Don't use 95% Ethanol for cleaning PVC

In unfortunate haste, I tried to clean some of the smell of the big plastic topped rotary encoder knob on my newly acquired HP 3582A Spectrum Analyzer (a standard in audio analysis).  Sniffing around the instrument, much of the smell seemed to be coming from this knob, possibly because of it's flat plastic surface being a sponge for odors like cigarette smoke.

I used Everclear (95% ethanol) and Q tips.  Fairly quickly it started creating streaks and even sandpaper like bumps in the PVC surface.  (It didn't do much for the smell either.)

I vaguely remembered many years ago hearing some electronics maven (probably an old tech at a surplus store) tell me that 91% Isopropyl was safer to use on plastic than 95% ethanol.

But quickly scanning through expert opinions on various sites, I was not finding anyone distinguishing the properties of ethanol and isopropyl on PVC.   Both could be used briefly but longer would cause streaking, read a typical opinion.

Finally, I found this authoritative table, which indeed shows that isopropyl is safer on PVC.  Ethanol is the WORST of the simple alcohols, gets a C rating.  Isopropyl is among the best of the alcohols, gets an A1 rating.  Butanol is A2.

https://www.calpaclab.com/pvc-polyvinyl-chloride-chemical-compatibility-chart/

I'm actually thinking the Pledge floor cleaner, designed for vinyl floors and based on Butanol and surfactants, might be the safest and effective.  It's supposed to be diluted 1/64-1/32 also, fwiw, which makes the Butanol very dilute.

Some pledge polish for hard surfaces (put on a cloth first) seemed to remove the smell and replace it with nice lemony scent.  But the lemony scent wore off and the original smell returned.

Linear vs Minimum Phase Digital Filters

https://troll-audio.com/articles/linear-and-minimum-phase/

Wow, I had never thought that the "linear phase" filters used as CD brickwall filters are so called because they have no phase distortion!  All frequencies are delayed equally.  This requires an acausal filter to realize (which could be an analog system with delay lines).

The price paid for this magic of linear phase is the pre-ringing artifacts.  The pre-ringing is at ultrasonic frequencies and typically quite small.

Reverting to causal minimum phase filters get you no pre-ringing, but the post ringing is far larger, and the pulse itself is distorted because of phase shift before the cutoff point.  (Just one example is shown.  The phase distortion and post ringing can be played against each other in different ways.)

Audyssey Multi EQ Editor

My current kitchen surround system is finally sounding pretty nice, using the analog outputs of the Oppo BDP95, duplicating the surround sides to the backs with 10ms delay (simply because I'm using Behringer DEQ set to 0ms, it's minimum latency is 10ms).

Using my 2005 Yamaha 7 channel receiver with Hafler 9300 amplifier for the front speakers.

I was playing A Night At The Opera by Queen DVD-Audio, and the Brothers in Arms by Dire Straits DVD-Audio.  The Queen disc especially uses the surround channels with great artistic flair.

But if I were to get an actual up-to-date surround processor with all the latest processing, something I occasionally think about, I would want the Audyssey Multi EQ Editor which makes it easy to customize.  Here's an old list of processors that have this feature:

The following existing AV Receivers will support the MultEQ Editor: Denon AVR-X6300H, AVR-X4300H, AVR-X3300W, AVR-X2300W, AVR-X1300W, AVR-S930H, AVR-S730H, AVR-S920W, and AVR-S720W. Also, Marantz AV7703, SR7011, SR6011, SR5011, and NR1607.

So I need not spring for the extremely pricey Marantz 8805 to get this feature.

More importantly, I think, I've just purchased a pair of side surround speakers that can be mounted at ear level in the kitchen because they are so small: Gallo A'Diva SE's.  The back speakers will remain at the near-ceiling level they are now, because no room for more speakers there.  I'm not sure what I'll do with the current ceiling height side speakers.  They might be repurposed for front front-high-wide speakers and modified with my Infinity Walsh Tweeters and new woofers.