I’ve been really happy with our record deck since we inherited it a few months ago, but one common problem has been playing back 70’s and 80’s pop/rock LP’s that have been, shall we say, well loved. I had an idea while last re-aligning the cartridge/stylus that part of the treble reproduction issue I’ve been experiencing with these discs was that the cartridge was slightly vertically offset in comparison to the vertical alignment of the groove – almost as if the cartridge mounting is somehow twisted slightly on the arm.
The Dual 505-2 has no azimuth adjustment to speak of, but the cartridge is held in with a pair of bolts, and so the azimuth could easily be corrected by inserting a washer or some other small object to act as a shim. I didn’t have any washers to hand that were less than 1mm thick (way too thick for this project), so for the sake of experimentation I’ve experimented with a piece of copper tape retrieved from a no-longer-working hard drive enclosure. It’s less than 0.25mm thick, and easy to cut and fold to the right height.
To get a rough measurement of what was required, I chose an older duplicate disc and set it playing, and observed the end of the cartridge right above the needle riding the groove. I estimated that the left side of the cartridge (as it faced me) was about 0.5mm too high compared with the level of the LP spinning underneath it, so I cut a small piece of the copper, folded it to get the approximate thickness required and cut a bolt-hole through it, before inserting it between the cartridge and its mount.
After doing up the bolts and re-checking the overall alignment, I started the same disc playing and listened. Much of the treble harshness had gone, and vocal sibilant distortion was down around 50% – much more listenable for some of the older discs in our collection. What’s more, newer/cleaner discs are sounding much more dynamic, and their overall soundstage much more focussed – much more digital, one might say. Bryan Ferry’s “Boys and Girls” was a particularly problematic recording, but was much improved in this evening’s round of listening tests. The same improvement was noted on playing a slightly ratty copy of Michael Jackson’s “Thriller” LP. We’re closer to hearing the music, and further away from hearing the equipment playing it. That’s a good thing in my book.
Next on my list is to trim the copper shim to make the installation invisible, but it certainly proved my little theory and proves a nice illustration for anyone else wanting to try the same thing.