Triplanar RCA out to Balanced out for MP-1

Raul is correct. I would just add that the wire going to the "ground" side of the RCA plug is the one that should be soldered to pin3. Pin 2 gets the "hot" wire. You can do it yourself, but since Tri is colleagial with Atma-sphere, I am sure he would do it for you, too. I own both a Triplanar and an MP1 myself. I think you will be very happy with that combination and the "right" phono cartridge.

Dear Thom, I've been thinking that your scheme #1 for hookup is the way you'd do it if a cartridge really had a hot and ground side, i.e., the way to do it if you were to hookup a single-ended CD player to a balanced input preamp. Scheme #2 is the "only way to go", in my view. In fact, in my case I just hook up the tonearm cable shield to pin 1. This works fine with the MP1.

Cousinbilly, I gather your Triplanar has the optional external junction box with the standard female RCA receptacles. This allows you (or forces you) to use additional phono cables from the junction box to the preamp. Since you have decided to send it back to Tri, I encourage you to consider having him remove the junction box in favor of cables that go directly from the cartridge to your preamp inputs. Said cables would be terminated with male XLR connectors, of course. I think this is advantageous with low output phono cartridges, the likes of which you will be using.

Nandric, Try it both ways and see what happens. The very worst that can happen is hum; no risk of damage to anything except maybe your speakers if the volume is turned up too high. I own a Triplanar which I converted to XLR jacks from RCA jacks. I connected the shield to pin1. (I presume you know that hot from the RCA jack goes to pin2 and ground from the RCA jack goes to pin3.) I did not connect the tonearm ground wire to anything. It just hangs in the breeze. There is no hum. I've been using it this way for several years and with two or three different cartridges. If you DO get hum, just revise the ground connections, and you are likely to defeat the problem.

Interestingly, I converted my RS-A1 tonearm to straight thru balanced connection, for use with my MP1. I eliminated the female RCAs at the base of the tonearm and ran about 3 feet of Cardas wire straight from the cartridge pins to the preamp with XLR jacks. Once again, I connected the shield to pin1, but in this case I did have a hum problem which was eliminated when I grounded the body of the RS-A1 to the MP1 chassis.

Nandric, You made me think. The shield for the Triplanar tonearm wires contacts the tonearm body where via the clamp at the base of the mount. So in effect, the shield per se grounds the tonearm body to the preamp. This may be why I never needed to attach the tonearm ground wire to anything. Conversely, I isolated the phono wire shield from the RS-A1 body, where the wires exit thru the holes formerly occupied by the RCA jacks. This may be why I needed to create a separate ground between RS-A1 and MP1. By the way, the hum that I did have with the RS-A1 was annoying but very benign. Not at all capable of damaging a speaker. Moreover, the frequency of hum is way below anything seen by your beryllium tweeter. Fear not.

Nandric, Obviously you need to be comfortable with whatever you do, but I guarantee the hum associated with poor grounding of the tonearm will not hurt your speakers. It's 100Hz or below in frequency; even the midrange is not involved. Moreover, it is low level at normal listening levels, e.g., I was able to listen to and enjoy the RS-A1, hum and all, before I fixed the problem. Congratulations on your expensive speakers, however, and I do understand your desire to avoid damaging them. My Triplanar is about 15 years old, but Herb Papier, the original inventor and manufacturer, upgraded it to VII status as one of his last acts prior to selling the company to Tri Mai. In fact, Tri was visiting Herb to learn the art, when Herb did the last upgrade. I am not aware that there was any difference in grounding the shield or not grounding it at the tonearm side among various versions of the Triplanar. But you may be correct in that inference. Anyway, this is a simple fix.

BTW, My assumption that your hum will be 100hz or below is based on my guess that you live somewhere that has 50 Hz mains frequency. The hum will be at 100 Hz or at 50 Hz, depending upon the rectification of your amplifier. If you live with 60 Hz mains, then hum is at 60Hz or 120Hz.