Triplanar RCA out to Balanced out for MP-1

Triplanars come in two basic terminations:

1. Hardwired from cartrdige lead to connectors (either RCA or XLR).

In this configuration about 2.5 feet of cable runs inside a single braided sheath between the tonearm and a small rectangular box. This sheath carries both channels. The other side of the box feeds two braided cables - one for each channel, terminated in either RCA's or XLR's.

The question I was addressing is what's inside of this box - is there access to the tonearm's chassis ground.

As I mentioned earlier, any wire that connects you to the tonearm's metal components will do (for a pin-1 connection), but it's obviously preferable for there to be a cable shield which is tied to the tonearm - to run this to pin-1.

2. Hardwired from cartridge lead to a junction box with female RCA's - requiring an extra set of interconnects to run to your phono stage. This is *not* recommended because (a) you have an extra connection which degrades the sound, and (b) the Discoverey Cable Tri uses is outstanding.

Cheers,
Thom @ Galibier

Hi Cousinbilly, all ...

Well, I just received delivery of my Atma-Sphere MP-1, and made the balanced conversion on my Tri-Planar tonearm yesterday.

I documented the process with photos and procedural hints in this web page in the Tri-Planar section of my website:

http://www.galibierdesign.com/prd_triplanar_xlr_build.html

The photographic quality is only o.k., but it gets the point across.

Note, that since the ground is common to both channels, you need solder pin-1 to the braided shield connection in only one channel.

I opted to solder the pin-1 connections in both channels and risk a ground loop. My reasoning was, that I could recover gracefully by lifting the connection to one of the shield connections inside the black junction box.

Inside the junction box, you'll find three wires soldered together: (a) the black ground wire used for single ended operation (b) and two yellow wires - with one going to the shield of each channel.

Strictly speaking, you don't have to open up the black junction box to do this job. You can clip off the black ground wire flush with the outside of the box and be done with it (or, alternatively leave it hanging free).

I tidied up the installation and made it more reversible by pulling the black ground wire back into the junction box, coiling it up, and tucking it into the box.

As an aside, your MP-1 will sound a bit soft (Ralph calls it "dead") for the first 20 hours, so don't let this alarm you.

I was a bit surprised that any metal film resistor (Caddock upgrade) along with Teflon capacitor (V-cap upgrade) could start out life sounding soft.

Ralph tells me that while many Caddocks have the characteristic "tizzy" signature common to metal films, these particular Caddocks do not.

Enough about the MP-1, this thread is about conversion of the Tri-Planar for balanced operation. Back to our regularly scheduled programming ...

Cheers,
Thom @ Galibier

 
Nice job on the step-by-step documentation Thom - the pictures considerably add to the explanation. Thanks for taking the time to create it.

My MP-1 took roughly 120hrs to flesh out the full measure of harmonics it is capable of delivering. The V-Caps take a while. After its had enough break-in time for you to gauge, I'd be interested in your take.
 
Tim
 

For many it is confusing,seeing that the cartridge outputs are referred to as pos/neg.The real situation is that the "pos" is non-inverted and the "neg" is inverted.Using the tonearm ground as the XLR "ground",usually paralleling the tonearm ground to the two XLR jacks.

With the grounds set up in this manner, there is no chance of a ground loop.