Any Tascam M3700/32 users out there?

dgcarbu

New member
Any Tacam M3700/32 users out there? Hi everybody, I'm new to the forum so please excuse my ignorance. I've been a Tascam user for many years, and have recently aquired an M3700 upgrading from my M3500.

Does anyone know of any upgrades to the VCA Automation or other components that would eliminate the word clock/sync sound bleeding over to the audio section. After a 3 hour visit to a reputable audio tech, he was able to isolate the noise coming from the Automation part of the board using a device called a HOUND2 audio sniffer-type instrument.

I've been used to my quiet M3500 for the past 11 years, and I also have worked/installed a couple of M3700 in previous studios I've set up for other engineers, and have not experienced the steady smpte-like tone resting at the headphone out with all faders and pots turned down in this M3700. Any help is greatly appreciated. :(
 
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I have two 3700's that I bought new in 91 or so. (32-in versions each with JL Cooper add-on circuitboard for the extended capability automation). I have no problems with smpte noise although I did experience this years ago..IE:.....I DO know how that obnoxious smpte whine gets into the signal through the use of improper gain staging and improper external hookups.

Of course, you could have something defective in there. But..to track things down, your question doesn't give enough detail. You might want to clarify the following things ...

1.. Are you getting smpte noise when you have external sync'd "stuff" hooked up to the 3700 via any of the four smpte in/outs on the back? Or is it that you're getting smpte noise with NO smpte cables and external "stuff" hooked to the console?

2. Which mode are you operating in..snapshot or dynamic.

3. Does the smpte actually "print" to tape or pc when you record? Ie:..do you hear the whine on monitors when you play a single recorded track back? Or is it only heard in your headphones?

4. Do you have any/all your large faders in vca bypass ...or not? Are any/all the faders in vca mute ...or not? Look at all your mutes for any one strip...and the bypass switch. Be sure you're familiar with how those relate to the vca.

5. Do you have any/all the vca bypass switches activated for the 8 sub faders ? Master?

Improper internal gain staging and/or improper outboard gain staging of incoming smpte signals can all contribute to jacked up smpte whine appearing on the busses. To track things down, gotta know the above details. Plus others...but that's a starting place.

Just turning down the faders doesn't isolate the problem...as you've already seen.
 
Noisey M3700

Hi BRDTS,

Thanks for the feedback, I'm looking for all the help I can get. As far as the conditions when testing the mixer, it's with nothing but it's own power supply and my headphones hooked up to it. To isolate the headphone circuit, I hooked up my studio amp with monitors to see if I could here the same thing out of either Control Room A or B, and I do. To answer all your questions in order:

1. Tested w/ only it's own power supply and my headphones. Later with an amp and monitors.

2. Mode not applicable, everything is in static/ambient conditions.

3. Same answer as #1.

4. Tried going through all switches and faders throughout the board. No change.

5. Same answer as #4.

6. Again, with nothing hooked up to the board, the sync smpte-like signal is still heard with all volume controls down, or up for that matter.

I very much appreciate your help, I wish I new someone nearby with an M3700. I spent all day trying to get a hold of someone at Tascam Operational /Technical Support, just when I thought I made contact, the first person that answers transfers me and their automatic answering system tells me to try back later.
 
Okay, next things to try....

1. A test to verify the console is set in a correct gain-staging structure...to narrow down that THAT isn't why smpte whine is getting through.......

All faders, sends, trims, returns set to zero. All of them..channels..little faders..subs...master. All mutes (all of them) set to "on"......which is a good setting to have at all times anyway for circuits you don't use.

Plug in phones and turn up the "phones" knob to 1/4 ...which is nominal level as would travel out a line output to a mixdown/monitor medium . Any smpte noise? If not, good. Before proceeding, turn on your monitors and verify no noise there too. Continue with the test. If there is noise, there's another thing to try at point "2" way down.

(By the way I know you've had experience with the 3500 and 3700..but here's a digression.....of course it is possible ...possible..to hear noise if you, at this point, jack up the headphone volume knob to full...but that would be understandable because then you're pushing the circuit WAY past nominal and you can easily reveal smpte noise...console noise..hiss...clunks...and any other circuitry noise junk known to man...which I could also do on an SSL....the key here is to focus on gain-staging...working the console at it's nominal range throughout the path.

If you say "yeah, but I HAVE to turn the headphone knob way up to hear anything"..keep in mind that the headphone jack on a console is already a weird invention...you don't find it on an SSL. The "headphone" connection on the 3700 was NOT designed around the careful gain-staging/quiet circuit considerations that the rest of the console was designed around..The headphone jack is mainly there for convenience...a quick, non-critical reference of things....even if you have to crank it up into noise territory to actually use it...which many folks DON"T...ONCE they understand that a better gain-staged heaphone feed can be had from using ANYTHING other than the headphone jack on a console...IE...feed control room "B" or the "studio" feeds (which also give you access to the talkback feature) to a good quality headphone amp and distribution box. If you're working by yourself, hey, you probably won't bother with an elaborate, clean, headphone feed....which I probably wouldn't either. But, it's useful to focus on the "role" of this particular circuit in the console.....it's NOT there for critical listening, noise filtering, or mixing.

Anyway...

If noise is gone at the headphone jack, fire up your monitors and verify noise is not present there also. (Same standard applicable...don't crank up your power amp to 11 to "prove" that noise is there because at "11"....certainly noise/hiss from several places will be there, quite possibly even the smpte whine).

Now test a real signal on a real 3700 path....

Turn the 3700 manual to page 73...which is the pull-out gain staging diagram for the whole console. A signal meter and tone generator plugged into channel 1 line or tape input would be good to use intially...the 3700's internal tone oscillator isn't useful for this test because you can't route it only to an input.

Go to channel one and set up a test signal path that starts at channel one and travels all the way to the final place of the master fader... In practice, most knobs end up being set up to no more than 1/4 their full range and end up pumping plenty of clean gain well within nominal range. Faders...about the -10bd mark...especially the master fader. Don't set faders at their "0" marks...you shouldn't have to be anywhere near zero in a conservative gain structure. Try -5 or -10.

With the signal flowing from a tone or person playing, singing etc, turn your 3700 "control room" volume knob up to 1/4 (about the second line from off)...which at my place results in even little JBL 6328's putting out about 85-90db. Check the signal via your monitors. Are you picking up any smpte noise? If not, you've probably got a lot better gain-staged levels now than you did back when you were hearing the noise. Apply this kind of setting structure (p73 is so useful for this) for all other channels you use.

Are your 3700's output meters bouncing around within range..no red ol lights, meters not pegging? If so, good. Stop the signal for a moment and listen. Hear any smpte whine? If not, good. Start the signal again and record it to somthing..tape..pc..whatever. Is the signal being "captured" at a good healthy level on the recorder/pc? Within it's -10 or +4 range without a lot of overs? If so, it sounds like your problem has been taken care of by better gain staging.

If you're STILL getting the smpte whine, try this....

2. Open the little door behind the lcd screen on the right side of the 3700. Use a screwdriver an hit the "reset" button. Now, flip the dip switches to put the console into various smpte frame rates or mtc rates...hitting the "reset" button each time. Pp 33-34 and others go through the modes. Do ANY of these modes make the smpte noise go away? Some of the midi modes...in theory..completely turn off the internal computer. See if any of these settings knock the noise out.

If no go and you're in California, I'd take the 3700 over to Montebello and leave it with them to see what they can do. Or at the very least, call Jimmy at Montebello Tascam service and ask if he sees any service bulletins ever issued about the whine in a 3700.

Like I said earlier, there may be something broken in the console or it may just be a gain-staging issue. I can make smpte whine happen in several ways if I try. If I crank various combinations of sends/returns/faders into out-of-nominal-range land.....or hook up an external smpte clock to the 3700 and a then a bunch of unbalanced sync equipment to that clock...and then run faders at +5...+10 etc ..or my 3700's control room volume knob at half or 3/4 up....and then crank up my monitors way loud at the power amps...yeah, I can give your ears a most irritating, unpleasant experience. But in normal ranges of the equipment, I hear and print a really clean signal every time.
 
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