Triplanar RCA out to Balanced out for MP-1


Hello all, especially Doug Deacon

Well,,,,,, my Atma-Sphere MP-1 mklll has just arrived. much joy. Now I need to reterminate my RCA out from the Triplanar to a balanced out.

I am a competent solderer.

All suggestions and hints welcome
cousinbillyl
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.
Hi Tim,

Well, I know where the MP-1 is going to end up - having lived with one for 3 days in my home away from home, at the Rocky Mountain Audiofest in October. The only new component in the system was the Classic Audio T-3 (field coil) speakers.

About 36 hours into the break-in (see below for my accelerated process), my guess would be that you and Ralph are dead-on about the 120 hour number.

Break-in is normally an asymptotic process - with the first quarter or so yielding the vast majority of the change, but with subtle yet significant improvements occurring over the remaining period.

I think it's inappropriate for a manufacturer/dealer to "review" a component that we carry, as our motives should be treated as suspect. You need to be wary of false prophets ... and false profits ;-)

At the same time however, I think it's safe to say that the bulk of manufacturers and dealers inhabiting this forum are motivated by their vision of musical reproduction. While we may occasionally step over the line of propriety, it comes from a passionate desire to spread our individual view of the gospel.

I am comfortable however in talking about the break-in process of the MP-1, and a good deal of this can be generalized about the break-in of other components.

It's important to remember that the system profile of an owner purchasing an MP-1 or other expensive product is that they're likely to have a highly resolving system. They will set the bar quite high for any "stranger" introduced into their system. Because of this, injecting an un-broken in component into their signal chain is likely to result in initial ambivalence - assuming the remainder of their system is reasonably optimized and fully broken in.

On Tuesday night, I began my interconnect re-wiring project - converting a single ended interconnect to an XLR terminated output in order to run my see-dee player through the balanced inputs.

This allowed me to accelerate the burn-in process by employing a burn-in track along with my Hagerman inverse RIAA circuit. This handy device drops the signal by 40dB and puts an inverse RIAA equalization on the signal as well. It allows you to run a CD player signal through your phono stage, and if you like, to listen to tunes.

I ran the burn-in signal through the phono stage as follows:

CD player --> Hagerman Inverse RIAA --> Phono input --> Preamp Main Out --> Power amps

A few explanatory and cautionary notes are in order (Ralph can comment if I've missed anything obvious):

1. The 40dB drop of the Hagerman inverse RIAA is fine for an MM level phono stage. Dropping a 2 Volt CD signal by 40dB will result in a 20mv output feeding the phono stage. This is about 4-5 times the normal MM cartridge output - well within the overload margin of any competently designed MM phono stage. The MP-1's overload spec is 250 mV, BTW so your o.k. running it here as well.

2. With the MP-1's 60dB of phono stage gain, the resulting output would be VERY loud if you were to play this signal through your loudspeakers, so beware.

3. When burning in as above, remove any loading resistors from the phono stage. They might unnecessarily challenge your CD player. It's safest to present a 47K input impedance to your CD player.

4. Be sure that the phono source is selected.

5. The amplifiers do not have to be powered on. They will show their grid resistor load pair (100K) to the preamp output, so current flows through the system without the power amps being powered on.

This first 36 hour period has resulted in substantial changes to / improvements in the MP-1's character. With the Christmas rush and such, I did not take an intermediate checkpoint between the 6 and 36 hour point.

At 36 hours, the top end really began to open up - to the point where (when plugging my analog rig back in), I started to think about loading resistors. For the first 5-6 hours, my XV-1s was running wide open (47K load) and still sounded closed in. Now, we're approaching where they'll end up - needing a load somewhere in the 50-150 ohm range.

Whether it's the V-Caps, the Caddocks, the wire, or everything isn't all that relevant to me, but the character of the break-in reminds me of a cartridge I'd like to have back in my quiver some day - the Ortofon SPU Royal-N.

This cartridge had a break-in process that many do, but to an extreme. It took a while for this cartridge to connect the dots and to speak with a single voice. A point in time arrived (about 24-30 hours in) where the frequency bands no longer seemed disjointed, the cartridge sang with a single voice and the magic flowed.

I've heard the break in process of V-caps described as a cyclical series of improvements and disappointments, before everything gels into a coherent sonic whole. This (connecting the dots) may well be what these individuals are describing.

Well, at 36 hours (last night's checkpoint) the dots are beginning to connect - like hands outstretched which are trying to touch each other. They're not quite there yet, but it's tantalizingly close. I'm noticing a slight suckout in the midrange. The bass is extraordinary - both in power and more importantly in texture - being extremely tactile and "fleshy" which is a direct result of the top end filling in (bass texture comes from extended treble).

I'll report back next week ...

Cheers,
Thom @ Galibier