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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
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phusis OP
1,248 posts
 
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.
jea48
4,678 posts
 
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.
phusis's avatar
phusis OP
1,248 posts
 
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.
jea48
4,678 posts
 
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.
.
phusis's avatar
phusis OP
1,248 posts
 
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.
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