millar

SD 664 com send noise

15 posts in this topic

Trying to setup a T1 ifb with my 664 to use the com send for the boom op. I am getting a lot of noise from the output of the com send at the back of the unit. Anyone had this issue? I am sending it at 0db (the lowest allowable level from the com menu) from the 664, mic level in to the ifb (also set to mic level). The levels seems right but the noise (hiss) is awful. I plugged the output of the com send into another board and listened to it and the hiss is coming from the 664 so I don't believe it has anything to do with the transmitter.

I am feeding a comtek transmitter from aux 1 and it sounds great.

Thanks,

Millar

Vancouver, BC

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The COM is unbalanced. I don't know if that helps.

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Remember that the com out connector is a stereo ( not a balanced ) Ta3. So you need to wire it choosing either pin 2 ( L ) or pin 3 ( R ). Your noise might be coming from phase canceling both signal thru the balanced Common mode rejection circuitry of the balanced input of your IFB.

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Thanks, I will make a new cable and see if that fixes it.

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I am sending it at 0db (the lowest allowable level from the com menu) 

 

You may want to rethink that...

I don't have that machine, but 0dB is around Line level.... (+4) 

-30 or -40 is mic level... Doesn't that adjust down to -30 or -40dB? But don't touch that for now...

Try setting your IFB to line level and leave the rest of your set up as it is....

Line level out, line level in.....   Mic level out, Mic level in....

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If you wired your TA3 to XLR cable 1 to 1, 2 to 2 and 3 to 3, selecting the RTS1 input option on the transmitter should feed the source you've selected in the Com Send Menu: Left, selecting RTS2 on the T1 should feed the source you've selected in the Com Send Menu: Right. It's probably less fiddly overall with less chance of operator error to build the properly wired TA3 to two XLRs breakout cable and use the line level input setting on the transmitter.

 

If you wired your TA3 to XLR cable 1 to 1, 2 to 2 and 3 to 3 and have selected the same program material for both left and right in the Com Send Menu on the 664, as Pascal says above more than likely there's phasing issues at the input of the T1 and you should expect a thin and noisy input signal even when gained up an extra 40 dB by selecting mic in on the T1.

Best regards,

Jim

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I've found something strange with my 664

 

Apart from my normal balanced out Lectro's I have some 3 x 100 receivers for my MM400's

 

OK so the 100 has an unbalanced output.

 

Wiring an output lead (with the suggested attenuation) into an XLR ( p1p3 earth p2 Live)

i find there is a residual signal visible on the meters at a strong level but inaudible.

This with no rf equipment operating and even with the 100 turned off!!!???

 

A ceramic capacitor of 104 across earth and p2 gets rid of it.

 

mike

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Hi Mike

I have a noise problem with my 2 Sennheiser g3s connected to my 664.  Both my g3s arrived brand new with a unbalanced CL100 stereo locking minijack to male xlr cable.  There is a blue rubber band around the cable which in very faint writing has CL100 written on it

After some experimentation I conclude that my 664 doesnt like unbalanced cables though Sound Devices claim the 664 can take unbalanced sources on its inputs.
If I only have this unbalanced cable plugged into the 664 I can see and hear noise on the channel - a lot of noise.

Sennheiser ship their more expensive 2000 series with a balanced version of this cable which works fine with the 664 - No noise.

These have an all metal xlr casing and the rubber ring has CL500 on it as opposed to the unbalanced cable which has a blue plastic part on the xlr connector and a light blue rubber ring which has CL100 on it.

So the cable isnt the only problem here.  The unbalanced cable caused no problems plugged into a SQN mixer which means that the 664 has a problem handling unbalanced inputs.  Im not sure if all 664s have this problem or if its just a batch of them but I was surprised that Sound Devices suggested I send it back when I complained about the noise.  They have so far refused to tell me whats wrong and what is involved in fixing it which I find dishonest.

I was asking on another post about this in an effort to trouble shoot it and got abuse from various people for not knowing what was going on and not RTFM etc etc.  There seems to be a lot of people on this forum who delight in giving out to people for not knowing something or tell them they should be away troubleshooting instead of asking on this forum, which I consider to be a part of troubleshooting!!  I don't really like engaging with people who get a kick from spewing out abusive comments and feeling superior because they know something that someone else doesn't know.  I find that anti-social and anti-educational.  

One of the principles of education is that "THERE IS NO SUCH THING AS A STUPID QUESTION"
 

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#: 9   Posted (edited)

deafone: " the 664 has a problem handling unbalanced inputs "

hmmm, the one I have access to does not, as long as they are wired properly according to the 664 manual...

Edited by studiomprd

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StudioM: "hmmm,  mine does not, as long as they are wired properly according to the 664 manual..."

I'm betting you do not have a 664..............

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StudioM: "hmmm,  mine does not, as long as they are wired properly according to the 664 manual..."

I'm betting you do not have a 664..............

 

Yeah is it the 664 in your mind you refer to?  the one that works like a dream ...  I mean is a dream.

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One of the issues that comes up frequently in this forum, is a misunderstanding of what balanced and unbalanced circuits are. In a balanced circuit, the electrical potential to ground is the same for both signal leads. In an unbalanced circuit, the ground is typically used as one of the signal paths, and the electrical potential to ground is not the same for each side of the signal path.

Therefore, a 3-pin connector of some sort works for a connection to a balanced circuit, while a 2-conductor connector works for connecting an unbalanced circuit.

If either an output circuit or the input circuit it is feeding is unbalanced, in no circumstances does the use of a balanced cable make the circuit balanced unless that cable incorporates some means of establishing two signal leads with a separate ground and each signal lead has the same potential to ground, such as with a balancing transformer.

With the exception of Incorporating additional circuitry or a balancing transformer, a cable does not make an unbalanced circuit into a balanced one and it still requires that the other end of the circuit is balanced.

For long cable runs, balanced circuits make a big difference in CMRR (Common Mode Rejection Ratio), but for a run of just a few feet, they seldom make any difference -- unless, perhaps you live at the base of a radio transmission tower.

Proper wiring for any cable is important, but simply using a 3-pin to 3-conductor cable (I.e. two signal leads and a separate ground) does not turn an unbalanced circuit into a balanced one.

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Hi Mike

I have a noise problem with my 2 Sennheiser g3s connected to my 664. Both my g3s arrived brand new with a unbalanced CL100 stereo locking minijack to male xlr cable. There is a blue rubber band around the cable which in very faint writing has CL100 written in. it

After some experimentation I conclude that my 664 doesnt like unbalanced cables though Sound Devices claim the 664 can take unbalanced sources on its inputs.

If I only have this unbalanced cable plugged into the 664 I can see and hear noise on the channel - a lot of noise.

Sennheiser ship their more expensive 2000 series with a balanced version of this cable which works fine with the 664 - No noise.

These have an all metal xlr casing and the rubber ring has CL500 on it as opposed to the unbalanced cable which has a blue plastic part on the xlr connector and a light blue rubber ring which has CL100 on it.

So the cable isnt the only problem here. The unbalanced cable caused no problems plugged into a SQN mixer which means that the 664 has a problem handling unbalanced inputs. Im not sure if all 664s have this problem or if its just a batch of them but I was surprised that Sound Devices suggested I send it back when I complained about the noise. They have so far refused to tell me whats wrong and what is involved in fixing it which I find dishonest.

I was asking on another post about this in an effort to trouble shoot it and got abuse from various people for not knowing what was going on and not RTFM etc etc. There seems to be a lot of people on this forum who delight in giving out to people for not knowing something or tell them they should be away troubleshooting instead of asking on this forum, which I consider to be a part of troubleshooting!! I don't really like engaging with people who get a kick from spewing out abusive comments and feeling superior because they know something that someone else doesn't know. I find that anti-social and anti-educational.

One of the principles of education is that "THERE IS NO SUCH THING AS A STUPID QUESTION"

I'm experiencing exactly the same thing as are at least 1-2 other people I know. I've let SD know on the forum.

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BAB: " I've let SD know on the forum. "

direct contact: that is a good thing...

the OP has said that he was asked to send his unit back to SD...

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Sound Devices fixed the problem after I sent the unit back and also posted a page on their site explaining this known issue with unbalanced devices.

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