Topic: Sound Field 350 / Sound Devices 744T - Ongoing Issue, feedback appreciated

[jimmyrow]

sometimes the headlights/brake lights go out on my car and i've found that kicking them usually does the trick.

That would explain all your car problems lately ba. 

[/hijack]

[T.J.]

maybe you should just dump the 350 and switch to a schoeps doublemidside rig.

no way dude, I on ly put up one mic and don't even have to worry abotu patterns. 

yeah, but the fear of incomplete recordings would nullify any type of convenience regarding patterns.

+T for your troubles focker and keeping a cool head. i'd be freakin' the F' out. tough situation indeed.

[mmedley.]

Just got off the phone with Focker. I did not even know this thread was here until he told me about it. From his explanations on the phone and in here I would bet it is a ground loop issue between the 2 units. The first thing that came to mind is the Schoeps tubes since one of the NT units has to have the "ground lift" enabled when using the same battery to power both NT's. Thanks for that info CFox. This leads me to believe that there is a grounding issue between the units.

I have also read where many people on the SD site have experienced hearing the timecode on their 744t's while others have been lightly shocked when touching their SD units.

Here is a thread specifically that comes to mind for registered users of the SD support site...few posts below for non-registered users...

http://forums.sounddevices.com/showthread.php?t=1580

Just got my 744t back from service and noticed something odd. When plugging in the headphone output to return to my 442, I find that if I touch the "tip" of the 1/8 stereo plug to any of the non aluminum parts of the 744t I can hear timecode on my 442. No other timecode, power or audio connections present...just have the 1/8" cable plugged into the B input of my 442 and then touch the tip of the other end to the 744t.

Charlie,

Tried this with my 744. The only time I heard a hint of timecode was when I put the 1/8" tip right on the tc out pin of the Lemo 5.

Question is, do you hear it normal operation?

Reminds me of the old joke:

"Doctor, it hurts when I do this"

"Then don't do that..."

I do not hear it in normal operation with the cable fully inserted but I find it odd that I've NEVER heard it before in all the times that I have plugged in a return cable and the first time I plug one in when it comes back from the mother ship I hear timecode as I insert the cable when the tip first touches the connector. And as I said...I hear it on EVERY conductive surface of the 744t. So...is this normal or do you think something could be amiss?

Charlie

Matt,

It's very simple. 1/8" in to 1/8" in stero cable connected to B input of 442. I touch the other end to ANY non aluminum metal part of the 744t and I hear timecode loud and clear in my 442 headphone return. When I plug it into the headphone out on the 744t, I hear timecode as it first touches the out ring and it goes away when fully inserted.

Don't know what a recording would accomplish here?

Hi Charlie,
This is not unique to your recorder, as we have duplicated what you are hearing on a 744T recorder here at SD HQ. However, I was only able to hear it when I had a cable connected to the TC Out. Do you have the TC Out connected to a cable?
Under those conditions, TC is audible by touching non-aluminum parts of the chassis such as screws or the outer ring of the HP jack, but it in no way affects recorded program. I also tested this with a 788T, and this does not happen, probably due to the improved design of the 788T, which grounds the chassis much better than previous models.

Charlie,

I asked because all I get on my 744 is ground hum. No timecode at all. I wanted to listen to the sound myself just to see what else might be lurking in there. It was more curiosity than anything else.

Even with a TC cable attached, I don't get TC bleed....

Could just be minor variations among units.

Edit:

Here is a thread about the shocks...

http://forums.sounddevices.com/showthread.php?t=1343&highlight=shock

I was recharging my unit, and updating the firmware etc, when I noticed a few new things.

If I touch the case with a sensitive part of my hand (e.g. the back) I get quite strong electric shocks. If I stroke it I get the characteristic 50 Hz buzzing effect in my fingers.

I did a Repair on the IN drive, 2 errors found, one fixed. Did the same for the CF - 0/0.

Only offered file type is now .wav - has .bwf been ditched?

I had battery charging trouble - four flashes. Disconnected mains, turned off and removed and replaced battery and it sorted itself out. Can I no longer change battery while connected and running?

The manual gives no advice about what to do when this happens - is there a newer manual? I couldn't find one to download.

Best, T.

Hi Matt,

I think it has always done this a bit, just now seems worse.

Your support is many thousands of miles away, and about to get more so! What needs to be done? Something wrong with the power supply unit? I have a separate charger, so if it is life-threatening I may be able to charge my batteries externally, but of course that means the blasted Timecode will turn to gibberish if I get a decent lunch, yes?

You are right, I was charging the unit whilst updating the firmware. From what you say the charge light system still contains features which are now no longer documented in the manual. Are there other such things? I noticed that the new manual was a slightly smaller file. Should I blend it with the old? At the least, the manual needs to tell us to unplug and re-plug when setting the time - I might well not have thought of doing that late on a Friday, and I very seldom have internet access whilst working.

The BWF extension has been removed to remove problems caused by software that doesn't recognize the extension. There was no difference between .wav and .bwf except the extension.

I remember wondering when I first came across this, just who managed to persuade everybody that this was the 'industry standard'. I'm sure it wasn't you guys - I did a film with Nagras which the overseas post-production converted to .bwf, resulting in chaos in the uk cutting rooms. I've personally had nothing but grief arise out of .bwf and wish it good riddance!

Best regards, T.
Reply With Quote

There's nothing 'unusual' about that, Tony. And there is nothing odd about your machine's power supply either. We get the same here with the 722s and their power supplies. (We have over a dozen of them.) Those in the US probably don't notice it because the mains supply is lower, and their higher mains frequency (60 Hz Vs 50Hz) may also make the tingles less noticable.

The reason is because the power supply is a switch mode job. The earth pin on the UK plug (adaptor) of the supply is not connected, so you will have a very high resistance on that. The Australian plug (and all the others supplied for the power supply) only has two pins - no earth pin.

Also because it's a switch mode supply, there is no direct load element such as a transformer inside the supply. The input is usually rectified before being used to drive the oscillator stage, and the diodes doing that probably have a high forward drop, so a DMM is likely to read high across it.

Because there is no earth connection, the output is effectively left floating, so you can get something like half the main voltage to ground, though with no real current. We see a similar thing with many laptops that don't earth their power supply. There is no danger as such, you just get tingles. The 7xx's give an interesting effect though with the clearly noticable buzz as you run your fingers over it, as you mentioned. The effect is simply a 'feature' of the design of the power supply.

If the machine is connected to anything else like a computer, mixer or workstation etc, that has an earth somewhere, then the audio or firewire cable sheilding will effectively ground the machine, so you will not get the tingles. It only happens when the machine is not connected to anything other than it's powersupply, because that leaves the machine floating.

[rokpunk]

Interesting reading above...

It does indeed sound like it could be a grounding issue, which is sort of why I'd like to see a test run with everything powered with AC from a single grounded outlet....even if it's not typically run powered this way in the field. In any case, good luck troubleshooting...+T for your woes.

[muj]

I agree, sounds like a 7xx issue.  what a hassle.  maybe you should just dump the 350 and switch to a schoeps doublemidside rig.

it's a 7xx issue but it's directly related to the 350.  Something between the two is off....no idea what though. 

impedance mismatching?.lol..strangest taper prob i've read about.good luck bro

[F0CKER]

Thanks for the feedback everyone.  After I finish up taping the shows I've got lined up this week I'l be sneding it back to Sound Devices with all the feedback posted here.  Thanks!  I do think it's starting to get narrowed down, and that helps.

[baustin]

sometimes the headlights/brake lights go out on my car and i've found that kicking them usually does the trick.

That would explain all your car problems lately ba. 

[/hijack]

how do you think i get your schoeps capsules working if they make a bad tape? 

[boojum]

F - is there anyone close to you who could lend you a 7xx to run the mic(s) with?  That could help, maybe.  I sure hope you can shoot this bug soon.  It is starting to get to all of us.  I would sure love to see you post a note saying the rig was 100% for each time you used it.

Keep us posted.

[F0CKER]

F - is there anyone close to you who could lend you a 7xx to run the mic(s) with?  That could help, maybe.  I sure hope you can shoot this bug soon.  It is starting to get to all of us.  I would sure love to see you post a note saying the rig was 100% for each time you used it.

Keep us posted.

Actually ran a 722 awhileback when I sent my 744 off to SD because I thought it was a deck issue at first..then the issue happened with the 722 so I was convinced it was a 350 issue.  Now I think it's the 350 and the 7xx series...directly related to the power supply.  They started selling a new power supply a little while back, I think I was one of the first to buy it.  We'll see how it goes, but for now, I'm gonna send the whole rig to SD.  I trust their service standards more...plus I think it's an issue with the deck, as a result of something with the 350....

[boojum]

GB -  Well, SD is a lot closer for one.  And you can call them on the phone for a little hand-holding if you need to.  And they are really good guys out there.  They have always done right by me.  Even when they were tempted to tell me to ship the unit back because I was too dumb to own it.  LOL  Their staff is sharp and easy to get along with.  I sure hope you come out of this all fat and happy.

Cheers

[F0CKER]

boojum, I' ve decided to sell the 744 and get a mod'd R44 instead...too many issues and, frankly, I needed the extra cash too.  So hoepfully my issues will be reoslved with a new deck...and the extra cash repairs the rotting deck at my condo.

It's all about fixing the decks.

[jimmyrow]

It's all about fixing the decks.

Now THAT is funny!!!   +T for getting all your issues (well, at least two of them) solved 

[F0CKER]

Yeah, trust me Jimbo I've got plenty more issues.  This is just the surface.  My life is like a whack-a-mole game lately....I beat one issue and something else always pops up.

All I want is to win the fuzzy bunny eventually.