Eisenson's Revenge Chapter 99

Eisenson was the audio salesman and tinkerer who my friend George will never forgive for having an out-of-phase speaker system.

I myself have made so many major mistakes, often for weeks or months at a time, that you really do have to wonder.  Of course I believe that you can get an intoxicating effect, not to mention appreciation of music, or just plain old enjoyment out of a seriously out-of-whack sytem (as long as it doesn't sound extra harsh or annoying).  To deny that is to be a bit smug, I have always felt.  Also, one can't always be deploying one's inner audio engineer to ensure that all aspects of reproduction are technically correct.  Most of the time, one simply wants to enjoy.  I know Eisenson got great pleasure from the far reaches of the high frequency response, and perhaps when paying most attention to that he ignored the reduction in bass (or it was even helpful...).  It has always been my view that no one 'reproduction' is perfect, and many are good enough in one way or another to reveal some facet of the music with greater clarity.

Well in my latest mistake, I apparently had the subwoofers totally turned off since some experiment, perhaps written about here, from weeks ago.

I first noticed that when I selected the "movie" mode (which reduces bass in the periphery to make it less peaky there) it had little effect.  Then a week later I figured the exact cause of this discrepancy.  First I noticed one sub turned off (I remembered thinking "I'll notice this right away") and also the DAC muted (I had to do that for the other channel).  I was doing some kind of impulse test, perhaps before the first recent LP recording a few weeks ago).

My crossover is at 125 Hz, so a sub loss cuts out quite a bit of real bass.  But it all sounded fine.  (I wasn't doing much if any serious listening, the room has mostly been set up for showing movies and I've been to lazy to move the listening chair into the center.  But I might have listened to an LP or two, thinking it sounded a bit dry.  And then I wondered why recordings sometimes sounded better on my kitchen system when I was mastering them than in my living room system where I was recording them.  All clues I ignored, until I didn't.

Re-testing the antiskating force

 I've picked up some used records (from deceased or moving audiophiles) and started recording them (while often inspires me to record some of my own--which are usually better).

Occasionally I've noticed some groove chatter in mostly one channel which made me think antiskating was wrong.

I always run my Dynavector D17 version 3 (Diamond Cantilever) moving coil cartridge at maximum tracking force, 2.25g, but for awhile around 2022 I was running the antiskate near the maximum setting of 3.5g on the Ittok LVII.  That had two benefits.  For one it seemed to track better on some high velocity test I used, and it seemed to provide useful additional horizontal damping.

At some point I changed the antiskating back to 2.6...I now can't remember if that was just "temporary" (because it passed the silent groove) or part of a series of tests (perhaps reported here).

So the present mistracking was bugging me, perhaps 2.6 was too low and I needed to go back to 3.5.

I first tried the silent area (not a "groove" as such) test on my Orion test record (the one I bought most recently as "unused").  2.6g antiskating force nails it.

But it always occurs to me that silent area tests don't simulate the additional skating force that occurs in heavy modulation.  So I ran the 5 band tracking force test on the same Orion record.

That's a killer test because, contrary to what the announcer says, there are probably few if any cartridges that can play all 5 bands.  It starts at the maximum nominal level and goes up from there.  It's harder than the tests on Shure test records.

With 3.5g antiskating, I couldn't play band 4 without serious distortion.  With 2.6g antiskating, I could play band 4 with only minor distortion.

I also compared needle drops and didn't see any improvement with 3.5g antiskating.  In any case, the tiny resonances around 10 Hz are now looking to be rumble related rather than horizontal arm resonances as such.  Other turntables produce that too, though it often reaches higher in frequency with bearing noise.  The Linn keeps all it's motor and bearing noise below 10 Hz, so even though it's sizeable there it produces less coloration overall.

So it looks like 2.6g is indeed the correct antiskating adjustment, and some used records may just have asymmetrical record wear (possibly from misadjusted antiskate).

I still think an arm with much more horizontal damping would be desirable for the Dynavector cartridge.  The ultimate arm for the cartridge is the Dynavector arm with magnetic adjustable damping.

Antenna Grounds Tested

 My kitchen is now connected to 3 external antennas, two with FM whip antennas, and one shortwave antenna.  Shortly I will get foundation repair and some leveling which could potentially disrupt the integrity of their grounding (to underground rods which are "bonded" to the main panel ground through a long underground wire).

All 3 wires have coax cables coming into the house.  The shield of the coax cable of each is connected to ground in external grounding boxes.

I disconnected all 3 coax cables from their receivers and measured their voltages and resistances to one another.  There were trivially small millivolt voltages I didn't write down.  The resistances were consistently around 0.5 ohms, 0.56 was my first measurement from the front to the back coax.

But this only proves they are bonded together, not that they are bonded to house ground.  So I got a 3 light AC wiring tester, for which one line lights up if the ground is good.  I plugged that tester into a 3 to 2 wire adapter to bleed off the ground test current.  I then plugged the 3 to 2 wire adapter into a bottom ac outlet so it did not contact the plate screw (which would ground it).  I connected a wire to that to the ground tab and now I can test anything for being an "acceptable" ground to this simple tester.

I tried the sink faucet and the dishwasher panel, they are not acceptable grounds.  The "grounded" light did not light up.  (The dishwasher is perhaps "multiple insulated" and the "stainless steel" is really coated in non-conductive coating.  The sink faucet is connected via PVC pipes.)

But the Grounded light did light up when I connected the wire to the shields of each of the 3 coax cables coming from outside.

I connected an ammeter in line with the wire going to the ground adapter, and measured 1.336 mA current with each of the 3 antenna coaxes.  This was actually better than the 1.333 mA I measured going back to the ground on the same wall socket.  (By contrast, there was only 0.05mA current measured to the kitchen sink faucet, though that was noticeably higher than not being connected at all, or me just holding the wire.)

Now I have some measurements I can repeat after the house leveling.

House ground resistance is supposed to be below 5 ohms.  I'm not really measuring that, but it appears my antennas and AC outlet grounds are no more than about 0.5 ohms apart, which represents the resistance of the ground wires and coax grounds, and indicates they are all bonded to house ground.

*****

After the foundation piering, I retested 2 of the grounds.  The third ground is temporarily disconnected and needs to be moved but is probably ok.

I first measured the ground to the roof peak antenna, the Magnum Dynalab ST-2.  At first it read 1.3150 ma, or about 2% lower than before.  But testing the actual house ground, it was also reading about 2% lower at 1.313.  Then when I tested the ground to the Godar 1000 antenna, it measured 1.32ma.  Retesting the other antenna again, it was now reading 1.32ma also.  So it looks like 1-2% fluctuation is normal and comparing antenna ground current with house ground current at the same moment works.  (It could be the "hot" line that is varying slightly, because what I am measuring is current flow from electrical hot to test-ground through a resistance built-in to the ground tester.)

Before the foundation work was done, I unscrewed all ground wires from their ground blocks outside but left them touching for protection.  I also loosened the plastic shields around the ground wires from being attached to the house.  Before doing the re-test, I screwed the two ground wires being tested back in to their grounding blocks outside.