XLR to stereo 3.5mm cable?

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I have a Sony camcorder which has a 3.5mm socket labelled "external
mic, plug in power". I'm a keen musician and have a good quality
condenser microphone which has an XLR output. I want to connect the two
to give me better quality sound on the camcorder.

The internal mic in the camcorder is stereo, so I can only assume that
the external input is made for a stereo mic. My condenser mic is mono.

I was hoping that someone could advise me on how to construct a lead to
connect the mic to the camcorder. I have a couple of old XLR leads that
I'm happy to chop up, and I've got a spare 3.5mm stereo jack for the
other end.
`
Also, what does "plug in power" mean? I usually use 48v phantom power
with my condenser mic, but it has the facility to put in a 1.5v battery
if I need to.

 

[niftydog]

I have a Sony camcorder which has a 3.5mm socket labelled "external
mic, plug in power". I'm a keen musician and have a good quality
condenser microphone which has an XLR output. I want to connect the two
to give me better quality sound on the camcorder.

The internal mic in the camcorder is stereo, so I can only assume that
the external input is made for a stereo mic. My condenser mic is mono.

I was hoping that someone could advise me on how to construct a lead to
connect the mic to the camcorder. I have a couple of old XLR leads that
I'm happy to chop up, and I've got a spare 3.5mm stereo jack for the
other end.
`
Also, what does "plug in power" mean? I usually use 48v phantom power
with my condenser mic, but it has the facility to put in a 1.5v battery
if I need to.

Yes, the input will be stereo. The "Plug in power" thing is a facility
to power small condensor mics, it's usually insufficient (2V or
thereabouts) to power "real" mics, only those little hokey things that
Sony makes. You'll definitely need your battery powered mic; It steps up
the 1.5V from the battery to the correct bias voltage for the capsule.

You might also need to carefully tweak the gain settings (if any) on the
camcorder. It likely also has an AGC which may or may not have settings
to adjust. Sometimes you can also run into difficulty using balanced
microphones with unbalanced inputs; Namely there's not enough signal
present and the gain required to bring the level up also introduces
noise. The fix for this is a little more involved - I built a
transformer unbalancing box out of two old microphone transformers.

But, first thing to try is just the straight cable adapter:

Within the mic cable will be two wires (or two twisted pairs of wires)
and the shield braiding. Wire one wire (or pair) to the tip of the 3.5mm
connector, the other wire (or pair) and the shield should both be wired
together to the sleeve. Then the ring (the third connection) should be
shorted to the sleeve.

This is the bodgey way of unbalancing your mics balanced signal. The
non-bodgey way involves a microphone transformer and will result in
twice the signal amplitude which is often a necessity. But, try the
bodgey (easy!) way first as it might get you by.

nifty

 

[Eeyore]

I have a Sony camcorder which has a 3.5mm socket labelled "external
mic, plug in power". I'm a keen musician and have a good quality
condenser microphone which has an XLR output. I want to connect the two
to give me better quality sound on the camcorder.

The internal mic in the camcorder is stereo, so I can only assume that
the external input is made for a stereo mic. My condenser mic is mono.

I was hoping that someone could advise me on how to construct a lead to
connect the mic to the camcorder. I have a couple of old XLR leads that
I'm happy to chop up, and I've got a spare 3.5mm stereo jack for the
other end.
`
Also, what does "plug in power" mean? I usually use 48v phantom power
with my condenser mic, but it has the facility to put in a 1.5v battery
if I need to.

This isn't a design question.

Posted to rec.audio.pro and rec.audio.tech.

Graham

 

[Richard Crowley]

It is one of my most popular web pages...
http://www.rcrowley.com/CamAdapt.htm

It means the 3-5v that consumer devices (camcorders, MD recorders,
computer sound cards, etc.) provide to power the FET impedance
converter transistor in electret condenser microphone capsules. It is
very very roughly the consumer equivalent of 48v phantom power,
but a much lower voltage, and single-ended (contrasted with balanced
pro microphones).

There are adapter devices which provide balanced mic inputs and even
P48 power for stereo mini-phone consumer equipment. For example...
http://www.beachtek.com/dxa6.html

 

[Eeyore]

Yes, the input will be stereo. The "Plug in power" thing is a facility
to power small condensor mics, it's usually insufficient (2V or
thereabouts) to power "real" mics, only those little hokey things that
Sony makes.

The input can't be *both* stereo and powered for cheap electrets.

I expect it's a mono input.

Graham

 

[Scott Dorsey]

It's a C-1000 isn't it? Please tell me it's not a C-3000.

Right, and it's got some godawful AGC on it to begin with. You really,
really don't want to use the input on a consumer camcorder if there is
ANY possible way around it.

But, if you absolutely HAVE to do it, tie tip and ring together and
connect through a 10 MFD film capacitor to one end of the secondary
of a 1:1 transformer. The other
end goes to the sleeve. The primary of the transformer goes to pins
2 and 3 of the XLR from the mike, with pin 1 on the XLR tied to the
chassis of the box and to the sleeve of the 3.5mm plug.

Plug-In-Power is a really boneheaded idea. Sony puts some DC on the
input, and since it's a crappy unbalanced line they can't do the usual
phantom power trick, so it's differential between signal and ground.
This screws up dynamic mikes and transformers plugged in there, unless
you have a DC blocking cap to keep it out. This is just another reason
why all of these consumer camcorders have no business running single
system audio. If you care about audio, record it on an audio recorder
and synch them up in post.
--scott

 

[niftydog]

The input can't be *both* stereo and powered for cheap electrets.

Yes it can, else my minidisc is performing miracles!

nifty

 

[Eeyore]

Yes it can, else my minidisc is performing miracles!

Ok - the mini-jack has 3 connections typically.

Ground, 'DC bias power' and signal.

Does the ring contact serve 2 functions ?

Graham

 

[niftydog]

Ok - the mini-jack has 3 connections typically.

Ground, 'DC bias power' and signal.

Does the ring contact serve 2 functions ?

I've never had cause to look into how it works, all I know is that it
does. The folks at minidisc.org would definitely have the answer to your
question.

nifty

 

[Mr.T]

If you care about audio, record it on an audio recorder
and synch them up in post.

This is always my recommendation too. The camera audio can be used simply as
a reference to sync to.

MrT.

 

[Eeyore]

This is always my recommendation too. The camera audio can be used simply as
a reference to sync to.

With modern crystal based sound recorders - 'wild sound' presents no problems.

Graham

 

[Boris Lau]

Right, and it's got some godawful AGC on it to begin with. You really,
really don't want to use the input on a consumer camcorder if there is
ANY possible way around it.

Quite a lot people hack the OS on their Sony Camcorders, for enabling
DV-In, Zebra patterns and disabling AGC. If you do that, you have a
consumer-quality line-in with level meter on that thing.

For a start, look at:
http://www.hardwareanalysis.com/action/printarticle/1464/

It takes some research to find tables on the net with all the register
setting for a particular camera model, but the new features you can
activate with that are worth it. Been there, done that.

With these modifications you can use any mobile mic2line preamp to hook
up your mic to the camcorder. You can't use the preamp built into the
camera, because it can't be used without the AGC. This is true for the
consumer camcorders without a touch screen.

All the best

Boris

 

[Rv!]

"Scott Dorsey" <kludge@

Right, and it's got some godawful AGC on it to begin with. You really,
really don't want to use the input on a consumer camcorder if there is
ANY possible way around it.

Seeing your username as "cludge" I just thought of a possible kludge that
would be interesting to try regarding AGC.

<Thinking>
If we were to inject a sub-sonic or super-sonic "sidetone" to the camera mixed
with the actual audio we want, we could set the "sidetone" level such that the
AGC would operate "much less, if at all." The sidetone, if recorded successfully,
could be filtered in post. I would imagine the AGC will react to a signal outside
the audio passband "if sent high enough" to get (forced) through any possible
filters."

I wonder if this would add "unacceptable" artefacts?
</thinking>

Rv!

 

[Roy W. Rising]

"Scott Dorsey" <kludge@

Seeing your username as "cludge" I just thought of a possible kludge that
would be interesting to try regarding AGC.

<Thinking>
If we were to inject a sub-sonic or super-sonic "sidetone" to the camera
mixed with the actual audio we want, we could set the "sidetone" level
such that the AGC would operate "much less, if at all." The sidetone, if
recorded successfully, could be filtered in post. I would imagine the AGC
will react to a signal outside the audio passband "if sent high enough"
to get (forced) through any possible filters."

I wonder if this would add "unacceptable" artefacts?
</thinking>

Rv!

I would expect the "wanted sound" to bounce the AGC anyway, to the extent
it adds to the "force tone" when present.

 

[Rv!]

I would expect the "wanted sound" to bounce the AGC anyway, to the extent
it adds to the "force tone" when present.

Nice to see you've still got your original name Roy...
I was thinking of running the sidetone as a high enough level to push the AGC down
a "fair amount" so the normal level audio would be recorded lower than usual. Only on
hard audio peaks would the AGC kick in further. If that worked I could see the
AGC working more like a "high-level" compressor. Just a thought, but an interesting
one I might just try from the scrap-box.

Rv!

 

[Ben Bradley]

In sci.electronics.design,rec.audio.pro,rec.audio.tech, On 21 Nov 2006

This is definitely a kludge but it could indeed be an improvement.
An ultrasonic signal should indeed activate the AGC, yet be filtered
out by an anti-aliasing filter in front of an ADC (or equivantly, be
filtered out digitally in a "1-bit" ADC). But with anything less than
an excellent filter, the ultrasonic tone may be aliased to an
annoyingly audible frequency in the recording. I suppose it's worth
trying.

If it were my camera I'd open it up and see if I could disable the
AGC (presuming it's still done with analog components) and add a
potentiometer with the shaft coming out a hole drilled in the case for
a gain control. I did that very thing to a Radio Shack cassette
recorder about 30 years ago, but back then everything was thru-hole
and (relative to now) big components. Surface mount makes such mods
more challenging, especially with middle-age eyesight, but "we have
the technology..."

I would expect the "wanted sound" to bounce the AGC anyway, to the extent
it adds to the "force tone" when present.

Perhaps so, but it could still be a great improvement over what the
AGC does to straight audio.

 

[Arny Krueger]

"Scott Dorsey" <kludge@

Seeing your username as "cludge" I just thought of a
possible kludge that would be interesting to try regarding AGC.

<Thinking>
If we were to inject a sub-sonic or super-sonic
"sidetone" to the camera mixed with the actual audio we
want, we could set the "sidetone" level such that the AGC
would operate "much less, if at all." The sidetone, if
recorded successfully, could be filtered in post. I would
imagine the AGC will react to a signal outside the audio
passband "if sent high enough" to get (forced) through
any possible filters."
I wonder if this would add "unacceptable" artefacts?
</thinking>

It appears that the AGC on some consumer cameras can be turned off by
fiddling with their firmware.

 

[Eeyore]

"Scott Dorsey" <kludge@

Seeing your username as "cludge" I just thought of a possible kludge that
would be interesting to try regarding AGC.

<Thinking>
If we were to inject a sub-sonic or super-sonic "sidetone" to the camera mixed
with the actual audio we want, we could set the "sidetone" level such that the
AGC would operate "much less, if at all." The sidetone, if recorded successfully,
could be filtered in post. I would imagine the AGC will react to a signal outside
the audio passband "if sent high enough" to get (forced) through any possible
filters."

I wonder if this would add "unacceptable" artefacts?
</thinking>

That ought to work.

I'd got for a subsonic tone myself.

Graham

 

[Peter Larsen]

"Scott Dorsey" <kludge@

Seeing your username as "cludge" I just thought of a possible
kludge that would be interesting to try regarding AGC.

The first fix to attempt is to lengthen the release time if the pcb
and/or circuit design allows the required cap and/or resistor
replacement.


Peter Larsen

 

[Peter Larsen]

That ought to work.

This AGC issue is yet another example of loss of audio knowhow at the
manufacturers, Sony did an excellent overmodulation protection circuit
on their 510 portable r2r and then promptly forgot all about it.

I'd got for a subsonic tone myself.

A firmware hack is described on a web site linked to somewhere in the
thread, the minimum required change might however be just to lengthen
the release time.

Graham

Peter Larsen