FX Audio Tube-01 Buffer/Preamp

What can I say, people talk (mea culpa, this was on another site), every once in a while something slips past my defences, lodges in some crusty cerebral nook and there you go, the kid finds himself tempted by some doo-dad or other. The lower the price of said doo-dad the greater the temptation, it seems. (See: Lepai tripath, Minimus 7, others.) Long story short, I recently splashed out a lofty $32 on an FX Audio Tube-01. After farting around with the thing the past few days I can say I agree with what's being said about this gizmo on that other site-- up to a point. (I'm posting here rather than there because I'm not particularly fond of the dust-ups those cats seem to dig, particularly when one fails to precisely echo the prevailing sentiment.)

Yes, the FX Tube-01 is worth the money. The build quality is surprisingly high. It does do what it purports to do. It does sound good. Yes yes yes. And yes.

However, there is also, it seems to me, a bothersome artificial boost on both the bottom and top end. (Think of dynamic range expanders, that kind of effect.) Further, the gain on this thing is bonkers. Anything beyond a quarter turn of the volume knob is deafening; consequently, the bulk of the usable range is crowded into a very small space, which makes fine adjustments challenging. This is true whether the amplifier in use produces 100 wpc or 8.

I should note that I'm using the supplied wall wart and not a regulated power supply, which, some say, boosts the performance of the Tube-01 to even more impressive heights. Use of the stock tubes is also discouraged, and this advice I have followed, although I can't say I noticed any significant differences with the two pairs of substitute tubes I've tried.

All in all, a mixed bag. Is the Tube-01 a superlative buffer/preamp? Um, no, wouldn't go that far. Is it the best $32 buffer/preamp you're likely to encounter? By golly, it just might be.

My opinion, only, friends. (Take with all the salt you need.)

Cheers.
 

John Frum

Secret Society Member
No, see, you're doing it wrong.

When you buy an inexpensive piece of hi-fi, and it doesn't actively disappoint, you're obligated to haul a megaphone up to the highest point in your area and proclaim "giiiiiiiiiaaaaaaannnnntttt kiiiiiiiiiilllllllerr!", then compare it favorably to gear you can't afford to touch in real life.
 

opa1

Moderator
Staff member
I ordered the FX. Had it for a few days. Changed tubes etc. My findings were the same as yours. Too much gain. I only tried it with the TPA amps. Needless to say it went back where it came from. :)
 

TubeHiFiNut

Administrator
I use the $350 Schiit Saga with the Class T and Class D amps and believe that they do sound better with a preamp. :)
 

mhardy6647

Señor Member
Has anyone checked to see how hard it would be to swap in a different volume pot?
I wondered that, too :p I also wondered whether the gain anomaly that folks've been complaining about is a linear pot 'stead of a logarithmic one. Mind you, I thought about trying to figure out if the symptom was consistent with, or exactly the opposite of, a linear pot used for volume control... but my brain started to cramp up even thinking about thinking about it :smoke
 

TubeHiFiNut

Administrator
Has anyone checked to see how hard it would be to swap in a different volume pot?
I wondered that, too :p I also wondered whether the gain anomaly that folks've been complaining about is a linear pot 'stead of a logarithmic one. Mind you, I thought about trying to figure out if the symptom was consistent with, or exactly the opposite of, a linear pot used for volume control... but my brain started to cramp up even thinking about thinking about it :smoke

I'll pop the case open when mine arrives.

Would it be total overkill to put a Slagleformer in there? ;) ;)

(Just kidding.) ;)
 

TubeHiFiNut

Administrator
The FX Tube-01 arrived. Fit and finish is impressive for a $31 component.

I'll swap out the Saga for the FX-01 and see how it stands up.

The amp I'm currently listening to is the Allo Volt+D with the added Capacitance Module (stock 19vdc power brick). Sounds decent with the Saga so should be a good test for the FX-01. :)
 
I'm thinking this forum might be inhabited by enablers.

I now have to order one. I'm hoping it will provide more juice for my Pass ACA amp which requires more gain than the Saga to play at more than moderate volume.
 
OK. First listen. Via the Pass ACA amp (built by a guy that had no idea what he was doing - that would be me), ancient RS CD3400 portable source (with issues and playing only on battery power these days but with a line out and still somehow pleasant and analog sounding) and Elac Debut 6.2s. Cables are Blue Jeans except for a Monster mini plug to RCA for the geriatric CD3400.

The beautiful sounding but passive Saga couldn't drive the ACA past barely moderate levels. This FX Tube Audio-01 Buffer/Pre gives the ACA some juice it can use. Liking it, even with the stock tubes. The upgraded GE 5654 JANs arrive Tuesday but I'm finally enjoying the Pass amp at slightly above moderate volume. And digging it even with a poorly recorded "Best of Procul Harum" CD.

Funny thing is that I was surprised to have a Little Bear Tube Buffer (which I believe may be the same internals with a different case and power supply) with the upgraded GE tubes already, but I'm thinking that the FX is a bit less thick and more agile. Very listenable. I have no problem with volume 12 to 1 o'clock volume levels with the flea weight Pass amp.

This cheap stuff sure is fun to experiment with. YMMV.
 
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The FX Tube-01 arrived. Fit and finish is impressive for a $31 component.

I'll swap out the Saga for the FX-01 and see how it stands up.

The amp I'm currently listening to is the Allo Volt+D with the added Capacitance Module (stock 19vdc power brick). Sounds decent with the Saga so should be a good test for the FX-01. :)

I couldn't get enough juice out of the Saga to hear the Pass ACA amp play anything beyond low to low/moderate volume. The FX-01 has some juice. Obviously not the same delicate pure sound of the Saga.

I'm going to have to pull out my HeathKit 12V power supply in Aqua crinkle finish. Pics to follow.
 
UPDATE but for "Enquiring Minds" only:

Not only replaced the FX-01 for the Saga in my modest back room stereo but also replaced the stock tubes in the FX-01 with the GE JAN 5654s.

Wow! Smoother and bigger sounding than the stock tubes.

All I can say is that my DIY Pass ACA has never sounded better driving the ELAC Debut 6.2s. I'm sure some of this synergy is due to the tipped up top and bottom end of the FX-10 alluded to by others earlier. But via a modded Sony XDR-F1HD tuner, both the Pass amp and Elacs sound so listenable in ways they haven't previously. And they play loud......even when conveying a rerun of NPR's "Live From Here".

Digging it. YMMV.
 

mhardy6647

Señor Member
UPDATE but for "Enquiring Minds" only:

Not only replaced the FX-01 for the Saga in my modest back room stereo but also replaced the stock tubes in the FX-01 with the GE JAN 5654s.

Wow! Smoother and bigger sounding than the stock tubes.

All I can say is that my DIY Pass ACA has never sounded better driving the ELAC Debut 6.2s. I'm sure some of this synergy is due to the tipped up top and bottom end of the FX-10 alluded to by others earlier. But via a modded Sony XDR-F1HD tuner, both the Pass amp and Elacs sound so listenable in ways they haven't previously. And they play loud......even when conveying a rerun of NPR's "Live From Here".

Digging it. YMMV.
Heh, same rerun we just listened to, I reckon :p
 

TubeHiFiNut

Administrator
UPDATE but for "Enquiring Minds" only:

Not only replaced the FX-01 for the Saga in my modest back room stereo but also replaced the stock tubes in the FX-01 with the GE JAN 5654s.

Wow! Smoother and bigger sounding than the stock tubes.

All I can say is that my DIY Pass ACA has never sounded better driving the ELAC Debut 6.2s. I'm sure some of this synergy is due to the tipped up top and bottom end of the FX-10 alluded to by others earlier. But via a modded Sony XDR-F1HD tuner, both the Pass amp and Elacs sound so listenable in ways they haven't previously. And they play loud......even when conveying a rerun of NPR's "Live From Here".

Digging it. YMMV.
That is a very complete and thorough review - also poses some very interesting questions. :)

The DIY Pass ACA must have fairly low sensitivity? The Saga (with the 6SN7 buffer engaged) drove a bunch of different SE and PP tube amps through 40' of interconnect without issue.

Maybe different speaker sensitivity? Except for the Rogers LS3/5a at ~86db efficiency (driven very nicely by the Saga/CazTech SET845 combination), the speakers I've used with the Saga as preamp are all between 96db and 104db efficient.

Perhaps amplifier input impedance? The tube amps are all 100K ohms or greater input impedance.

Nice to hear that the $31 FX-01 was able to step up and drive the ACA to satisfying levels. :)
 
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