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Incremental Review (completed) - HeadAmp Pico Slim

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Thread Starter 

This is what I call an "Incremental Review", because I can go into so much detail that if I waited until I actually finished writing everything I want to post a review, it will never get posted.  So expect an incomplete review at first, with more and more getting added as time goes by.  It will feature high quality images to accompany the review which click through to 2MP size.

 

Product: HeadAmp Pico Slim

 

A lithium-polymer battery powered portable headphone amp featuring a 255 step digital volume control with up to 110db attenuation and 60 hour battery life.

 

Packaging:

Dimensions of Box: 6.8125" x 5.625" x 2.6875"

 

A plain white box with a large sticker identifying the product inside.  It's definitely function over form, with the function being to protect the contents inside.  This doesn't pose a problem as a mail order only product.  

pico_slim_box.jpg

 

Contents:

 

- Pico Slim

 

- Leather like carrying case

 

- User Manual

 

- Worldwide (100-240v) capable AC charger with interchangeable tip capability and Micro-USB output with 1600ma output capability

 

- North American tip for AC charger (if you bought for US usage, otherwise Justin will ship with appropriate tip depending on your country of use)

 

- optional 3 foot Amphenol Micro-USB cable for $10 extra if you want to charge from a usb power source.  I did not get this.

 

Photos of Contents:

 

Inside, you'll find a nicely printed user manual

pico_sim_manual_front.jpg

 

And here is the back of the user manual....if you can really call it a user manual.  It's more of an information sheet.

pico_slim_manual_back.jpg

 

And here is a view of the inside of the box.  4 cutouts hold the contents, there was also a foam sheet on top of it all to protect from the top side.  The foam did not look appropriately spaced for the contents as the middle compartments look way too big.  The North American tip is small so maybe that's why the space is too big for it.  It looks like a bit more space for the AC adapter would have made it fit better without crumpling the center compartments.  Maybe if you get the optional Micro-USB cable it would take up the top compartment completely and require the large size.  The amp in it's leather like case itself fit nicely into its assigned slot with plenty of foam around it.  I think this box could take a beating without any worry of damaging the amp inside.

pico_slim_box_inside.jpg

 

Interchangeable tip AC adapter.

pico_slim_ac_adapter_top.jpg

 

Tip changing mechanism on AC adapter

pico_slim_ac_adapter_bottom.jpg

 

Assembled AC adapter

pico_slim_adapter.jpg

 

Product Details:

 

Price:

$399

 

Dimensions:

rectangular area - 2.125" x 1.5" x 0.375"

including all protrusions - 2.3125" x 1.5" x 0.375"

 

Available Colors:

black or silver

 

Design:

 

- This amp is light, I have no way to weigh it accurately but I can tell you it is very light.  Sure, it's thin, but it feels lighter than it should based on other electronics this size, especially ones made of metal.  It must be the light lithium polymer battery coupled with aluminum.  I like the lightness, it would be easy to hold while jogging, or light in the shirt pocket.  This gives it more versatility in it's possible use scenarios in a portable setup.

 

- This amp trades thinness for length.  It is slimmer than most amps, but also ends up being longer than many too.  Though thin is more pocketable and the length is still short enough to fit into any pocket easily.  This tradeoff in dimensions helps portability greatly.

 

- The body is made of aluminum, on silver it looks to be polished and black seems to be anodized.  The aluminum is very thick feeling and has no give at all when pressed, it is a very solid piece and feels durable.  However, reports show it is easy to scratch and some units even came with slight scratches on them.  Unfortunately, because this is not type 3 hard anodizing, mine will be staying in it's case at all times.  So all the nice attributes of thinness and lightness are lost for my use.  If you don't care that it remain pristine and don't mind scratches from rubbing your DAP or whatever you put it against, then the form factor can really help you out.  An outer layer of type 3 hard anodizing would give it a completely different look though, and this amp is style as well function so this is probably at least one of the reasons Justin did not choose to go this route.  At least if you get silver, any light scratches can be polished out.  This is one o the reasons I picked silver after the initial reports on scratches came in.

 

- The volume control has a matching color aluminum knob with grip points and a detent on the face helping to indicate current volume setting.  The volume control stem itself seems to be a plastic affair and it wobbles a bit if you press on the knob, this could be a weak point in the design if it was dropped on the knob.  My knob is not perfectly aligned as when I turn it you can see it shift positions of it's tilt slightly, like the center does not point straight up.  This is just an observation and should not affect anything as it is not so noticeable.

 

- The power switch is clear plastic and glows red when the amp is on.  It toggles back and forth, with the on position being away from the headphone jack.  This gives it a little bit more room for larger headphone connectors.

 

- The 1/8th inch jacks are on opposite sides of the body,  the output shares sides with the power switch and volume control.  The input 1/8th inch jack sits next to the micro-usb charging jack on the opposite end with the charge indicator light.  The light glows red when charging and turns off when charging is complete. 

 

- Each of the switches and ports are clearly marked by what looks to be laser engraving.  The front and back of the body is engraved too and looks nice.  It is very clear and well done.  However, for some reason in my usage I'm always seeing the Pico Slim logo upside down.  I guess I like inputs on the left, outputs on the right with the volume control for my right hand. 

 

- The top and bottom halves of the case don't seem to match exactly.  When you view it from the end, you'll notice the cutout shapes are not symmetric and are slightly different size.  I also notice the two case halves seem to bow out just slightly from each other, just enough to cause a tight joint at the corners to show a slightly visible gap in the center of the case when viewed on the long side.  Justin explains the cause of these snafus in post 3 below.  In fact, with further examination I'd say that the top and bottom halves look like they are made from different batches or different suppliers.  The top piece is much more rounded around the holes, while the bottom half has more distinct edges around the cutouts.  The top half looks more artistic with a hand made polished look where it only needs to be smooth but not precise, while the bottom half is more what I expect out of precision craftsmanship.  I would prefer if both halves matched the bottom half machining style.

 

- The leather like (not sure if it's real or not) carrying case seems to double the thickness of the amp.  At least it helps prevent scratching the nice polished surface if you decide to use it.  It is black and has the Pico Slim and HeadAmp logo impressioned into the leather.  It does have stray threads poking out here and there though and the edges sewn together don't line up exactly.  The inside of the case seems to be felt, maybe to prevent scratching the amp.  It does leave some fine lint on the amp though.  The bottom of the case is only a thin piece of the material.  I wonder how long it will last if you push headphones into the jack while holding only the edges of the case.  That thin piece is not strong enough to hold the amp up under that pressure and seems to stretch.  Now I have to make sure to hold on to the bottom of the amp when inserting headphones so I don't stretch that piece any further and cause it to break or sag.

 

Here is the amp sitting on top of it's case, notice the nicely machined volume knob with the detent.  You might be able to see the slight gap on the long side of the case and the hole cutouts not lining up exactly.  The edge of the case can be seen in this shot, it's not so finely finished.

pico_slim_on_case.jpg

 

The front of the case, notice with the words the right way, the knob, power switch,  and output jack are on the left.  Notice the volume knob is slightly bent downward in this photo.  You can see the thin bottom piece of leather holding the amp in.  You also see the case edges are not lined up perfectly so a bit of leather pokes up when looked at from certain angles.

pico_slim_case_front.jpg

 

The back of the case.  A nice deep stamped impression of the HeadAmp logo.

pico_slim_case_back.jpg

 

Here is the right side with the micro-usb charge port, the charging indicator light, and the 1/8th inch input jack

pico_slim_front.jpg

 

Here is the back of the slim, and the left side with the volume knob, output jack, and clear power switch.  The 4 screws are on the backside, and the screw that holds the volume knob on can be seen.  Yes, I have a limited edition unit with a lifetime warranty and lifetime batteries.  Only the first 250 units are limited edition.

pico_slim_back.jpg

 

So just how small is the pico slim?

 

It looks and feels really small in the hand.

pico_slim_hand.jpg

 

It looks very thin in the hand as well.  Notice the non matching size and style of cutouts for the top and bottom halves of the case for the input jack.

pico_slim_fingers.jpg

 

 

Here it is compared to a uDac-2, the uDac looks not so small compared to the Pico Slim.  That side gap is more obvious in this photo.

pico_slim_on_udac.jpg

 

Here it is compared to a Ray Samuels Tomahawk, my previous smallest headphone amp.  It's way thinner.... notice the hole cutout asymmetry in this shot?

pico_slim_tomahawk_thinness

 

But longer...

pico_slim_tomahawk_length.jpg

 

Specifications:

 

- 1/8th inch stereo input and output jacks

 

- up to 60 hour battery life

 

- up to 4.2V output voltage - max voltage depends on battery state of charge.  LiPo batteries start at 4.2V full charge and almost linearly taper down to 3.7V when 10% battery is remaining.  So it's safer to actually claim minimum 3.7V max voltage if you were to think conservatively.

 

- up to 250mA output current

 

- 255 step 0.5db interval digital volume control with 110db attenuation and low noise - this is the main draw of this amp for me.  Perfectly matched left and right balance at every volume level, with enough attenuation to listen with the most sensitive IEMs on hot sources.

 

- 36V peak to peak input voltage - It can take the hottest input sources without clipping, many other digital volume controls only take input voltage up to the power supply voltage

 

- Micro-USB charge port - 300mA charge current, max 3 hour charge time, charge with included charger or any usb power source that can deliver a minimum of 300mA.

 

Usage Impressions:

Power Switch:

 

- The switch is very easy to turn on and off, it flicks left and right.  On is away from the headphone jack so you gain additional space for wide connectors.

 

- The switch glowing red when on helps easily identify whether the amp is on or off.  It also serves purpose of saving space by taking care of a power switch and power indicator light in one place.

 

- Holy smokes, don't turn the amp on with sensitive IEMs plugged in and on your ears.  There is a very loud thump that comes through.  I heard the thump on Grados and it was really annoyingly loud.  I never actually tried it with IEMs but I don't want to damage my hearing testing it out.  My recommended solution is to turn the amp on first and then slowly connect the headphone, you won't hear much noise that way.  I don't know if the thump can damage headphones but I don't want to test that out, so I'll continue to do it this way.

 

- On power down, you hear the sound quickly fizzle away.

 

- The battery is supposed to cut-out if the voltage gets too low.  This protects the LiPo battery from getting damaged.  You should not allow the battery to stay in a discharged state, so if the Pico Slim ever shuts off by itself, the battery is too low and should be charged immediately.  In fact, for optimum battery life, don't discharge the cell too far.  Maintaining the cell at moderate charge levels at all time will prolong the life of the battery.  Avoid keeping it fully charged and unused, as well as avoid keeping it at a low charge level.  With a lifetime battery warranty I'm not too worried about this limited edition unit.  But Justin will only replace it if the capacity is less than 50% of original.  For the non-limited edition models, you can purchase a replacement battery when necessary and put it in yourself.  It is just 4 screws and a simple connector inside, much easier than trying to replace a battery in an iPhone.

 

Volume Control:

 

- The Pico Slim volume knob starts at about 6:30 and tops out at 3:30, a 270 degree sweep.  Hmm, maybe the knob is a bit off and the intended sweep is from 6 o'clock to 3 o'clock.  Anyways, this amounts to about 1 degree per volume setting.

 

- The resistance and smoothness of the pot is good, not too loose so it swings wildly at the slightest touch, not so tight that it jumps far when you try to do fine adjustments.  This is important when the knob is as small as it is.  I've encountered amps where it is difficult or almost impossible to move the knob 1 degree as it's too tight and the knob too small causing you to jump above and below the volume you want as you try to settle in on it.  You can easily make fine adjustments with the Pico Slim which you will see is very important for another reason later on.

 

- The left and right volume are perfectly in sync no matter what the volume may be set at.  This is tremendously important for me as all my other amps with analog volume controls have left/right mismatch quite significantly at the low volume settings.  With sensitive headphones it means I can't listen quietly or the volume will be off balance.  By the time things balance out, the volume can be much higher than how I want to listen.  The Pico Slim solves this completely as there is never channel imbalance.

 

- Occasionally while changing volume you will hear clicking sounds.  If turn the knob too fast, you'll notice it jumping volume levels sometimes.  However, if you turn it at a normal and careful pace, you will notice no sudden jumps in volume and it feels nothing like a digital control with the volume change feeling seamless.  You can find any volume you want on the dial, this is not like those 16 step digital volume controls of the past.  255 steps is enough to feel analog, especially with it spread among 270 degrees of rotation.  However, at very high points in the dial (above 12 o'clock), the clicking when changing volume becomes much louder and happens with the slightest rotation.

 

- The volume control taper is unlike any analog pot I've encountered.  In analog pots I normally encounter, the volume starts low, the first few degrees make barely any change, then it hits a point where the volume increases quite rapidly.  A little bit after this point when the volume level is already quite high, it seems you can turn the pot a lot more and only have slight gain in volume.  So basically, 99% of the attenuation happens in the first few degrees of rotation, then in the next 20-30% of rotation you've already used up most of the attenuation, and the rest of the volume pot is just slight change in volume compared to how much changed at the beginning.  What this results in is very poor control of low volume, where the slightest movement changes the volume dramatically.  This also results in fine control at high volume, where you can move the volume knob quite a lot and the volume swing is noticeable but not tremendous, allowing you to fine tune exactly how high you want volume at the expense of having any control at the low end of the volume pot.

 

The Pico Slim is almost completely opposite to the behavior of analog pots.  Starting with no sound at the beginning of the volume dial, the sound comes up slowly and evenly giving incredible control over ramping volume at low levels feeling so linear.  In fact it takes quite a bit of rotation to move from very low to normal volumes, so you have great control there.  However, once the volume is high, because the gain difference for the same degree of sweep is the same at any point in the volume dial, that same slight turn goes from moderate to loud to super loud just as quickly as it went from silent to low, to moderate.  It does not have the taper of the analog dial so you actually have a harder time fine tuning at high volume as you have to turn it more carefully.  A moderate turn can change the volume significantly, and trying to get it only a little bit higher when already high, you have to turn the dial very carefully. Much less than you'd expect when you're used to the analog pot.  You can still get the exact volume you want, you just have to use precision turning to get it, which helps when the pot is as easy to handle as the one on this amp.

 

- 110db attenuation is incredible.  It is the only way to start with zero detectable sound and work your way up precisely to the volume you want to listen to.  With my Shure se530, I can hear nothing at 6:30 (lowest setting), I can begin to hear something at 7 o'clock, and my normal listening volume is around 9-10 o'clock.  So I have over 90 degrees of rotation with very linear control of the volume if I want to listen quieter than normal on the se530.  With many other amps, I have about 12 degrees of control from loud enough for me to as soft as I can set it, even with my full size headphones.  The Pico Slim volume control is by far my favorite one....really...by far.

 

- Hiss is one area where things are still not as perfect as I hoped it would be.  In fact, I have to say that the hiss to volume ratio of this amp is one of the worst performers I've encountered.  I've not encountered an amp that the hiss level rises with the volume setting at the rate this does.  I can detect very slight hiss using the se530 at just 7 o'clock on the volume dial.  The hiss goes up as the volume goes up, and by 9 o'clock which would be on the lower side of a normal listening position, the hiss is obviously there and prevents the feel of complete blackness in the music.  It is not a loud hiss, it is actually quieter than nearly all my other amps, but I can't say this amp can produce a perfectly black background, at least not with sensitive IEMs.  In fact, even with less sensitive headphones which require turning the volume dial up more to get the volume you like, the hiss can become audible in many cases where there is no hiss with another amp.  With a hotter source this is less of a problem because you would set the volume dial lower.  But with a quieter source like an iPod, this becomes more pronounced.  At the same volume level, the Pico Slim hisses significantly more than the Ray Samuels Tomahawk with any headphone I try.  With full size headphones, it can hiss at what you would set for a high listening volume especially with quieter sources.  Because the volume control on the Pico Slim controls the gain, I wonder if this is the reason hiss increases at a much faster rate with the Pico Slim than other amps which use a fixed gain and increase amplification in a different way.  The best workaround I can see for this is to use the hottest source you can, so you can keep the volume dial at as low a setting as possible.  Do note, this hiss level even at high listening volumes with the se530 is still significantly less than the hiss level I get with all my other amps and sources even at volume level zero (except the Tomahawk which is my only silent amp).

 

- One aspect of hiss where the Pico Slim performs very well is the inherent hiss not related to the particular volume setting.  On nearly all amps and DAPs I've tried (RA1, XP7, xin supermicro, HDP, uDac, uDac2, iPod, iPhone, panasonic and sony PCDPs....pretty much every single headphone jack from anything), they hiss with many of my headphones even at a volume level of zero.  With the se530, this hiss level ranges from obviously there to very loud.  However, with the Pico Slim, just like my Tomahawk (the only amp I've found that doesn't hiss noticeably with the se530), it has no easily detectable hiss at a volume level of zero.  However, while the tomahawk can maintain no easily noticeable hiss even when the volume is set at normal listening volumes, the Pico Slim hiss becomes detectable and obvious at normal listening volumes on the same se530.  So in terms of hiss with IEMs, the Pico Slim is the second best amp I've ever encountered, coming second to the Tomahawk.

 

Conclusion on Usability:

 

Due to multiple factors listed above...

 

1.  110db attenuation with precision control in 0.5db steps

2.  Very low inherent hiss levels

3.  Perfectly balanced left/right matching through entire volume range

 

....the Pico Slim is the only amp I've ever encountered that lets me enjoy a high sensitivity IEM like my se530 comfortably with a normal line out source.  All my other amps except the Tomahawk hiss at a level that makes them completely unusable or at least not enjoyable with the se530.  The Tomahawk has no hiss but has volume inbalance at the beginning of the volume pot which....by the time the sound equalizes....the volume is already above my comfort level.  The Pico Slim is the one and only amp so far that lets me really use this headphone and get near silent backgrounds and set the volume to exactly where I want it.  And I have to say, the se530 is not the most sensitive headphone out there.  This leaves me with headroom to get something even more sensitive like the UM3X, which I was afraid of getting before because I wouldn't be able to find an amp I could use it with...until the Pico Slim.  The only flaw I wish didn't exist is the hiss level tracking the volume level so closely.  If this amp had zero hiss, it would be the perfect headphone amp for IEMs.  With this complaint, it can only be the "most perfect" headphone amp for IEMs that I have encountered yet for people like me with sensitive hearing and sensitive headphones.  Not perfect, but as close to perfect as we have today.

 

Sound Impressions

 

This amp is designed for IEMs, so that is all I really wanted to compare it with.  The only other amp I have that I can enjoy using with IEMs is the Ray Samuels Tomahawk.  All my other sources or amps either have way too much hiss or too much volume gain to be something I'd want to use with IEMs.  Now I've been using the Tomahawk for a couple of years now so I have gotten use to the sound.  Both amps have no trouble driving any of my IEMs.

 

Originally I wanted to talk about how different IEMs sound on the Tomahawk vs the Pico Slim but then I realized after listening a while it was pretty pointless as the same traits exist no matter which IEM I was using but for a few unique circumstances which I will go over. 

 

The Tomahawk and Pico Slim sound quite different.  The Tomahawk is lusher and fuller while the Slim feels leaner.  It seems the Tomahawk fills out notes longer while the Slim has quicker attack and decay.  At the same time though the Tomahawk rounds out the edge of transients a bit while the Slim feels more precise.  In some situations, when the song or source is harsh the Tomahawk gives a more pleasing rendition to my ears.  However, I do feel there is a slight loss of detail in the Tomhawk which the Slim picks up.  The exact preference here depends on the song. 

 

The Tomahawk has more center focus while the slim gives a wider soundstage.  A singer centered sounds very focused on the Tomahawk and a slight distance away.  In the same situation, the Slim presents a different image, one that is wider and closer to you.  The wider nature of it does not present as convincing an image of a singer in front of you.  In fact, I would say the Tomahawk presents sounds with a more distant feeling with a soundstage in front of you and to the left and right away from you.  The Slim presents a wider and closer soundstage.  It goes far left and far right, but all of it seems to be on a plane directly lined up with your ears.  I had always thought the presentation was very different between the Tomahawk and Slim and with lots of listening I have concluded this is simply the case and not just some weird combination at the time.  I've tried different volumes, headphones, and songs but the feeling still holds.  I don't know what about the amp can make the soundstage differ so much. 

 

The bass seems a bit stronger or maybe more emphasized on the Tomahawk than the Slim.  Though maybe what I am really hearing is the bass is filled out more because the Tomahawk is lusher while the Slim hits and decays faster.  The Slim definitely is not missing any bass, it just seems to be a slightly different quantity than the Tomahawk. 

 

One big difference I heard from the Slim when paired with certain headphones was graininess in some singer's voices.  It was especially apparent on the Shure E4C and TripleFi.  On the SE530 and Turbine Pro Copper it was much less of an issue though still detectable.  On the Tomahawk, this grain in the voices is much reduced and it is rendered much smoother and pleasing.  When comparing, it seems most voices sound nasally on the Slim when they sound normal on the Tomahawk.  Now I don't think an amp can create graininess, and pure tones sound perfect on either amp.  My guess is the graininess is in the song or source and the Slim is accurately portraying it while the Tomahawk is rounding it away with it's smoothness and lushness.  My source for the testing is the DacMagic which I use pretty much exclusively with my IEMs and thus I wonder if it just does not do voices with the naturalness and smoothness that the Saturn and HDP I normally use wih full size headphones does.  I'd say due to the presentation differences of the voice being much closer to you, wider and not as focused, and with more detail coming through from the source, it is causing this difference in sound in how voices are portrayed.  The good news is one time that I did use the Slim between the Saturn and HD800, I did not detect any of the graininess in the voices and everything was rendered very well.

 

What I would say is the Slim is a neutral and detailed amp while the Tomahawk is on the warm side.  If treble detail bothers you and you prefer a more relaxing sound, the Tomahawk sound is better.  I think the Slim lets the source shine through, it feels more transparent, less coloration, and imparts no signature of it's own that I can describe.

 

I did take a chance to power the HD800 with the Slim and at the volumes I listen at (which is apparently pretty low compared to most) it had no trouble driving the HD800 with clarity and poise.  I'm pretty sure if you listen loud though it should not be able to deliver like a full size amp due to it's modest supply voltages. 

 

 

Pros:

- Amazing Volume Control - this is the single most important factor that makes this amp shine.  Impeccable control of volume with perfect left/right channel matching at any volume and without having objectionable background hiss at normal listening volumes.  I have not encountered this with any other product.  The steps are sufficiently small to be indetectable and give very fine control of how loud you want to play to your exact preference and not having to set a volume biased by hardware limitations.

 

- Small, Thin, Light - Very portable

 

- Long Battery Life - low maintanence hassle, just charge it up once in a while and it should never run out of power

 

- Neutral and Detailed sound - lets your source shine through clean and clear.

 

- Beautiful - the amp simply looks great out of the case.  Solid and still block of metal with a nice hand polished finished and clear laser engraving.

 

Cons:

- Easy to scratch - The amp is too beutiful with a finish so fine it is unfortunate that you have to keep it covered up or risk easily scratching it.  The aluminum is quite easy to put a scratch in it which will ruin the amazing looking finish.  So then you have to keep it in the case.  Well the case doesn't look nearly as good as the Slim itself, and it adds almost double the bulk.  So you either have a beautiful but likely scratched up Slim or a perfect but ugly Slim.

 

- Power Switch easily blocked by L plugs - Frequently at the end of the day I have to rotate or unplug my headphones from the normal position because I can't turn it off because the switch is blocked.  If I rotate it the other way the volume control will be blocked, if I rotate it 90 degrees nothing will be blocked but the plug sticks straight up and looks silly. 

 

- Low output sources reveal hiss - The Slim is amazing when driven at full line level.  But if you have to use something that drives at a much lower level, you have to raise the volume higher which starts to create hiss at a higher level than something like the Tomahawk.  The hiss comes up fast with the gain and it doesn't matter the headphone sensitivity.  The Signal to Noise ratio feels to be smaller than other amps though still sufficiently high since the input voltage range is huge and can be used to make up the difference.

 

- Loud power on thump - I almost forgot about this because I've already developed the habit to bypass it.  But I would not expect an amp to thump like this at power-on and it is unfortunate that this one does.  It is one of the loudest power-on thumps I've ever heard in any headphone related equipment ever.

 

- Suceptible to RFI interference - if put on top of an iphone, it will occasionally pick up and transmit to the headphones the GSM buzz.  Not at a deafening level luckily, but it is not immune to the sound.  By moving it away from the iphone that no longer becomes a problem.

 

Conclusion:

 

The Pico Slim is right now my favorite headphone amp.  Yes, favorite.... this is due to multiple factors.  It is the only amp that has delivered two important aspects for me which has eluded me for a long time.  Number one is lack of detectable hiss at normal listening volumes when playing music with even the most sensitive IEMs.  The only other amp that has done that for me is the Tomahawk.  Most other products I have encountered have variable range of hiss from moderate to massive.  The second is complete perfect volume control with all of my headphones.  This has eluded me until now.  The Tomahawk was able to control my full size headphones well, but all of my IEMs were still played at too loud a level by the time the left/right levels matched when using my full size sources.  This was alleviated a bit if I used my ipod as a source, but when driven by lineout of my full size components it is much too loud for my sensitive IEMs and I ended up playing at uncomfortably loud levels.  This is the first time ever I can achieve as loud and as quiet as I want with any of my headphones I have without being near the limits of the volume dial on either side.  It is truly incredible. With this amp I am no longer afraid of sensitive IEMs.  I can now look forward to one day getting the UM3X without fear of hiss and loud volumes.

 

Second, the size, weight, battery life make it very little hassle to own and use.  You aren't constantly replacing batteries, it charges up with the micro-usb connector which is basically commonly used by many cell phones.  I use my cell phone charger to charge it up so I don't even have to bring an extra charger out.  And I only have to charge it once a week or less.  In fact I have never had it run out of power on me and I will charge it at most once a week.

 

So if you are like me and have trouble with hiss or getting the volume low enough to use your most sensitive IEMs, this is the amp for you.  It is simply the only amp I can use to enjoy my IEMs on my full size components without any compromise in how loud I want to listen.  Now, I can use this amp to fairly compare IEMs as the level of hiss and volume matching are no longer a factor biasing the sound.

 

Interesting Quirks:

The Pico Slim seems to be susceptible to static discharge affecting it.  When wearing my Turbine Pro Copper, it transmits static electricity through the headphone to connected components when I move in my chair.  Though usually it goes through and just knocks my DacMagic off usb sync, a few times it has caused the Pico Slim to lose one channel or another, sometimes both completely.  It's not permanent and can be fixed by turning the unit off and then back on.  But it's still strange and none of my other amps have ever been effected this way.  It could be related to being a digital volume control and the chip being put into some weird state.

 

Another more serious problem also caused by static is sometimes it does not lose a channel completely, but maybe the overall volume seems to go down a bit.  But maybe you don't notice it because it might be a song change or something.  Anyway, what happens is 15 minutes later when I go to touch the amp it is hot!  Really hot.  Normally the amp runs completely cold, it doesn't create any heat at all.  But when it gets into this weird state it is just dumping all the battery power to heat.  The battery life is going to be on the order minutes not hours when this occurs.  It's probably really bad for the battery too as it is getting so hot. 

 

So the thing you have to avoid when using the Pico Slim is hitting it with a static discharge.  If you did and you notice any change, you should just turn it off and back on.  You don't want to be in that weird start where it starts draining the battery life crazy or have degraded sound quality because the circuit inside is in some odd state.

 

- Update 2-25-2011 - quirks section added

- Update 12-20-2010 - sound impressions, pros and cons, conclusion - Review Completed

- Update 10-16-2010 - operational details and usage impressions added

- Update 10-15-2010 - additional photos, more detailed thoughts into the design.


Edited by bcwang - 2/25/11 at 4:00pm
post #2 of 21
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post #3 of 21

Just wanted to mention something on this

 

 

 

Quote:
- The volume control has a matching color aluminum knob with grip points and a detent on the face helping to indicate current volume setting.  The volume control itself seems to be a plastic affair and it wobbles a bit if you press on it, this could be a weak point in the design if it was dropped on the knob.  My knob is not perfectly aligned as when I turn it you can see it shift positions of it's tilt slightly, like the center does not point straight up.  This is just an observation and should not affect anything as it is not so noticeable.

 

Each top/bottom half is machined together.  They are screwed together, and then the front/back panel holes are milled.  Then, the boxes are disassembled and a number is engraved inside each half.  Later, after polishing & anodizing, the boxes are reassembled back to original sets based on the # engraved inside.  You can mix and match any top and bottom, but with machining tolerances, holes may be off by a few thousandths of an inch.  For the volume control shaft, as the amp is way too small to have any kind of nut that attaches it to the panel, I had the hole made precisely so that the shaft can neither wobble or rub too much against the enclosure making it too hard to turn.  Unfortunately, the vendor I used for the polishing/anodizing did not follow my instructions and mixed all of my boxes up, so some top halves were black, some were silver, this meant I could not reassemble them as original sets.  Sometimes resulting in the hole for the volume shaft being a few thousandths of an inch too big, hence the slight movement you are referring to.  

 

This has been fixed, because I am now working with a new supplier.  My tolerance for people not following my directions is gone.  And anyway, if you dropped the amp on the knob, the knob only has a few thousandths of an inch clearance on the sides and behind it, which would prevent anything from moving more than that amount.


Edited by justin w. - 10/14/10 at 5:08am

HeadAmp Audio Electronics - home of the Pico and Gilmore amps.  Now with Audeze, Fostex, HiFiMAN, Sennheiser, and STAX.
Find us at www.HeadAmp.com

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post #4 of 21
Thread Starter 


 

Quote:
Originally Posted by justin w. View Post

Just wanted to mention something on this

 

 

 

 

Each top/bottom half is machined together.  They are screwed together, and then the front/back panel holes are milled.  Then, the boxes are disassembled and a number is engraved inside each half.  Later, after polishing & anodizing, the boxes are reassembled back to original sets based on the # engraved inside.  You can mix and match any top and bottom, but with machining tolerances, holes may be off by a few thousandths of an inch.  For the volume control shaft, as the amp is way too small to have any kind of nut that attaches it to the panel, I had the hole made precisely so that the shaft can neither wobble or rub too much against the enclosure making it too hard to turn.  Unfortunately, the vendor I used for the polishing/anodizing did not follow my instructions and mixed all of my boxes up, so some top halves were black, some were silver, this meant I could not reassemble them as original sets.  Sometimes resulting in the hole for the volume shaft being a few thousandths of an inch too big, hence the slight movement you are referring to.  

 

This has been fixed, because I am now working with a new supplier.  My tolerance for people not following my directions is gone.  And anyway, if you dropped the amp on the knob, the knob only has a few thousandths of an inch clearance on the sides and behind it, which would prevent anything from moving more than that amount.


This would explain why the top and bottom halves don't meet exactly in how the holes should line up, one side being slightly wider than the other.  This might also explain why the gap between the top and bottom halves on the long side is not perfectly even with a larger gap in the middle like both ends are bowed out just ever so slightly.  Too bad, I never expect perfection in the physical aspect of any product, but this one could have been even closer to perfection of build precision had the supplier simply followed directions.

post #5 of 21

If you had to give a review of this product in 15 words or less, what would it be?

post #6 of 21
Thread Starter 
Quote:
Originally Posted by The Monkey View Post

If you had to give a review of this product in 15 words or less, what would it be?


I couldn't do that even if I tried as I'm not done evaluating it yet.

post #7 of 21

Intriguing preliminary review. I am potentially interested in this as a second uberportable pocket amp for my ES5. However the ES5 is very sensitive so I wonder about the volume-matched hiss. Only one way to find out...

 

Justin, I do wish that you would get some retail product out to Hong Kong (Mingo, Kingsound...) This amp must be heard!


Edited by cooperpwc - 10/16/10 at 5:29am
post #8 of 21

I only detect the hiss well above what I would call  normal listening levels with my JH13 and 16. If that helps.

post #9 of 21
Quote:
Originally Posted by cooperpwc View Post

Intriguing preliminary review. I am potentially interested in this as a second uberportable pocket amp for my ES5. However the ES5 is very sensitive so I wonder about the volume-matched hiss. Only one way to find out...

 

Justin, I do wish that you would get some retail product out to Hong Kong (Mingo, Kingsound...) This amp must be heard!



First, this test needs to be done with the source unplugged.  If he is hearing any hiss, I would like to hire him to be a test instrument.  My most sensitive IEM is the Westone ES3X (I also have the ES5), which on paper should be at least as sensitive as the SE530, and my hearing tests well within the "perfect" range.  I can't hear any definitive hiss until the volume control is up significantly, way past any listening level.  It is true that at very high levels, hiss is going to be greater than a very good amp with an analog volume control.  This is just because the digital volume controls on the market do not have >100dB signal-to-noise ratios.  It's a trade-off to get the level of attenuation and channel matching that a digital volume control can offer.  

HeadAmp Audio Electronics - home of the Pico and Gilmore amps.  Now with Audeze, Fostex, HiFiMAN, Sennheiser, and STAX.
Find us at www.HeadAmp.com

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post #10 of 21
Thread Starter 


 

Quote:
Originally Posted by justin w. View Post





First, this test needs to be done with the source unplugged.  If he is hearing any hiss, I would like to hire him to be a test instrument.  My most sensitive IEM is the Westone ES3X (I also have the ES5), which on paper should be at least as sensitive as the SE530, and my hearing tests well within the "perfect" range.  I can't hear any definitive hiss until the volume control is up significantly, way past any listening level.  It is true that at very high levels, hiss is going to be greater than a very good amp with an analog volume control.  This is just because the digital volume controls on the market do not have >100dB signal-to-noise ratios.  It's a trade-off to get the level of attenuation and channel matching that a digital volume control can offer.  


Yup, tested with the source unplugged....in my review I stated there is no easily detectable hiss with a volume of 0, just trying it again in a quiet environment with the se530 with no source connected, I can tell the difference between the headphone being plugged in or not.  It is very slight and requires careful listening to hear it.  Maybe I shouldn't call it hiss, but it is noisier with the headphone plugged in than not.   I can only hear it if there is no sound around me.  Yes, even with se530 which isolates sound a claimed 37db of isolation, I can still hear enough noises around me in a general environment that would make it difficult to discern this very slight hiss.

 

Now, as you turn up the volume dial, I can hear the hiss move up with it.  At 9 o'clock which I might listen to the se530, I can hear the hiss without effort and even if there is sound around me.  From my experience with being on this forum for so long, the level of hiss I hear is probably inaudible to the majority of you at 9 o'clock.  But you might turn the music up much higher to hear what I already hear at 9 o'clock.

 

Now just because I can hear the hiss doesn't mean everyone else can.  It is my second quietest amp by far with the se530, and I got many of my other amps because people said they are "pure black", or "completely silent" or "absolutely hiss free" which I found to be far from the truth.  Now remember, I can hear music coming through this amp with the se530 around 12 degrees ahead of off, that is how sensitive my hearing is.  For reference, my first experience into real amps started with owning the RS1 and getting the RA1 because all my sources hissed with the RS1.  The RA1 hissed, Grado claimed it shouldn't so I sent it to them and they tested it and said it didn't hiss and sent it back where I still heard it loud and clear.  It was not slight and I couldn't believe they couldn't hear it.  Then I got the XP-7 which everyone claimed was silent, but the hiss was very loud to me with the RS1, I couldn't imagine using an IEM with it.  I eventually got ad797 opamps because they were said to be quieter.  Finally I could listen hiss free with the RS1, well as hiss free as I can tell in a normal environment.  However that amp still hisses with my IEMs.  I never got it quiet enough that I can do a real hiss test with it with open air grados.  And on and on......So this is a reference point to where my level of hiss detection is.


Edited by bcwang - 10/16/10 at 4:21pm
post #11 of 21
Thread Starter 
Quote:
Originally Posted by justin w. View Post
If he is hearing any hiss, I would like to hire him to be a test instrument.


If you are serious Justin, I'm willing to test for you.  In the pursuit of having less hiss in amps, I'll do what I can.

 

 

 

On an unrelated note, I nearly blew my ears out with my Macbook Pro today trying to see how the onboard sound is.  My friend told me there was a way to hold some key down so when you press up and down on the keyboard, you move in 1/5th increments for each volume step instead of the default amount.  Well the "command" key wasn't it because that moved it from 0 volume to full volume....on my se530 no less!  I had to pull the headphone from the jack.  And I also learned the Mac stores separate volume settings for when a headphone is and isn't connected.  So when I thought the volume was at the lowest setting, plugging in the headphone nearly blew my ears out again when it jumped to the previously saved 100% position.  External volume dials only for me from now on, I can't take any more of these easy mistakes.  My ears need a rest now.  

 

And by the way, the macbook pro hisses so loudly it is unusable for me with the se530.  Then I used the uDac-2 to try to listen to music but I couldn't get the volume low enough and balanced without causing me discomfort due to my ear drum attack previously, plus it still had hiss which bothered me now that my ears were sensitive.  It really makes me appreciate what the Pico Slim can do for me.

post #12 of 21

The volume trick is Option + Shift + Function (not necessary on aluminum BT keyboard) + whatever function key controls the volume (F11 or F12 on my keyboard).

 

See here: http://www.mactricksandtips.com/2008/03/changing-the-volume-more-accurately.html

post #13 of 21
Quote:
Originally Posted by The Monkey View Post



If you had to give a review of this product in 15 words or less, what would it be?







How about, 'If you are the owner of highly sensitive IEMs, buy yourself this amp right now!'



I'm using it with se530s as well and it is simply a godsend. You really won't be able to believe the precision of the attenuation till you hear it.



@bcwang, thanks for making this review. Looking forward to updates with other phones. Oh, nice photography, too!
post #14 of 21

Great review! The bit about the loud thump on power on worries me.


Edited by sparktography - 10/17/10 at 3:45pm
post #15 of 21
Thread Starter 

Finally had a chance to complete this review!

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