Audio Cable Vodoo

by Wayne Mitzen

Here's a letter I sent to Larry Crane editor of Tape Op after hearing about AC power cords that make a difference:

Hello Larry!

NOT FOR PUBLICATION

Uh.. dude, you really don't want to get into the whole cable esoteric crap that the consumer audio guys do. In fact a few years back AES sponsored a blind test that a bunch of audiophiles failed discerning (10) 741 opamps (one of the lowest-fi opamps out there, typ. used for DC servos) chained together vs. their "golden-ears" Litz (sp?) cable.

A few things; one I worked in a hifi golden ears (GE) shop. As a test , we took an Advent tweeter, placed it on the used shelf with a tone generator/amp, starting at 19K...94dB @ 1M every few days we'd drop it by 1K.

Now the GE's, sitting there telling people how good that 130.00 3' pair of Litz cables would sound didn't hear a thing.

The only guy that noticed was the hippie dude, he mentioned (at around 13K) that he'd shut off all the old Advent projector TV's we also sold but could still hear the Horiz squeel... Hmmmm

OK... LISTEN - MAJOR POINT HERE:

Interconnect cables are not arbitrarily selected. A certain cable with certain virtual impedance is used to connect inputs and outputs with characteristic impedance and transfer function. This is basic math...basic physics.

For instance, imagine a coax cable (similar to the BNC stuff you just bought for your PT rig) except that it's 3" in diameter, the connector weighs about 30 pounds and is as big as your head, hollow with nylon spacers placing the center at the exact distance for 50ohms, and you have to gas it with anhydrous nitrogen to keep it from flashing over and so you can push 40,000 watts with an 8,000 volt plate voltage thru it at 100Mhz. This is what I dealt with designing FM radio transmission facilities.

Here's a great photo - http://www.coutant.org/mtwilson/04.jpg

That ain't me by the way; no association, just a cool pic - it's the guy from the radio station on Mt Wilson http://www.coutant.org/mtwilson/index.htmlBTW: see those "pipes" in the background - they ain't no pipes, that's 3" rigid transmission line.Now tell me about your uper expensive BNC cable for your PT rig...

Just imagine how fucked something can get if it's just slightly off in matching the load?

It's happened to me on multiple occasions, due to a lame-ass tower guy slightly screwing up the connection to the antenna/transformer (you can see a CAD drawing at http://home.comcast.net/~ajawamnet/page4/page4.htm ). Or, a hell of a lot of ice accumulates on the antennas ( those things in the aforementioned CAD drawing that look like convoluted arms - those are CP 40KW ERI FM bays) due to a nasty winter storm..

There's a property known as VSWR (ask any ham dude or even a trucker with a CB, or any cable plant guy that installs CAT5 cable/fiber - why they use a Time Domain Reflectometer) this is the power reflected back to the source from the load. It's always there and is expressed as a ratio - usually something like 1:1.18 is tolerable by a transmitter; which is a 10K-40K power amp that typically has a tube in it that's the size of a large coffee can.

Another great image - http://www.coutant.org/mtwilson/06.jpg

That's a lot o' power.

I'll tell you what happens - Now image the aforementioned bad connection, ice, god knows what. What happens when there's a slight mismatch is that MOLTEN BRASS/COPPER falls about 400' on to peoples heads.

We actually had a mismatched 4 bay ERI (what's shown on my website mentioned above) that went FLAMING and dropping molten metal onto a senior citizens home that was co-located under the tower farm.

So AGAIN I STATE:

YOU DO NOT ARBITRARILY SELECT A CABLE BASED ON THE TYPICAL "VOODOO SHIT" PROPAGATED BY VENDORS THAT ARE NOTHING MORE THAN MR. HANEY FROM GREEN ACRES. (Yea, Mr Douglas, gots me some o' dat der cable for yer stereo ... http://www.maggiore.net/greenacres/gacast.asp )

Here's the thing, ask any pro that's working with processors running in the Ghz range and any guy that designs RF stuff, and he'll tell you that all the crap about this cable and that cable is usually pure BS.

PLEASE NOTE: there are differences in cables - these are calculable parameters that are used by actual engineers with the equations to back it up for use in specific circuit topologies that require the most efficient and coherent transfer of energy.

As to the guy from Requisite that states "equipment break-in.." what you're hearing is actually components aging. For instance, electrolytic caps exhibit a change as they age; in fact, if you look at any of the catalog pages of electrolytic caps on Digikey.com you'll see a rating for expected life at the Absolute Maximum thermal condition. See here:

http://www.digikey.com - just type/paste ELECTROLYTIC CAPACITOR into the search box

OK, let's deal with a tuned circuit, running at 2.4 GHz, well beyond the paltry 20-20K audio guys deal with. This is what's in your 802.11 card on your laptop.

Now, most vendors try to eliminate manual tuning tweeks. They try to go with fixed values for resistors, capacitors, inductors. This get's the cost down in mfg; that's why it's $40 for B/G wifi card.

Now let's say this "breaks in". OK. Because of the tight tolerances and tuning of the RF circuits, the peak drive current to the final amp will be affected, causing as much as a 45dBv reduction to the input of the final.

EFFECT: NO MORE ONLINE PORN FOR YOU...

If you really want to know what's up call me 703-618-2430 (yea, I know you're too busy) but hey here's the chance to actually learn a bit about the underlying crap you so duly use in your day-to-day stuff). And you want busy:

-- I'm currently working designing hardware for many companies here in DC

-- I have over fifteen side jobs including designing over 130 PC boards a year - such as this one http://home.comcast.net/~ajawam1/g010707d.pdf I'm currently working on two right now that have over 1500 components each (actually 8 channel audio distro systems for homeland security radio comm.)

-- play over TWO HUNDRED gigs a year with Jon Fritz ( http://www.jonfritz.com )

-- mixing/mastering Twisted Tower Dire's release for Remedy records in Germany (do a google on them)

-- working with various live sound/studios in the area fixing all the crap that major retailers sell with out a clue as to what they're doing

-- have three kids

-- designing and assisting various CAM operators with CNC machine controllers

-- designing preamps for various audio people

-- designing my own equipment since no one seems to again, have a clue as to what's up

-- dealing with promo for Jon's stuff and paying with it from the side jobs I do

>>>>NOTE: So I get a response from one of the editors at mediabase - asks if I got a response I reply:

Thanks... Naw, I didn't think he would. My guess is he's going thru the "rock star" mentality with his mag. Typical .... give'em a few years to temper his 'tude and he'll be OK...

I've been thinking of expanding it and publishing somewhere, have to do a bit more "research" ("I'll have the roast duck and mango salsa..."); get some screenshots off of my lab equipment. It's part of my theory that audio "pro's" that carry the title "engineer" have a long way to go. I remember about 15 years ago AES papers were actual studies with actual peer-reviewed dissertations and real math in them. I was hoping that a consumer protection unit would take the lead on some of the wildass claims these consumer audio companies make. "He who waits for legislation waits for no one" I guess...

I was speaking with Rupert Neve a few years ago, we were trying to get him to do a DSP card that would emulate his comps/limiters/etc... and with a real nice front end. I asked him how he liked Texas vs England (he and his wife recently got US citizenship). He was still encumbered with the whole AMEK- Harmon thing and IC's were about the only thing he could do.

So I asked him what he was doing and mentioned something like, " ... so I guess you spend a lot of time fixing the old modules people pull from your old consoles and are so enamored with..." and his response was that he couldn't understand why audio "engineers" were so into those things..."they sound God-awful..." was his response. He mentioned something on the order of, " Wayne, you know how far along semi and passive technology has come? Why would anyone use that stuff?"

And it wasn't a marketing ploy to sell Harmon stuff (believe me - I got the impression that he was about fed up with that whole affair). It's true; 'cause right after I spoke with him, I benched a few of his old micpre/EQ's some studio ripped from an old NYC studio's console. Man, they sucked. Massive noise, pure sine waves turned into funky waveforms well into the audible range, THD out the ass. I blamed it (reason for my question to him) on the dried-out coupling caps and aging transformers (delamination is a primary cause of transformers sounding weird after a while).

But hey, that's what sells - pure hype... shame he doesn't make any $$$$ from the old stuff. I wonder how well his new Portico (he's free from Harmon) stuff is selling?

And in the long run, I've never heard a 14yr girl say, "did you hear all the transient intermodulation distortion in that last Black Eyed Peas single? I'm not downloading it!!"

"I don't have much of an appetite..."