Portable Headphone Amplifiers

If I don't really know why I have so many headphones, then I sure don't know why I have so many headphone amps. I usually keep two in the living room, two in the bedroom, and at least one in my laptop case.

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C&C XO Amplifier

This is a fine headphone amplifier. The unusual shape makes it look like a hip flask, which is apparently intended to make it more comfortable to carry in a pocket or strap to an arm. I don't do either, so the shape is nothing more than an artistic statement.

The LEDs serve several purposes, including indicating battery/charging status and headphone impedance selection. There are four slide switches on the end opposite the volume control. These allow you to select headphone impedance (two settings,) gain control, bass compensation, and sound field. This is one of the few amps I have with effective, yet unobtrusive, signal processing. The unit seems to charge completely in about 6 to 8 hours and will function continuously at relatively high output for more than five hours on a charge. I haven't had the unit discharge completely yet, so I have no idea how long it actually will work on the internal batteries.

Perhaps the only irritating feature on this unit is the automatic shut-down in the absence of an audio input. I've actually had the unit shut down when I simply paused my player to use the bathroom. The problem is that you sometimes have to fiddle with the unit to get it to come back on. I've found that I have to turn off my player, turn off the amp, turn the player back on, and then turn the amp back on. If you just turn the amp on and off, it will play for just a fraction of a second and then shut down again.

  • QUALITY: Excellent quality and finish (available in several colors,) with smooth controls and positive connections. It's really difficult to find flaws with the unit.
  • PERFORMANCE: Excellent performance. Low residual noise coupled with superior power output make this a very pleasant amplifier to use.
  • PROS: Strong construction, fast charging, multiple sound-processing options, neat leather sleeve, great sound, works well with headphones of varying impedances (has selector switch for headphone impedance.)
  • CONS: Case is really just an open sleeve that slips over the unit (no belt loop or other method of securing it), battery life seems a bit less than with comparable units, battery strength indicator is subjective (the LED dims), operating manual is marginal.
  • VALUE: Fairly expensive, but worth the money if you have demanding headphones. Finish, packaging, and accessories are all first-class.
  • OVERALL OPINION: This is a great match for my more demanding headphones (like my Sonys) but is not my first choice for traveling. I tend to use the XM4 when I travel and need the "ooomph", or my PA2V2 if I just need some good sound.
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    Gary's PA1 Amplifier

    This is one of Gary's first headphone amps (www.Electric-Avenues.com). It is remarkably unchanged from his early prototypes. I don't know much about electronic circuitry or amp design, but this is certainly a very impressive headphone amp both in power output and low-noise operation, especially considering that it runs on two 1.5 volt AA batteries. The quality of Gary's construction is super and has held up without a problem over the years. His new amp designs and the construction of the units is far ahead of this one (see below), but I still use this amp all the time with headphones connected directly to the line-level audio outputs from my satellite receivers. (Why run it through the TV or a separate receiver when you can just run the cable to your chair and hold the amp and volume control in your hand?) I use rechargeable NiMH batteries in my unit and it works just great. I keep a thick rubber band around it, as the plastic case wasn't really intended to lock closed, but this just keeps it from slipping off the arm of my easy chair.

  • QUALITY: Has some typical first generation issues, being hand-built and housed in a simple plastic box, but no performance or durability problems so far.
  • PERFORMANCE: Excellent performance. Low residual noise coupled with adequate power output make this a very pleasant amplifier to use.
  • PROS: Lightweight, uses AA batteries, neat clear lid to view circuitry and power LED, great sound, very reasonable price.
  • CONS: Case not intended for rough use (see above), volume knob oversized (you can just replace it), no internal recharging circuit.
  • VALUE: A great deal of bang for the buck. It beats the hell out of the $90 - $120 headphone amplifiers being sold at the time.
  • OVERALL OPINION: Superseded by the PA2, which is superior in just about every respect, this amp is a sentimental favorite of mine. Buy a PA2V2 and you'll be happy.
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    Gary's PA2V2 Amplifier

    I originally thought that this was an earlier version (PA2V1) of Gary's current PA2V2 amplifier (www.Electric-Avenues.com), but Gary tells me that this is actually one of the earliest PA2V2s, with the same components as the current model. This amp performs better than his PA1 (above), plus it has a lot of additional features and improvements. For one thing, it is smaller, lighter, and mounted in a nice plastic enclosure that screws together. The volume knob is now much smaller, but has a durable non-slip rubber finish. The internal batteries are rechargeable through a sub-mini jack on the front panel and Gary helpfully includes a wall-wart power supply to recharge the unit. The amp circuit board is about half the size of the PA1 circuit board, which is amazing. As always, sound quality is excellent and performance is pretty much flawless. This is the amp I take with me when I travel. I don't think that you will match this amp's performance for less than $125.

  • QUALITY: Far superior to the PA1 amps, with a durable plastic enclosure. I've had no problems at all with my unit so far.
  • PERFORMANCE: Good power output with low residual noise makes this a favorite.
  • PROS: Very small unit, comes with rechargeable/replaceable batteries and charger, excellent audio performance, lifetime warranty, very reasonable price.
  • CONS: Toggle switch for power sometimes flips on/off when placed in luggage, input and output are not marked and I often forget which is which.
  • VALUE: I give this an unreserved "Best Buy" rating. The performance to cost ratio is very high. Don't waste your money on a "Boostaroo" or some other toy amp.
  • OVERALL OPINION: You won't be sorry if you buy one of these amps.
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    Generic CMoy
    Amplifier (in
    Penguin Mints tin)

    This is a generic CMoy (Chu Moy) amplifier circuit built in a Red Penguin mints tin. For some reason, building headphone amps in mint tins, especially Altoids tins, is very popular. The basic CMoy circuit works just fine and sounds good, but the amplifier is just not anything exceptional. It uses a 9-volt battery and the battery is not rechargeable unless removed from the tin. The on-off toggle switch is on the side of the tin, where it is subject to accidental movement. Anytime I put this in a suitcase or laptop case, it ends up being turned on and the battery drains. The builder did a very nice job of protecting all the soldered joints from accidental contact with the metal of the tin. The power LED is connected with push-pull connectors, so it can be easily relocated. Overall, a nice job, but not my favorite amp to use or travel with.

  • QUALITY: Good workmanship shows up in the insulated solder joints and attention to detail.
  • PERFORMANCE: Very good sound, typical of CMoy design.
  • PROS: Novel appearance, relatively small, smooth volume control, proven circuit design, good workmanship.
  • CONS: Switch on side is vulnerable to accidental movement, uses 9-volt battery instead of less expensive AA batteries.
  • VALUE: This was not very expensive and works very well for the price.
  • OVERALL OPINION: If I were going to use this amp on a regular basis, I would move it to different enclosure and shift the switch to the same end as the volume control and jacks. Since I have other amps I like better, I just keep this one because it's novel and works OK the way it is.
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    Little Dot II++
    Tube Headphone Amplifier

    It's a slippery slope. You get a decent set of headphones, plug them into your laptop/desktop/receiver headphone jack, and then you wonder why they don't sound like they did in the store. Where are the highs? Why is the imaging so poor? What happened to the dynamics? What's all that background noise and where did it come from? In the case of my Sony MDR-SA3000s, I wondered why they sounded so harsh and fatiguing. It doesn't take you long to figure out that (1) you need better source material, and (2) you need to improve the electronics and amplification between the source and the headphones.

    Tube amplifiers are generally esteemed by audiophiles because of their "warm" sound, as they are free of most of the anomalies (usually non-linear performance) that originate from solid-state designs. (This is not to say that there aren't many high-quality solid-state amplifiers that perform exceptionally well.) The Sonys have exceptional definition, and in combination with most solid-state amplifiers they sound strident or harsh. (This is based on my listening trials at a local audio store.) Connected directly to my laptop or desktop, they sounded downright irritating.

    Enter the Little Dot II++. Designed and made in China, this amp is only about the size of a large paperback book (if paperback books had glowing tubes and transformers glued to them). Little Dot continuously upgrades their basic design and the tubes they supply with their tube amps. I understand from some audio and headphones forums that these are a big improvement over previous models, though I have no personal experience to verify this. But my experience with this particular amp has been extremely positive. The headphones that are most frequently plugged into this are my Sony MDR-SA3000s and Grado SR325is.

  • QUALITY: Nice quality build, but not as finished as some of the more expensive amps. I haven't taken mine apart yet, but that should be interesting.
  • PERFORMANCE: Typical tube sound complements my Sony MDR-SA3000s and Grado SR325is very nicely. It's not really fair to compare this to solid-state designs, so I may have to reserve judgment until I spend more time with other tube headphone amps.
  • PROS: Inexpensive (probably half the cost of a similar US-made amp), "warm" tube sound, manufacturer very helpful, product is continuously being upgraded (both design and tubes), permits you to change tubes for desired sound/quality, very compact for tube amp, simple to set up and operate, internal jumper to change input impedance.
  • CONS: Noticeably microphonic (many tube amps are), have to return to China for service, must be re-tubed at intervals, not portable at all.
  • VALUE: Very good headphone amp for the price. Little Tube is clearly trying to improve their amps on a continuous basis. Even with shipping from China, this is half the cost of US-made amps.
  • OVERALL OPINION: Again, this is a "portable" headphone amp only in the sense that you can pick it up and move it. Little Dot makes a hybrid tube headphone amp that can actually be packed in a suitcase with a good chance of surviving, but this one can't. On the other hand, you could take it to work on a regular basis, as long as you treat it carefully, and it would probably survive. Mine just sits in one place, next to my easy chair and my Fubar II DAC.
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    Little Dot Micro+
    Headphone Amplifier

    This is also a very small amplifier, undoubtedly the smallest in overall dimensions that I own. The case is tough extruded aluminum and it has a very solid feel to it. It is made by Little Tube and is one of a series of solid-state and tube amplifiers. You can find more information on it at www.little-tube.com if you're interested in the type of chip it uses and other details. It has internal, lithium-ion batteries that are recharged through a jack at the bottom of the unit using the (included) wall-wart power supply.

    Oddly, the input and headphone jacks seem slightly oversized in diameter. Most of the 1/8" plugs I use are slightly loose when inserted, to the point that some are actually intermittent in one channel. I could probably have them replaced, but it's a fairly minor issue. Perhaps Little Dot got some slightly out-of-spec connectors.

    I am, however, a bit disappointed in the power output of this unit. While I have not measured it, the unit simply does not have the gain that most of my other amps have for a given input level. The PA2V2, for example, uses roughly the same voltage power source as this amp, but it plays significantly louder at full gain. On the other hand, for virtually all reasonable uses, this amp is plenty powerful enough.

  • QUALITY: Excellent quality and durable case.
  • PERFORMANCE: Very clean sound, but gain/power output is not on the same level as most of my other amps.
  • PROS: Tiny and very easy to carry, uses rechargeable LiIon batteries, strong aluminum case, includes patch cord and charger.
  • CONS: On-off control is integrated into volume control...you have to reset the volume whenever you turn it off, noticeably less gain than other amps.
  • VALUE: Very good value for the price. Quality is obvious during first use.
  • OVERALL OPINION: I take this unit along with my Cowon U2 and my Ultimate ears when I want to save space and weight. If these are not a concern, I usually take my Cowon M5 and another amplifier, depending upon what type of headphones I plan to use. This is a good buy for someone looking for a tough little amp for traveling and who doesn't need to listen at high volume levels.
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    Michael Gaspa's Amplifier

    This amplifier has a bit of a twist: no volume control. This is not uncommon in audiophile components, as it eliminates a non-linear component and a potential source of noise. I can't argue with this line of thought. This is, after all, the only amp I have for which I can vouch that there is absolutely NO noise when you adjust the volume. The amp works fine and sounds great. I did have one issue with it, though. Due to the impedance mismatch with my Cowon iAudio M5 player, I was getting some excessive noise from the data signal to the M5 remote display. I had a couple resistors added to the input of the amp and that improved the situation greatly, though it didn't eliminate it. (I later found that this happens with several amps, so I just changed the settings on my iAudio player so it doesn't scroll.) This amp uses a 9-volt battery and does not recharge the battery while it's in the amp. The rocker switch for power is located on the side and seems to be less vulnerable to accidental movement than a toggle switch would be. A nice, solid performer.

  • QUALITY: Very well-made in a durable enclosure. By eliminating the volume control, a potential source of failure or noise is absent.
  • PERFORMANCE: Works like a champ. Sound quality is great.
  • PROS: Low profile with no protruding knobs or switches, no volume control problems, rocker switch less vulnerable to accidental movement than toggle switch.
  • CONS: Uses 9-volt battery instead of less expensive AA batteries, a bit large in size, battery must be removed to recharge, lack of volume control means that player must be accessible to change volume.
  • VALUE: Very good product for the price.
  • OVERALL OPINION: This is probably my second or third favorite amp after the PA2V2 described above. Very handy for travel.
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    MP Mini Headphone Amplifier

    This Chinese-made amplifier was very cheap...and I found out why when I received it. Due to some miscalculation, the space for the battery is about 1/8" too shallow for a standard 9-volt battery. As you can see from the pictures, if you insert a battery, the cover plate cannot be screwed back on the end. With that aside, the amp works just great. The enclosure is aluminum and very durable. The controls operate smoothly and the graphics are subtle, but legible. The controls and jacks are soldered directly to the circuit board and their attachment to the end panel is the only thing that supports the circuit board inside. It is not mounted to the box at all.

    I gave this away to a friend, who happens to have a lot of duct tape.

  • QUALITY: Nice quality, except for that huge design flaw. The ends of the case use four machine screws each to fasten them to the amplifier.
  • PERFORMANCE: Sounds just fine...considering the battery is hanging out the tail end.
  • PROS: Durable construction, sound is more than adequate, good quality enclosure (though not enough of it).
  • CONS: Uses a 9-volt battery instead of less expensive AA batteries, battery does not fit completely inside the case, circuit board is supported directly by the control soldered to it.
  • VALUE: This amp cost me less than $15.
  • OVERALL OPINION: If you don't mind using duct tape to hold the battery in, this amp is just fine.
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    Practical Devices XM4 Headphone Amplifier

    There is no way on earth that I can summarize the many features built into this amp. You're just going to have to go to the Practical Devices website to read about this unit.

    Overall, it's a nice amp. It works as advertised (all the functions I've been able to test, that is). Power output is pretty good...better than the Little Dot Micro+ and about the same as Gary's PA2V2. The operational features are pretty cool, but I don't think I've done anything with them other than turn the unit on and off. (I'll check the battery level every so often, but only because I can.) I'm just not so sure that it's worth twice as much as the PA2V2.

  • QUALITY: Exceptional quality in the circuit board, case, and controls.
  • PERFORMANCE: Sounds great with just about any headphones or earphones. Capable of very high volumes.
  • PROS: Durable construction, sound quality is superior, power output is above average, numerous user features, rechargeable battery lasts a looooong time, unit turns off without disturbing volume setting, variable stereo crossover is actually helpful, DIP socket allows chip upgrades, auto-off feature saves battery life, direct voltage display for battery useful for assessing remaining charge.
  • CONS: Expensive, rechargeable battery/charger is a $25 option, crossover adjustment seems vulnerable to damage, operation and features can be a bit overwhelming.
  • VALUE: Fairly expensive, but provides appropriate performance and value.
  • OVERALL OPINION: This is a tough one. To be honest, I still grab my PA2V2 amp (above) instead of this amp when I get on a plane. The PA2V2 is slightly smaller and much simpler to use. The sound quality of the PA2V2 is comparable to that of the XM4, though the XM4 is definitely superior in construction and features. Overall, I think that the XM4 is probably too much amp for my meager needs. At roughly twice the price of the PA2V2, it basically sits at home when I travel, used only when I need a boost for my "home listening" headphones. But if you want to impress somebody in the airplane seat next to you, the XM4 is a good place to start. (Note: It won't impress women at all...trust me.)
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    Twinstarr Black Amplifier

    Very nice amp. Sometimes called the Twinstarr Black Apheared 47, this unit is constructed of top-notch materials and has some very attractive graphics on it. The audio performance is well above average and makes just about any headphones sound great. It uses a 9-volt battery that must be removed to be recharged. It is slightly larger than some of the other amps. The only thing I don't like about this amplifier is the blue power LED. It is unbelievably bright. The people sitting next to you on the plane will complain about it and will suspect it is a laser. I have actually used it to find things in a hotel room so I wouldn't have to turn on the light. It is not just bright enough to read your watch...it is bright enough to see all the way across the room.

    Sound quality is exemplary, with good power output even using high-impedance phones.

  • QUALITY: Very well-made with attractive graphics.
  • PERFORMANCE: Great sound, even at high output levels.
  • PROS: Great sound, nice case and graphics, doubles as a flashlight, company stands behind their products.
  • CONS: A bit larger than some other amplifiers, blue LED is much brighter than necessary, uses 9-volt battery instead of less expensive AA batteries.
  • VALUE: Premium-priced unit, but quality of construction and sound are commensurate.
  • OVERALL OPINION: Definitely a good match for quality headphones. This amplifier really makes my Grado SR60 headphones sing. This is a bit more expensive than some alternatives.
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    ProAudio HPA-01A
    Headphone Amplifier

    Somebody put a lot of work into this amplifier. I have not seen any exactly like it in some years, but there were several for sale on eBay over a period of a couple months by ProAudio (I believe). This amplifier is much larger than the others and is constructed inside a very nice transparent blue plastic box. One reason it is so large is that it uses two 9-volt batteries, not just one. It also has a jack for the connection of a 24 VDC power supply (not included) to recharge the internal batteries, if they are NiCad or NiMH batteries. The main circuit board is over 2" by 1-1/2" in size. Other than the size and weight of this unit, the only downside is that the on-off toggle switch is on the bottom (or end) of the unit, opposite the volume control and jacks. This makes it very easy to turn on or off accidentally. If you put it in a pocket, it really needs to sit sideways. The output from this unit is pretty impressive and it will drive just about anything you want it to. Sound is very good, though I occasionally hear some noise in the volume control when I move it.

    The toggle switch is definitely a big negative, and so this amp is most often relegated to bedroom duty with headphones connected to the satellite receiver. It works great for this purpose, and the end-mounted switch doesn't cause any problems. The same thing applies if you like listening to CDs or radio in bed.

  • QUALITY: Built like the proverbial "brick s**thouse", even if it is in a plastic case. A lot of the wiring is point-to-point using discrete conductors.
  • PERFORMANCE: Capable of high output with low residual noise.
  • PROS: Built extremely well, great power output, can use rechargeable batteries and charge them in the case, external power connector.
  • CONS: Bigger and heavier than most, toggle switch mounted on bottom (end) of case subject to movement, battery life is not that good with NiCad or NiMH batteries, requires a 24 VDC charger (which is not very common or easy to find).
  • VALUE: This cost less than most amps and was worth every penny.
  • OVERALL OPINION: Not that useful for travel, but does a great job around the house and when mowing the lawn. This is capable of deafening you.
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