What is the "better / best " method to multi-boot different OSes natively WITHOUT VirtualBox(es) ?

Ralf Mardorf ralf-mardorf at riseup.net
Mon Oct 26 07:20:40 UTC 2020

On Sun, 25 Oct 2020 23:02:45 -0500, Valeri Galtsev wrote:
>> On Oct 25, 2020, at 4:52 PM, Ralf Mardorf <ralf-mardorf at riseup.net>
>> wrote:
>> However, galvanic isolation is absolutely safe, unless getting in
>> contact with both conductors, which is impossible in our scenario and
>> even very unlikely when repairing gear.   
>Hm, if galvanic you mean DC isolation (i.e. AC transformer), then I
>disagree. In case of AC stray capacitance (which always exists)
>conducts some of AC line voltage to "DC isolated" part of equipment.
>Only optical isolation is full isolation, but we didn’t learn yet how
>to transfer sufficient power using purely optical connection. In
>general, DC isolation, like transformer, is safe, but transformer has
>stray capacitance, and what usually saves the day that low voltage
>part kind of shunts what comes through stray capacitance by not to
>small resistance. There may be less usual situation when highly
>isolated from everything piece of equipment has big capacitive
>coupling to “ground” which can be charged gradually through small
>stray capacitance of transformer (rectifier of one sort or another
>will be in play, call it “stray rectifier"). Even though it falls
>under what you call “galvanic isolation”, it represents big danger for
>a human, as big capacitor can sustain significant current for long
>enough time to do harm to living being.
>My apologies, if I misunderstood you.

230 V  L°----------------° <- Don't get in touch with this conductor.
50 Hz

       N°----------------° <- Touching this conductor is ok.

230 V  L°-----+ || +-----° <- You can touch this conductor ... 
50 Hz         | || |
              | || |
       N°-----+ || +-----° <- ... as well as this conductor, just don't
                              touch both at the same time.

In Germany the isolation transformer usually is an adjustable
transformer, so it's possible to troubleshoot and repair 230 V as well
as 120 V gear. Troubleshooting disconnected gear is hard to do ;).

Indeed, I've forgotten that some circuits contain big capacitors, so
discharging using a resistor is usually done (and sometimes even the
screwdriver is used, not recommended ;).

CRTs and other special gear are something else, far away from a
scenario of a hot computer metal case.

On Sun, 25 Oct 2020 22:34:36 -0400, Kevin P. Neal wrote:
>I've seen that happen. Guitar players hate it when they walk up to a
>mic, start singing, their lip touches the mic and ZAP! They really
>hate that. It looks weird, too. Ever seen a guitar player react like
>he's been punched in the face right as he starts to sing? I have.

On Sun, 25 Oct 2020 18:14:12 -0600, Bob Proulx wrote:
>Ralf Mardorf wrote:
>> >Please explain the risk(s) associate with antistatic wrist straps.  
>> IMO it's a risk for a human being to wear an antistatic wrist strap,
>> when getting in touch with gear that is connected to the mains.  
>ESD wrist straps have a resistor in series to prevent exactly this
>problem from occurring.  It's on the order of a 1 M ohm value.  This
>protects the wearer in the event they touch live AC mains.
>(Meanwhile...  I always preferred the heel straps myself.)

I wouldn't bet on an Alibaba anti-static wrist strap and even not on
branded products, as long as expensive smartphones authorized for
the European market, equipped with original batteries catch fire when

Audio gear sometimes provides a ground lift switch, then ground isn't
directly connected, but still connected by a capacitor (and sometimes
it's completely cut off, not recommended ;).

Good old MIDI is/was isolated by working opto-couplers. Nowadays USB
MIDI seemingly isn't isolated anymore and for classic MIDI sometimes
there's not enough power to power the opt-couplers or the signal
suffers from bad edge steepness.

However, as a musician and audio engineer I don't trust grounding.
Without doubts grounding is perfect in professional video and audio
studios and probably in a server farm, too. Anywhere else in the real
world grounding often is fishy.

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