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The Nickel amplifier is the most power you can put in your pocket.  About the size of a 9 Volt battery, this powerhouse delivers over 250 mW of continuous stereo power to a 32 Ohm load.  With essentially zero noise and distortion.  Analog in, analog out, nothing fancy – just raw, audiophile quality power.

You always carry your phone, right?  And you probably subscribe to at least one streaming or download service.  So why carry a full-on duplicate in the form of a music player?  Plug a Nickel amp between your phone and your ‘phones, and you’re set. The phone is the source, the Nickel is the real amp, and your headphones are, well, the ‘phones.

Why do this?  Because the dirty little secret is that most cellphones actually have very good if not great D/A converters.  They do a splendid job of turning those ones and zeros into music.  So why does your phone sound bad?  Because what comes after the D/A stage – the amp – simply sucks.

Amplifiers are expensive to build.  They take lots of power.  They produce a lot of heat.  They need lots of voltage, and it should be clean voltage – not running a bunch of digital processors and RF stages.  That means a quality amp is really not suited for putting inside a cellphone.  So guess what – most manufacturers don’t.  They go with the built-in amp from whatever board-level chipset they have and that’s that.

It’s like taking a new McLaren supercar and putting a set of rollerblade wheels on it.  All that potential performance hamstrung by a shoddy amplifier.  Great source, great D/A, and probably great headphones too (most definitely great, if you use ours).  And a poor amplifier right in the middle.

Thus, Nickel.  Nickel becomes the REAL amplifier of your system.  It has a very high input impedance, meaning the amp in your cellphone is basically bypassed.  It’s there for show only, it doesn’t deliver any power, just buffers the signal from the D/A converter to the Nickel.

Nickel takes over.  It’s built for one purpose, and that purpose is NOT to sound sucky.  Nickel was designed from the ground-up like a high-end home audio component.  A discrete power supply isolates the analog section from the digital.  A dedicated, isolated battery charger keeps the battery conditioned.  A low power microcontroller watches everything and shows you the status on a set of ultra-bright LEDs.  And it all comes together in glorious harmony.

Those rollerblade wheels?  Yeah, there still there – but they’ve been removed, tossed in the trunk, and a set of ultra-grippy Pirellis now reside in their proper space, filling up the wheel wells and hurtling that car in any direction the driver decides.  Your D/A speaks nearly straight to the Nickel, and it’s a revelation in capability.

Nickel starts with a single concept: make an amp, as pure as can be, and as small as possible.  Purity means simplicity.  Analog in, analog out.  No need for multiple signal-mutilation stages.  Just take what you’re fed, make it a little bigger and a ton stronger, and feed it back out.

We start with a Texas Instruments INA1620.  This is a brand-new chip, but we managed to procure a reel for production before you could even buy them from Digikey, Newark, or other distributors.  It’s RFI/EMI hardened as needed for a mobile device.  It’s got a ton of output current – 140 mA continuous per channel.  It’s got a lot of solid performance potential.  And it’s tiny – so we could literally jam it, and the associated passives, between the input and output jacks (yes, they really live there).

Surrounding the amp is a full-on custom developed network of high-performance passives.  All 1% precision resistors.  Film caps on the front end and loads of C0G (read: expensive and high quality) ceramics abound.  Why do 2 microfarads of capacitance on the power rails when 22 could be done – yes, we took it to 11 (times recommended, that is).

Feeding that amp is a 100% dedicated power supply.  We use the TI TPS65133 power controller which generates a dedicated ±5VDC power supply that is used solely for the 1620.  Not for the microcontroller.  Not the LEDs.  Nothing but ultra-pure, massive-capacity power (well, within reason – a quarter of an amp continuous per rail), with exceptionally low noise, reserved for your audio enjoyment only.

The battery feeds into that power supply.  It’s a tiny battery by cellphone standards, but for headphone amps?  It’s more than big enough.  It’s a 280 mAh lithium polymer battery.  But not just any style – it’s over-built, to handle a full 1.5C continuous charge.  We run it only at 1C, which means it runs extremely cool – and can be recharged 1000 or more times, without concern.  It also has its own integral RF shield on the bottom, to help isolate any radiated noise when charging.

And speaking about charging, we use the TI BQ25040 to charge that battery.  It’ll take that battery from starving to stuffed in just 30 minutes.  Running straight off the USB +5V input pin, that charger turns on any time it’s connected to a USB port, and it tops up that battery, pronto.  Conditions it too, floating the full-charge as needed to maintain proper battery health.  Because no one – NO ONE – likes a flabby battery.

Overseeing all this activity, and adding some brains to the brawn, is a Microchip 16F1503 microcontroller.  It’s responsible for seeing what’s going on and determines who gets to actually play.  Like a skilled coach, the ’03 decides when to turn on or off each of its team members, and in what order.  And it speaks to you via colors – green, yellow, and red – to let you know the status of the battery.  It even winks those LEDs at you when it’s charging.  Because brawn without some brains is dangerous.

Now about the audio jacks.  We use high retention force TRRS jacks.  No, we didn’t stutter, they are TRRS – four connector.  Why, you ask?  Well three are for audio – left, right, and ground.  The fourth is for a microphone signal.  If your headphones have a microphone or button on the cable, Nickel will happily pass that signal through to your cellphone.  And they are high retention, so your cable won’t just fall out.  You need to physically push it in AND pull it out.  It’s deliberately deliberate.

Plus, they do something else really wonderful.  They sense when you plug a source or headphone in and report to the ‘03.  And when both report present and accounted for – the ’03 decides it’s time to wake up and turn things on.  Each jack has a tiny switch inside that signals the ’03, who then decides when stuff should happen.  Or, if you remove either cable, when stuff should stop happening.  Because that just makes sense, doesn’t it?  Turn on when you have a signal AND headphones, turn off when you lose either one.

We also use a short-depth USB micro B connector.  Why?  Because, for some unknown reason, there exists micro B cables that have very short connectors.  And we don’t like to discriminate (well, against cables – we hold a grudge against those who like the sound of stock headphones that come with your cellphone).  So we use a connector that is guaranteed to work with any micro B cable ever made.  Serious.  We mean it.

Additionally, all those connectors are a source of potential failure.  Not just from freakish gorillas using them, but from electrostatic discharge.  Shocks.  And RF noise injection.  From noisy RF sources.  Like a cellphone.  Which probably resides really close to the Nickel.

So we did what any self-respecting set of engineers would do.  We over-engineered the crap out of them.  We added full class IV (that’s 4) ESD protection, to handle up to 32 kV (that’s 32,000 volts – about 150 times higher than the highest voltage in your home) discharge on any input without an issue.  And the RF filtering is designed to handle 10 times the legal limit of RF noise at 1 centimeter.  ESD and RF just don’t stand a chance when you have zealots doing their work.

We also added protection to the +5V on the USB, too.  Because maybe you’re a hardware hacker and you built a one-off USB jack that for some weird reason sources 80V.  well, we can handle it.  And we can handle up to 30 amps of current, too – so we’re pretty protected there.  Yeah, the little transorb will pop – but nothing will blow up or catch on fire.

All of this electrical wizardry was then stuffed on a tiny printed circuit board.  This PCB features four layers, each with a specific function.  The bottom is where the analog tends to live.  Above that is the ground plane – keeping things quiet and evenly referenced.  Above that is the power supply traces, sending power here and there.  And on top lives the digital world, playing with LEDs and TRRS switches.

The layout is as critical to the Nickel as everything else combined.  Just like a great recipe is the foundation of a fabulous dish, or a set of blueprints makes a mismash of walls become a mansion of beauty, the PCB layout is a work of art.  Well, we think it is.  Ground plane fills, stitching, tight layouts, minimum-length traces, and smart placement makes it all work together perfectly, with essentially zero RF interference or noise pickup.  Plus, it’s really cool looking, being white with black ink.  Why?  It just looks, well, science-y.  And we like that.

Wrapping around all this engineering is a deceptively simple looking package.  It just feels good in your hand.  The right proportions, angles, radii all combine to make something nearly fidget-spinner worthy.  Molded from hardened polycarbonate (you know it as bulletproof glass), with just enough texture to make it grippy without being rippy, and our logo and input/output marks molded right in and filled with bright white paint.  Its seamless appearance appears sculpted from a single block, and the ultra-tight tolerances on the jacks and lightpipe shows the quality of tolerancing we held in this production.

The sum therefore all comes together.  Nickel.  A real audiophile amplifier, shrunk down to tiny-pocket size.  And capable of running for 9 or more hours on a single charge, and recharging in just 30 minutes (oh, and it’s quiet during charging, too – feel free to keep using it).  Add Nickel to any cellphone and experience what real audio from your phone can be.  Feed your headphones quality power – and they’ll reward you with sonic excellence.

And now for a more mundane set of prose…

The Nickel amplifier is capable of producing high levels of power.  Nickel will supply 150 mW into 50 Ohms, 250 mW into 32 Ohms, and 270 mW into 16 Ohms.  Nickel is stable into an 8 Ohm load making it ideal for nearly any headphone on the market.  A fixed 6.5 dB of gain allows higher headroom than most phones and DACs can generate but is low enough to maintain nearly the full dynamic range of volume control from any source.

We measure our amp at realistic values.  All measurements are made at 179 mV RMS output level – where you typically run your IEMs.  THD is below 0.005% across the audio bandwidth.  Signal to noise is above 96 dB – regardless of charging status.  Bandwidth runs from 8 Hz to 80 kHz.  And thanks to the DC coupled output, the damping factor is over 100, giving the amp an iron grip on your headphones.  All with less than 1 degree of phase shift and phenomenal channel separation.

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Specifications

Performance
Frequency Response8 Hz to 80 kHz
THD+N< 0.005%, 20 Hz to 20 kHz
Gain6.5 dB
Power Output250 mW Continuous, 32 Ohms
Damping Factor> 100 @ 32 Ohms
Run Time8 Hours, typical
Charge Time30 minutes from full discharge
Physical Properties
Length50mm
Width30mm
Height18mm
Weight20 grams
Audio Jack3.5mm TRRS (mic pass through)
Charging JackMicro USB
Power IndicatorRed/Yellow/Green
Body MaterialPolycarbonate
Material Properties
Melting Point1728 Kelvin
Speed of Sound4900 meters per second
Young's Modulus200 Gigapascals
Brinell Hardness1600 Megapascals

Measurements