The Accidental Tweak


Recently I turned my system on as usual and started listening to an album I know pretty much by heart. Halfway into it, a small voice in the back of my head started saying the system sounds really good today.

And it did sound fine. Maybe even... better than usual? No way I thought, I haven’t done anything to it. I must just be in a good mood.

It was not a life-changing improvement; just a bit more airiness, a tad more definition.

My Krell preamplifier made a world of difference when I introduced it to my system. I bought it in a still-working but near-death condition, and I started a regimen of fixing problems, listening for a couple of weeks, taking measurements, troubleshooting, fixing more stuff, all the while keeping tabs on bias and temps and DC offset.

The inside of this pre is gorgeous - all discrete, top-shelf components, not an IC in sight, the PCB laid out as if by a choreographer; it harks back to Krell’s long-gone heyday.

The cover was off during that process, ostensibly so I could check on stuff, but honestly I didn’t mind admiring the beautiful audio craftsmanship inside. Eventually its maladies were cured and I screwed the cover back on, I figured better before I spill a cup of coffee over the PCB.

Then it hit me: something did change, the cover went back on. Presumably that’s what I was hearing: it must have completed a Faraday cage around the pre’s sensitive single-ended circuitry, restoring shielding it probably needed because it sits inches from a pair of large, EMI-spewing monoblocks. The cover blocked the EMI / noise and that’s what I was hearing - or rather, not hearing.

But the true beauty in this is that I made this tweak completely unbeknownst of myself. In my mind I was putting a lid back on, not completing a Faraday cage, thus my brains never had a chance to develop the smallest expectation. To the opposite, I was trying to convince myself that I could not possibly be hearing anything (even though I was hearing something), because I had done nothing to my system.

So I know for sure that the sound improvement I heard, albeit subtle, was real, and that I believe is a rather unusual treat in this hobby.

Would love to hear similarly unintended improvements that happened to you guys.

 

devinplombier

Yes I’ve read that rationale. Whether that’s an audible problem (chassis generated EMI) or not, I don’t know. A chassis can be designed and built to attenuate externally generated EMI, or not. When I built stuff, I too avoided parallel tracings even though it looks nicer. Does DNM sound good?

I heard an amp a long time ago, and for solid state, I would say it sounded quite good (I am a tube person myself).  I would expect a grounded chassis to work to shield what is inside, but true shield appears to require some extreme measures.  Wires entering the shielded inside would carry RFI and other unwanted stuff into the chassis. 

My server/DAC has a special compartment within the chassis that is a faraday cage.  To minimize unwanted stuff getting in, even the digital signal is not allowed to pass through into the cage--it is first converted to an optical signal before passing into the cage.  Is this helpful?  I don't know, but, that is how sensitive parts of the server/DAC are treated.

EMI/RFI contamination could be downside of cover off. I have trifield  meter, certain closely placed components could give off relatively large amounts of EMI/RFI, transformers are notorious for this, mu-metal shielding around these.

…ahhh, raising my hand to this tweak: years ago, took the cover off my tube pre-amp and son-of-gun, it just sounded better. Now i have to clean the darn pre-amp twice a year to rid the dust that collects. Had to study forever the “best” way to clean audio… today - using Caig gold solutions and lint free cloths to do-the-job. Although “cleaning” is an entirely separate subject… carefully cleaning gold connections is a key focus to complete the cleaning process. 
 

Without the cover, it sounds more than a fraction better - it sounds like “good-fun” better. (The amplifier without a cover does not have the same effect in my system)

“Keeping the Cover Off Forevaugh”