Wednesday, December 17, 2014

Blue Input Captain Micro-Transformer AN214 Tweak: A Lost Black Art?

Used to be one of the most closely guarded “proprietary trade secrets electronic tweaks” of the AN214 IC amplifier, does the blue input captain micro-transformer tweak still relevant in the 21st Century? 

By:Vanessa Uy 

It is probably one of the most coveted and one of the most closely guarded proprietary trade secret when it comes to the electronic tweaking of the AN214 IC amplifier during the Great Car Stereo Wars of Cebu during the 1980s. The results – more often than not – tend to provoke commentaries and in a nutshell it is either you’ll love it or you don’t and for almost a quarter of a century, no particular individual has yet claimed for inventing the famed tweak and announced it, with adequate proof I hope, over the internet. But does the blue input captain micro-transformer tweak of the AN214 IC amplifier still relevant in the 21st Century hi-fi scene? 

First of all the “blue input captain micro-transformer” referred to in this procedure looks to me like a balun transformer – i.e. a balanced-unbalanced impedance matching transformer - whose one side is a “balanced” center tapped winding and the other side (primary or secondary winding?) is a two-terminal winding. The blue color denotes the impedance or DC winding resistance of the transformer. In the past, such transformers are used in ultra low noise microphone preamplification systems that allow a balanced three-terminal microphone to be used in an unbalanced two-terminal preamplification system or an unbalanced two-terminal microphone to be used in a balanced three-terminal preamplification system without introducing audible 60-cycle hum. “Blue input captain micro-transformers” are also used as a galvanic isolation transformer of line-level signals in spring reverb systems. I’ve also heard that during the late 1980s – from my older working musician buddies – that blue input captain micro-transformers can be used as an excellent electric bass guitar pick-up, although orientation of the transformer is critical akin to that of the P-90 type electric guitar pick-ups.  

I suspect that whoever first formulated the blue input captain micro-transformer tweak of the AN214 IC amplifier – who (Edwin?) probably was a graduate of Cebu City’s Ivy League engineering colleges around the late 1970s to the early 1980s – was an electronics communications engineering student who got the idea of trying to use the working principles behind intermediate-frequency transformers or IF transformers used in AM / FM tuners as a novel tone control system. Given the Baxandall type bass and treble tone control system can only accentuate the low and high frequencies of a line level audio signal by much, a parallel-resonant high-Q band reject filter formed by the blue input captain micro-transformer and whatever value capacitor is connected across it operates the same as an IF transformer found in radio tuners albeit one that is capable of handling line-level audio signals that ranges in amplitude from 100-millivolts to 1-volt peak-to-peak. 

The blue input captain micro-transformer tweak of the AN214 IC amplifier is usually placed in the negative feedback section of the Baxandall type bass and treble tone control preamplifier circuit often paired with the AN214 IC amplifier system. As it is in parallel of the bass and treble arm of the negative feedback of an actively amplified Baxandall tone control circuit, the high-Q band reject properties of the blue input captain micro-transformer tweak with a paralleled capacitor that ranges in value from 100-picofarads to 2.2-microfarads are a bit exaggerated due to the active amplification but the inherent 24-decibels worth of signal attenuation is cancelled out due to the active amplification of the said circuit. Resulting in a rubbery Bill Laswell type bass and shimmering treble reminiscent of low powered zero negative feedback single-ended triode amplifiers using 2A3 power triodes. 

From my ear’s own perspective, I bet that an overwhelming majority of “affordable” hi-fi audio gear manufactured during the late 1970s and the early 1980s were designed for inherently “colored” hi-fi loudspeakers. Most of them are certainly not equal to the task of driving a genuinely low coloration hi-fi loudspeaker available at the time – i.e. the Quad ESL-63 – although at that time, only a very few hi-fi enthusiasts can afford the famed Quad electrostatics. Basing on most “affordable” still perfectly functioning early 1980s era hi-fi loudspeakers populating the garage sales of my neighborhood, they are quite very colored in comparison to a mid-1990s era Sonus Faber Concerto hi-fi loudspeakers. Thus the blue input captain micro-transformer tweak of the AN214 IC amplifier was primarily designed to “filter out” the most colored band of most affordable audio gear of the early 1980s – i.e. the midrange or the mid-band part of the audio spectrum. Nonetheless, the blue input captain micro-transformer tweak of the AN214 IC amplifier give the masses a taste of that “illuminated from within” musicality of 2A3 power triode equipped zero negative feedback single-ended triode audio amplifiers.  

Friday, December 27, 2013

Can Those Mystical Mpingo Pucks Work On the AN214 IC Amplifier?

Known for its ability to improve the sound of every hi-fi amplifier in an inexplicable Peter W. Belt style, can those “mystical” Mpingo pucks do audiophile wonders on the AN214 IC amplifier? 

By: Vanessa Uy 

It may be have Shun Mook that first made a name for themselves in the hi-fi world with those “mystical” wooden Mpingo pucks of various shapes and sizes that inexplicably – as in a mysterious Peter W. Belt style effect – improves the sound quality of every electronic equipment, tube or solid-state. But can those “mystical” Mpingo pucks be used to improve the sound quality of the “lowly” AN214 IC amplifier? 

Made from Mpingo – an African Blackwood, a flowering plant in the family Fabaceae – Mpingo wood is often harvested from slow-growing African swampwood. Though its harvesting is tightly regulated to avoid endangering the overall population of this rather rare swampwood, most of Mpingo’s applications is with those mystical wooden pucks manufactured by Shun Mook that inexplicably improves the sound of electronic audio equipment whenever the wooden pieces came in contact with it. 

Even though the executives at Shun Mook are yet to roll out their version of these Mpingo wooden pucks for use with various integrated circuit-based power amplifiers – like the AN214 – often found in use in entry-level multi-channel surround sound ready home theater equipment, it might provide an audible improvement for this family of entry level power amplifiers. As in perhaps an overall increase in overall musicality? 

Wednesday, December 26, 2012

Does Your Car’s AN214 Amplifier Have An Alternator Load Dump Filter?

Logic dictates that the car’s 12 volt DC system never rises above 13.8 volts DC, but does your car’s AN214 amplifier equipped with an alternator load dump filter, nonetheless?

 By: Vanessa Uy

Some “mainstream” electrical and electronics engineers may consider the practice of installing an over-engineered alternator load dump filter for your car’s audio system to be a “tweak-extravaganza”, but have you ever wondered what these “mainstream” electrical and electronic engineers complaining about back in the early 1990s when their do-it-yourself installed car audios went kaput in just eight months after installation?
Well, maybe they should have done their research about one of the “electrical nasties” that can be encountered in a typical automotive 12-volt DC electrical system called alternator load dump. Alternator load dump occurs when the load to which a generator is delivering current to is abruptly disconnected which causes a very brief – but sometimes very high – spike in voltage. In a typical automotive electrical system, this applies to disconnecting the car’s battery while it is being charged by the alternator.

Automotive technicians using electrical measurement equipment have since found out that the voltage generated by an alternator load dump can be as high as 87 to 120 volts and could take up to 400 milliseconds to decay or return back to 13.8 volts. This can be enough to burn out the solid-state electronics of car stereos and their associated power amplifiers. But is there a solution? A typical alternator load dump filter consists of an L-C or inductor-capacitor filter where the inductor is rated at around 100 to 300 milliHenries at 1 ampere while the capacitor is a 1,000 microfarad 16 to 25 volt electrolytic capacitor connected to the car’s negative ground.

An over-engineered alternator load dump filter for an AN214 based automotive audio amp can be advantageous because an over-engineered L-C filter can also filter the hum of atypical full-wave-bridge 12 Volt DC power supply tapped in your home’s 220-volt 60-Hz AC wall socket. A knowledgeable electronic enthusiast can even wind his or her own inductor for a fraction of a cost of a commercially made one. Just wind a 30-foot long piece of number 20 AWG magnet wire on a ½-inch plastic transformer bobbin then place the laminated E-I silicon-steel cores to increase its inductance into the 100 milliHenry range.

To make the capacitor part of the L-C filter alternator load dump filter last almost indefinitely, use an electrolytic capacitor in the 35-volt range. An alternator load dump filter consisting of a 300 milliHenry inductor and a 10,000 microfarad 35-volt capacitor can limit the voltage spikes to 18-volts during an alternator load dump – which is more than necessary to protect the AN214 IC and related electronics since according to their spec sheets, automotive audio IC amplifiers can supposedly withstand voltage spikes as high as 48 volts for 500 milliseconds.

Monday, November 28, 2011

Does Meticulous Circuit Layout For The AN214 Still Matter?

It may just be a “mere” 3-watt IC power amp, but does meticulous circuit layout still matter for the AN214 if you want the ultimate in sound quality?

By: Vanessa Uy

If you have been experienced as I am when it comes to audiophile-grade audio power amplifier design, chances are you may have already encountered power amplifiers whose circuit layouts are definitely not worth the solder that binds them – sound quality wise. But can a reasonably good sounding DIY amplifier still be had without resorting to break-the-bank exotic and esoteric components? Well, the answer is definitely yes, and if you’re interested, read on.

Tweaking does still matter even if you are designing a power amp from a fairly generic circuit. And if possible, you can keep the negative feedback levels of the power amp design to a minimum, provided that the resulting harmonic distortion is reasonably low and of low harmonic order. To my ears, very low measured harmonic distortion never resulted in subjective improvement in sound quality. After all, if mainstream consumer electronic manufacturers like Sony or Pioneer wanted everyone to know how low the harmonic distortion of their power amplifiers are, Sony and Pioneer could have long ago provided as a free add-on 20-thousand US-dollar Hewlett-Packard FFT machines to their power amplifiers.

Even passive parts lay-out is of paramount importance, too. From my experience in designing AN214 power amp modules, I always made sure that the resistors – even if they are not esoteric audiophile-approved types like Vishay – should be oriented in phase on the master board. Proper orientation of resistors on the left and right channel is very important if you want your power amp to have natural-sounding stereo imaging and sound-staging; And orientation of fuses matter too – even changing the power supply fuse from a quick-blow to anti-surge results in a subtle-but-audible change in sound quality.

Lastly, the wiring has to be oriented in the same direction as well. With experience, you could even tweak the sound of your AN214 by strategically using a combination of solid-core and stranded wire where they provide the most benefit in improving subjective sound quality. This is very important when the AN214 you are designing is either used as an audiophile-grade power amplifier or a practice guitar amplifier that you want to sound like an EL84-tube equipped guitar amp.

Monday, August 23, 2010

AN214 Versus Wicked Bitch Wives From Hell

Ever since high fidelity audio became a domesticated hobby, an overwhelming number of women had been taught to hate it with extreme prejudice. Can there be a middle ground?

By: Vanessa Uy

As a woman – the last time I checked – I won’t be stomping over political correctness when I talk about the hot-button topic of why an overwhelming number of women are conditioned to grow up to abhor high fidelity audio in all forms. Before you accuse me of turning into another female misogynist – like former Alaska governor Sarah Palin managed to do during the 2008 US Presidential Campaign, I’m just initiating a frank discussion about where the facts and myths lie when it comes to why an overwhelming number of women – conditioned or not – tend to hate hi-fi with extreme prejudice despite being one time in their lives an avid music fan.

Fortunately, women who are accomplished musicians seldom – if ever – complain about the size of their musical instruments. I’ve yet to hear an accomplished woman pianist or cellist mouthing off why can’t piano and cello makers create a great sounding Steinway or a Pietro Pallotta – even a Bösendorfer - the size of a late-model Nokia mobile phone. Never mind a full-sized heavy metal concert compliant Marshall stack.

Unfortunately, an overwhelming number of women non-audiophiles tend to listen with their eyes – instead of their ears – judging that smallness and cuteness as a really plus point in hi-fi instead of ultimate sound quality. They are never impressed by a lab-gear looking audio gear that sounds as if Yungchen Lhamo and the rest of the Tibetan Freedom Concert performers sound as if they’re as if right in your listening room. Just give them something small and unobtrusive and they’ll be happy – even if it sounds like crap to us audiophiles.

Pain-in-the-ass interior decorators are partly to blame too. Amusingly, a typical modern floorstanding hi-fi loudspeaker occupies the same amount of space as a pair of tiny monitor on a 24-inch tall stands. The difference is that a cabinet measuring 950-mm tall with a 200-mm x 200-mm footprint simply “looks” more intrusive from a pain-in-the-ass interior decorator’s perspective than a 350-mm x 200-mm x 200-mm speaker on a 600-mm pillar. Maybe pain-in-the-ass interior decorators should be subjected to high-altitude induced hypoxia while in your living room to make it appear bigger in their heads before they eventually succumb to altitude-induced cerebral edema.

So where does this leave the AN214 enthusiasts? Well, despite almost 40-years of the women’s liberation movement, an overwhelming number of women are still conditioned to hate with extreme prejudice big sized hi-fi gear that sounds like live music. The “older” members of this bigoted sorority would rather “sleep” with an original Rolling Stones member that have their living rooms look like a Rolling Stones concert stage. Given that the AN214 amp – despite its great sound – always look like a piece of authentic lab gear, wicked bitch wives from hell will probably always hate it till the end of time – or when hell freezes over whichever comes first.

Tuesday, June 1, 2010

Those Cheap Chinese DVD Players: Real Hi-Fi?

Given that they managed to display exemplar sound quality despite of their cheapness, are those cheap Chinese made universal DVD players real hi-fi?

By: Vanessa Uy

For the DIY audiophile who cut his or her teeth on assembling AN214 amplifiers, bargain basement Chinese universal DVD / CD players may seem to be too good to ignore. Despite of their cheapness – some are no more expensive than a second-hand Kalashnikov – but do these 25 to 30 US dollar Chinese made universal DVD / CD players truly qualify as hi-fi? Bad news first – they won’t play the high-resolution audio layer of SACD discs, their DVD Audio performance can be crappy when you don’t use a good external 24-bit 96-Khz capable DAC – more on the Redbook CD performance later .

The DVD Video performance is a few notches below that of entry-level DVD players of leading brands like Pioneer, Sony, Philips, etc. But these el cheapo Chinese players make up for it by their capability to play uploaded Internet site videos without being converted first to Video CD or DVD Video. I mean it can play those despicable militant website rant videos and child porn videos that were hastily burned into CD-R or DVD-R that wont run major brand universal DVD / CD players.

Surprisingly, these cheap and cheerful Chinese universal DVD / CD players raison d’être is in playing your stockpiles of supposedly obsolete 16-bit 44.1-Khz Redbook speck music CDs – although you should avail yourself of a good external digital-to-analog converter in order to find out the magical properties that many have discovered with such players. The model we tested is a Hug DVD-H6757 DVD Video player whose primary raison d’être is to play those “pirated” compressed DVD videos – mostly illegal porn that supposedly illegal in my neck of the woods, some even has stars as young as me.

Sound quality wise, this particular lowly Hug DVD / CD player managed to play CDs like a thousand-US dollar CD player from 1995 – especially when hooked up to external DACs that were languishing unsold for years in our local second-hand hi-fi shop. But first select the digital SPDIF out mode to raw. It sounds so gorgeous at this setting when connected to an external DAC when playing Redbook spec CDs. It made the Orelle DA-88 DAC and the Audio Alchemy Digital Decoding Engine version 2.0 that were sitting idly by since 2003 sound as if their processor chips were upgraded so that the anti-aliasing filters of the analog output stages can be configured to a lower-ordered configuration. Making it sound as if the still-audible –to-me phase and group-delay distortion near the 20-Khz roll-off point had been magically removed. In short, the Hug DVD Audio Alchemy DAC combo or the Orelle DA-88 DAC combo sounds as if it was a thousand US dollar CD player from 1995 – considering the current price (2010 that is) of the set up is still a few dollars less than a brand new Kalashnikov.

Sadly, given my political views when it comes to fair compensation of ones labor, I cannot wholeheartedly recommend the Hug DVD-H6757 universal DVD / CD player that my older audio-buddies and I tested for a number of reasons. The company who manufactured the DVD player, probably based in Guangdong Province heavy industry district, has not reassured their buyers about their workers getting adequate 401-K plans, healthcare, and not being paid slave's wages. And also the company should be more forthcoming on the issue of using prison labor as often is the practice in the Chinese mainland – as in Free Tibet and Uyghur political detainees. Hard to recommend a product made by a company clueless about what happened in that notorious FOXCONN plant where the workers where defenestrating themselves just to end their suffering. If the American hi-fi loudspeaker manufacturer takes the time to remind prospective customers – and those fortunate enough to be invited in one of their plant tours – of their commitment to providing their workers a liveable wage and decent healthcare and dental plans.

Another thing that bugs me about initiating an audiophile equivalent of a carrot mob to promote the Hug DVD / CD player is that given the open business / close politics stance of the Beijing Communist Party functionaries, the company’s R n’ D budget might be siphoned off to develop a Green Dam Youth Escort-type electronic censorship device. One that could be installed in a latter generation of Chinese made universal DVD / CD players. Imagine you being unable to play your Tiananmen Square Massacre remembrance DVD documentary because your newly-bought Chinese made DVD player has now an automatic Green Dam Youth Escort-type electronic censorship device. Same goes with your Minzhu and Dalai Lama / Free Tibet DVDs or anything referring to that tragic June 4, 1989 massacre on Tiananmen Square.

Or given if the DVD’s e-censorship system is like the Green Dam Youth Escort internet censoring tool in capability, you can’t watch your Garfield DVDs anymore because this cat’s fur looks like the color scheme of the Dalai Lama’s tunic. Your Uyghur friends’ home movies will be censored because it will use the Green Dam color-based censorship excuse and classify it as hardcore pornography. Yes according to the Green dam Youth Escort color-based censorship scheme, it doesn’t discriminate between pink skinned farmed pigs and Uyghurs. Maybe Taylor Swift was fortunate enough not to be playing near Xingjian Province during the Uyghur riots because the Chinese authorities probably can’t tell her apart from the local Uyghur population.

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.