I bought a used Grado GF3 off teh 'Bay to use as a hum tester. Wrote email to Grado to see what current stylus teh recommended? they replied that it was a blue. Found a NOS blue on the 'Bay for $39, so I got that. All the while I've been playing Mr Lin's Silver against my fleet of carts. I was fooling around with this old beater and decided that if it was blue, I'd better paint it blue. Got some metallic blue Rustoleum and Wally World. Came home, masked it (kind of) and sprayed away with the old stylus carrier in. Let it dry for a few hours and mounted it up in cast headshell that turned out to be too heavy for the AT150MLX.

Stuck in the new stylus and fired it up. Sounded pretty close to the Silver, but set it aside while I tested "more serious" cartridges. Today I'm doing some hum testing on a couple of TT's so I have Mr Lin's Silver in & out while I eval hum regions across the playing surface. Decided to get the "GF3-BLUE" out and see if it was the same - NOT. Less hum all the way across the record. Using headphones so I can hear subtle differences - not subtle). AND, bigger rock sound from Pink Floyd ("Animals") - really lush and "groovey". Wow - what have I done? You think the metallic blue paint created a pseudo hum shield? Frankenstein smile4s again :) :music:

Bump - anyone else have any luck modifying a Ggado to help eliminate the hum?

Interesting.... I had to look up what's in Rustoleum. I got Water, Acrylic Copolymer, Acrylic Polyurethane, Copolymer Acrylic Copolymer, Strontium Zinc Phosphosilicate plus colors and propellant's. Maybe something extra for metal flake. I dunno.....

I have read about some success using NuMetal™ to isolate turntable motors and power supplys. I haven't tried this my self. I did once try to add an additional ground. That didn't work.

I too have the hum on my Thorens 166 and recently tried it on my 124 thinking since the table was a different design, my Gold may not hum....no luck. What's funny is the hum on the 166 was consistent..it started mild at the lead-in and increased towards the center of the label. On the 124, it is quiet at the lead-in gets louder toward the center of the record, then dissapates again towards the label (I too use hyper-sensitve cans to hear everything). Sheilding is the issue for Grados...you may be on to something!! Perhaps some metalic Krylon or even POR-15 (used as a rust coating and inhibitor).


James R.

The Rustoleum I used said Metallic Enamel on the can. Sort of a bright hot rod blue. I thought it was just going to be a joke for me so when friends came over, they'd say what's the blue cartridge. But now I dunno? There are conductive paints, there are paints with high levels of magnetic reactive components (think stealth). I'm hoping one of us is in the industrial coatings business and can help with some experiments? Old Grado carts are pretty cheap on the 'Bay. A few trials should not be too big a deal if we can find some of the coatings?

You just put a thin layer of metal on the outside of an unshielded cartridge... there is metal in that paint, and alot of it. The overspray looks like glitter.

Nice job!

Evan

BTW, maybe you should try gold leaf :)

Very interesting! So, the entire cartridge (except for the stylus assembly) is painted, top too? but not the back where the connecting pins are? Could the metallic paint be grounding the Grado to your headshell too?

This is very interesting Broc. I'm thinking maybe silver "radiator" paint would have a higher metalic content. This is a worthy research project. Maybe the nice folks at Grado would lend some support. If it works out, it can only help sell more cartridges. And we could free up space on the AK server by eliminating the Grado Hum database. Anyone volunteering to be the lead investigator?
Keep up the good work Broc
Bob

Hi,

I was reading your post on this Grado Hum. I use quite a few Grado Blacks and greens on my TT's. No noticeable hum. At what volume is the hum heard?

Sounds like you are on the right track with the shielding.

John.:music:

This is very interesting Broc. I'm thinking maybe silver "radiator" paint would have a higher metalic content. This is a worthy research project. Maybe the nice folks at Grado would lend some support. If it works out, it can only help sell more cartridges. And we could free up space on the AK server by eliminating the Grado Hum database. Anyone volunteering to be the lead investigator?
Keep up the good work Broc
Bob

Broc, how about contacting Micheal Fremer thru vinyldavid and see if he's up to it (that article should keep the letters to the ed. going for months):D.
I'm not volunteering, but, justen from NC should do this. His record cleaning/destroying thread was one of my favorite pieces of reading in quite a while:smoke:

Craig

I second stuwee's nomination of justen taking this on.
Bob

Well lets see, I don't know these folks other than through AK. You'all that are on personal terms with them may want to weigh in?

I understand that we can experiment on older used cartridge bodies. But I still think we need someone from the industrial coatings community to help guide this? If any of you'all are associated with any like that, maybe you could discuss it with them.

Since stealth paints have been made the last few years, I suspect there are coatings with the right properties? I just don't know which ones? I'm thinking high iron content with a conductive film?

So onto my paint job. I did not want to have to mask each pin on the back so I just wrapped a piece of tape around all four pins. Got a little overspray there, but no big deal. I also did not want to hide the Grado logo and model number so no paint on the front. Top, bottom and both side got a pretty good blast.

How much hum. Well I had Mr Lin's Silver and this GF3. I had lashed up the GF3 to be a hum tester with the old stylus carrier (broken cantilever). The silver hums a bit, like I said in the eval, I estimate <5% of normal signal music signal strength. It's apparent in the headphones, but not in the speakers at normal listening levels (Infinity RS5000). I mounted the shell with the GF3 and passed it over the platter while running (to test my concept), it was about the same as the Silver. After the paint job, it was about 1/2 the former level. Clearly less than the Silver. I did and A-B with both a few times to be sure.

See this thread : http://www.audiokarma.org/forums/showthread.php?t=155518