Isolation Transformers Used For Audio Systems and Grounding

[wmhart]

I have had productive experience in the past using isolation transformers that plug into a household wall receptacle-both 240/120 and 120 to address various issues over the years in connection with my audio system and associated components. As one example, my tone arm is a lateral tracking air bearing arm and runs from a relatively large (for audio applications) compressor-- 1/2 to 1 HP, 6-13 gallon tank. These compressors typically create a nasty electrical zap through the audio system, even when on a separate or dedicated line (aside from their mechanical noise which I address through appropriate soundproofing). My understanding was that all of these transformers I used in the past had a secondary that was grounded to the main household ground, i.e., neither an isolated ground, nor a 'floating' ground as used in some medical or lab applications. Despite that, the transformers were effective in preventing the compressor 'zap' from crossing over into the audio signal.
I currently have two large isolation transformer set ups for my hi-fi. One remains in storage because it is balanced power- a large wall mounted cabinet style, designed to be wired into the electrical system, not a black box that simply plugs into the wall. It is my understanding that this is generally not something that can be installed in a residence in compliance with Code. My intention with that unit, an Equi=Tech, is to eventually install it in an outbuilding with a separate service path and meter (like a rental house on our property), so that the ground for that set up is unique to that building and is not shared with the main household electrical system.
In the meantime, I've just had a licensed electrician install an isolation transformer to feed a subpanel of dedicated lines for my system in the house. The secondary is effectively grounded to the main ground for the house-- a Ufer system.
In a discussion about the benefit of this, an EE pointed out that if I am grounding the secondary to the main household ground, it is not truly isolated. That much I understand and agree with-- but, does that render the transformer useless? My past experience says no: I still obtained benefits using the other isolation transformers mentioned in my first paragraph, above, though they were also grounded to the household grounding scheme.
So, to crystalize the question-- why and how am I getting a benefit from the isolation transformer(s), even though the secondary is grounded to the main grounding path?
I'm not an electrician or engineer, but rely on folks that are. No shortcuts or Code avoidance objectives here--consider me a knowledgeable enthusiast with a healthy respect both for code compliance and for those who have training and experience in their fields. (I'm actually a retired copyright lawyer who has been involved in music and hi-fi for many decades).
Many thanks in advance for your insights,
bill hart

 

[GoldDigger]

An isolation transformer can block conducted voltage transients on both ungrounded and grounded circuit conductors. In particular a transformer with shielded windings can block much "arcing" noise generated by contacts closing and opening under load.
There are other ways of doing this that may be more economical.

Sent from my XT1585 using Tapatalk

 

[wmhart]

An isolation transformer can block conducted voltage transients on both ungrounded and grounded circuit conductors. In particular a transformer with shielded windings can block much "arcing" noise generated by contacts closing and opening under load.
There are other ways of doing this that may be more economical.

Sent from my XT1585 using Tapatalk

Thanks, GoldDigger- I guess the answer is that some electrical "gremlins" (term of art) occur on the + and - so though I'm not getting the full benefit of isolating from grounding noise, it's better than nothing. The air compressor example was egregious, but even with dedicated lines in my last house for the system, certain lights and appliances elsewhere in the house would create noise-- I would assume that is because of shared ground.
I just moved into a new place in Austin, after 35 years in NY and setting up the system here, while fun, has been harder than I remember. Maybe age, I dunno.

Another electrician raised the possibility of being able to do a switch bypass of the transformer to compare it in and out of the system, but the little reading I did on that suggested it would create a whole host of other problems, and that in fact, isolation transformers were used just for the switch over process- e.g. like back up power system when the main electrical system goes out, to prevent all kinds of hazards to the connected devices. I'm going to leave well enough alone.
One other question, I guess it is part of the subjective v objective schools of audio- burn-in of this stuff. That transformer has Jah-knows what amount of copper wire in the windings, all fresh from the factory. The sound, "off the pallet" seemed to have more gravitas, but the high frequencies seem a bit hard. My experience with cable, generally, is that it sounds better after some time--so, I hope this is the case with the transformer. My suspicion is, EE/Tech types may relegate this to utter BS, or a psychoacoustic phenomenon-- it isn't the cable that's changing, but my ears are getting conditioned to it. Sorry if this goes into one of those provocative areas that this forum doesn't deal with. (There's all kinds of witchcraft in high end audio, some of which sort of does something, whether better or worse is hard to say-- I try to keep it simple).
Many thanks for the quick reply.

 

[GoldDigger]

Not to assert that there are no such things as witches, I have to state that most of the Forum members do not deal in witchcraft or religion, and I think that that level of subjective audio effects are beyond me.

I do not believe in $500 electrical receptacles and cords, but will gladly accept money to install them.

Note that the use of Comic Sans font indicates sarcasm.

 

[Ingenieur]

A cable has 3 basic parameters
R, L and C
they determine attenuation, phase shift, any filter response/action
measure a new cable at 1/2 dozen frequencies
burn/listen it in
remeasure
if these haven't changed I can't see how sound would

 

[wmhart]

Thank you. I am, right now, just enjoying playing some music I like, so that's the good part, not all the fiddling. I will reach out to the forum with questions on occasion (voodoo-free). Regards, and have a good 4th.
bill hart

 

[gar]

170630-1946 EDT

wmhart:

My suggestion:

1. Get a screen room manufacturer to build a room for you.

Build the room on shock mounts. In the 1930s WWJ (WWJ 's first broadcast was around 1920, https://en.wikipedia.org/wiki/WWJ_(AM), one of the first AM radio stations), built their entire studio system on shock mounts (a large building) to minimize adjacent road vibrations from large trucks affecting broadcast audio quality. In those days Mack trucks ran on solid rubber tires.

Make the interior as anechoic as desired.

The screen room creates a Faraday shield. Not a magnetic shield.

This room should be located far enough away from any stray AC magnetic fields so as to not affect the equipment in the shielded room.

2. Ground your screen room to its own earth grounding system.

3. Make all your equipment operate from a DC source. Bring the DC power into the room thru appropriate low pass filters referenced to the screen room shield.

Just outside the screen room you might place a DC battery which looks like a low pass filter except except at higher frequencies.

4. Somewhere adequately away from the screen room locate an isolating AC to DC power supply.

I doubt you would do this. But some of this still applies to an AC system.

I would use two isolation transformers. These should be totally encapsulated in epoxy, sound reduction. These transformers are connected in series. The second transformer output is grounded to the screen room shield, and its isolated grounding system.

Each transformer has internally an electrostatic shield between primary and secondary. So the output transformer's internal shield is connected to the screen room shield.

The input or first transformer has its shield connected to the AC power EGC.

.

 

[infinity]

In the meantime, I've just had a licensed electrician install an isolation transformer to feed a subpanel of dedicated lines for my system in the house. The secondary is effectively grounded to the main ground for the house-- a Ufer system.
In a discussion about the benefit of this, an EE pointed out that if I am grounding the secondary to the main household ground, it is not truly isolated.

From the NEC perspective you cannot truly isolate the system either by installing a transformer or installing a new system in separate structure. The separate building scenario would still have an EGC installed with the feeder which is connected to the EGC/neutral bus at the house. Any 120/240 transformer would require that the neutral be bonded with a system bonding jumper which connects it to the building grounding electrode system. in either case you cannot escape the connection of the two systems together.

 

[GoldDigger]

What you can do is make an effort to keep transient noise off the EGC which connects your equipment to the main EGC to neutral bond.
If possible that includes putting filtering on the EGC serving the noisy equipment. I think that the NEC does not prohibit this.

Sent from my XT1585 using Tapatalk

 

[wmhart]

170630-1946 EDT

wmhart:

My suggestion:

1. Get a screen room manufacturer to build a room for you.

Build the room on shock mounts. In the 1930s WWJ (WWJ 's first broadcast was around 1920, https://en.wikipedia.org/wiki/WWJ_(AM), one of the first AM radio stations), built their entire studio system on shock mounts (a large building) to minimize adjacent road vibrations from large trucks affecting broadcast audio quality. In those days Mack trucks ran on solid rubber tires.

Make the interior as anechoic as desired.

The screen room creates a Faraday shield. Not a magnetic shield.

This room should be located far enough away from any stray AC magnetic fields so as to not affect the equipment in the shielded room.

2. Ground your screen room to its own earth grounding system.

3. Make all your equipment operate from a DC source. Bring the DC power into the room thru appropriate low pass filters referenced to the screen room shield.

Just outside the screen room you might place a DC battery which looks like a low pass filter except except at higher frequencies.

4. Somewhere adequately away from the screen room locate an isolating AC to DC power supply.

I doubt you would do this. But some of this still applies to an AC system.

I would use two isolation transformers. These should be totally encapsulated in epoxy, sound reduction. These transformers are connected in series. The second transformer output is grounded to the screen room shield, and its isolated grounding system.

Each transformer has internally an electrostatic shield between primary and secondary. So the output transformer's internal shield is connected to the screen room shield.

The input or first transformer has its shield connected to the AC power EGC.

.

I actually contemplate a purpose built free-standing building on the property. We had a feasibility study done during due diligence on the house purchase, although we just moved in at the beginning of April but it is an historic house, so in addition to funding the build-out, there are many additional approvals needed by the Historic/Landmarks Preservation folks. I am really less concerned about electro-magnetic radiation and all the RF/Wi-Fi/whatever in the air than the noise caused by the electrical system powering the gear, though I've joked about Faraday rooms many times. (Ever watch "Better Call Saul"?- the character of the brother suffers from something that has caused him to go into deep shielding mode).
I found your post fascinating, as an historical matter, though taking things to extremes. I first read it as a "if you are really nuts, then..." but I think you actually posed this as an example of the lengths to which one can go. There are some blokes outside London that make Living Voice branded products that developed a large battery supply with charging capability and capacity sufficient for a large system; their studio/workshop is in an old Edwardian era factory outside London. This profile of the shop at large is dated, but if you scroll down, this shows the battery system, which they've now improved and tripled in size and have been marketing in one form or another for at least 10 years now: http://www.6moons.com/industryfeatures/livingvoice/definitive.html I'm also fascinated by antiquarian audio equipment, such as old WE, Klangfilm, old single ended amps, and early broadcast turntables like the EMT. (Much of my system follows similar design concepts with a modern execution, and doesn't look "old" but the vintage stuff gives me the same thrill as seeing or driving a pre-war car).
I do have one component that runs from lithium batteries with an umbilical to a charger that isn't that far away. I didn't buy it for its electrical design, as such, but its sound, which is marvelous: full bandwidth, very musical and alive sounding, even in the bass region, using the DR version of the Reflector 6H30 tube, something that isn't so easy to find these days (at least genuine ones). However, as you can gather, the designer really wanted to eliminate the sound of the wall current as a variable. I've found black box power conditioning to do something to the sound- in some cases, it as it is an improvement over what comes out of the wall, but it's all relative. You are, in a sense, "playing" your power with audio gear- so I take the point about running from DC rather than AC, with appropriate filters.

I know a little about studio design, and contemplate a floating wooden floor over a poured slab, but I don't really want a dead sounding room, acoustically. I find them claustrophobic sounding- I also like rooms that don't feel like "bunkers" but, as you no doubt know, glass is a devil in terms of reflective surfaces, so using clerestory type windows, out of the field of play, to let light in, is one way to get light without bite. In the meantime, before any heavy construction projects--my check writing hand is sore- I decided to set up the system in a loft space at the top of the house, which benefits from some of the construction methods used in the 1880's (though that space is modern, rather than historical, like the main floor, which has the vibe of an old Western museum). That is what led me to the question about the isolation transformer I just installed as part of the household electrical system, since i have another one really best suited for a dedicated service path in a dedicated building, delivering balanced power (the Equi=Tech cabinet).


Although we are somewhat far afield from electrical issues on some of these points, the loft space in the house itself has the potential to sound extremely good- all walls in the interior are made of shiplap, so after nearly 130 years of the Texas heat and sun, it is almost like petrified wood. It is covered downstairs with cheesecloth and period recreated wall paper that is suspended, not glued over it; upstairs, where the hi-fi is, it is drywall against the shiplap.
Right now, my main focus, aside from electrical (which admittedly didn't sound bad at all before the isolation transformer, at least compared to the power I was getting north of NYC, which had its issues despite being in the "country") is 'dialing in' the system to the room- component placement and settings. I plan to have an acoustician with "ears" help by doing measurements, both acoustic and physical and guiding me on eliminating bass modes and achieving the best clarity and impact. I'm not of the buy more gear school; i have a good system- to me, it is about optimizing its potential and much has to do with its interplay with the room. Fairly small physical adjustments to the horn array and dynamic woofers and subwoofers make significant differences. Ultimately, I'm not a constant tweaker- once dialed in (it took a few years in NY), i'd rather not mess with the equipment but just use it as a vehicle to enjoy my vinyl collection.
FWIW, I'm not much of a DIY'er (at least my wife didn't marry me for my home improvement skills), but I developed a really effective silencer box for my air compressor that drives the tone arm. I took some initial ideas from an article on the web, but modified the design considerably, and had a contractor cut and assemble the materials-- it works extremely well.
Thanks for your post. It was thought provoking in the extreme.

 

[junkhound]

Voodoo, witchcraft, etc. just some audio comments for discussion.

Gar forgot to mention that IF the screen room has solid steel walls, the magnetic fields are stopped also. Also, a 'good' isolation transformer will have full box shields on both primary and secondary. :ashamed:

No doubt there are a few six sigma folks (e.g Stevie Wonder?) who have hearing more discerning than a 120 dB 0.05 Hz bandwidth spectrum analyzer, but have never met any nor seen any double blind testing of data from such a person. My teenage grandson can hear up to 22.8 kHz pure sine wave at 30 dBSPL (my tests), so do know some folks are exceptional that way.

A 1920 study found that 98% of double blind listeners could not tell the difference between a master 78 rpm recording and a live orchestra! Wow, probably 98% now could tell the difference due to education in what to listen for ? That 1920 study had the turntable/amp/speakers etc and orchestra both 'hidden' behind a thick curtain, that in itself certainly killed many harmonics.

Have met folks who actually believe it impossible to build a class D amp with the 'warmth' of a linear tube amp! All it takes is the right PWM compensation to duplicate any 20 kHz and below linear system, including AB tube amp saturation effects -- but then, one would never find that level of PWM control in a $100 class D 1 kW amp. Besides, what technical engineer type wants to distort the original signal ?

Same for silver plating on audio wires, whoopee. Some marketing types make a few bucks off the gullible though, as if response t 20 megahertz makes any audio difference. Gold is prettier.


Question for OP:
Why bother with tone arm, et al, is it simply the mystique of vinyl (or cellulose) platters?
Granted that common digital audio such as mp3 is pathetic technically at only 16 bits and 44 kHz, but IMO 500kHz 64 bit systems are beyond human discernment?

BTW, my 72 YO "post chain-saw ears" cannot tell an MP3 copy from the original 15ips 1/2" reel to reel recording.

 

[Ingenieur]

Custom motor generator set
5 kva should do it
seperate sound insulated metal shed
on concrete pad with vibration isolators on the mg set
120/240/1 in
69/120/3 out
hook everything up line-line
seperately derived impedance grounded neut (actually ground since no intentional load)
perhaps a tuned lc filter for the impedance
seperate ground grid <1 Ohm
perhaps a grounding xfmr to isolate from other grounding systems

or not

 

[wmhart]

Question for OP:
Why bother with tone arm, et al, is it simply the mystique of vinyl (or cellulose) platters?
Granted that common digital audio such as mp3 is pathetic technically at only 16 bits and 44 kHz, but IMO 500kHz 64 bit systems are beyond human discernment?

BTW, my 72 YO "post chain-saw ears" cannot tell an MP3 copy from the original 15ips 1/2" reel to reel recording.

I'm happy to answer as long as you don't regard this as a CD v. LP or digital v. analog argument. I'm after the music in a very 'in the room' way.
My usual answer to your question is that I like the sound of the LP, played over a very good front end, tied to a system that is very transparent in the midrange. If the midrange sounds grainy or artificial, I'm not happy. (I can listen to a piece of music on a boom box to get the essence of song and performance but I'm talking about the "why" of optimum sound for me). If you are familiar with commercial loudspeaker history, my first serious listening started when I bought a pair of the original Quad Loudspeaker ---the one designed and first marketed in 1957. I bought my first pair in 1973, and it changed how I listened-- if you have ever heard a pair properly set up, using a modest tube amp or solid state amp that can handle the weird load, they are uncanny, spooky, they are so good. They suffer from no deep bass, beamy high frequencies, a narrow sweet spot and a tendency to arc if overdriven, so they were hardly practical speakers in the more modern world, but I kept using larger electrostats from Quad, modified by some folks in California back into the '80s. (I have just now had my original pair, which I think is better than the later bigger ones, restored for a second, vintage system that is still being restored).
The horns- which I got into in 2006-- often regarded by hi-fi people as shouty and inappropriate for any thing but loud sound reinforcement, have a similar ability to sound very transparent in the midrange, and can give you dynamics like nothing else. (There is no crossover between the amp and mid horn on my speaker array and the amp is a relatively modern SET (Lamm), which design itself has strengths and weaknesses. Lamm overcame some of the more pronounced weaknesses of the design in 1999 and he uses an algorithm, he doesn't actually tune his gear by ear.
With that as context, you can hear the differences between the sound quality of a good recording on a record and digital over such systems. Granted, some vinyl records sound very two dimensional or are gimmicked by so much studio trickery that there is no "there" there-- but on acoustic material, which is usually best for evaluation of midrange (I listen to hard rock and non-audiophile recordings of all sorts, not just string quartets or female voice), the records still have some quality (perhaps a euphonic distortion), but a less analytic character that sounds more like real music in the room if everything else is 'just so'. Why and whether this is so is the subject of endless debate. Some aspect of it has to do with timing of the fundamental and the decay of the note; there is something almost too precise about digital, though it has gotten much better. Not just the hardware but the ability of engineers to work with it.
The other answer is that the early CD players sounded pretty bad. Much has changed. But, state of the art digital is crazy money and my excuse has been that I'd rather put the money into improving the sound quality of my analog system than buy an expensive CD or Transport and DAC that approaches analog. I do know that some folks can short cut by getting a relatively inexpensive player, like an Oppo, and use it solely as a transport to drive a high quality DAC. The DAC market is constantly changing, as are the digital formats in the streaming area. I have admittedly hit the wall since there is much music I cannot access on LP. I will likely buy a high quality Redbook capable digital front end at some point, simply to have access to more music. (I tend to go for obscure post-psych folk, prog, porto-metal and variants of the stuff coming out of the UK and Europe from around 67-72 or 73, when the singer songwriter trend took over, and LA became the epicenter. I listen to some pretty offbeat stuff that is not easy or cheap to obtain as original pressings but some legitimate CD reissues had been made over the years and there was a period where the LP was abandoned and the only way to get the music is on a CD). Some of the best sounding recordings, to my ears, are simple two track, often old jazz. Very little mixing and editing.
Though my hearing has clearly degraded in the high frequencies due to age- I'm about 10 years younger than you, I think my sense of what sounds 'real' and my judgment about system presentation have become better with age. I'm still very much a midrange guy who wants utter transparency, grainlessness and no sense of a reproducing mechanism involved. Getting good bass involves a whole other set of parameters, and that's been the rub for me for many years- blending electrostatic panels or horns to bass drivers that aren't room sized horn loaded monstrosities.
Sorry for the hi-fi guy prolix response, but I believe it was necessary to answer your question. Again, I don't want to provoke debate over digital v analog. I've come to accept digital for work, and for access to music, but my preference remains analog; many new vinyl issues are either natively digital or if reissues, derived from a flat digital transfer for mastering to vinyl, they don't sound bad, some sound very good- again, because there I think the mastering engineers have learned to work with it, but compare a reissue made from a flat digital transfer to an original pressing, and there's much more there that adds to the musical experience, even if it is not as "accurate" in one sense or another. Sometimes, other factors make the reissue better than the original. Aqualung by Tull is an example. I published a comparison of many different pressings a couple years ago, and one real winner was a remix, taken from the multi-tracks, that fixed a lot of problems in the original mix, and was done in the digital domain.
PS: I've also spent time with archivists who 'restore' old, almost unlistenable recordings. I've heard digitally reworked versions of the original Benny Goodman at Carnegie Hall concert-1938? taken from the original transcription discs, and the processing, and the choices made by the archivist took something that sounded grainy and click ridden and converted it into something that had impact, depth, and was very musical. That was as much about the artistry of the archivist/restorer as the equipment. I do not think this re-do is available yet commercially. So, I'm not hardcore anti-digital by any means.

 

[Ingenieur]

I'm surprised this thread has remained open

1 he is not employed in the electrical industry
2 presents opinion as scientific fact
that an lp is more 'musical' or 'dimensional' is silly
both are no more than a signal comprised of magnitude/phase components
a cd and an lp source have been run thru a differential signal comparator
the output is random and well below 110 dB
inaudible and likely not even reproduced by the electronics/speakers

I have been an audiophile since the early 70's
I subscribed to Stereophile in 73, when it was a stapled pamplet of folded 8.5x11 paper and you never knew when it would arrive
it was more 'grounded' then
It and others like absolute sound have become industry shills ($10,000 cables!) so esoteric and mystical as to border on the occult lol

now to each their own
but don't blow sunshine up my arse lol

 

[wmhart]

I'm surprised this thread has remained open

1 he is not employed in the electrical industry
2 presents opinion as scientific fact
that an lp is more 'musical' or 'dimensional' is silly
both are no more than a signal comprised of magnitude/phase components
a cd and an lp source have been run thru a differential signal comparator
the output is random and well below 110 dB
inaudible and likely not even reproduced by the electronics/speakers

I have been an audiophile since the early 70's
I subscribed to Stereophile in 73, when it was a stapled pamplet of folded 8.5x11 paper and you never knew when it would arrive
it was more 'grounded' then
It and others like absolute sound have become industry shills ($10,000 cables!) so esoteric and mystical as to border on the occult lol

now to each their own
but don't blow sunshine up my arse lol

My apologies. Other than responding to the question about why I prefer vinyl as my principal medium, my original post dealt with a question about the isolation transformer I just had installed. I had indicated afterwards that I would avoid the subjective v. objective debate. I will confine myself to electrical questions. I do not ask that you buy in to my views on audio, nor did I offer them for that purpose.

 

[wmhart]

From the NEC perspective you cannot truly isolate the system either by installing a transformer or installing a new system in separate structure. The separate building scenario would still have an EGC installed with the feeder which is connected to the EGC/neutral bus at the house. Any 120/240 transformer would require that the neutral be bonded with a system bonding jumper which connects it to the building grounding electrode system. in either case you cannot escape the connection of the two systems together.

Thank you for this. I was under the impression that an entirely separate service path to an outbuilding that was separately metered (like a guest/rental house) could have it's own electrical system and ground, distinct from the main house.

 

[wmhart]

What you can do is make an effort to keep transient noise off the EGC which connects your equipment to the main EGC to neutral bond.
If possible that includes putting filtering on the EGC serving the noisy equipment. I think that the NEC does not prohibit this.

Sent from my XT1585 using Tapatalk

Got it. I still need to speak directly to the tech side of the manufacturer. I know some filters were put into the box as part of the package, but don't have all the details. Thanks.

 

[Ingenieur]

My apologies. Other than responding to the question about why I prefer vinyl as my principal medium, my original post dealt with a question about the isolation transformer I just had installed. I had indicated afterwards that I would avoid the subjective v. objective debate. I will confine myself to electrical questions. I do not ask that you buy in to my views on audio, nor did I offer them for that purpose.

this site is for industry professionals
not lay inquiries or diy
http://forums.mikeholt.com/faq.php
just pointing it out

 

[Ultrafault]

I would suspect that the common mode noise rejection is being defeated by power source noise that is not common to all audio equipment. This can be achieved via induction from non code compliant egc current. Or different inductive coupling to supply circuits that serve parts of the audio system. A isolation transformer can only cover up the former. If all circuits that feed audio equipment are fed from the same source and protected from magnetic coupling with other circuits I feel you do not need to add any pseudo theory. I am thinking about doing my senior design on a simmilar issue we are having with our lab equipment.

Sent from my SM-N910P using Tapatalk

 

[wmhart]

this site is for industry professionals
not lay inquiries or diy
http://forums.mikeholt.com/faq.php
just pointing it out

OK, when I called Mike Holt's office and asked if they had techs to consult at a fee, the woman in the office explained I was welcome to post my query on the forum, even though I explained my background. I do not want to be engaged in any discussion that is inappropriate and if I am disqualified from being here as you've said, I have no objection to being removed from the board. My thanks to those who answered my questions.
bill hart