I'm a big Herbie's fan, and just wanted to report the very good results I've had slipping strips of 1/32" and 1/16" Grungebuster material between the power cord female connector and the IEC inlet.
This is an idea passed on to me by an audio buddy, who sent me some extra custom-cut O-rings (washers) of Grungebuster material from Herbie's to slide over the femaile PC connector, ensuring that it "wedges" between the IEC and PC connector so that it can provide some isolation and grunge-busting, but not so that it can prevent an electrical connection. My friend thought they worked very well, providing not earth-shattering but definite improvements, and I agree. Prior to ordering custom washers myself, I decided I'd try them out.
I first put one of the washers on my source, the Bel Canto PL1 - the 1/16" thick one. This source was always a tiny bit lagging behind the Bel Canto DAC3 for RBCD (using the PL1 as a transport via AES/EBU) in terms of excitement - just a tiny bit smoothed over, and dynamics were a touch on the laid back side, and the bass slightly on the thin side though detailed.
With the washer in place, depth and imaging was immediately better. Leveled the playing field with the DAC3 for imaging and excitement. Bass still lighter, still more laid back, but the PL1 walks more firmly and decidedly down this differing path - so now there are two distinct sources that I really enjoy! I have a van den Hul PC on this and there was no issue with fitting.
I put a 1/32" washer next on the DAC3 with Synergistic Research Master Coupler, and noticed a bit more apparent detail, but that's about it. I was actually questioning whether or not I should keep it there, when I put the other 1/32" washer onto the Discovery PC on my XA30.5, and suddenly the system was more coherent than before. Not night and day, but took the "edge" off, or at least made me cease questioning whether to leave the washers in place. I'm leaving them there!
I decided to experiment with some preamp tube dampers that I haven't needed since my tube days, and using them as footers for the Bel Canto uLink, with a Supersonic Stabilizer on top - again, an incremental step in the right direction!
So I next started cutting strips and squares of GB material after I used up the gifted washers. After some experimentation, I have finally settled on 2 x 1/32" washers on the XA30.5, with some 1/16" pieces ensuring contact between the thinner washers and the IEC/PC connectors. The rest of the system, the Pass Aleph Ono, X1 power supply, and DAC3 have all been treated with strips of the 1/16" material.
I've also put very thin strips of 1/16 on the male AES/EBU connector (so that it goes around the pins and sits between and contacts the chassis connector and male XLR connector), tonearm connector and wire of the 5-pin connector on the Simplex, and inside/outside of my banana Z plugs, so that they contact both the inside of the bananas, as well as the speaker post, by slipping half the strip in the opening and leaving half of it out, so that it wedges between the plug and the interior of post.
The most obvious difference with all the treatment is that the soundstage moves forward a bit, center fill and mid fill* is more complete, and grunge is decreased. *I didn't know that mids sounded a bit "hollow" until using all of these tweaks; in fact, I didn't know this could be possible to have a "scoop out" of image density. This last bit was most noticeable once I put the strips into the banana Z plugs, pretty cool! I encourage you to try it out for yourself.