DIY balanced interconnects

I second Kirkus about the dubious need for 600 ohm termination resitor over short distances. However, I agree with Ralph that if you want to go exceptionally long distances then 600 Ohm should get better results. Horses for Courses.

What length does Oldears need?

Kirkus, thanks for the explanation. According to the designer of my DAC, the outputs are fully balanced (truly electrically balanced) in that as leg 2 goes up in voltage, leg 3 goes down by the exact same amount. So it sounds like it is differential.

Now, my VAC Auricle Musicblocs have balanced inputs. If I recall correctly according to one of the engineers at VAC this is accomplished via the "Williamson Method" (which I think is a name used in one of their older amp designs) and I believe uses an input transformer.

Perhaps you or Ralph can comment on this. From the sounds of it this does not appear to be a differentially balanced design.

Thanks to Atmasphere and Tvad for the help.
I also checked my manuals:
The aleph ONO spec is listed at 150/150 ohms which Pass states is low enough to drive most any load.
The cary 303/200 spec is not given in my manual probably beacause the user can change jumpers between 3 or 6 V out or the digital volume control which means the output impedance would vary by choice.
The Theta DSPro Gen 5 spec out is 13 ohms/phase
The BATVK30 balanced input spec is listed at 100Kohms/phase.
The BATVK30 output spec is listed as 750 ohms (differential?)... but I have modified the output caps to 4.33 uF per leg instead of 1uF/leg to make sure I would not lose low freq into the aleph 0s, enen tho V. Khomenko states the 1 uf caps will drive any load over 10K.
The Pass Labs aleph 0s input impedance is specified as 12Kohms differential.
At any rate, I am hoping the technical solution using $69 of parts for 3 XLR pairs and one AES/EBU cable will give me enough satisfaction in my system, to be able to put the well reputed Kimber KCAGs up for sale to someone who might appreciate their characteristics.
thanks again!

ebu

For example, my Neumann microphones are set up to drive 150 ohms. What this means is that if you don't load them at 150 ohms (if instead you have a load of 1000 ohms or higher), the output transformer will express the inter-winding capacitance rather than the turns ratio, and you will get coloration and no bass.

Atmasphere, the vast majority of Neumann mics have an output impedance of 50 ohms, and they've traditionally specified a loading of >1K. It's only some of the classics (i.e. U67) that are switchable to lower impedance, and they still need to be loaded at at least 300 ohms.

Right, Kirkus, my Neumanns are U67s. After doing some measurements with them, we found that the transformer was more linear when driving a lower impedance- even 600 ohms was too high.

The 600 ohm standard arose from the characteristic impedance that was created by spaced telegraph cables, and was later adopted by the phone companies, later still by recording and broadcast equipment manufacturers.

These days that standard is considered obsolete, 1K and the like are common input impedances, as a result the standard is somewhat diluted. We wanted to be assured that our gear would support existing hardware that it might get connected to, as there is still quite a bit of collectible tube equipment out there like Ampex tape machines that are on the same standard.