XLR to Minijack Repair

[Chris]

I have two and 1/2 stereo adapters that take mic/line level inputs and
match impedance (not sure on this one) to a 8/32" stereo phono jack
for a video camera. We suspect that some of the x-formers are bad in
the unit. Would this most likely be Low to high Z x-former or just
1:1 isolation transformers. The 1/2 side that works shows almost a
short circuit on both sides of the x-former. However several of the
ones that don't work show 5~600Ohms pure DC resistance. The 500Ohms
sounds more normal for a small signal x-former than nearly zero. I
plan on tracing the circuit with a scope and an injected sine wave to
see where my signal disappears. However I am not able to find the x-
former on the net. It has BEI MA392 R.2 RoHS stamped on the side. No
other info.

Thanks,
Chris Maness

 

[Gerard Bok]

On Thu, 25 Mar 2010 15:26:18 -0700 (PDT), Chris
<christopher.maness@gmail.com> wrote:

I have two and 1/2 stereo adapters that take mic/line level inputs and
match impedance (not sure on this one) to a 8/32" stereo phono jack
for a video camera. We suspect that some of the x-formers are bad in
the unit.

One other possible source of confusion stems from the fact that
there is no standard XLR wiring schema.
So next to some units being faulty, you may be looking at wiring
discrepancies. There is balanced vs unbalanced.
And USA (2 cold, 3 hot) versus European (2 hot, 3 cold)

--
met vriendelijke groet,
Gerard Bok

 

[Ron]

On 26/03/2010 10:35, Gerard Bok wrote:

On Thu, 25 Mar 2010 15:26:18 -0700 (PDT), Chris
christopher.maness@gmail.com> wrote:

I have two and 1/2 stereo adapters that take mic/line level inputs and
match impedance (not sure on this one) to a 8/32" stereo phono jack
for a video camera. We suspect that some of the x-formers are bad in
the unit.

One other possible source of confusion stems from the fact that
there is no standard XLR wiring schema.
So next to some units being faulty, you may be looking at wiring
discrepancies. There is balanced vs unbalanced.
And USA (2 cold, 3 hot) versus European (2 hot, 3 cold)

The standard for XLR wiring is 1 ground, 2 hot, 3 cold. It wouldn't make
much difference if 2 and 3 were reversed as long as pin 1 was always ground

Ron(UK)

 

[Ron]

On 26/03/2010 14:06, Dave Plowman (News) wrote:

In article<XK-dnZnmXt9eEzHWnZ2dnUVZ8g-dnZ2d@bt.com>,
Ron<ron@lunevalleyaudio.com> wrote:
The standard for XLR wiring is 1 ground, 2 hot, 3 cold. It wouldn't make
much difference if 2 and 3 were reversed as long as pin 1 was always
ground

It certainly would if using two mics close together...;-)

Well yeah, on the other hand, two mikes close together may require the
polarity of one to be reversed. But lets not complicate matters <grin>

Ron

 

[Dave Plowman (News)]

In article <XK-dnZnmXt9eEzHWnZ2dnUVZ8g-dnZ2d@bt.com>,
Ron <ron@lunevalleyaudio.com> wrote:

The standard for XLR wiring is 1 ground, 2 hot, 3 cold. It wouldn't make
much difference if 2 and 3 were reversed as long as pin 1 was always
ground

It certainly would if using two mics close together...;-)

--
*Just give me chocolate and nobody gets hurt

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Chris]

On Mar 26, 7:42 am, Ron <r...@lunevalleyaudio.com> wrote:

On 26/03/2010 14:06, Dave Plowman (News) wrote:

In article<XK-dnZnmXt9eEzHWnZ2dnUVZ8g-dn...@bt.com>,
    Ron<r...@lunevalleyaudio.com>  wrote:
The standard for XLR wiring is 1 ground, 2 hot, 3 cold. It wouldn't make
much difference if 2 and 3 were reversed as long as pin 1 was always
ground

It certainly would if using two mics close together...;-)

Well yeah, on the other hand, two mikes close together may require the
polarity of one to be reversed. But lets not complicate matters <grin

Ron

Any idea on what the impedance of the x-formers would be?

Chris

 

[Dave Plowman (News)]

In article
<8f23cd42-142f-47b7-883f-ac6869eefa2d@n39g2000prj.googlegroups.com>,
Chris <christopher.maness@gmail.com> wrote:

Any idea on what the impedance of the x-formers would be?

Usually something like 600 ohms to 50,000.

--
*I wished the buck stopped here, as I could use a few*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Mark Allread]

Dave Plowman (News) wrote:

In article
8f23cd42-142f-47b7-883f-ac6869eefa2d@n39g2000prj.googlegroups.com>,
Chris<christopher.maness@gmail.com> wrote:
Any idea on what the impedance of the x-formers would be?

Usually something like 600 ohms to 50,000.

If nothing better comes up, you could probably get by with a resistor

"H" pad attenuator for each channel of your audio. The four 1/4 Watt
resistors can be fit into the XLR connector if you build it carefully.

This won't provide ground loop isolation like a transformer, but it will
bring your (0 to +8 DB) 600-ohm line-level audio source down to the
approximately -15 DB, 50k-ohm home-entertainment audio standard.

It won't help you with your XLR microphone-level audio, unfortunately.
That starts out at about -50 to -60 DB at 600 ohms. You'd have to use a
mic. to line level amplifier if you went with an attenuator, which is a
bit inefficient and can bring up your noise floor. Not to say I haven't
done it or that it didn't work pretty well.