An unusual discovery: I own two VAC-1 PSUs.... and they don't sound the same.

0 Members and 1 Guest are viewing this topic. Read 2030 times.

Xcalibur

  • Jr. Member
  • Posts: 42
First, a bit of preface to this discovery.  About a year ago I moved, and while re-connecting my VHP-2 and VDA-2 I accidentally swapped the associated VAC-1 PSU units for them.  I didn't discover this until just the other day, while I was removing the VHP-2 from the setup.  I also own a tube amp, and have discovered in the last year I prefer the tube sound (it isn't better than the VHP-2 per se, for the record, I just really like the weightier midrange presentation) so I was moving the VHP-2 out to be with the TV as a headphone solution in that setup.  The vast majority of my listening the past year has been from the VDA-2 to the tube amp.

So, while I had things unplugged I figured I would swap the power supplies back to the components they originally came with.  While doing so I noticed something unusual:  they do not weigh the same.  The newer VAC-1, which came with the VDA-2 and purchased nearly a year after I bought my VHP-2 and VAC-1 combo, is considerably lighter than the older unit is.  I thought this was a bit odd, but components are changed and updated all the time and didn't worry about it further.

The following day I sat down for a listening session, and couldn't shake the impression that the music sounded different.  Immediately noticeably was a considerable loss of bass, both in presence and in weight/drive.  It wasn't subtle at all, and in a system that is already bass shy it was not welcome.  The other major change is a very obvious shift in tonal balance towards the midrange, resulting in a rather nasal character that lacked warmth and emotion.

Wondering what could be wrong I thought to the only thing that had changed in the setup, and swapped the older VAC-1 back in with the VDA-2.  Everything now sounded exactly like I have been accustomed to hearing for the last year.  Intrigued, I did a series of A/B comparisions between the two VAC-1 units.  Here is a summary of my thoughts in the differences.  Unit A will be the older, heavier VAC-1 and Unit B is the lighter and newer one.

- Unit A consistently has stronger bass.  Not only in terms of presence but also in terms of weight and slam.  The control and speed of the bass is not quite as good though.
- Unit A shows a much "sweeter" tonal balance.  In addition to the stronger bass the treble presence is also stronger, which has the effect of making sibilance sound harsher.
- Unit B's tonal balance is nasal and less pleasant, but in exchange for this has the effect of reducing sibilance and harshness in the music very noticeably.  While there is less bass what is there is lightening fast, with leading edges and transients better defined.  It's very easy to hear on piano music, where the moment of impact of hammer to string is a much more visceral event.  Unit A cannot reproduce the bite that is supposed to be conveyed with this instrument, sounding blunted instead.
- Unit B consistently sounds more detailed, with greater note separation.  At first I thought the greater detail was a result of the midrange emphasis.  Afterall, if you change tonal balance different details in the music are naturally brought forward.  However I began to notice clear signs that the actual level of resolution and detail retrieval is higher.  Case in point, during a particular song there is a set of background vocals set against the background instrumentation.  These vocals always sounded a bit indistinct to me, as though they blend into the background of the music.  While listening to Unit B, these vocals felt clearly distinct from the rest of the music.  I also noted a sort of trailing off effect to the vocal line at the end which I had never heard before.  I switched back to Unit A and specifically listened for this effect in this song, but could not hear it.  This speaks to an absolute increase in the level of note separation in my mind.
- Unit A exhibits superior dynamics, where as Unit B exhibits a bit more finesse.
- Unit B was able to make instruments sound real for me for the first time with a number of tracks, compared to Unit A which was never able to do so.  By this I mean it was able to remove the sense of listening to a recording of the instrument and impart the feeling of listening to the actual instrument itself. 

I'm not sure what to make of it.  Since both VAC-1 units work properly I can't assume one is defective, and I'm surprised CIA would approve a design revision that would change the performance of the unit this noticeably.  Has anybody else had an experience like this?  I'm torn at this point over which VAC-1 to leave paired with the VDA-2, since there are aspects to each units performance I like and dislike.  The tonal balance of the newer unit is a big minus for me, it sounds nasal and downright unpleasant at times, but the improvement in resolution is akin to getting an equipment upgrade for free.  Now that I've heard the improved clarity I'm finding it hard to go back to the older unit, despite not liking the tonal balance.  The lack of bass is also a big problem, but one I can live with.  Technically this is the unit pairing that was meant to be since this newer VAC-1 is the one that shipped with my VDA-2, but I'm on the fence overall as to what to do.

I'd love to hear Dusty weigh in on this with his thoughts if possible.  Am I hearing an isolated incident or was the VAC-1 redesigned at some point to cause this change in performance?

At any rate, since it was an unusual discovery I thought I would share.  Thanks to those who took the time to read!

CIAudio

  • Facilitator
  • Posts: 1402
    • http://www.ciaudio.com
Sorry to hear you are having this odd issue.
There have never been any changes in the VAC-1 other than the B version got a new front panel. We have used the exact same circuit, transformers, etc for many years and both versions weigh the same.
The only other change is the newer models have a 18g coaxial output cable, older models had an 18g "zipcord" type.

You can give us a call if you'd like us to test them for you.

Xcalibur

  • Jr. Member
  • Posts: 42
If I hadn't swapped them by mistake I probably would never have known.  To me, though, the differences between the two are not subtle.  I think what is foremost on my mind is if this is plausible or if psychoacoustics is playing some role here.  The change in tonal character seems pretty blatant to me, but I've discovered firsthand how much listening impressions can change depending upon the day and conditions.

The main reason I shared the story is because I really just found it fascinating that a power supply could have such a noticeable effect, especially considering they are the same type of unit.  I know the older unit is out of warranty, and the new one probably just so, so I think I will give it some time and see if my impressions hold up.  That, and I'm not sure what to think of the whole situation because one doesn't necessarily sound worse than the other, just different..... and I'm not sure which set of strengths I prefer if forced to choose one or the other.  If my perceptions do not change I may contact you to put the dilemma to rest.  Regardless, thank you for the reply!