Another question to fellow EX1 owners

craftech wrote on 3/11/2009, 9:36 AM
Bob (farss) has already responded to an e-mail I sent him regarding this problem, but I thought I would post it here anyway to get more input that may help all of us who own the Sony PMW-EX1.

The Problem: I am not sure if the LIne Input on my EX1 is working properly.

I used a Behringer Eurorack MXB1002 Stereo Mixer for years with my VX2000 with
no problems. Two 1/4 inch balanced Main outputs at (according to Behringer) +28dBU unbalanced or
+22dBu balanced..................

..........into an XLR plug, XLR extension to VX2000, then XLR to 3.5
stereo mini into VX2000 camera. VX2000 Mic/Line switch was set to Line and
it always worked perfectly. Main Output slider from mixer was usually set to -10dB
most of the time for great sound.

With the EX1, I just tried it last weekend into Channel 2 with Channel 2 set
to Line. Second switch set to Ext.

Channel 1 was the on board Mic. Channel 1 set to Mic. Second switch set to
Int.

Channel 2 (Mixer) was barely audible on either Auto Gain or Manual. So I
tried combining the L and R outputs from the mixer into an XLR to send it to
Channel 2 on the camera and it was the same. I ended up setting the switch
to Mic (and EXT) instead of Line just to get audible sound from the mixer
which of course clipped the sound on Channel 2 pretty badly at times.

Am I missing a setting for the Line Input? EX1 manual says the Line input is
+4dBu. With + 28dBu (according to Behringer) coming out of the mixer, the last thing I would think was that it would be muted (little signal on the EX1 Channel 2 audio level meter).

What has been your experience with the Line Input on this camera?

Thanks in advance.

John

Comments

farss wrote on 3/11/2009, 3:35 PM
One additional thought. Did you try adjusting the Trim settings in the menu?

According to the manual they only affect the external mic inputs. From what you've just described though, that switched to "mic" you ended up with distorted low levels something is fishy. Seems to me you overloaded the front end preamps and then that was seriously attentuated. I'd try adjusting that input trim setting.

I'd check all this for you but my own EX1 is still elsewhere :(

Bob.
craftech wrote on 3/11/2009, 5:03 PM
One additional thought. Did you try adjusting the Trim settings in the menu?

According to the manual they only affect the external mic inputs. From what you've just described though, that switched to "mic" you ended up with distorted low levels something is fishy. Seems to me you overloaded the front end preamps and then that was seriously attentuated. I'd try adjusting that input trim setting.
=============
Not distorted low levels with mixer connected to the Channel 2 XLR input switched to External Mic setting. Overdriven levels to clipping caused periodic distortion. Plenty loud enough when it didn't clip. In fact it sounded good.
Trim wasn't touched (default setting). Maybe the solution is to hook up the mixer the way I did (Ext Mic) then use the Trim to lower it to prevent clipping.

But still, the mixer should work properly with camera switched to Line Input which has no adjustment that I could find in the manual.

Thanks again Bob.

John
farss wrote on 3/12/2009, 5:53 PM
I just connected an old Audio Multiburst Generator up to an EX1.
This unit outputs a tone sequence at +8dBm @ 600ohms. With EX1 gain control at 10 I get the meters within 2 bars of clip. Most likely the limiter in the EX is stopping me from clipping.

I'd say that Sony specs of +4dBu are accurate. When I get back to my "lab" tonight I'll attempt to measure the input impedance of my EX1 tonight. I suspect part of the problem lies in the difference between dBu and dBm.

Bob.
craftech wrote on 3/12/2009, 7:48 PM
I just connected an old Audio Multiburst Generator up to an EX1.
============
I looked this up:

It is all based upon an old 600 ohm reference. Today's equipment is much higher.

0 dBu is .775 volts
+4 dBu is 1.23 volts +4 dBu is supposedly for "Pro Gear" inputs like the EX1.

My VX2000 is considered "Consumer Gear" which is supposedly looking for -10 dBv at it's line input.

If my consumer gear mixer puts out +22 (balanced) to +28 dBu (unbalanced) then it is putting out roughly + 26 dBu or so which is around 15.5 volts.

20log(15.5/.775) = +26 dBu

1 volt = 0 dBv

-10 dBV equipment produces a voltage of .316 volts.

20log (.316/1) = -10 dBV

The difference between +4 dBu and -10 dBV is 11.8 dB.

There is an 11.8 dB difference between the zero reference or nominal signal level of equipment rated at +4 dBu versus -10 dBV.

According to the chart on this page:

If I am looking at this correctly, if I set the Main Output slider on my Behringer MXB1002 to 0 db (which is a -10dBv device) it won't put out enough voltage for the +4 dBu Line Input on the EX1. It looks like I have to drive it to the point of clipping by setting the Main Output slider past 0 allowing the red LED Clip light to flash to get enough volts for the Line In.

In that case it may be that I cannot use this mixer with the Line In on the EX1, but rather the Mic In with either a pad, or the Trim adjustment raised to keep it from clipping.

But I still don't get how the 15.5 volt output of the Behringer MIxer factors in?


Am I reading or understanding this wrong?

John
farss wrote on 3/12/2009, 8:40 PM
"It is all based upon an old 600 ohm reference. Today's equipment is much higher."

In theory line inputs today are much higher input impedance. How much higher is the question. The consummer stuff seems to be 10K to 100K. Mic inputs are around 1K or a bit higher. Pro line inputs can still be transformer isolated 600 ohms but that's only the really expensive stuff.

The old school dBm's reference is 1mW, typically at 600ohms. I used to work with 150ohm balanced lines as there is less HF loss on long unequalized lines and less noise and crosstalk at 150 ohms. Our meters had switches for 600ohms and 150 ohms. No one gives much of a damn about all this stuff today :(

We also used to use transformers that matched 10K ohms to 600 ohms. Those transformers are hard to buy today.

"But I still don't get how the 15.5 volt output of the Behringer MIxer factors in?"

Well if the EX1's line input was 1K ohms guite a lot as I really doubt the mixer could drive that many volts into 1K, 10K maybe, 100K no problem.

"Am I reading or understanding this wrong?"

You've pretty much got it right.
Even with our Wendt mixer into a PD170 switched to line I have to wind the mixers output up very high to drive the PD170.

Bob.
craftech wrote on 3/13/2009, 5:56 AM
"Am I reading or understanding this wrong?"
--------------
You've pretty much got it right.
Even with our Wendt mixer into a PD170 switched to line I have to wind the mixers output up very high to drive the PD170.

Bob.
-----------
So then I guess there is nothing wrong with the Line Input on the camera negating the need for a service trip to Sony Professional. It sounds like I shouldn't use that mixer with the Line Input on the EX1.

I guess that means I have to use the Mic Input on the EX1 for that mixer and keep the dB setting on the mixer's Main Output set to -10 dB as I do when I use it with the VX2000 then adjust the Trim on the EX1 so it doesn't clip.

What EXT MIC setting in the Trim menu of the EX1 do you suggest to keep the EX1 from clipping?

Thanks Bob.

John
farss wrote on 3/13/2009, 6:53 AM
"It sounds like I shouldn't use that mixer with the Line Input on the EX1."

YES. I've yet to find ANY mixer that let me use line level inputs on any Sony camera that had XLR inputs. That test set fed enough level into the EX1, the Wendt made it with the gain control on the PD170 at 10, just.

The reality I find myself in is not much at all sends +4dBm. No desk at a venue will. As one sound guy said to me, well yes technically that's the point at which at amps would clip, it's also the point at which we'd likely bring the ceiling down! So they're more likely to be sending -20dBm. That's not enough for Line and really too much for Mic on our cameras.


"What EXT MIC setting in the Trim menu of the EX1 do you suggest to keep the EX1 from clipping?"

General advice on setting the Trim is to set it a value such that you do not need to set the gain control knob below 5.



Just as a tip for anyone who takes feeds from desks that they have no control over. I have 2x 10dB "H" pads and 2x Lundahl 600:600 ohm transformers in my audio kit bag. All of those are inside XLR plug-socket modules. Having them on hand has saved me having to clean up any audio feeds from desks. Total cost of those bits of kit, AUD 500, having clean audio, priceless.


Bob.
craftech wrote on 3/13/2009, 8:04 AM
Thanks again for doing all that for me Bob. I truly appreciate it.

Regards,

John