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Decklink Studio, Mixer, Y cable?? PLEASE..

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Tony Ienco
Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 11, 2011 at 11:42:46 pm

Firstly, I would like to express my gratitude to all the helpful people on this site, would never have got this thing going without the help and advice.. I thought I knew everything I had to know about wiring audio and video but QUICKLY realised, I know very little about balanced signals...

Basically with the help of another forum member I got good audio from channel one and two into my mixer... My Mixer.. It has two BALANCED Mono inputs that I am using for channel one and two.... the remaining inputs on my mixer are unbalanced. It is a Yamaha mixer... The remaining channels are Left Right Stereo BUT the LEFT only says Mono, so I assume you use just Left for Mono, ONLY PROBLEM is it is UNBALANCED.. So when I hooked up Channel 3 and 4 to the mixers Mono chanels 3 and 4 with Balanced TRS cable, I got nothing but LOUD distortion and crackling...

To my question? If I use a 6.5mm TRS(Stereo) cable to 2 x 6.5mm Mono Jacks (ie: Y Cable stereo to Mono) plug the stereo end to the decklink and the mono ends to the LEFT AND RIGHT of one of the mixer channels? will this eliminate the distortion and solve the problem???

Thanks in advance.
Tony.

Tony


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Justin Strauber
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 12, 2011 at 4:06:18 am

Exactly what mixer are you using? Usually mixers with stereo inputs like that are balanced TRS.


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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 12, 2011 at 6:47:08 am

Thanks for the reply, it is a Yamaha MG82CX but every time I plug any of the Decklink output channels into 3/4 and 5/6 Left (Mono) Inputs, I get LOUD distortion. The only ones I don't get that from is the dedicated Mono channels 1 and 2???

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 12, 2011 at 7:17:32 pm

here is a picture of your mixer -
http://static.musiciansfriend.com/derivates/19/001/327/896/DV020_Jpg_Jumbo_...

You CANNOT use the XLR inputs. You must use the TRS 1/4" inputs.
The Mic inputs will distort. In addition, you can see that the top knob is called GAIN - this is the trim control for the inputs - this appears on almost every mixer in the world. Turn all of these knobs all the way down (fully counter clockwise) and you will have no problems.

The XLR inputs are for -60dBu microphones only. No line inputs.

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 12, 2011 at 9:39:51 pm

I was NOT using the XLR inputs, I was using the LEFT Mono input, but the instructions Clearly state these are unbalanced and it doesn't matter where the gain was it made no difference at all. It looks like I either need a new mixer with more balanced inputs or perhaps I will build up the Jaycar kits that convert Balanced to unbalanced.. Thanks for the help anyway.

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 1:35:56 am

your distortion problem has nothing to do with this. For what you are doing (Decklink TRS balanced out into Yamaha mixer TS mono input), this is NOT going to cause distortion. Your distortion is happening because your signal coming out of the Decklink (+4dBu analog for example) is distorting the analog input of the mixer.
Almost every analog mixer in the last 20 years from Mackie, Behringer, Soundcraft and Yamaha can handle a +4dBu input from a source. If your mixer is distorting on these LINE inputs, then something else is wrong.

Would you like me to read the manual for you ?

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 1:39:57 am

Well I cannot for the life of me see what else it could be? Even when I plug Channel 1 & 2 from the Declink into the Left mono line input, it distorts where as it works PERFECTLY in the first two mono inputs of the mixer?

I am not sure if you are being sarcastic about reading the manual for me? I have read it several times. If you could offer any other advice as to what it might be, I would be great full.

Thanks
Tony.

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 1:48:15 am

1) here is the manual -
http://www2.yamaha.co.jp/manual/pdf/pa/english/mixers/mg82cx_en_om.pdf

from page 8 of the manual -
Let’s take a look at one of the most commonly used units in
audio: the decibel (dB). If the smallest sound that can be heard
by the human ear is given an arbitrary value of 1, then the
loudest sound that can be heard is approximately 1,000,000
(one million) times louder. That’s too many digits to deal with
for practical calculations, and so the more appropriate
“decibel” (dB) unit was created for sound-related
measurements. In this system the difference between the
softest and loudest sounds that can be heard is 120 dB. This
is a non-linear scale, and a difference of 3 dB actually results
in a doubling or halving of the loudness.
You might encounter a number of different varieties of the dB:
dBu, dBV, dBM and others, but the dBu is the basic decibel
unit. In the case of dBu, “0 dBu” is specified as a signal level of
0.775 volts. For example, if a microphone’s output level is –40
dBu (0.00775 V), then to raise that level to 0 dBu (0.775 V) in
the mixer’s preamp stage requires that the signal be amplified
by 100 times.
A mixer may be required to handle signals at a wide range of levels, and it is necessary match input and output
levels as closely as possible. In most cases the “nominal” level for a mixer’s input and outputs is marked on the
panel or listed in the owner’s manual.


REPLY - so 0VU on this mixer is .775 VAC, and 0 coming out of the Blackmagic is about 1.26 VAC. So the "zero's" will not match.

from Page 15 of the manual
Sound is faint,
distorted, or noisy.
❑ Are the channel GAIN controls, LEVEL controls, STEREO Master control set to
appropriate levels?
❑ Are two different instruments connected to the XLR-type and phone jacks, or to the
phone and RCA pin jacks on one channel? Please connect to only one of these
jacks on each channel.
❑ Is the input signal from the connected device set to an appropriate level?
❑ Are you applying the effects at an appropriate level?
❑ Are microphones connected to the MIC input jacks on channels 1 to 5/6?
❑ If you are using condenser microphones, is the PHANTOM +48 V switch turned ON?

REPLY -
from page 56 of the manual -
ST CH LINE
INPUT (CHs 3/4,
5/6)
–34 dB
10 kΩ 600 Ω
Lines
–46 dBu (3.88 mV) –34 dBu (15.5 mV) –14 dBu (155 mV) Phone jack
+10 dB – 2 dBu (0.615 V) +10 dBu (2.45 V) +30 dBu (24.5V) (unbalanced)

THIS MEANS THAT YOUR INPUT 5 + 6 can handle a 10dBu signal (2.45 V) without distortion. If you are getting distortion, it's not because your mixer can't handle it on inputs 5 + 6 - unless the input preamp is blown (broken).

Do you have something else (besides the blackmagic, like a professional VTR, like a Beta VTR with XLR outputs) that you can stick into inputs 5+6 to see if you get distortion ?

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 1:52:18 am

Yes thank you I have a DVCAM deck so I will take the audio out of that and try it in the 3/4, 5/6 inputs..

Didn't think of that, quickly assumed the inputs were not balanced causing the distortion, since Blackmagic make such a point about using Balanced cables....

I will post back in a little while. Most helpful. Thank you.

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 1:57:41 am

Tony -
I have re=read your post. I am starting to believe that you have a problem with your inexpensive mixer. Any of these line inputs should be able to handle the BALANCED input - even the unbalanced ones. The only thing you are possibly doing wrong is your trim (gain) control - and you said that the gain control only affects the XLR input - so you probably have a problem with the mixer. Behringer makes terrific very inexpensive mixers, so you should try one of them to resolve your issues.

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 2:00:58 am

No, the gain does effect the 6.5mm BUT even with the gain turned down to about half of 1 (one) the distortion is do loud it is terrible. I have been looking at a Peavey mixer? I have read many reviews on the internet about the Beringer, none of them favourable, because I defiantly considered buying one 2 weeks ago..

Tony


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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 4:45:52 am

Well, I plugged the deck into only the Mono channel of 3/4 and 5/6 and works perfectly, clear as a bell. So I naturally assume the Mixer is OK. As I stated earlier, when I plug Channel 1 or 2 from the Declink, (the two channels that work great in the mixers mono channel 1 & 2 Balanced inputs), into 3/4 or 5/6, I get the same bad distortion... So hence you can see my reason for believing it was a Balanced issue. I can't assume there is a problem with Channels 3 and 4 coming from the Decklink, cause they work great in the Mixers 1 and 2 channels.. Most confusing? Not sure where to go from here.

Tony


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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 5:31:31 am

Something very interesting I just tried which still leaves me scratching my head. The stereo output of the mixer go to a pair of Behringer MS-20 Powered speakers. I unplugged these and used a pair of computer powered speakers and when I plug into Channel 3/4 now, it is fine???? So I don't know what that means. Are the speakers at fault? Why doesn't it happen when I use Channel 1 mono and 2 mono... I guess these are the million dollar questions.

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 10:58:03 pm

the MS-20 is an inexpensive set of speakers that uses RCA or stereo mini plug inputs - it is expecting to see a very low level signal coming into it. I don't know how you are feeding your speakers from the mixer.

If you used a set of professional speakers (even Behringer B1030A, or B2031A), it can handle a +4dBu signal without issue, where the MS-20 only can handle a -10dBu signa - that is a 14 dB difference between the two products.

Peavey mixers are fine, but not popular in our industry (they are marketed thru musical instrument stores only - but Mackie, Soundcraft and Behringer are also sold thru Music stores as well).

When you say you used "computer powered speakers" - what does this mean ? What brand ? What is the input to these speakers. You need professional speakers - everyone from Behringer, Mackie, Samson, Tannoy, Yamaha, Roland, etc, etc. make teriffic pro speakers that are inexpensive.

I bet anything there is nothing wrong with your mixer - or your Blackmagic card.

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 13, 2011 at 11:15:56 pm

I agree TOTALLY, I have believed all along it isn't the Blackmagic card, the mixer I was in two minds about.

I was only testing with what I had around, before I go out and spend more money on a guess, which is what I have been doing. I have two mixers now, because at first I was sure it was the mixer. So before I go out and buy a decent set of speakers, I want to make sure they are the cause.. I have a beautiful Luxman Amp in the garage that is collecting dust. It hasn't seen much use and although it is overkill, if this is the issue, (speakers) I will hook up the Luxman and I have my eye on a pair of bookshelf Cerwin Vega's.

I just used a pair of Altech Lansing Self Powered speaker. Although they are not As good as monitors or hifi speakers it was an experiment. I just hooked them up to the TS Left and Right OUTPUT on the mixer via RCA and RCA to 6.5mm Adapters. Which is exactly how I have the MS2's Hooked up.. AND yes I have tried several different RCA cable etc. At the moment I am using a good pair of Monster RCA's. I am still experimenting.. Now I am about to get the Luxman, dust it off and hook it up with a cheapo pair of NON powered speakers I have.. Depending on the out come, I will leave it like that and get a GOOD pair of Bookshelf's.

Tony


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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 14, 2011 at 1:16:13 am

Well Bob all I can say is everything I try confuses the Hell out of me even further...I am really grateful for all your experienced, educated information and advice...
If I could take a little more of your time to explain my further confusion even further, and whether after all this I MAY? have a faulty Decklink? I firstly plugged in the amp and some UNpowered speakers of course.

1. First thing that happened. Left Channel DEAD Or One channel Dead?? This has been happening a bit from time to time even after trying different TRS cables...I only had Channel ONE and Two out of the Declink into Channel One And Two of the mixer.
2. Unplugged DEAD Channel, and I was getting sound from BOTH speakers???? Panned Left to Right Both working.. Declink Channel ONE only into Mixer Mono TRS channel One ONLY.. Yet sound from both speakers? Is this Normal???
3.Plugged the DEAD Channel Back in, now working... Got the little NEW Peavy 6 Channel Mixer out and tried that. All worked so far.
4. Plugged Channel 3 and 4 out of the Decklink into 3 and 4 into 3 and 3 on the Peavey Mixer and both sets worked fine.. Only tried One set at a time. So Chan1 and 2, then 3 and 4 but no distortion at all.
5.Plugged everything back into the yamaha INCLUDING channel 3 and 4, Which have never worked in the yamaha mind you, and EVERYTHING worked for the first time.. Again only 1 and 2 at one time then 3 and 4, but this has been the way I have tested all along. Thought I would try to get two channels at each time before moving to 4.? Went back to the original configuration and there was the distortion all over again on Channels 3 and 4 of the mixer.

I am LOST.. ? Never had an issue this Bazar, and I have seen some Bazar issues.. I used to work as a computer tech, Microsoft Certified and come across my share of weird things. Not audio related of course?

DO YOU have any idea of what the Hell is going on here. I have tried everything I can think of now, short of pulling the Decklink out and re-setting it. unfortunately I don't have a spare PCIe Slot. But I have tried removing the large connector on the back and putting it back in making sure it was firmly in and tightened.

Tony


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Nick Stephens
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 14, 2011 at 6:57:20 am

Hello Tony,

The distortion you are experiencing is because you are only getting half the waveform (the positive half with respect to ground). The other half effectively becomes a square wave (which never sound nice).

A balanced signal consists of 3 wires:
1 - Ground (Sleeve on TRS)
2 - Positive signal with respect to ground (Tip on TRS)
3 - Negative signal with respect to ground (Ring on TRS)

If you plug a balanced signal into an unbalanced input you will often only be terminating the Tip and the Sleeve (Ground & Positive with respect to ground).

What you need to do is connect a short link wire between the Ring and the Sleeve, effectively combining the negative signal with respect to ground, to ground.

Some unbalanced 1/4" sockets mechanically connect Ring and Sleeve, but not all, sound like yours do not.

Bear in mind that this effectively "unbalances" your entire input cable so you lose all the common-mode rejection advantages of a balanced signal. Depending on the signal level, length of your cables and environment, this could be a real problem.

I suggest you get a better mixer that helps you keep everything balanced. A good quality, low cost mixer is the Allen & Heath Zed 14 which also has an internal USB audio interface. Great for getting audio in and out of your PC!


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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 14, 2011 at 8:54:40 am

Well Bob and to all reading this post. I MAY have finally solved it... Although I have changed all cables many times, I finally just thought I would go out and buy a whole set of new cables.. ALL OF THEM.. As Well as this I removed the large connector on the back of the Decklink card and sprayed it with contact cleaner.. Put everything back with new cables and everything is working perfectly... FINALLY... But with out speaking too soon, I will try it again FIRST thing in the morning cause often that would be when the left channel would play up.

So Bob and all that offered assistance I am MOST grateful and I hope this post may help others... Even when I was certain all my cables and spare cables were fine, SO FAR they obviously were not.

Tony


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Bob Zelin
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 15, 2011 at 4:31:00 am

Hi Tony -
this is the unfortunate lesson that we all learn. When you do plumbing, when you do painting, when you do body work on your car, when you do lawn work, when you cook food, or WHEN YOU DO PROFESSIONAL AUDIO OR VIDEO WORK - if you don't have tools that work, then you are screwed, and you will suffer. This is easy for me to say, because it's not my money. But I often have said - you can't be a taxi cab driver if your car is breaking down all the time.

If you are relying on junk lying around your garage, then you will always continue to suffer. If you do this for a living, you should only have one goal - to buy PROFESSIONAL EQUIPMENT, and not the cheapest thing you can get your hands on. Ever try to paint a room with .99 paint brushes from the dollar store ? Ever try to get a dent out of your car from crap you get in the auto section at K-Mart. It doesn't work - does it ? If you are doing PROFESSIONAL VIDEO, you need PROFESSIONAL EQUIPMENT, and Blackmagic is a unique company that makes superior quality equipment at super low budget prices. But if you don't have EVERYTHING ELSE - that includes REAL cables, and REAL outlet strips (not the skinny white wires with the 4 outlets on the end) - then you will continue to fail and suffer.

I know that all of this ultimately costs money. Perhaps you should consider robbing a store in your neighborhood to get what you need.

Bob Zelin



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Tony Ienco
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 15, 2011 at 4:37:52 am

Well Bob, with the UTMOST RESPECT, Even with the new cables, the same thing is happening. I don't mind spending the money, but I like to make sure what the problem is before I go and lash out.. I have just ordered a $600 dollar Allen & Heath Mixer so I will see how it goes tomorrow, BUT I believe you may have mislead me and put doubts in my mind... You specifically said IT WILL NOT BE THE MIXER?? I Feel it still could be because channel 3 and 4 on the mixer are doing the same thing when I plug 3 and 4 or 1 and 2 out of the Declink into it. If I am wrong, and I will know tomorrow, I will eat my words. I do agree that it is very unlikely to be the Decklink but do not agree about the mixer at this point as it is the only thing left in the chain to be at fault. Thanks all the same.

Tony


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Nick Stephens
Re: Decklink Studio, Mixer, Y cable?? PLEASE..
on Dec 15, 2011 at 4:55:01 am

Tony, please read my post again.
I guarantee that the problem you are experiencing is because your mixer does not terminate Sleeve to Ring on the unbalanced 1/4" inputs.
Apart from the "distortion" you describe, the other big clue is that they are using TRS connectors for inserts and almost certainly using the same component part for the line inputs.
You could "fix" the mixer by opening it up and soldering a wire between Sleeve and Ring (either on the socket or the PCB, whichever is easier).
Or you should use standard 1/4" TS (mono) jack to jack cables (which obviously connect Sleeve and Ring by design).
I have to agree with you that Bobs posts have been somewhat misleading and unnecessarily sarcastic, patronizing and derogatory. This is why I posted my response to clarify the facts for you.
Glad to hear you are getting an Allen & Heath, the Zed 14 in particular is a good mixer and excellent value.


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