Headphone output [resolved]

[peterq]

Hi,
Can I connect a 4pin xlr to ot tap for headphone? Do I need to parallel a 8ohm resistor? Thanks

[Paul Birkeland]

Yes you can use the cable.  Resistors are not required.

[peterq]

Hi Paul,
Thanks for the explanation, I see somebody sold a stereomour ii on head-fi which was built by you. What's the purpose of the black cable and resistor connecting to 4pin xlr socket?

(https://www.head-fi.org/threads/sold-custom-bottlehead-stereomour-2-45-headphone-amp-built-by-pb.947014/)

[Paul Birkeland]

Those provide a balanced output.

[peterq]

I think 4pin xlr is a balanced output if I wire them to ot directly, even without the black wire?

[Paul Birkeland]

The black wire provides an earth reference for the XLR jack.  On that particular build the output transformer secondaries are floating and four resistors connect on the XLR jack to the shield pin to provide a balanced reference to ground for the output.

[Tom-s]

On that build; the XLR output is balanced via the resistors and the speaker outputs are normal single ended? The ground reference for black speaker wire goes via the XLR wiring; correct?

Edit: my interest in doing this started with this post. https://forum.bottlehead.com/index.php?topic=13246.msg121054#msg121054

[Paul Birkeland]

On that build; the XLR output is balanced via the resistors

Yes.

and the speaker outputs are normal single ended?

This statement and the above statement can't be true at the same time.  The speaker output is just in parallel with the HP output and is also balanced.

[Tom-s]

This statement and the above statement can't be true at the same time.  The speaker output is just in parallel with the HP output and is also balanced.

My brain doesn't get how it's both balanced around 8 ohm and 16 ohms at the same time.

The amp is currently set up for 8ohm on the speaker taps and 16ohm on the headphone jack..

Here's the picture to go with it. Trying to figure out the wiring.

[Paul Birkeland]

Our output transformers are not wound like the typical 0-4-8-16 ohm output transformers with a single secondary winding that has taps pulled for the various impedances.  From what I remember of that build, the speaker output was not optimally setup but worked well enough to include.  The customer wanted it mostly for headphone use, but having the speaker posts function seemed worth the effort rather than plugging the holes.

[peterq]

I made two xlr adapters today and connect to my hd 800. The amp has enough power to drive hd800 and no hum noise when no music playing.
For sound signature, I need more listening, for now I think overall is good, natural and balanced, no emphasis on any frequency, but the high frequency is not as airy as ec super7. The mid to low is very good.

[peterq]

The current setup is using 8ohm tap I believe.