So I raided that spare change jar and purchased the FX TUBE-03 with tone control.
This unit will eventually go into my little art studio for late night company while I doodle. But in the mean time I got antsy and needed to settle my curiosity if this unit even works. I'll start out by saying the unit was well packaged for shipping. Instruction manual was pretty light but I could figure it out. Been snowing off/on here the past week, traffic sux and my ext. pwr supply is at my other house now so wall wart had to do, however I did have some GE JAN 5854W tubes already burned in so didn't bother with stock tubes. The unit was initially connected between my oppo BDP and ARC SP-15 pre, then on to ARC vm-220 monoblocks and out to Maggie 1.6s, it was allowed to warm up for a 1/2 hour before any "listening" took place. 1st up was a SACD copy of Norah Jones as I know this one well on my system. Other music was played but not worth mentioning here.
With tone controls centered and volume level set accordingly my first impression was a bit lack luster. Highs were somewhat muffled and no sparkle to speak of, mids were present and tonality was acceptable but perceived a bit forward and constricted in space, bass was a tad flabby in sound and lacking in deep richness in addition to that very centered between the panels with hardly any overlap or spread beyond the panels, very little openess or air about the sound. I made some adjustments to the tone controls (bass down a detent or 2 and treble up a couple 3 detents) and it sounded some better but didn't bowl me over.
Light bulb went off and I remembered I have a pair of burned in 1945 Sylvania JAN-6AK5 tubes in a buffer on one of my other systems. Did the swap, gave it time to warm, poured one and sat down for a "listen".
Starting out with controls flat I immediately noticed an over all tone quality improvement including some amount of increase in air/space around the instruments and a bit closer to that sparkle I was looking for, that "tang" sound of a drumstick tip hitting a cymbal or the proper sound of a high hat and not 2 trash can lids being smacked together. I continued to notice some lack in spatial information and environmental detail of the music but better than the GE tubes, in addition the midrange still sounded a bit over centralized or compartmentalize if you will. Although the bass tightened up exponentially and was much fuller plus more natural sounding I was still not hearing that fundamental stuff I normally hear and enjoy. It's as if 30Hz was the limit and then began roll off with nothing below 25Hz. Published specs are 20-20kHz +/- 1.5.
So, with the 1945 tubes and little tone control nudging I was able to achieve a somewhat satisfying sound out of this little unit, but once I took it out of the loop I could instantly hear it's limitations as everything I was familiar with on this recording returned. I thought maybe it didn't play well with the oppo so I put it line between my streamer w/quad dac and SP-15 thinking it might "warm up" the sound a bit. It did but the previously identified artifacts were there once again.
In conclusion:
I never expected this little $52 item to compare in sound to a $30,000 system as that wasn't the point here. However by connecting it into a system of that quality any shortcomings would become abundantly obvious and allow me the ability to identify these things, so going forward my expectations of this unit can be much more accurate. The FX TUBE-03 will never reside with my ARC system as that is not what I bought it for. Once a better quality power supply is aquired I will be more than happy with the performance of this little unit where I plan to use it in my world. Of course YMMV but between initial cost, tube upgrade and a better power supply, it's a worthy little unit in my opinion and I'll be keeping mine.
Eventually it will be part of a system of stuff left over or displaced to include dbx 1bx-ds, dbx 120x (for sub control), Carver m400 cube, ADS speaks and a small 12" infinity sub w/plate amp.
Hope this writing helps someone here.