I've never seen Ron Carter making ads for a magnetic upright pickup.
Furthermore, I think mag pickups are the last candidates to give a more DB like tone.
They make a real DB sound like a giant P Bass!
Ron Carter has been using a piezo pickup installed on the soundpost of his bass for years, but I don't know what he's using now.
You may want to first read the Palatino megathread here:
Palatino Megathread part I
Many modifications are described there.
The choice of strings is also very important.
Good luck!
François
P.S. Here's what I found on
Jonas Lohse's Double bass gear guide:
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Kurmann, Stephan
http://www.soundpost.ch
Audiotechnik Arber & Co, Edisonstr. 7, CH-4053 Basel
Soundpost
Type: piezoceramic
Mode: aktiv
Preamp: incl.
The pickup element is attached to the sound-post, that is to inside the body. To suppress interfering frequencies, the soundpost is wrapped with wool completely. For the connection to the amp, a small jack is drilled into the lower block.
Endorsed by Ron Carter.
The double bass model is no longer available, only violin model is still in production.
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Some manufacturers listed there offer some designs which include a piezo fingerboard transducer, like the K&K Bass Master RB and the King Doll Head Piezo.