Cheap Amp Review: Lepai LP-2020A+ vs. Topping TP30

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Cheap Amps Face Off: Lepai LP-2020A+ vs. Topping TP30

Brent Butterworth

These are good times indeed for cheapskate audio enthusiasts. Thanks to the rise of geek-friendly Internet merchants such as Parts Express and Monoprice there are all sorts of audio products out there at prices so low that in some cases they almost might as well be free.

But Are They Any Good: Both Are Low Priced

The question, of course, is how good are they?  

One category where the prices seem impossibly low is tiny integrated amplifiers. These amps typically have one or two inputs, a volume control, and maybe 10 or 20 watts of power per channel. You're probably not going to hook these up to a $2,000 pair of high-end tower speakers, but they seem just the ticket for, say, an old pair of JBLs or Polks, or a new pair of Dayton Audio B652s.

And check out the prices! The Lepai LP-2020A+, rated at 20 watts per channel, is just $26.88.

But wait a minute! Parts Express also offers the Topping TP10-MK4, which costs $72 but is rated at just 10 watts per channel into 8 ohms. Both use Class T amplifier technology, so named because it comes from a company named Tripath. It's a trademark, not a recognized amplifier class; it's really just a variant of high-efficiency Class D (switching) amplification. 

"What gives?" I wondered when I saw the two amps. Sure, the Topping looks a lot nicer, but does it have any other advantages that would justify its nearly 3x greater price?

I just had to find out. But rather than simply listen to them and tell you that one offers greater "inner detail" or more of a "liquid midrange," I'd do what most reviewers can't: I'd run some lab measurements on them to find out what's really going on.

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The Contestants

Brent Butterworth

Getting Ready for the Comparison

I bought myself an LP-2020A+ a few weeks ago, and a pair of Dayton B652 speakers. The B652, though, turned out to be an amazing deal -- not what anyone would call a refined-sounding speaker, but surprisingly listenable, especially for $32/pair.

As luck would have it, my colleague Geoff Morrison happened to have a Topping TP30 sitting around, which seems to be basically the same amplifier as the TP10 MK4 with the addition of a headphone jack and a USB digital input. Of course, the TP30 is no longer available.

So I had my two contestants. Judging from specs alone, the LP-2020A+ might actually seem superior, with 20 watts per channel instead of 10. However, I couldn't find anything on the Parts Express site that said how that 20 watts was measured. For an amplifier power measurement to mean anything, you need to specify the impedance it was tested into (usually 8 or 6 or 4 ohms); the level of total harmonic distortion plus noise (THD+N) at which the power rating is given (usually 0.5% or 1% or 10%); the frequency or frequency range at which the test was run; and the number of channels driven.

As you can see in the back panel shot above, the TP30's a better-built product, with a sturdier case and higher-quality speaker-cable and RCA connectors.


After this article was posted, a reader (thanks, Jerrold!) emailed to point out that some LP-2020A+ owners have been upgrading their units with a more powerful, 5-amp supply like this one from Amazon. Which inspired me to revisit the specs on the Parts Express site. The LP-2020A+ page on that site rates the power supply shipped with the LP-2020A+ tested here at 2 amps. But the power supply I received is rated at 3 amps. The amplifier itself is labeled for a 2-amp supply.

OK, let's plug 'em in and see what happens.

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Lepai LP-2020A+ Power Output

Brent Butterworth

Testing the LP-2020A+

To see if the LP-2020A+ lives up to its 20-watts-per-channel power claim, I used my Clio 10 FW audio analyzer to run a distortion plus noise vs. power sweep at 1 kHz. The total harmonic distortion plus noise (THD+N) level is on the Y (vertical axis), while the power output (in watts) is on the X (horizontal) axis. Here's what I got.

8-ohm load, both channels driven
9.1 watts at 0.5% THD
9.9 watts at 1% THD

Into a 4-ohm load, the LP-2020A+ kept going into protection mode (output muted, blue light around volume control flashing) before the sweep finished, no matter how I set the sweep parameters. I ended up measuring the max output by hand. The highest output I could get at 4 ohms was 9.4 watts at 1.5% THD+N.

Notice also that the distortion plus noise runs very high at low levels: 0.5% and 1% THD+N between 0.1 and 2.4 watts. The vast majority of your listening will be at these low levels, not in the 5- to 8-watt region where the amp performs its best.

These measurements are into load resistors -- so-called "dummy" loads that tech geeks like me use because they give us a consistent baseline (as opposed to speakers, whose impedance varies a lot). I knew, though, that some inexpensive Class D amps depend on having a speaker connected in order to work correctly; the speaker's capacitance and inductance sucks up all the radio-frequency energy generated by the amp. So I ran the same sweep with my Hsu Research HB-1 Mk2 speakers (impedance 7.7 ohms at 1 kHz) connected instead of the load resistors. Results were almost the same: 8.9 watts at 0.5% THD, 9.8 watts at 1% THD.

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Topping TP30 Power Output

Brent Butterworth

Testing the TP30

The above chart shows the Topping TP30 measured under the same conditions. The green trace is into an 8-ohm load, the purple trace is into a 4-ohm load.

8-ohm load, both channels driven
9.3 watts at 0.5% THD
10.3 watts at 1% THD

4-ohm load, both channels driven
16.4 watts at 0.5% THD
17.4 watts at 1% THD

Notice how the TP30 outperforms the LP-2020A+ even though its specifications are inferior? Just goes to show you -- amp specs mean nothing unless the testing conditions (THD+N level, how many channels driven, load impedance, etc.) are given.

Notice also that while the TP30's distortion plus noise as low levels isn't great, it's much better than the LP-2020A+, staying under 0.5% at levels between 0.4 watts and max output.

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Topping TP30 Frequency Response

Brent Butterworth

Frequency response is the measure of how evenly an amplifier reproduces all frequencies of sound, from bass to midrange to treble. For an amplifier, the ideal result is a dead-flat line at 0 dB.

I'm putting the TP30's results here first because I was able to get a normal measurement from it. More about the LP-2020A+'s weird results on this test coming up.

Frequency response, 8-ohm load, ref. level 2.83 volts (1 watt)
-0.32 dB at 20 Hz
-0.50 dB at 20 kHz

Channel balance error at 1 kHz, 8-ohm load, ref. level 2.83 volts (1 watt)
right channel +0.11 dB higher than left

Again, not an amazing result, but for an inexpensive amp it's just fine.

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Lepai LP-2020A+ Frequency Response

Brent Butterworth

When I tried to measure the LP-2020A+'s frequency response using the load resistors I mentioned before, I got strange results. The bass rolled off sharply, down -3 dB at 76 Hz. However, I didn't notice a lack of bass when I listened to the LP-2020A+, so I thought the result might be due to some idiosyncrasy of the LP-2020A+ when driving load resistors. 

So I decided to measure the frequency response by connecting the LP-2020A+ to one of my Hsu HB-1 speakers, placing a microphone in front of it, doing a standard frequency response on the speaker, then repeating the measurement using the Topping TP30 instead of the LP-2020A+. You can see the result in the graph above, where the blue trace shows the result with the TP30, and the green trace shows the result with the LP-2020A+. These results are with the LP-2020A+'s tone controls deactivated.

Frequency response, 8-ohm load, ref. level 2.83 volts (1 watt)
+4.86 dB at 20 Hz
0.00 dB at 20 kHz

Channel balance error at 1 kHz, 8-ohm load, ref. level 2.83 volts (1 watt)
left channel +0.21 dB higher than right

Note that the LP-2020A+'s bass response is actually -1.26 dB below that of the TP30 at 30 Hz. For some reason, the LP-2020A+ has a weird boost at 20 Hz. Given that there's so little 20 Hz content in movies and music, and that only the largest speakers and subs can reproduce 20 Hz, it's not something you'd hear. Not like this little amp could deliver audible output at 20 Hz anyway.

Basically, the timbre, or tonal balance, of these two amps is about the same.

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Lepai LP-2020A+ Tone Control Effects

Brent Butterworth

These are the effects of the tone controls on the LP-2020A+ -- again, measured by running the amp through a Hsu HB-1 Mk3 speaker. The blue trace is the effect of having the bass and treble controls turned up all the way. The red trace is the effect of having the controls turned down all the way.

Maximum boost and cut for both is on the order of 10 to 12 dB, which is a fairly large range. Note that these measurements are taken at a reference level of 1 watt. If you crank these controls up all the way at louder listening levels, the LP-2020A+ may not have enough power to deliver the boost you see here.

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Listening Notes and Conclusion

Actual Listening

How do these differences translate to the actual listening experience? To find out, I compared the two amps at matched listening levels connected to the Hsu HB-1 speakers. I noted one thing right away: The Topping TP30 could use a little more gain. I had to turn it all the way up to get good volume when I used my iPod touch as a source -- even though the HB-1 is a reasonably efficient speaker.

To my ears, the LP-2020A+ has a coarseness in the midrange and lower treble that makes voices sound a little edgy. On saxophonist Terry Landry's recording "Amazonas" some of the latin percussion instruments had a bit of a buzz to them, almost as if they were broken. However, the LP-2020A+'s upper treble range sounds a little more extended, as the measurements suggested; the TP30 sounds a little soft in the treble by comparison. But the deep, powerful bass notes that open Holly Cole's "Train Song" sounded tighter and less boomy through the TP30.

Overall, I'd say the TP30 sounds better, although both have strengths and weaknesses. I guess some might prefer the sound of the LP-2020A+. And I guess some might not even notice a difference.

The Final Word

It appears from my measurements that the Topping TP30 is what I would call a "real amp": You can connect it to almost any speaker and it'll deliver a decent listening level and clean sound.

The Lepai LP-2020A+, though, seems to incorporate some engineering compromises that allow it to hit its ultra-low price point. It makes basically the same amount of power into an 8-ohm load as the 4x-more-costly TP30.

Here's my recommendation: Get the TP10-MK4 if you're putting together a serious desktop audio system or a budget bedroom or living room system. Get the LP-2020A+ if you just want something that makes​ a decent sound, like for a garage system or to play lite jazz in a waiting room.