Welcome, Guest
Username: Password: Remember me
NOTE: This is a "Community" forum. Please be mindful that community members are here to help as part of a community effort. We therefore appreciate your effort in keeping this forum a happy place!

If you have a specific issue (e.g. hardware, failure) and want help from our support team, please use our tech support portal (Support menu - > Contact Us).
Thanks a lot of your help in making a better community.
  • Page:
  • 1

TOPIC:

Output phase 2 x 4 HD outputs 1 week 19 hours ago #65550

  • jan.didden
  • jan.didden's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 86
  • Thank you received: 7
Something funny. I am using a 2 x 4 HD as a DAC and single ended to bal conversion.
Stereo signal into optical, outputs set as follows:
input 1 to output 1
input 1 to output 2, inverted 
(outputs 1 & 2 form the L output, balanced)
input 2 to output 3
input 2 to output 4, inverted 
(outputs 3 & 4 form the R output, balanced)

What I found is that there is no diff signal between outputs 3 and 4 in this setup. There is, if I un-invert output 4.
It seems that output 4 is already inverted even if not set to invert in DC.

Did I make a mental mistake, and if not, anybody else found this issue?

Edit: the measurement I made some time ago on building a bal output from input 1 on output 1 and 2 with output 2 inverted show a clear THD advantage - the 2nd harmonic spike on the se output is cancelled, as expected, by the bal operation.

Jan
 

This browser does not support PDFs. Please download the PDF to view it: Download PDF

Attachments:

Please Log in or Create an account to join the conversation.

Last edit: by jan.didden.

Output phase 2 x 4 HD outputs 1 week 17 hours ago #65557

  • dreite
  • dreite's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 1778
  • Thank you received: 777
This would be unexpected and obviously incorrect operation.
I will try on my 2x4HD unit.

That said, IIRC, you will see an absolute polarity flip on all outputs.

Dave.
The following user(s) said Thank You: jan.didden

Please Log in or Create an account to join the conversation.

Output phase 2 x 4 HD outputs 1 week 15 hours ago #65560

  • jan.didden
  • jan.didden's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 86
  • Thank you received: 7
Yes I would be interested to know what you find.
An absolute flip on all outputs wouldn't be a problem.
IF you find a stuck output I would think it would be software.
I know a thing or two about electronic design and I can't image a flip on one output by some wiring error unless it is a design error.

Jan

Please Log in or Create an account to join the conversation.

Output phase 2 x 4 HD outputs 1 week 15 hours ago #65561

  • dreite
  • dreite's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 1778
  • Thank you received: 777
I don't see any issue with mine.  I gave it an input on the TOSLINK jack and routed Channel 1 to all four outputs.  They're all the same.

Dave.
Attachments:

Please Log in or Create an account to join the conversation.

Output phase 2 x 4 HD outputs 1 week 15 hours ago #65562

  • jan.didden
  • jan.didden's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 86
  • Thank you received: 7
Same here. All pretty much perfect, the AP sees -0.03deg from 0deg/180deg.
I am now going to look at the cable. A short in one of the cables would also explain it.

Edit: It's the cable ... It's a cable with a 3-pin male XLR on one side, and two RCAs on the other.
What I would have expected (and I asked specifically before ordering) is that the two hot RCAs would go to pin 2 and 3,
and the RCA screens (preferable only one to avoid ground loops) to pin 1.
But in these cables, the two RCA screens both go to pin 3 and 1, while both of the two hot RCAs go to pin 2!
It seemed to work as long as I didn't invert one of a pair, but of course the signal coming out of the XLR would be single ended.

And of course as soon as I inverted one of the pair, the result at pin 2 would be near zero.
I guess I am lucky that the 2 x4 HD survived, must have some series resistor on the output for just such a stupid occasion.
But, with another pair of homemade cables I had lying around it all works as expected.
miniDSP off the hook ;-)

Another mystery solved, thanks Dave for motivating me to dig in on a Sunday evening!

Jan

Please Log in or Create an account to join the conversation.

Last edit: by jan.didden.

Output phase 2 x 4 HD outputs 1 week 13 hours ago #65563

  • dreite
  • dreite's Avatar
  • Offline
  • Platinum Member
  • Platinum Member
  • Posts: 1778
  • Thank you received: 777
Good update!

Yes indeed, and if you remember, there was a long discussion on a DIYaudio.com thread regarding the appropriateness of grounding Pin 3 via an adaptor/cable on the output XLR of an audio device when doing a balanced to unbalanced conversion.
This is a tricky one because some components will not have any issue with this, but some will.  A capacitive load de-coupling resistor on active outputs will probably save the day should this happen.  But you can't count on it!

Some of the professional gear is actually designed to sense a Pin 1/3 short and automatically increase gain 6db on the Pin 2 side to compensate.

It's much more straightforward to adapt an unbalanced source to a balanced load than it is a balanced source to an unbalanced load.
Some vendor cables may not always be wired correctly to do what you want to do.

Cheers,

Dave.

Please Log in or Create an account to join the conversation.

  • Page:
  • 1
Moderators: devteam