Use of isolation transformer


For about a week now I've been using a 160 watt isolation transformer over my NuForce DAC-9 D/A converter(power consumption: 9 watts). I was recommend this by an audio-friend who said that my HTPC and "analogue switching amp," a NuForce Stereo 8.5V3, could possibly "contaminate" the power to the DAC-9 (via the return-wires, I suppose?) being that they're all coupled through the same power distributor(i.e., I don't use a power distributor per se - the bare wires are connected directly; leadwire to leadwire, return- to return, and earth to earth). Actually, about a few months ago I started out by placing an isolation transformer over my HTPC, to good sonic effect, and then proceeded with an extra one over my DAC-9 to possibly "shield" it from whatever noise may be emitted backwards through the power cord from the power amp - or even from the power wall-outlet. There was nothing conclusive or overly presumptive about the use of isolation transformers as proposed by my friend(who has incorporated the same tweak in his, in some respects, roughly similar stereo setup) in regards to the hypothesized effect or its theoretical (dis-)advantages; it was simply a suggestive "what if?"

Now, the use of an isolation transformer over the DAC-9 has a definitive sonic effect, and one that I would also call an overall improvement. My immediate, and remaining impressions are that a more finely resolved/differentiated top end, a more full sounding and clearly outlined midrange(more organic, even), and a better integrated and "coherently distributed" low end. In fact, coming about these three frequency spectrums in a rather disparate fashion, necessary it may be, feels a bit awkward in that the overall impression is that of a rather homogenous presentation.

However, another friend of mine who came over some days ago, remarked, upon listening to my setup, that while he conceded the mids had become more full and present sounding since his last listen(i.e., prior to the iso. transformer over the DAC), and better integrated with the low end as well, he found that the reverberative nature of the top end had become somewhat constricted - and to be honest, I had thougt about this as well. Moreover, he now found the width of the soundstage had been narrowed, instead hearing a more center-focused soundstage. This, also, I could confirm via my own impressions, though contrary to him I find it to be a more distinct quality, and even disagreed on the narrowing of the soundstage width.

Being that my friend had made verbal the observations on the top end's reverberative less lively nature, and that I found this to be in tandem with my own impressions, I thought it possibly illuminating to remove the isolation transformer from the DAC powerline and see how its omission would affect the reproduction in this area. In short, after a few seconds of listening with the transformer removed it was clear to me that the sound had not only changed, but also (subjectively) deteriorated; the overall presentation seemed to have fallen apart as if a connective (invisible) glue was missing, the center-fill and fullness of the mids lacked sorely, the ease of flow likewise, and the top end appeared less resolved and now exhibiting a white-ish or pale "color" patina to it; a more withdrawn, less spacious and anonymous sound - simply not as involving. That is also to say: the top end energy or reverberative nature seemed in no discernable way to improve or correct the beforementioned "shortcoming," if indeed that's what it really is.

Having now re-inserted the isolation transformer over my DAC the sonic presentation has yet again fallen well into place, though periodically the round-ish nature of the highs, extremely well differentiated and resolved they truly are, continue to come off a tad uninvolving with some music as if the slightest "edge" is missing. Everything in me tells me the general imprinting of the isolation transformer is that of leading to a definate sonic improvement save for this small issue, making me believe that another issue in my audio chain could have been addressed this way. It could also be that over time one has become more or less accustomed to a slight excess of energy in the highs, or simply a specific sonic nature here, that the more finely resolved and organic presentation leads me to believe sometimes that something is missing. Or, that the fullness of the mids and (soundstage-)center presence has somehow reverted attention from the highs to the lower frequencies. Anyhow, it's an interesting and overall satisfying developement of the sound, but also one that may have exposed improvements or changes could be made elsewhere - if indeed over more time I should conclude that more top end reverberative energy is needed.

I would appreciate the input of others who're using isolation transformers in front of their stereo setups as well - be it either (though preferably) with smaller and separately placed isolation transformers, or large singular ones used over the outlet group feeding the entire setup - possibly even on a related note to what I'm writing above both with regard the general nature of the perceived sonic changes isolation transformers lead to, as well as more specifically, where noticed, the reverberative or overall nature of the highs.
phusis
This will turn into a circus..

Until then: I use a pair of powerline conditioners. One of which is basically an isolation transformer. It also converts the 120v/0v AC mains into Technical power/balanced power 60v/60v AC.

For the op, one additional step you might try IS getting a isolation transformer which changes the incoming voltage from single ended 120v/0v to balanced power of 60v/60v AC.
And see if it improves you sound even further.
I am betting it will improve your sound even more.
Good luck.
06-02-12: Elizabeth
This will turn into a circus..

How do you mean?

For the op, one additional step you might try IS getting a isolation transformer which changes the incoming voltage from single ended 120v/0v to balanced power of 60v/60v AC.
And see if it improves you sound even further.
I am betting it will improve your sound even more.
Good luck.

I've thought of this, but practical circumstances may prevent me into realising it. I live in a apartment, and the size (and noise) from such a rather large isolation transformer could become troublesome being that it's not easily hidden. Thanks for the advice, though - I'll have it in mind.
I have been using what Elizabeth has mentioned on my front-end, and it does a great job. The DIY balanced transformer I wired was not expensive, and easily fits in a 11" square box. I put a pair of handles on top, and wired a Porter Port outlet in the box. It is dead quiet even up close with an ear right next to it, and does not run hot. You can read about it in my virtual system. wiring it balanced instead of wiring it as just an isolation transformer helps a great deal sonically.
Can you rewire a medical grade isolation transformer so that it becomes a balanced transformer?
Generally any post about anything can turn into a circus here.. This topic is just a little more likely.
It is no fault of the op.
And a balanced isolation transformer can be small, and make no noise.
Phusis,

A test you may want to preform on your current ISO transformer is to check the AC phasing to see if it matches the AC wall outlet your other equipment is plugged into.

If the output of the ISO xfmr is in phase with the wall outlet there should be little or no difference of potential, voltage, between the hot contacts of the two receptacles.

If the two are out of phase the voltage will be 240V nominal.

Jim
I have been using balanced isolation transformers with my main system for the past 8 years now. I've experienced sonic improvements in every area. I've been able to get one large transformer, and two smaller ones (sidemounted) into a single enclosure weighing approx. 115 lbs. that fits comfortably in my equipment rack. I get no audible hum whatsoever from this setup.
Can you rewire a medical grade isolation transformer so that it becomes a balanced transformer?
06-02-12: Sabai
Depends on the transformer design and voltage rating.

Here is one example.
If the xfmr has dual primary windings and can be wired for 120V or 240, and the secondary has 2 windings that can be wired for 120V or 120/240V out then yes.

The two primary windings would be configured, wired in series, for 240V. The two leads, H1 and H4, would connect to the 120V mains.

The two secondary windings would also be wired in series.
The center tap of the two series connected winding X2 and X3 will tie to the chassis of the transformer, equipment grounding conductor of the feed power cord, and the green equipment ground terminal screw of the receptacle that is connected to the output of the xfmr X1 and X4.

Two things I should disclose here.
To meet safety codes the balanced power configured ISO xfmr must be wired with a cord and plug for powering the unit. (This makes the unit a NON NEC code issue.

And more important the 120V secondary must be GFCI protected.

For a hard wired ISO xfmr many recommend the primary to be fed balanced power 240V and the secondary single ended 120V. (Hot with a neutral grounded secondary.)
.
Jea48,
Thank you very much for this information.
Thanks to all for the replies. I would seem a balanced isolation transformer, feeding all components, is a viable solution both with regard to size and noise level - disregarding cost, not that I believe it'll be an excessive figure. I'll have this in mind, and consider such a solution in the near future.

Yesterday, however, I made a (seemingly) minor correction with the ISO transformer over the DAC-9 that addresses my quibbles on the slight softness and rather center-focused presention; earlier when I started out with an ISO transformer over my HTPC, the initial setup led to an overall sonic character(i.e., pronounced softness and center-focus) quite simliar to that heard when the second ISO trsf entered before my DAC a little over a week ago. The friend of mine who'd been the "architect" of this initiative had in the meantime found out (first and foremost through hearing) that the wiring of the ISO trsf, and how they were hooked up with the lead- and return-wires to both DAC and outlet(secondary and primary side respectively), had significant impact on the sound. Being that our ISO trsf's were alike(same brand and wattage size), he relied on and found a way to (visually) localize the wires on the ISO trsf that were to be connected to lead and return(or 'hot and cold') on both sides, and once I had implemented this change over the HTPC, for a change it was, the sound fell into place: the soundstage opened up providing a more evenly distributed presentation, and a natural "edge" had found its way back into the sound as well. All was good.

Now, the ISO trsf I had used over my DAC to begin with, for I replaced it yesterday, was of the same brand and size, though the wiring(two yellows) on the secondary side was placed physically different and in such a way to make it hard(in effect, impossible) to differentiate them and determine which one needed to see the lead- or returnwire(also, the particular ISO trsf seemed to be of a different batch judged by the color of its label). I therefore wondered whether the wiring on the secondary side here had been swapped in regards to producing the desired sonic outcome, even though I had loosely assumed they were connected correctly. While it would have seemed most obvious to simply switch over the two yellow wires to see how that turned out, I instead opted for another similar ISO trsf I had been given(with the others), being that its wiring(i.e., their physical placement) equalled that of the one used over the HTPC exactly, indicating it might have been from the same batch as well(also judging by the label color). And sure enough, after replacing one ISO trsf with the other over the DAC-9 and getting the wiring right, the sonics fell into place as described above - and with everything sounding somewhat more full, clearly chiselled out, see-through, and organic/natural than before the ISO trsf entered the stage, so to speak.

06-02-12: Jea48
Phusis,

A test you may want to preform on your current ISO transformer is to check the AC phasing to see if it matches the AC wall outlet your other equipment is plugged into.

If the output of the ISO xfmr is in phase with the wall outlet there should be little or no difference of potential, voltage, between the hot contacts of the two receptacles.

If the two are out of phase the voltage will be 240V nominal.

Jim

Jim -

Perhaps you're addressing what I'm getting at above? But thanks, I'll try this out. I must stress that the ISO transformers I'm using only sports four wires (per trsf) in all, two on each side.
I must stress that the ISO transformers I'm using only sports four wires (per trsf) in all, two on each side.
06-04-12: Phusis

Phusis,

Yes I assumed that to be the case.......

That is why I suggested you check to make sure the 120V AC grounded output of the ISO xfmr was in phase with the 120V branch circuit that feeds the rest of your IC connected audio equipment.

Basically it sounds like that is what you have done through listening tests by switching the secondary output leads of the xfmr. (Changing which one of the output winding leads that is made the grounded neutral conductor.)

My test would have told you if the xfmr secondary hook up to the 120V receptacle phasing matched that of the 120V branch circuit wall receptacle.

Just insert one test probe of the volt meter in the "hot" small slot contact of the receptacle that is connected to the output of the ISO xfmr and the other test probe in the "hot" small slot contact of the wall receptacle.

If the 2 hots are in phase the voltage should read near zero volts.
If the 2 hots are out of phase the reading will be 240V nominal.
.
I've got a few. 300W, 2 and 5 KVA. The latter 2 step-downs fed 240V, wired for balanced and $100 each off Ebay (not included shipping). All I want them to do is reduce noise and if they changed the sound any more than that, they wouldn't be there.
Jea48(Jim) -

Thanks again for your reply. I'll have a friend over with a voltage meter this coming weekend, and we'll then make the test and see what it reveals.

I'm guessing my sonic evaluations, being that they're consistent in both cases, will translate into at least the same phasing configuration over both ISO trsf's in relation to the wall outlet phasing, and I would further assume the current configuration being in-phase - though that's certainly only a big assumption. Is there even a general consensus on differentiating the in-phase and out-of-phase sound when ISO trsf's are in use? I seem to have made no similarly discernable sonic observations in regards to power phasing when no ISO trsf's have been in use, I must add, but from the day I started making my own power cords(prior to the ISO's) I've seen to it that all of my equipment is hooked up in-phase, so the in-phase sound, in whichever way it's discernable here, has been my reference for some time now.

06-06-12: Ngjockey

... All I want them to do is reduce noise and if they changed the sound any more than that, they wouldn't be there.

Indeed, though I'd be thinking how noise in its different incarnations (and sources) really affects sound and what its omission would be perceived as, for how do I even begin to fathom or decide in advance what is a by-product of other than the more overtly perceived noise? It's system dependend, for sure, and my general rule of thumb is that of estimating on a gut-level whether restrictions enters the sound, things go largely unchanged, or something good comes of the initiative. An economical principle dictates that where anything other than the latter is the case, it won't be implemented; certainly less is sometimes more, and I don't thrive on chasing noise reduction or use of excessive filtering per se. All of my cables, both power and IC's(and in a sense speaker cables as well), are unshielded and assembled in a minimalist way, and are either braided(IC's and the balanced, digital AES/EBU cable) or "lightly" twisted, which is sort of a build-in feature that acts as a kind of a shield anyway - though without the use of anything other than the wires(and their insulators) themselves, and of course the electrical characteristics that comes of their different configurations. Shielded cables have oftentimes turned me sonically off, so to speak, and therefore I don't shield them. The use of ISO trsf's in my setup, configured properly, very obviously seems to do good, and therefore they stay.
Is there even a general consensus on differentiating the in-phase and out-of-phase sound when ISO trsf's are in use? I seem to have made no similarly discernable sonic observations in regards to power phasing when no ISO trsf's have been in use,
06-06-12: Phusis

It has the same effect as 2 dedicated 120V branch circuits that are, or are not, fed from the same Line, leg, from the electrical panel.

It will be interesting to see what the voltage reading will be as compared to what sounds best to your ears.

A word of caution.... If the ISO xfmr is wired out of phase,
with respect to the wall outlet the rest of your IC connected audio equipment is plugged into, the 240V nominal power is real power. Not phantom or capacitive coupled. 240V can be lethal.
Ok, measurements from today's test are revealed below. I must add that my setup - DAC, poweramp, and HTP - is star-grounded, and I live in a 2nd floor apartment(build '58) in Denmark. None of the ISO transformers are grounded.

Wall outlet voltage was measured no more than 195 volts(?) - it should read around 220 volts under normal circumstances. My friend speculated as to whether the low voltage reading had anything to do with the apartment being somewhat old, and it being on 2nd floor. Other outlets in my apartment were tested as well, all reading 195 volts.

(DAC ISO trsf readings)
The potential between confirmed phase-in - i.e., from wall outlet on the primary side of the ISO trsf - to the (assumed) phase-out on the secondary side of the ISO trsf measured 44 volts.

The potential between phase-in and (assumed) null-out on the secondary side of the ISO trsf measured 259 volts.

The potential between phase and null on the secondary-only side of the ISO trsf measured 211 volts.

(HTPC ISO trsf readings)
The potential between phase-in and (assumed) phase-out on the secondary side of the ISO trsf measured 76 volts.

The potential between phase-in and (assumed) null-out on the secondary side of the ISO trsf measured 292 volts.

The potential between phase and null on the secondary-only side of the ISO trsf measured 202 volts.

Well, given the lower numbers(44 and 76 volts respectively) my friend strongly suspected both ISO trsf's were "working" in-phase, though some theorizing went into why the numbers didn't approach zero. In that the different components in my setup are "seeing" each other through the star-grounding, he wondered whether that could account for the strange readings here. Also, why the large voltage readings between phase-in and (assumed) null-out over both ISO trsf's?

Comments are welcome.
Ok, measurements from today's test are revealed below. I must add that my setup - DAC, poweramp, and HTP - is star-grounded, and I live in a 2nd floor apartment(build '58) in Denmark.

Denmark,.... my bad for not checking your bio.... I thought I was responding to someone that lived in the USA or Canada.

None of the ISO transformers are grounded.
Are you saying you are floating the secondary of the ISO xfmrs? Neither secondary lead of the secondary winding is intentionally connected to ground creating a grounded neutral conductor and thus a new separately derived grounded AC system?

If the secondary of the two ISO xfmrs are indeed floating you have created a potential electrical safety hazard.

Does the branch circuit and wall receptacle in your apartment have a safety equipment ground?

If the secondary of the ISO xfmr is floating the voltage measurements you took are basically meaningless other than maybe giving you the AC polarity orientation of the ISO xfmr. The measured difference of potential measurements are more than likely due to capacitance coupling of the primary winding to the secondary winding.

If one lead of the ISO xfmrs were connected to the main electrical service grounding system the voltage measurements would have been more like in phase zero volts or maybe just a few volts.
Out of phase close to 390V. Approximately twice the 195V mains voltage of the apartment.
.
UPDATE:

I've eventually decided to remove the isolation transformer over my DAC(though the one over the HTPC remains). Over time, in the wake of this ISO trsf's initial inclusion and being properly configured(/wired), I (still) had the recurring, fluctuating feeling of a slight "rounding" of or padded nature to the sound that left me wanting for a little more edge and reverberative breathing room, so to speak. Lower to central mids seemed to have grown in size and presence, bringing with them a beguiling warmth and intimacy, and high frequencies appeared slightly more resolved. However, the longer I lived with this sonic character, if you will, the more I longed for a more vibrant and expansive field of sound.

So then, immediately in the wake of uncoupling the ISO trsf over the DAC-9 I missed the presence and warmth from earlier, as if the presentation had turned somewhat out of focus, slightly more "pale" in its musical color, and becoming a tad uninvolving. Yet, at the same time the distribution of the soundstage now seemed more "even," no longer curving out towards the listener, and leaving more room/space to voices which sounded more dense and sharply carved out. Overall the presentation felt slightly more lean and distanced.

In the days since, now a week ago, I've settled into the sound sans DAC ISO trsf, and haven't felt wanting for more warmth or intimacy nor experienced any fluctuating "there's something not right with the sound"-feeling. I can still recall, if prompted, the sound now being a bit leaner, but it's not lean as such - I find. Now I treasure my NuForce poweramp being warmed up over a couple of hours and what it brings to the sound(although it sounds just fine when immediately turned on), whereas before (with DAC ISO trsf) I almost felt as if the sound became a tad too smooth and warm/closed-in when the poweramp had been left on for some hours; if it's any bearing I believe it tells me something important about the sonic balance as is..

It's worth mentioning that my initial trying out the ISO trsf over the DAC was recommended by a friend who'd tried out the same in his system, and so the initiative was not inspired by my own ears in search for a corrective tweak to the sonic balance, or otherwise, of my audio setup. It would appear then that at least in this regard - i.e. the overall tonal balance - my setup is pretty much spot-on to my ears as is.

Right now I'm not in a hurry to try out another isolation transformer solution, but I suspect there're combinations that would work very well without adding the, to my ears, too pronounced softening and enlargement of the sonic image.
Just to add to the thread:

I believe that any soundstage variations heard without the transformer, whether they are preferable and pleasant or otherwise - are distortion, artifacts caused by the "imperfect" power that an isolation transformer seems to rectify. I use isolation transformers in my setup and I think that they provide clean power and cause the black background of the audio to be deeper, and the music that springs forth from that blackness is all the clearer because of it.

But, "distortion" is such a loaded word. A play of pleasing distortions can do wonders that perfectly boring and clinical clarity cannot. In some cases, adding a small bit of barely audible noise as DSP to a track can create harmonics that cause an impression of significantly increased clarity. I guess it's like how some people actually swear by adding the tiniest sprinkles of salt into their soda, as it will sharpen the taste and actually cause a sweeter effect if the amount of salt isn't excessive. Crazy, right? If an isolation transformer mutes those good distortions by removing slight irregularities in power from your wall outlets, then that can be a bad thing and result in a sound that is less desirable to some human ears, regardless of whether or not an audio analysis tool measures it as clearer.
Timestretcher --

Thanks for your reply.

I'm thinking: why even presume the effect of any given isolation transformer automatically equates into what is always essentially "right," i.e. that is supported by actual lowering of distortion figures and less "artifacts," and would otherwise result in a more "true" audible presentation - whether we like it or not? I'm not trying to turn this into a "all is relative"-matter, but it's the presumption that "even though it's right [say's who?] THEY may not like it."

I could also ask: why do you prefer the sonic outcome of the use of an ISO trsf in your setup and not I in mine? Are you more in-tune with the essentially more "true" sound this is supposed to produce, is it a matter of preference(then why the claim of a reference?), because of the synergy effect that falls out either positively or negatively, or..? From a rather simplistic standpoint I take it the use of an ISO trsf in general would result in a more clean, or should one say a more "desirable" power, but what is the possible multitude of factors that could arise with regard to the different implementations of an ISO trsf, and its specific characteristics into size and type and so on? Would they not also bring variations into the sonic picture, so to speak, that puts into perspective whether the use of an ISO trsf is always essentially for the better?

The use of a specific 160 watt ISO trsf over my D/A-converter proved to have some merits, mainly lending an added sense of warmth and intimacy to the sound, however the named "rounding" of the highs gave me the impression of a cushion-effect or a slightly padded and (too) gentle sonic nature; I found it placed a damper on agility, edge, and sense of dynamics, even though the overall presentation with its notably smoothness, presence and warmth was very inviting. I'm not really saying the sound of my setup sans ISO trsf over the D/A-converter is (again) all for the better, but it's notable how I now seem to find the overall balance of the sound more natural and clear-cut, saved perhaps for a slight lack of warmth. Also, and not least: the enlargement of the lower to central mids (w/ISO trsf over DAC) to me always felt slightly out of proportion, and so doesn't translate into what I regard as a "natural" presentation of the soundstage. Any which way you want to put this, to me it's a slight deviation from what is intuitively "right."
>Any which way you want to put this, to me it's a slight deviation from what is intuitively "right."

Is it possible that "natural" and what is in the recording on the CD or source you use for playback are not the same. Adding some small bit of power line distortion to the signal from the CD could produce a more natural sound, whereas a "pure" reproduction of the CD itself would seem artificial? As hearing is ultimately subjective (everyone has slightly differently shaped ears and ideas of what is pleasing, too), it could be down to that.

And who knows, I could be wrong about an iso transformer being a magic bullet solution. What it fixes in clarity, perhaps it could compromise in some other area? And then there is the question of specific iso transformers - are some better or worse than others? Maybe some models actively harm your signal path, others have no effect and some are good? I do not know how their designs would impact these things but in my ignorance I'll open-mindedly say that anything is possible.
In series from the wall receptacle I am using a medical grade transformer into 2 power conditioners into a power regenerator (for DAC and transport) with excellent results.
I just replaced the stock power cords on my isolation transformer and power regenerator with DIY cabling using Oyaide plugs and IECs. This is a huge improvement across the board. Highly recommended. I may upgrade these DIY power cords later but for now they are doing a great job.
Sabai, which Oyaides did you use ? I use the Oyaide P-004 and C-004 male and IEC plugs in conjunction with the R-1 outlets. They do make a significant improvement.
Gbart,
For the isolation transformer I am using an M1 and C-004. I have Oyaide plugs and IECs on Supra LoRad DIY throughout my system. I run power cords in series with the LoRad on one side, Bybee AC Quantum Purifies in between, and Hi Diamond and Synergistic Research on the other side. I find the effect of the series is much greater than using any single cord.