Review by
Vincent Caponi

The Trends brand name is no stranger to Stereomojo. The original Trends Class T mini amplifier won our famous 11 amp shootout a couple of years ago, stunning many much larger and more expensive contenders. The company continues to expand their line of components that feature ultra small size as well as ultra small prices.

The Trends PA-10 Tube Preamp is an affordable and compact hybrid Swiss army knife type of preamp.  It is a versatile unit that supports a variety of pre-amplification applications and as well as a wide array of acceptable tube options that promise fun for people like me who like to tinker with old vacuum tubes, volt meters and the like. The practice of substituting or changing out tubes is what we call "tube rolling" - we take one set of tubes out and "roll" in another. Why? Tubes are like ice cream; they come in many different flavors but almost all of them taste (or sound) good. They can sound radically different even within the same brand name or tube type and it's fun finding which one is your favorite. You really cannot do much to change the qualities of a solid state amp (some people foolishly try to use cables to achieve that), but you can with tubes. True, some people do experiment with changing out electrical parts in solid state amps, but it takes a pretty high degree of electrical knowledge and soldering skills to do that and they always risk blowing up their projects. Tubes? Much easier and less risky.



The sample unit arrived direct from David Ho, Marketing Director at Trends Audio.  As always, we thank David for trusting us with his product for review. After some research I learned that I was reviewing the standard version, identified by the two rectangular black capacitors.  There is an SE version also available ($265 direct) with upgraded Evox capacitors which are white in color as opposed to the black in this version.  The SE also comes with an upgrade to the standard version's Chinese made 6N11 tube, a Russian made 6H23N "special".  These tubes are all of the 6DJ8/6922 family.  I was really looking forward to tube rolling, especially after I learned that repositioning of three jumpers on the circuit board and a simple re-bias procedure of the DC voltage, the PA-10 becomes a 12AU7 type tube preamp.  Now how cool is that?!  

This miniature-sized "chameleon" functions as a headphone amp, linestage preamp, or you can use the higher gain "Phono" input to connect low output audio devices such as an iPod or your computer's sound card.  The tinkerer in me was looking forward to being able to experiment with two different tube families.  I had several vintage NOS 12AU7 varieties waiting in the wings to try. Though I was sent the standard version of the PA-10 for review, I was sent both the Chineese 6N11 as well as the Russian 6H23N, which is included as "standard equipment" in the SE version. If that’s too confusing, take a look at this chart:

The PA-10 is not a full tube-driven product because, as their website states, “Two MOSFETs are used as the output driver which perform the warm, comfortable tube sound and in addition, guarantee the high fidelity & sufficient driving power to the next power amplifier stage."

The tiny box provides two switchable RCA type inputs, one for use with CD players and other line level audio devices, the other labeled "Phono".  According to the website, this input is sufficient for a  "small output phono amplifier or PC/Mac/iPod".  Hmmm.  An input labeled "phono" usually infers that the circuit has some type of RIAA curve built in, but you wouldn't want to run a "PC/Mac/iPod" through such a drastic EQ. Read on and this will all be cleared up for us further into this review.  

The PA-10 comes furnished with a 24 volt DC power transformer in the form of a wall wort, specially designed for extra low ripple and noise.  Hobbyists may want to experiment with other 24 volt DC sources such as lead acid batteries, which can potentially lower the noise floor further.

I presumed that the sample unit was biased at the factory for a 6DJ8/6922 tube, but which one?  I figured even had I known, it would be prudent of me to check the jumper settings and bias voltage for my tube selection.  I decided to try the upgraded 6H23N tube first, so biasing was done with that tube in place.  After downloading the technical notes from the Trends web site, I was able to confirm that the jumpers were in the proper position for the 6DJ8/6922 tube type, then I was able to fine-tune the bias to exactly 16.5 volts using a small screw driver to turn the two precise potentiometers.  The entire procedure took just a matter of minutes, thanks to the clear and concise instructions provided in the tech notes.  I am sure that with the proper tools most anyone would be able to perform the procedure.  Check out the chart below.

I did all of my listening through my reference CD player and music that I have stored on my MacBook Pro computer.  I decided to listen through the CD player first, so I connected a good quality cable from the player's output to the "CD" (line level) input.  The unit looked very high tech in my rack, a blue LED glowing up through the tube from the base to add a little drama and color.  There was a bit of hum that settled down after a few minutes of warm up.  I listened very casually for the first 50 hours, mostly as background music, as I wanted everything to settle in before any critical listening.

Associated Equipment

Eastern Electric M520 Integrated Amplifier (with internal preamp stage bypassed, using the Trends PA-10 in it's place)
Shenda Music Van CD Player
Apple MacBook Pro
Silverline Prelude Loudspeakers
Blue Jean Cables Interconnects
AKG K240 Headphones


I listened primarily to the 6H23N and a vintage1952 NOS RCA 12AU7 black plate.  I switched back and forth several times, changing jumpers and re-biasing each time.  I'll try to be as concise as I can as to which tube I am referring.  So how does it sound?

The CD "Chick Corea and Friends Remembering Bud Powell" was first up.  Excellent frequency extension at both ends, no roll off.  Very good detail, yet I would have liked the mid range to be a bit smoother and fuller.  The saxophones on some of the tracks could have been more involving as I found them to be a bit on the thin side.  There was also a slight edginess in the midrange that made me long for my vinyl.  Bass was deep and just a little on the slow side which was quite pleasing on some of the ballads, but not so much on the uptempo tunes.  The soundstage was quite respectable with excellent imaging. 

One specific song on this disk worthy of mention; the Bud Powell standard, Dusk in Sandi, was very enjoyable. This CD was recorded live-in -tudio and that really comes through in this ballad.  The timbre of the piano was free of color which gave the impression of a live performance. There are no horns on this track, just a piano jazz trio in which Christian McBride's bowed bass solo revealed the wonderful wooden timbre of the instrument.  The soundstage was quite impressive on this track too, bass centered and set back with Chick Corea off to the right. Roy Haynes’ drums were a back curtain to it all. Very nice sense of separation between the members of the trio.  I find in general that the PA-10 does small jazz combos very well.   Overall the music on this disc sounded good to quite involving on some songs.  My tube rolling mind was already wondering what that vintage RCA 12AU7 would do for this musical little amp.

It wasn't long after I began using the PA-10 that I noticed the metal enclosure would become quite hot, but I suspect the unit may have been designed with that in mind for the purpose of carrying heat away from the circuit board.  In any event, this didn't cause me any trouble during my entire audition of the component, but you need to be aware of it.



There were only a couple of problems that I found with the review sample.  One was the volume control being a little noisy when operating it just past the zero point.  I don't know if this was a problem isolated to this one unit or whether it is pervasive throughout the production, but noise should not be present at all. We have discovered that this problem is widespread and known to the manufacturer who is hopefully working to improve it – publisher.

Second, I found the gain on the CD (lower gain) input to be too high.  By the time I got a little past 9:00 on the control it was too loud for comfortable listening in my system.  I just learned that there is a revised version of the PA-10 out now which apparently addresses this issue. See the chart below for a comparison of the units.



Now, when I told you to read on earlier it was because I later learned something in regard to the "phono" input while surfing the Trends web site.  The revised versions have a small change to the silk-screened text on the back panel, yet one that clears up a big question for me, the vinyl junkie that I am.  The "higher gain" input previously labeled as "Phono" has been renamed PC/iPod.  There is a chart on the web site that shows the comparison to the version on which this review is based.  It states that on the original version of the PA-10 the phono input does not apply the standard RIAA curve that is necessary when playing all modern vinyl.  Bottom line, the RCA jack was just mislabeled and is not a "phono" input after all.

When using the PA-10  with my MacBook pro on the high gain input (mislabled as phono) it performed very nicely.  I was able to turn the sound card volume down fairly low and allow the PA-10 to do it's thing.  This application is very well suited for the PA-10 and I suspect from what I've read that the matching chip amp model TA-10 would be an excellent match for this unit. 



At this point I couldn't hold off any longer; Nipper (the RCA dog's name if you didn't know) was calling.  I powered off and let the unit cool down, then I got the volt meter out and removed the four philips-head screws securing the top cover.  A small pair of needle nosed pliers worked well to move each of the three jumpers (clearly labeled on the circuit board as J3, J4 and J5), to the 12AU7 side as indicated in the technical notes that I had downloaded earlier.  I inserted the RCA 12AU7 from my own collection, powered the unit up and positioned my voltmeter at the contact points for the left channel bias, as indicated in the notes.  I had to turn the precision potentiometer quite a few revolutions before getting to the +16.5 volts this time.  But once there it was quite stable, only fluctuating +/- 20 mV.  I repeated the procedure for the right channel, then rechecked both.  I was all set to give it another go.


First up with the vintage RCA 12AU7 black plate inserted was Jorma Kaukonen's "Blue Country Heart". As you may know if you've read some of my other reviews, this is one of my favorites that I like to include in my evaluation tests for it's impeccable acoustic American roots music, not to mention the terrific quality of the recording.  It was immediately evident that the PA-10 running with the 12AU7 was much warmer, more laid back and less dynamic without sacrificing much in terms of detail.  I later went back to the 6H23N to confirm what I thought I was hearing with this recording.   The music took on a more natural quality with the 12AU7, smoother midrange while vocals were noticeably less grainy.  In fact, with the exception of a slightly hollow color in Jorma's vocal performance, this recording came pretty close to the preamp stage in my M520 integrated with the right tubes.  In terms of foot tapping fun, the PA-10 certainly did not take anything away from this piece of genuine Americana music.

From this point on most listening was done with the RCA 12AU7, just switching back from time to time to the 6H23N and the Chinese 6N11 for comparison.  The 6N11 tube sounds fine at low-moderate levels, but tended to be a bit fatiguing, especially after listening for an hour or more to jazz with a lot of horns blasting away.  In all fairness to Trends, the 6N11 tube was not fully broken in; I pretty much started listening right away with that one without any burn in time.  Once I got a taste of the 12AU7 I just couldn't go back!


Odetta's "One Grain of Sand" CD is this wonderful singer at one of her finest hours.  The personnel on this recording consists of just two; Bill Lee on the double bass and Odetta on acoustic guitar and vocals.  The PA-10 did a very nice job conveying the emotion of Odetta's rich voice - just simple, heart felt American roots music at its best.  I noticed that her contra alto vocals were more pleasing through the PA-10 than soprano artists such as Alison Krauss. Perhaps there is a bit of a bump in the frequency response in that area.

Another CD I like to use for evaluation is "Best of Louis Armstrong and Ella Fitzgerald".  These are all mono recordings of standards recorded in the 1950's.  Armstrongs’s vocals sounded very natural and Ella's smooth vocals were quite good, although slightly lacking that last bit of airiness that I get with my reference system.  However, this characteristic only slightly reduced the sense of realism and is very commendable at its amazing $225 price. 

"Love Is Here To Stay" and "Stars Fell On Alabama" sounded wonderful in terms of soundstage.  Being a mono recording, Ella sounds as if she is standing a bit pulled back from Louis with his trumpet extending a bit further forward from his vocals. The 12AU7 did a much better job in terms resolving the vocal performances on this recording than the 6H23N, which portrayed the vocals with more color, and the trumpet sections during some songs were a bit too forward.  I love this recording, and thoroughly enjoyed listening to it through the PA-10.


I am not a big headphone user, never was, but I did put the PA-10 through its paces with my AKG K240 phones.  The music sounded very nice, not quite on par with the headphone amp in my reference CD player, but still very good audio quality through the PA-10.  There was a noticeable improvement in the analog out from my MacBook Pro, not only through headphones but also when sent through my M520 and Silverline loudspeakers. While the headphone circuit is not exactly state-of-the-art, that it is included at all in such an inexpensive tube product is laudatory.

The PA-10 is a good choice to consider for computer users who like to listen to quality music while you work, or pair it with a chip-based power amplifier and you can play your downloaded music through some good quality high efficiency speakers.

At the time of this writing there is also now a PA-10 GE version which runs only on a 12AU7 tube. Trends describes it as having a "relatively warmer mid range and excellent female vocals".  I suspect that the only difference between the SE (configured and biased for a 12AU7) and the GE is that the latter will come supplied with a 12AU7 rather than the SE's 6H23N. For the experimenter type of audiophile that I am, one of the configurable versions of the PA-10 is more appealing to me for their versatility.  For the plug-and-play type of audiophile the PA-10 GE should be worthy of consideration.  And not to beat a dead horse, but I think you know by now that the 12AU7 was my preference, which I suspect may be the very reason for the release of the GE version.  

There are certainly enough 12AU7 or 6DJ8/6922 varieties out there to choose from, so this amp can be a lot of fun!  In fact, I could see the PA-10 or one of the upgraded SE or GE versions being the beginning of a lifetime addiction to vacuum tube gear and tube rolling for many new or younger audiophiles.  If I have just one regret about writing this review it is this; why did I ever get rid of that vintage pair of Amperex 6DJ8 A-Frames that I had?  

The options are many with this affordable and versatile little amp that should satisfy the small piece of audio engineer that exists in many audiophiles. If you have ever entertained any curiosity about how tubes sound and how different brands, types and vintages of tubes can substantially alter the sound of your system, the Trends PA-10 would be a wonderful sandbox in which to experiment. The cost is low and there are many new and vintage tubes available at reasonable prices that will work with it. If you don't own a voltage tester, they can be had for under $20 anywhere from Rat Shack to Ebay.

As reviewers we owe it to you, our readers, to remain objective during our evaluations, taking into account factors such as the intended application, target audience and value.  Therefore we must go into the review process knowing that even if we have our own experiences with similar products, we cannot loose sight of these varying factors that may or may not make a given piece worthy of consideration for a particular individual.

The experimenter in me certainly enjoyed trying the various tubes that I had on hand.  The PA-10 is quite an innovative and versatile product, one which is worthy of consideration for iPod/computer listeners who are seeking a more musical experience from their high tech devices.  Priced at just $225 for the standard version, or $265 for the SE, the PA-10 is a nice value and a very cool little amp. Paired with a good chip based amp and high efficiency speakers I expect that the PA-10 may also be a good choice for use as a office or bedroom system where limited space is an issue, but good quality sound is desired.

That being said, the PA-10 posed a challenge for me because I am not the kind of person who listens to music through my computer very often, nor am I an iPod user, or even much of a headphone guy with my home system (much to my poor neighbors chagrin).  As such, I would not recommend the Trends PA-10 to someone who shares my listening habits.  If a dedicated home audio system is your primary or only listening source you would likely be better served to save your pennies towards a more refined, dedicated linestage preamplifier, one that will not outgrow your system if you were to upgrade other components.

If you want to pursue a small chip-based amplifier, the Virtue Audio is an alternative, though it is not a tube amp. It still has outstanding sound. You may want to read our review.


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