To understand the merit of this thing, you have to realize it is NOT an amplifier. It is a buffer. Meaning, all it does is pass a signal through a tube with almost no appreciable amplification. The catch is that it is preying on people thinking that simply having a tube in the chain is what makes the sound better. That's not the point. "Adding warmth" or "adding color" is not the point. The point of a tube - what makes it better for audio than a transistor - is the way a tube distorts when it amplifies a signal. Yes, the even-order distortion produced by overdriven tube circuits is more musically pleasant than the odd harmonics produced by an overdriven (clipping) transistor. (you can google using terms like "tube transistor distortion odd even harmonics" to better understand this)
If you're not amplifying the signal with the tube, there is no point. You're just adding the distortion inherent to the tube to whatever else in your chain you're already using to amplify. So if you're not REPLACING a transistor with a tube for the various steps in your signal chain, you are not gaining sound quality, period. In the case of this thing, you're also adding the distortion of an extra volume knob, and the bass and treble controls.
dnogsFull disclaimer: this is found info, and not something I can personally verify; but I do know what you're referring to with such buffer units and how many are sold as amps.
That said, the smaller version of this [FX Audio TUBE-01] was apparently tested by this Amazon reviewer and shown to, in fact, provide true signal amplification. Again: not the exact same device, and I can't verify that this person tested in an accurate way (and the Amazon review page is acting up slightly - hence the screenshot instead of a link). Still, it might be worth considering that this unit truly is what it says.
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Now *all* of that said? Since the TUBE-01 appears to be a true amp if this reviewer is accurate, since it doesn't have the bass/treb controls (which I agree with dnogs - just one more set of pots in your signal chain), and since it sells off Amazon for the same price as the TUBE-03 does at this drop ($34.99)...maybe that's the route to opt for?
Either way, it's tricky to find units at this price point. The way I see things, if you're curious; you should probably go for it. You'll either get what you paid for - no biggie; or you get a unit that pleasantly punches above its price.
@dnogs Since I'm about the furthest thing from an expert on these things, please correct me and I'll edit as needed. I try to keep my spreading of misinformation to a minimum where possible. ^_^
dnogsEvery buffer is an amplifier with amlification ratio set to 1. This device (and Tube-01) allows for changing ratio between 0 and a bit above 1 (1,2 - 1,3; didnt measure this). This is real amplifer, albeit not very powerfull.
I have it and I had Tube-01 previously. This one is better, but tube rolling is a must: the best for me are GE Jan series (aliexpress has 80'ies stock cheaper than Riveraudio, which didnt care to answer my quote mails - I am from Europe) and Mullards.
Whats interesting, with my Stax Sr-007MkI and SR-009 I can clearly hear the loss of the detail - even with best tubes (and I had AEG diamonds), but when on speakers (B&W 705S), this is inaudible - and the overall sound is more "pleasant"
I cannot explain this, but I've decided that even if that's some kind of placebo, than for the money - why not :)
JWoltersYes, that's clear, there is no comparison to e-stats. What I meant is that it's interesting that though there is a loss in detail, it still sounds more pleasant.
If you're not amplifying the signal with the tube, there is no point. You're just adding the distortion inherent to the tube to whatever else in your chain you're already using to amplify. So if you're not REPLACING a transistor with a tube for the various steps in your signal chain, you are not gaining sound quality, period. In the case of this thing, you're also adding the distortion of an extra volume knob, and the bass and treble controls.