Thursday, March 25, 2010

AN214: The Last Great IC Audio Amplifier?

Audio enthusiasts know that it is not the only “kid on the block” when IC audio amps are concerned, but how does the AN214 compare to others of its kind?

By: Vanessa Uy

Ever since I got on that steep learning curve called DIY hi-fi back in 2006, I also managed to gain familiarity with integrated circuit-based audio amplifiers with sound quality that rival that with the well-touted amps in the hi-fi world. There might be thousands out there and probably countless more that got marketed only to be discontinued 18 months later due to lack of demand, which I am fortunate enough to gain familiarity with some. So far, here are the shortlist of other IC audio amps and how they compare – in sound quality terms – to the AN214 and other venerable hi-fi amps.

The pedestrian-sounding-to-me types: those that fall into this category – believe it or not – are probably still in widespread production since their introduction during the 1990s as a building block of domestic karaoke machines and mini boomboxes. Like the LM1875 and LM383T – both are 5-pin TO-220 packages - which are even pressed into use as a cheap and cheerful guitar amplifier. They are easy to build using the recommended layout and heatsinking guidelines of the IC manufacturer and can work in the 12-volt automotive environment very well. But to me, I found the sound quality of both types wanting. Another widely used in karaoke and boombox units of the 1990s is the TA8216A 13-watt per channel IC audio amp. This 12-pin single in-line package IC in sound quality terms sounds just like any other run-of-the-mill solid-state amplifier.

Another one that falls into this category – although it manages to sound better in the musically important midrange band – is the LM2005T-M IC audio amp. Often used in bridge configuration in 12-volt automotive applications, it did manage to sound about as good as the AN214 during the 1980s. But when the alternative rock of the 1990s came – especially the Seattle-flavored David Geffen record label signed kind. The LM2005T-M was found wanting in portraying the analogue-like warmth and musicality inherent in these releases.

The ambitious-sound-quality-but-now-discontinued types: two great IC audio amps that came into my way fall in this category and they even exceed the AN214 in some important aspects of sound quality, but unfortunately they are discontinued after being available in electronics supply stores for 18 months in the mid 1990s. Like the HA1388 18-watt IC amplifier and the HA1393 19-watt IC amplifier. Both are 12-pin SIP IC amplifiers and could work very well in the 12-volt automotive environment due to its built-in ASO protect and surge protect circuits and became popular in some karaoke and boombox units marketed during the 1990s.

Sound quality wise, both the HA1388 and the HA1393 managed to sound like a EL84-equipped tube amp – make that a premium tube like an EL84 with the words Record by Mullard printed on the tube’s glass enclosure. Excellent sounding both IC amps are, they suffer from unacceptable levels of hiss – especially when used with speakers with sensitivities better than 93dB per watt / 2.8 volts at 1 meter. Probably having a signal-to-noise ratio no better than 69dB. The HA1388 and HA1393 can be also considered commercially extinct since it is only in antique audio swap meets that you have a chance of finding one. In guitar amp applications, they are better than the AN214 due to its tube-like tonality – making that aeolian mode opening riff of Judas Priest’s Breaking the Law sounds so symphonic as if it is played on a Mullard tube equipped Marshall amp. Unfortunately both the HA1388 and HA1393 are even rarer that the Record by Mullard type EL84 tubes.

The temperamental diva types: there’s an IC audio amp that gained popularity during the mid-1980s that fell into this category. The most famous one is the STK 439 IC amp, a 15-pin SIP containing two amplifier circuits and often used in single-ended mode. Using the two amps inside the IC package in stereo. The STK 439’s 24-volt operating range limits its compatibility somewhat in the car audio world, but it makes up in sound quality with midrange purity approaching that of dpa Renaissance integrated amplifier. Also, there seems to be no schematics of STK 439 in bridge configuration.

During the mid-1980s, the rivalry between the AN214 and the STK 439 in the DIY audio world seems almost to mirror that between the divergent design philosophies of Mikhail Kalashnikov’s AK-47 and Eugene Stoner’s M-16. I don’t know much about the present availability status of the STK 439, I only knew – from my older audio-buddies – that the left channel portion is prone to failure. Currently, I’m using two STK 439s with still functional right channels in monoblocked stereo.

I never knew one using the STK 439 in guitar amp applications, but it is safe to assume that it could sound rather too clinical in comparison to tube-based guitar amps. But the STK 439’s clinical nature can be very useful in monitoring less-than-pristine audio sources. Like my pet project of digitizing an old BETAMAX-based amateur home movie that captured a Twisted Red Cross-era punk band called The Wuds during their July 1988 concert in PHILCITE Cebu. The STK 439 is also very pre-recorded cassette tape friendly that it even managed to make some old cassette tapes that I recently bought from a garage sale sounds much more listenable and musical. Like the old Heavens Edge, Rumble Militia and even a 1992-era cassette of GWAR’s America Must Be Destroyed album.

Unfortunately, linear IC-based audio amplifiers are no longer popular in the DIY audio world. The pedestrian-sounding but widely available IC amps mention before are probably the only IC amps that anyone in my age bracket can DIY – barring switching mode Class D IC audio amps that tend to make Avril Lavigne sound like she’s hocking a loogie during her glottal stops. Worse still, most “affordable” – i.e. cheap – computer speakers with subwoofers tend to use switching-mode Class D IC amps in favor of efficiency rather than sound quality. The AN214 could probably be reign for the foreseeable future as the last great IC audio amplifier.