IC op amps. The output stage is driven by transistors.

I am totally new here. I am hesitant to write my first product review which would include product photos and internal product photos. I hope that someone else evaluates the FX-AUDIO Tube-02 Pro and creates a review for it.

Are psvane tubes compatible?

 

[GoneToPlaid]

I don't know if any psvane tubes are compatible. If there are any psvane tubes which are EF95 compatible, then they will work. I was initially enjoying using the Voskhod Rocket 6ZH1P-EV tubes, but I discovered that these tubes were more susceptible to noise and interference. For example, simply hovering my fingers close and around these tubes causes a noticeable increase in background noise. So I switched to GE JAN 5654W tubes. I have zero noise or hum issues with these tubes whenever I move my fingers or hands close to and around these tubes.

 

[Rogyupii]

I don't know if any psvane tubes are compatible. If there are any psvane tubes which are EF95 compatible, then they will work. I was initially enjoying using the Voskhod Rocket 6ZH1P-EV tubes, but I discovered that these tubes were more susceptible to noise and interference. For example, simply hovering my fingers close and around these tubes causes a noticeable increase in background noise. So I switched to GE JAN 5654W tubes. I have zero noise or hum issues with these tubes whenever I move my fingers or hands close to and around these tubes.

Hmm guess sticking with JAN5654W is the safest bet

 

[Sam21]

So if it is compatible with EF5...it is also compatible with these tubes:? 5654, 6AK5, 6J1, 6ZH1P, 403B, CV850, M8100, 6DL5, DP61, PM05 ?

How does this tube amp compare with Little Dot I+ ? here are the specs for LDI+:

 

[GoneToPlaid]

As I previously mentioned, tube socket pins 2 and 7 are tied together, making the this tube preamp compatible with any EF95 tube. I have been using GE 5654 tubes in my Tube-02 Pro for well over a year now. The Little Dot 1+ operates the plate and grid 2 at 144 volts, and operates the cathode and grid 3 and the screen at zero volts. The Tube-02 Pro operated the plate and grid 2 at 10.7 volts, and operates the cathode and grid 3 and the screen at negative 10.7 volts. Obviously the Little Dot 1+ will sound better. Yet the Tube-02 Pro is a lot of fun and the tubes will last years due to the much lower operating voltages for the tubes.

 

[Gaspar74]

My Tube 02 pro just recently wont output to RCA out, only headphones. Anyone else experience this? Ive opened it up and resoldered any questionable solder joints etc. Im thinking its in the Mute circuit possible. Ive tried unplugging it basically any normal tricks to stuff like this and still no sound from RCA out.