Power Cycling Mystery

I have a Meridian G68 that I use as a dac and preamp. I leave it on 24/7. Here's the mystery: When I power it off and then back on, it sounds better. I know that sounds crazy. Maybe I'm crazy. But I've noticed it a number of times over the last year.

I originally thought maybe it was heat. I turn it off, it cools down, I turn it back on, it sounds better. Hence it's the heat. But here's where it gets really weird...

If I power the G68 down and then turn it back on IMMEDIATELY, it still sounds better. So the change in sound can't be attributed to heat.

And it gets weirder...

The improvement lasts for WEEKS. Then, very gradually, things deteriorate. Eventually I notice a subtle harmonic distortion in the high frequencies and a general "haze" in imaging. So I power cycle the G68, and the distortion and haze go away. And things start all over again.

Is this even possible?

I and several people I know have noticed that every high end DAC we've ever owned benefits from a quick power recycle. I have no idea why but I suspect it has something to do with resetting clocks and flushing data (no need for knowledgable people to flame here....I'm just theorizing) I'd love to know why but the effects are clear enough to my ears that I now do it as a matter of course before most listening sessions.
vhiner, I think you're onto something here...I notice this to. My dCS is software based...so I am sure, like a laptop...it's a computer and resetting cleans something out.

There was a earlier thread on dCS clocks that recycling seems to do something...
It could be a simple relay that is making a bad connection. When you cycle it off, it will clean itself and make a new connection, at turn on.

Another possibility is, somewhere in the circuit, there can be a bad connection. The inrush current (at turn on) can cause a little arc, and temporarily weld/solder the contact back together. This also can happen inside a semiconductor itself.
Hi Bryon,

I don't see anything implausible about that, and probably the explanation is along the lines of the things the others have suggested. The circuit reset that occurs at power on undoubtedly clears out and affects a great many things, which may in turn affect subtle interactions between seemingly unrelated circuits, caused by effects such as noise coupling.

It's probably not possible to hypothesize anything more specific without knowing the details of the particular design, and perhaps even if those details are known.

The one additional point I would make is that I recall that some time ago you found that removing some unneeded modules and the top cover from the G68 resolved a heat problem it had. Are you still running with the top cover removed? If so, perhaps that is contributing to rfi that may be radiated from the digital circuits in the G68 into other components in the system, which could conceivably result in the haze and high frequency distortion you described via intermodulation with signal. The rfi conceivably being sensitive to circuit conditions that would be affected by a periodic reset.

In any event, you've discovered a simple tweak that is beneficial in your particular system, so I'd just go with it!

-- Al
Thanks everyone.

Vhiner - That's an interesting theory about the clock. If power cycling results in better clock performance, then it might also result in less jitter. That's consistent with the type of improvement I experience from power cycling -- less high frequency harmonic distortion and imaging haze, both of which I associate with jitter.

Hi Al - That's an interesting theory about RFI. I never thought of that. I will put the top back on and see what happens. Thanks!


Since you're already opening your unit and you notice power changes, you might want to consider upgrading the unit's fuse/fuses if you haven't already. The improvement surprises many people.
Vhiner - I had the unit extensively modified by Reference Audio Mods -- new PSU, new clock, etc.. I believe he also replaced the fuse. I will take a look. Thanks for the suggestion.

Al - I put the top cover back on and I didn't hear any difference. Still puzzled about why power cycling would improve things, but of course I'm no EE! :-)

Let me ask another stupid question...

Could there be any connection between the beneficial effects of power cycling and the fact that, when the unit is powered down, it often emits a broadband pop/thump? Could there be some kind of "buildup," the elimination of which results in better sound?

Electricity and it's effects on sound reproduction are a bit like quantum physics...just when I think I understand, I don't. But as with the rest of the universe, I enjoy plenty of things I'll never understand. Have you experimented with power cords and conditioners yet? I find they have profound effects on all things digital.
V - Yes, I fell down the rabbit hole of power products some time ago. But I can't say that I've spent much time in Wonderland -- it's a confusing place, after all.

Currently I'm using a Shunyata Hydra 8 and several Shunyata Python power cords. Can't say I have an exact idea of how they changed things, except to say that, collectively, they SEEM to have made the system a little quieter and made the high frequencies a little sweeter.

If I were to do it again, I wouldn't spend so much on power products. I would, however, keep my dedicated power line. That is something I believe in. I keep the rest to quell my audio nervosa.

Still puzzled about why power cycling would improve things, but of course I'm no EE! :-)
Hi Bryon,

Along the lines of my earlier comment, being an EE and an experienced digital and analog circuit designer, as I am, won't reduce the puzzlement :-). At least without having highly detailed familiarity with the specifics of the design.

With complex digital circuits, and particularly when software and/or firmware programs are also involved, puzzling and counter-intuitive phenomena are almost to be expected at times. And keep in mind that modern digital circuits are far more complex than they may physically appear to be, since some kinds of physically small integrated circuit devices commonly contain many millions of transistors each.
Could there be any connection between the beneficial effects of power cycling and the fact that, when the unit is powered down, it often emits a broadband pop/thump? Could there be some kind of "buildup," the elimination of which results in better sound?
My quick initial instinct is to say no, and to consider the thump to simply reflect a turn-off transient that would have no associated or secondary effects. And to expect that what is somehow responsible for the improvement you have observed is either the reset that occurs when power is turned on, or resetting or clearing that occurs by virtue of circuit devices being unpowered. But then again, who knows?

All the best for the holidays and 2012!

-- Al

Ahh, the rabbit hole. I find that removing something from my system usually reminds me how I got there in the first place....said the Mad Hatter to Alice. ;-)
Thanks, Al. I guess I'll have to live with the mystery.

V - Good point. It's easy to take things for granted until they're gone!

Have an excellent holiday, gentlemen.