DIY balanced interconnects

04-03-09: Atmasphere
Tvad, what you are missing is the output impedance is not the spec. For
example, the Modright might have a 100 ohm output impedance- if the
output winding is designed to drive 600 ohms then it would work fine. Ditto
Roland and Wadia. The output impedance is something very different from
what load the circuit will drive.

According to your latest information, a tube component with low output
impedance (the examples above were 300 ohms or less), and that has either
an output transformer or is direct coupled, will adhere to the 600 ohm
standard.

In addition, the important factor in the 600 ohm output impedance standard
is not the actual output impedance specification, but the design of the
transformer's windings.

How is a customer expected to determine if an output transformer's winding
is designed to drive 600 ohms, if there is no specification to indicate such?

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.