After writing this column for nearly a year, I seem to havefound my niche among Mix readers. I have been rewarded byquestions, comments, tips and suggestions; all are greatlyappreciated. Because Mix predates the project studio and the coverincludes the legend “Professional Audio and MusicProduction,” I was surprised to discover how manydo-it-yourselfers and knowledgeable technicians read thismagazine.
Just yesterday, a customer called up to send in an ADAT foroverhaul. Nine months before he had called with an emergency. I wasthe only person who suggested popping the cover to look at thebelt. (It had either broken or slipped off.) While all equipmentcarries a warning label—AVIS! Risque de Choc—Iencourage all engineers to investigate their gear safely. No boobytraps are set off when the cover is removed—though you shoulddisconnect the power and wear shoes and socks.
Get to know what's normal, buy a service manual, own good toolsand don't be in a hurry. At a minimum, you'll become more aware ofthe heat that is generated, which should make you more consideratewhen stuffing gear into an enclosed rackspace. Knowledge is power,success builds confidence, and experimentation helps you to ask theright questions. So, rather than talking deep-fried tech thismonth, I thought a few short stories—some related and somenot—might shed some light on this technician's perspective.First, a bit about me and my path toward maintenance.
TO SIR WITH LOVE
It all started in the late ‘50s as I watched my mom anddad play 45 rpm records on a little turntable with a fat spindleplugged into the back of a black-and-white TV set. (Figure 1 showsthe exact model in question.) My father got great pleasure fromhearing his favorite music; the “connections” fromturntable to speaker delivered more than “just sound,”it was about romance and passion and spine tingles.
When tubes and capacitors needed changing, I couldn't get closeenough, zooming in until he would say, “Get out of mylight.” An audio career may not have been my father's vision,but seeing his passion, hearing him sing with gusto—and witha very respectable voice, I might add—inspired me more byproximity than conscious effort. All I can say is, “ThanksDad!”
During the time I lived with my parents, we never owned a newTV. (Can you imagine that today?) Our second boob tube was asecond-generation B&W tube set that used cheesy printed circuitboards. Then as now, PCBs suffered from cold solder joints, andthis set had intermittent audio. At first I smacked the side of thecabinet to restore the sound to my favorite cartoons. My fatherknew to apply pressure to an I-F can—an IntermediateFrequency tuning coil—on the audio board. Later, I learnedhis “repair technique,” reaching in while the set wason, only inches away from the high-voltage anode of the picturetube. (It was only 15,000 volts or so, but the current was low.)Again, I ask, can you imagine this happening today?
The geek seeds were planted early for me, for most of my geekfriends and perhaps for you as well. Somehow, through all of theexperimentation, I avoided death by electrocution. That is to say,I have no idea what effect any accidental shock therapies mighthave had on my brain.
PAYING THE RENT/RAVING THE VENT
So I ended up in New York City, where the East Village is“just a little” more popular now than 20 years ago whenI arrived. Just a few months before leaving town, my shop leaseexpired, and the landlord wanted to double the rent. (Commercialleases are not bound by rent control, and $1,800 seemed a littlesteep for a measly 450 square feet plus six floors overhead ofpotentially leaking bathrooms.) When someone mentions building anaudio facility in New York City, I realize that thoseself-administered shock therapy treatments were beneficial. For me,the transition from the Big Apple to the Mini-Apple was mildlytraumatic, as any move would be. I was too busy getting back intothe biz to worry about culture shock; the biggest hassle wasgetting a quick cuppa cappa. What was formerly an enjoyable walknow requires a car.
In New York City, at least 90% of my biz was walk-in. Comparethat to the Twin Cities, where most business now arrives via UPSand FedEx, a factor that has radically changed one facet of myservicing technique. In New York, I could be a“cowboy,” providing reasonably fast turnaround, knowingthat any problem child could be “returned to day care forconflict management.”
Now, with shipping time and costs, all machines spend more timeon the burn-in rack. For a while, Panasonic DAT decks were soproblematic that post-surgery monitoring was extended to three daysto make sure they stayed fixed. This is not the way to increaseprofit margin, but the process eventually shed some light on thecause of the failures. The mysterious problems have since beennailed.
New Yorkers generally don't like to ship, because there's nospace to store the original packing materials. Add in the fear ofshipping damage and compare both to the ease of getting into a cab.If you must ship and don't own the original box, then use twoboxes. When possible, choose heavyweight, double-wall cardboard,rated for 275 to 350 pounds. Bubble-wrap the device in the firstbox and use packing peanuts in between the two boxes. Insure forthe list price. Don't ship the power cord unless it is unique.Include a description of the problem with the device.
But enough about me. Here are some random musings for you, alongwith the answers to some questions you've sent my way.
The rebirth of analog technology—and the cottage industrythat supports it—owes thanks to the CD and to digitalnaysayers. All of the enhanced digital formats that offer highersampling rates and bit depths will make digital audio moreaccurate, but none will endow it with analog's “elusive anddesirable idiosyncrasies.”
In the achievable-reality department, we all need to be carefulwhat we wish for. One example is 24-bit technology, where even themost expensive 24-bit converters barely achieve 21.5-bits.Admittedly, this is an impressive accomplishment—24-bits ismore than enough, and more samples will push the envelope of whatis possible. All the licensing and format wars aside, we need toincrease user confidence in digital technology so that it isconsidered sonically accurate by the majority and have long-termdata integrity.
GEEK PEAKS: THE RMS TITANIC
During the Stone Age, Peak Power ratings drew a consumer'sattention to a power amp's performance. (Eventually, RMS powerspecs were also published, revealing the truth.) RMS stands forRoot-Mean-Square, not Royal Mail Steamer, but the end result isabout the same. Consider that the Titanic had 2,200“peak” passengers. Sadly, the 705 survivors number only72 passengers short of the RMS formulae detailed in Fig. 2.
The peak-to-peak value of a sine wave is converted to RMS sothat it is “effectively” equivalent to that of the sameDC voltage. (For a square wave, the “peak-to-peak”voltage would simply be halved.) The bottom formula works inreverse to determine the peak-to-peak value from the RMS. Plug intoyour local wall outlet—the juice is 120-volts RMS or339.46-volts peak-to-peak.
Note: Visit www.whatis.com to get a detailed explanation on RMSand many other geek subjects.
Anyone who's ever built an amplifier knows the importance offeedback for reducing distortion and improving frequency response.I rely on reader feedback to better hit the target and to fill inthe gaps in my own knowledge. For example, the LA-4 upgrade projectdetailed in the November 2000 Mix replaced a RC4136 quad op ampwith two dual op amps. Two readers responded—Mark De Martini(formerly of Sigma Sound in Philly and now of Larrabee in L.A.) andJohn Roberts (of Peavey)—reminding me that a TL075 ispin-compatible, if you can find them (I couldn't). I still like mydualing-duals version, but anything is an improvement over theRC4136.
Regarding capacitor upgrades, a few readers told me thatPanasonic's HFS/HFQ Series were no longer available. This is notentirely true. The line is being discontinued with some inventoryremaining. (The FC Series is the replacement.) My most recentexperience at www.digikey.com allowed the option to checkavailability for each part and the FC Series, which is smaller bydesign and only available in the radial format. See Fig. 3 for acloser look.
Finally, I get asked for vintage schematics all the time. Onesource for a variety of documentation is www.triodeel.com,specializing in vacuum tubes, amplifier schematics and relatedparts (not to mention links galore—related and not, somequite humorous).
That's enough random wanderings for now. Next month, I'll beback with a bit more on digital recorders.
Send unused cross-country ski equipment to Eddie Ciletti atwww.tangibletechnology.com fora maintenance credit.