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focalpoint
24
Aug 12, 2016
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I received my amp in the most recent drop a few days ago and just got around to putting it through its paces. For the tests, I used two sets of speakers in addition to advanced measurement equipment. For speakers, I used both Klipsch RB-4 II (small bookshelf with a 4" driver and a horn) and an Ohm Model D (small floor speaker with a 10" woofer and a phenolic ring tweeter). For test equipment, I used a Keithley 2015P THD Multimeter, a Sencore PA81 Stereo Power Amplifier Analyzer, and an Audio Precision System One audio analysis system. My listening impressions, and measurements, were delivered after letting the amp play a tone into an 8 Ohm dummy load for 8 hours over a couple of days several hours at a time, and after having warmed up for 15 minutes.
I'd have to say that I enjoy the sound of the amp well enough. Paired with my efficient speakers I never felt like it was really straining to give me the volume I wanted, without much distortion. Mid-bass through treble was well defined, but the bass was much more reserved than I expected it to be. It's very quiet even with the volume turned up at no signal, surprisingly. Running in Class A certainly helps. The fit and finish was probably a 7/10. Some of the machined edges were a bit rough, and the machined knob manages to actually be *sharp* in one spot. The volume knob doesn't rotate perfectly smoothly through it's travel, it binds slightly in the middle. The transformer covers are a nice touch with the standard-spacing banana plug receptacles on the rear, but it's also obvious they're concealing small output transformers. With an output transformer, the more iron you have the better bass you'll get. Small transformers limit the low-end power available but large, good quality transformers quickly get expensive.
The tube this amp uses, 6AD10 has a pentode voltage amplifier and a 4.2W beam power tetrode section, so it can serve as both input and output tubes in one. These tubes were originally designed to be the integrated audio sections of entry-level televisions towards the end of the tube era, among other things. I couldn't get the bottom cover off due to the corner screws using something I don't have in my toolbox but I could see Nichicon electrolytic capacitors and possibly WIMA film capacitors inside, and the board looked well made. It seems to use a switching power supply.
While some individual variation is possible due to manufacturing differences in tubes and component quality, I did find the manufacturer's specifications to be somewhat...optimistic. Most surprisingly were the sensitivity and frequency response measurements.
The manufacturer proposes 3.5W into 8 Ohms with 500 mV sensitivity, in other words, with the volume control turned to maximum applying a 500 mV signal to the input jacks will cause the amplifier to deliver 3.5W into an 8 Ohm load. However, as shown on the "Sensitivity Into 8 Ohms" my example of the amplifier only delivered 2W; it took about 1.5V at the input terminals for 3.5W output. Into 4 Ohms, the amp fared even worse making about 1.7W with 500 mV, rising to 3W at 2V. At those power levels, I'd be worried about damaging something if operated that way long-term. The kink in the sensitivity charts occurs about 700 mV and gives about 3W into 8 ohms or 2.7W into 4 Ohms, and that's as hard as I'd really like to push it.
The frequency response was somewhat lacking as well. Gemtune specified 30 Hz - 40 kHz +/- 1 dB. (Generally, the level at 1 kHz is defined as 0 dB) The amp's upper -1 dB point is very close to 40 kHz so I'll give them that one (Freq Response 10-100K) but the low-end frequency response was disappointing. Makes sense why I felt the bass was lacking. The channels diverged by about 0.5 dB on the low end (less than the specified frequency response flatness by comparison, so that's good) and the -1 dB point was 46-55 Hz; at 30 Hz it's down to -2.3/-2.65 dB and at 20 HZ it's down to -4/-4.55 dB.
That's not to say I think the amp is a bad performer. I think it's a good, starter tube amp. It's not trying to be anything more than what it is, which is a slightly novel desktop tube amplifier with a sleek and minimalist design that will fit in nearly anywhere. The 6AD10 tube is an interesting touch, and they're available pretty inexpensively. You'll probably want a DAC to drive it, as testing with a cell phone and a small desktop computer showed that those devices just didn't have enough oomph to get more than 1-1.5W of output even at maximum hardware, OS and application volumes. If you have a nice PC with a good sound card, you could probably drive this directly. It only has one input, so keep that in mind.
Overall, this is a 3/5. It's value matches the price paid for it, and this type of performance is what you get for that price. A great splurge for a person just getting into audio in high school or college, someone who wants a small tube amp for their desk and wouldn't mind having someone ask about it, someone who likes oddball tube amps, or who just wants something a little different.
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Aug 12, 2016
JonasO
170
Aug 15, 2016
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Wow, that's a great review, thanks for taking the effort and sharing!
Aug 15, 2016
Federer
7
Aug 16, 2016
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Great great review. You should be getting paid for this !
Aug 16, 2016
focalpoint
24
Aug 16, 2016
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Hah, thanks! Massdrop thought the same thing too, actually, a year or so ago and asked me to create some content for them. They took delivery, but never paid my invoices. To whatever minimal credit it deserves, they never published the material either at least and for such a small amount of money it wasn't worth my time to bother trying to collect. I do get paid through my repair shop, Rain City Audio at least!
Aug 16, 2016
dividead
12
Aug 20, 2016
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I don't suppose you ever had the chance to test the miniwatt 2013. I'm quite curious to know how it compares.
Aug 20, 2016
Sloblo
407
Aug 26, 2016
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Seems like Massdrop's loss then. ROI on a quality honest review like that one is usually very good (especially if it is a positive one) It's actually for that reason I've started shopping more on here since there doesn't seem to be as much "I got this product for free by promising a good review" I seem to see so much on other popular sites... Looking at you *cough* Largest South American Rainforest/Webs Vendor *cough*
Aug 26, 2016
AlexPk
5787
Community
Aug 29, 2016
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That's a bummer. Mind if I email you some time to figure that out? I want to make sure you get whatever is owed.
Aug 29, 2016
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