Thursday, July 16, 2009

Don’t Forget the Heatsink

Despite of its relatively low power output does the AN214 IC still deserve the tender loving care of adequate heatsinking to achieve better sound quality?

By: Vanessa Uy

During the AN214 IC-based amplifier’s heyday in the early 1980s, heatsinking is usually of little concern due to the device’s relatively low power output that barely reaches 5 watts. Hobbyists back then – especially those that lack adequate knowledge on how semiconductor ICs work – usually bolt the AN214’s metallic tab / backside of it’s 9-pin single inline package to a piece of scrap metal to serve as an ad hoc heatsink. Or maybe to the aluminum chassis of the amplifier’s intended housing, without further concerns on how hot it might get during the AN214 IC’s intended lifetime.

Ideally, when operated under the right conditions, solid state devices tend to last for hundreds of thousands of years. Some of these inadequately heatsinked amps just manage to last up to 8 months at most. As most electronic engineering textbooks – then and now – often states that low-powered applications require minimum thermal mass, a few centimeters of sheet metal, to transfer the small amount of heat generated by a low-power semiconductor device to the ambient air. But is common-sense engineering good enough for the perfectionist audiophile-grade applications for the AN214?

The raison d’être of heatsinking IC-based power amplifiers – even low-powered ones – is to obtain the IC amplifier’s maximum output voltage swing as specified by the manufacturers’ spec sheets. This can easily show up under triangular-wave or sine-wave tests when the inadequately heatsinked IC-based amplifier can’t even output one-tenth of it’s intended maximum output voltage swing - on the cathode ray oscilloscope, the sine and triangular wave peaks would be melting or clipped like crazy.

Non-linear reactive loads like loudspeakers – or the inter-stage transformer of the MJ2955 PNP transistor-based booster amplifier – tend to have some unwanted effects on inter-stage amplifiers (the AN214). The resulting back-EMF of the load may attempt to swing beyond the power supply voltages applied to the amplifier. Thus in order for the IC’s output protection circuitry – assuming it has one – to work, then a heatsink is always a necessity in “controlling” the inductively-generated electromotive force of whatever inductive load that happens to be connected to the AN214 IC-based power amplifier.

To obtain the best theoretically possible sound quality from your AN214 IC-based amplifier, an infinite heatsink – or a realistic equivalent – is a must. To make your intended finned aluminum alloy heatsink approach the heat-dissipating performance of an infinite heatsink, its main body – the point where you bolt-on the IC / semiconductor package – should be thicker than 1/16 of an inch. And this part should be polished to maximize heat transfer. You can also add silicone grease with metal oxide to further boost heat transfer. After bolting-on the IC to the heatsink, you can paint the aluminum alloy heatsink’s surface with a mat black-colored oil paint – preferably thinned a bit with linseed oil – to further boost the heatsinks’ emissivity rating. If done properly, your AN214 IC-based amplifier now has the potential to perform its very best.

Thursday, July 2, 2009

Is the AN214 IC Amplifier Hi-Fi?

Given that it resides in the 12-volt world of car audio, does the AN214 IC amplifier fulfil the tenets of high-fidelity audio reproduction – namely a good to excellent sound quality?

By: Vanessa Uy

Today, we audiophiles – at least the sane ones anyway – judge an audio amplifier’s performance by its ability to realistically reproduce the sound of a recorded musical performance. As opposed to how many watts it can deliver or how low it’s overall total harmonic distortion – i.e. a good to excellent set of measurements, and even the amplifier’s circuit topology / technology.

The practice of using our ears – as opposed to a 10,000 US dollar multi-function audio analyzer – probably gained fashion (again?) back in January 1994. When Stereophile magazine released a correspondingly dated magazine with a riddle posted on the cover that goes “If either of these amplifiers is RIGHT…the other must be WRONG”. An idea probably influenced by James Carville’s book titled “We’re Right, They’re Wrong: A Handbook for Spirited Progressives” – a reactionary idea born out of chronic bullying by Rush Limbaugh and his global warming / climate change denying ilk directed at us liberals. It looks like our too liberal postmodern dictum of everyone’s opinion is right is our own downfall - at least according to Mr. Carville.

Returning to the world of hi-fi, it does seem like sound quality has indeed gained vogue in assessing the pride of ownership potential of audio components, especially audio amplifiers. The circuit topology and technology used seems no longer relevant, probably due to the single-ended triode “revolution” in Japan during the 1970s which made audiophiles around the world reexamine their views about what’s important about their hobby.

Given that the AN214 IC amplifier might be cheap, its hi-fi credentials easily manifest by the overall improvement in sound quality every time you over-engineer one. Use larger than necessary output transformers and the bass quality improves, just like its single-ended triode counterparts. Use larger than necessary heat sinks and the AN214 amplifier rewards you with a more agile pace, rhythm, and timing. In fact if you tweak the AN214 amplifier’s power supply with Rubicon Black Gate capacitors, it could even sound better – from a musical perspective – than a standard Pioneer A400 amplifier. The only way a Pioneer A400 can be more musical than a tricked-out AN214 amplifier is by doing a T. Evans Audio Design-style modification to its power supply.

During the AN214 amplifier’s heyday, many audiophiles – especially absolute beginners – have never been told about the wisdom of trusting their own two ears as the ultimate arbiter of sound quality. This is why back then solid-state high-powered full-complementary output stage direct-coupled power amplifiers were touted as the ultimate in sound quality. Even though most of them sound sluggish in the pace, rhythm, and timing department because their power supply capacitors have not been designed to take advantage of time-constants. Ad given that solid-state full-complementary amplifiers are relatively complex in terms of component count, tweaking one – especially if you are an audiophile on a budget – seldom makes fiscal sense. It is even cheaper – time and labor wise – to buy very expensive solid-state amplifiers from Mark Levinson, Krell, and Spectral.

So, is the AN214 IC-based amplifier hi-fi? If you trust your own two ears, then the answer is a resounding yes. If the music matter’s more to you than the circuit complexity of your audio amplifier, then maybe it is about time you should check out the AN214 amplifier - especially if you can’t afford exotic single-ended triode tube-based amplifiers, or if you live in a place where the 50 caliber Browning Machine-Gun cartridge is way more plentiful than 300B vacuum tubes. During the AN214 IC amplifier’s heyday, it might have the requisite resolution to play out the full beauty of Larry Carlton’s guitar playing on Michael Jackson’s Don’t Stop ‘Till You Get Enough.