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TI Shield on my Rega P25

Posted by Maprik (M) on March 2, 2009 at 09:48:45

My TT is a Rega P25 and my cart is a Cartridgeman Music Maker 3 (Grado-like body)

As many of you know the Rega TTs and Grado carts have an issue. HUM. The EMI from the motor and the unshielded Grado cart combine to give that everpresent hum that gets increasingly louder as the needle moves toward the center of the album.

I've tried many things to get rid of the hum. Mu metal around the motor and on top of the plinth, lead platter mats, the Project Speedbox SE was a big improvement (something about the way the speedbox slows down the motor to play at 33.3 with the belt on the 45rpm spindle). Still, the hum was there, just less of it. I've been looking at different carts and different TTs as a result of my frustration. But I LOVE the music of the Music Maker 3.

I have a pretty highly resolving system. Jeff Rowland Concentra I and Gershman Acoustic Avantgarde RX-20 speakers. On every channel other than the phono channel I can crank the volume up to 80 and it's dead quiet, put your ear on the speaker and you hear just the slightest hiss (I listen to the CDP at about 55). On the phono channel turn the volume to 50 and the hum is loud and clear. Normal LP listening level is about 55 - 60. At 60 when the record is over the hum is like an elephant in the room. So I knew that the music was being compromised in a big way. We all want black blacks right?

Enter Chris Da Costa and the tweakers asylum (username CDC). By accident I came across some posts by him about HRSCF boxes and intrigued, I contacted him. During our lengthy phone discussions he introduced me to the TI shield and it's various uses. I know, I'm clueless, but as it turns out no one in my audio group (about 10 guys) new anything about TI Shield either. So anyway, I decided to try it on my Rega P25 to see what it would do.

Following Chris' directions very carefully, I order some TI Shield from Michael Percy and got all of the parts I needed from Lowes. Total cost for shield and parts was probably about $50. I then wrapped the turntable motor with TI shield and ran the ground wire out through a hole I drilled in the motor cover to the ground of a $3 plug and plugged that in. Then I used another piece of TI shield and taped it down on top of the plinth just around the motor spindle but not beneath the subplatter (won't fit, not enough height) and ran the ground wire to a different plug and plugged that in.

Well, as you may surmise from the length and detail of my post, it works beautifully!

I could barely believe my ears when I plugged everything back in and turned on my TT. I turned the volume up to 50. Silence. 60. Silence. 70. Just a faint buzz from the speakers. I then had to put on a record to make sure that I didn't mess something up. My jaw dropped when I put on a reference track (Diana Krall Girl in the Other Room). Needless to say, with the hum gone the room just filled with the most natural crystal clear music I have ever had in my room at a volume of 55.

SO, Rega/Grado owners. Time to put away your hair shirts and end the suffering. Read up on the TI shield and then DO IT. Feel free to e-mail me for further clairifications.

Peace,

Phil

Edits: 03/02/09

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