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Author Topic: DMA8 audio dropouts noise Hordur Valgardsson Film Handler Posts: 25 From: Reykjavik, Alfabakki, Iceland Registered: Oct 2009 posted 12-26-2009 09:35 PM                        Hi all we have been showing various live events (metropolitan operas etc..) at our cinemas set up is : Topfield reciver connected with optical cable to DMA8 and a CP650 processor problem : - at random times audio played through the topfield satellite reciver makes alot of noise and audio drops out. to stop the audio noise we have to switch between inputs on the DMA8 - this problem does not occur in the TV (the topfield is also connected to a TV monitor via-scart cable) - the DMA8 goes to it´s default settings at random times wich causes a problem since the default setting does not have the optical input selected so if this happens we have to connect a laptop to it and reconfigure it. - i figure the problem is most likely to be caused by the DMA8, especially given the fact that it goes back to it´s default setting at random times, however there is no noise issue when we playback anything from other inputs through the DMA8 right now it has firmware DMA8 v2041 i tried to upgrate it´s firmware with DMA8 v2045 but i always fails, i also cannot open the log it always gives me errors when i try to view it. what makes this problem really annoying is that it happens totally randomly, is there a way to check if there is something wrong with the DMA8 unit itself before i get a audio specialist to check the optical cabling i figure the problem could also be the optical cable or some sort of interference or the cp650. any of you had this issue ?  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-27-2009 05:23 AM                     Is this the original DMA8, or the DMA8 Plus? I've only used the Plus. The Plus has an LED for each digital input which shows that a valid input signal is being received on that input; strictly speaking, I think it indicates that the DMA is seeing a valid clock on that input. I'm not sure if the original DMA8 also had these. If your DMA has these LEDs, what state is the one for the optical input in when you get the noise, and when the sound drops out? I don't know anything about the receiver; does it have a co-ax S-PDIF output in addition to the optical one? If it does, you could try connecting this to the DMA8. The original model has a co/ax S-PDIF input, the Plus does not, but it has two AES3id 75 Ohm inputs on BNC sockets, Digital 2 and 3. While the Voltage levels, and some of the metadata are not strictly correct, these inputs will accept a S-PDIF signal via a simple plug adapter. If your receiver doesn't have a co/ax output you could provide one via an optical to co-ax adapter; they're not expensive, and you might be ale to borrow one from somebody. I think it's unlikely to be the optical cabling that's at fault; if it was then it would be likely to just stop working permanently, and certainly not come back just by selecting a different input on the DMA. Some people do claim that Toslink optical is unreliable, but I've never had problems with it. You're not running it through a long cable, are you? The very large diameter plastic fibre is only suitable for short distances, ~10 metres or so. How long does the noise last before the sound drops out, and when you have the noise can you still hear the sound as well, or can you only hear noise? If you can still hear the sound as well then this is a pretty strong indication that the fault is with the DMA. Do you have anything else with an optical output on it that you could try playing through the DMA? I would say that the most likely cause of the fault is the DMA, followed by the receiver, with the cabling least likely. Hordur, I've just noticed that this is your first post. Welcome, merry Christmas and a happy new year.  |  IP: Logged Demetris Thoupis Phenomenal Film Handler Posts: 1240 From: Aradippou, Larnaca, Cyprus Registered: Apr 2001 posted 12-27-2009 05:47 AM                     Try a different optical cable. There are optical cables where the fibers are not long enough and thus have drop outs. This happens a lot with PS3 equipment as I have tried various optical cables to find a suitable one which works. One suggestion would be to use a cable where the fibers extend a bit out from the connector and snip them slightly until they fit in the Toslink connection. From there on you should not have a problem. Demetris  |  IP: Logged Hordur Valgardsson Film Handler Posts: 25 From: Reykjavik, Alfabakki, Iceland Registered: Oct 2009 posted 12-27-2009 09:35 AM                        Hi and thanks for your suggestions, great forums you guys have here we have the original DMA8 not the plus there are no led´s on it only a couple of buttons to switch inputs it is not possible to hear the original sound when the sound interuptions come, only a very loud digital interferance blasting into the auditorium, sometimes it lasts only a couple of seconds but sometimes inputs has to be switched back and forth on the DMA8 to be corrected. the optical cable length is around 20 meters and we do have a optical magnifier box, i guess that could also the problem, i hadn´t thought of that until you mentioned the cable length the receiver does only have an optical output for the sound (well it does also have HDMI wich should also transmit the audio) and we do have a scaler that has HDMI and optical inputs/outputs but then we would have to connect the optical out on the scaler to the DMA8 anyways to convert the signal for the cp650. also weird that i cannot flash firmware or view the logs in the DMA8 wich is another thing that points to the DMA8 being faulty also that it sometimes goes back to its default settings and the fact that sometimes inputs have to be switched to fix audio glitches. i guess the first thing to try is to move the receiver box and have no optical magnifier/repeater and use a short cable and try that. would you agree or is there something i am missing ? thanks  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-27-2009 10:42 AM                     I am unclear as to what this 'optical magnifier' box is; is this some sort of repeater to extend the length of the cable? If so, how long are the cables on each side of it? Has this worked ok in the past, or have you always had this problem? Try a short cable and see if this makes any difference, it's easy to do, and doesn't take long. If you could still hear the sound, along with the noise, then it would indicate that the digital signal was getting to the DMA, and being decoded, and that the fault was after this, but since you are not hearing the sound, then the fault could possibly be in the receiver, the cable or the DMA. Are you using any of the other inputs on the DMA for anything, and if so, are you having any problems when using these inputs? 20 m is rather longer than Toslink optical interface is designed for, though I have seen cables of this length. If the 'magnifier' is some sort of repeater then it should work, but some of these devices do not seem to be of very high quality. If it is simply a coupler, joining two cables together, then I think you may well get problems, due to the length of cable, plus the join between them. If a short cable cures the problem then I would suggest either permanently re-locating the receiver closer to the DMA, or installing an optical to co-ax converter close to the receiver, and then a length of good quality co-ax cable from there to the DMA. If you still get the fault with a short cable, which has been tested with other equipment, and known to be good, then it sounds like you might have a faulty DMA. Test with some other equipment connected to the optical input if possible. The fact that switching inputs, and then going back to optical clears the problem does tend to point to a DMA fault, but I think it's also possible that the DMA is receiving a poor signal, but is just about able to decode it. If however the signal gets slightly worse for a moment then the DMA may lose its clock from the signal, and not be able to decode it correctly, which might produce random noise until the DMA detected what had happened, and muted the signal. It's a pity that the original DMA doesn't have a valid clock indicator on the inputs. Once the sound has cut out does it stay that way, or does it come back after a while if you don't do anything? What format is the sound in, is it simple 2-channel PCM stereo, or multi-channel Dolby Digital or Dolby E?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-27-2009 01:09 PM                     Okay...on the update thing...the DMA8 really wants a proper com port rather than a USB interface...a USB interface will work to some degree but expect it to drop out/disconnect when the timing doesn't meet the DMA8's requirements. One has to have the proper software based on the DMA8's firmware to do an upload or you will kill it. Make sure you have software 2.0.4.1 running on your computer. The other thing to check on your 2.0.4.5 firmware is that it should be a *.bin file...Dolby's web site (if downloaded from there) is notorious for making everything a .exe file...you have to rename it As for a 20-meter Toslink...WOW. Consumer stuff just isn't designed for long distance and TOSLINK is a fragile cable too. Consider converting to coax using one of several converters (I use RDL and Kramer). In the DMA8...go into the settings and tick on the "silent switch" mode. This will add about 40msec of delay but should avoid the nasty digital spurts. I agree with starting with a shorter cable (5-meter or less). You can also tell the DMA-8 what inputs to cycle through (only have the ones that have something connected listed and leave the others unassigned). You can leave the Optical in the 1st choice position.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-27-2009 03:01 PM                     I just tried sending a signal over a long Toslink cable; I have one 10 metre cable and three 4 metre ones, all of good quality. A 4 metre cable joined to the 10 metre one with a passive coupler worked, a 10 metre coupled to two 4 metres didn't, and neither did three 4 metre cables coupled together. I'm still not clear what Hordur's 'Digital magnifier box' is, whether it's a repeater, or just a passive coupler. If it's just a coupler then I think it may well cause problems; my signal certainly didn't like going through two couplers. If it is a repeater, and it's close to the centre of the cable, then it ought to work, but I've had bad experiences with these devices, though never with just a single length of optical cable, either 4 metre or 10 metre. I would be inclined to avoid the use of Toslink fibre cables over this distance, even it the present fault does turn out to be elsewhere. There's a lot of optical dispersion and attenuation in this plastic fibre. Even if it works now, with a bit off fall-off in emitter output, or an increase in attenuation of the fibre as the equipment ages, it might not work in the future. This is taking the use of such fibre close to its limits. The effect that I get with the long coupled cable is not the same as Hordur is getting, but I'm not going into a DMA8. I have used the optical input on a DMA8 Plus in the past, but only with a 4 metre cable. What I hear is nothing most of the time. With the 10 metre and 4 metre cables and one coupler I occasionally get a brief burst of sound, and then nothing again. With the three 4 m cables and two couplers I cannot get it to work at all.  |  IP: Logged Hordur Valgardsson Film Handler Posts: 25 From: Reykjavik, Alfabakki, Iceland Registered: Oct 2009 posted 12-27-2009 05:32 PM                        I tried updating the DMA8 through a serial cable (A usb to serial adapter cable since my laptop doesn´t have serial port) so i guess i will need to get a laptop with a proper serial port, although i am skeptical that this usb-serial adapter cable is at fault since since it has worked and updated firmware through serial ports on various other devices) i am running remote software v 2.0.4.1 and got the .bin file 2.0.4.5 from sound associates wich installed our system regarding the optical box, it is a repeater my satellite guy installed and reccomended since we were unable to get the audio without using it web pageoptical repeater the box is at the same spot as the satellite reciver connected with a 50cm toslink cable then the 20meter optical cable runs from the repeater to the DMA8 thanks for your suggestions, to summirize and hopefully i am not missing anything - me not being able to update the DMA8 cause of serial-usb adapter cable and unrelated to the audio dropouts - audio drops out cause of long toslink cable and signal just baerly making it to the DMA8 - weird about the DMA8 going back to default settings, perhaps it is a combination of switcing inputs back and forth and the weak signal strength of the optical input confuses it ? - once the sound drops out it does come back without switching between inputs but it is faster if we switch between inputs - all other inputs on the DMA8 work fine the first thing i´l do tomorrow is move the topfield to the same spot as the DMA8 and stop this nonsense of using repeaters and 20 meter toslink to eliminate that as the problem. it´l also be interesting to see if the firmware upgrade will work with a normal serial port  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-27-2009 06:35 PM                     Hordur, From what you've added since your first post, I now think it's more likely to be the cable that's the problem. quote: Hordur Valgardsson the box is at the same spot as the satellite reciver connected with a 50cm toslink cable then the 20meter optical cable runs from the repeater to the DMA8 That's a very cheap device, 20 metres of cable on one side of it is also pushing things to the limit. You might do better with two 10 metre cables with this thing in the middle, but moving the receiver closer to the DMA would be better if you can, or using a good quality optical to co-ax converter and then good quality co-ax cable if they have to be this far apart. I wouldn't recommend extracting the audio from the HDMI signal and then sending this over optical either; you'd then be using two interfaces which are only designed for short distances. I've never upgraded the firmware on a DMA8, so I can't comment on that. I've got a few other things to add, but it's past midnight and I'm going to bed now. Let us know how you get on.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-27-2009 08:06 PM                     I've done the upgrade many times without problem. I do use a SocketCom PCMCIA adapter though. I note the optical repeater you list has only one review and it is not favorable...noting that it has a very weak level. This is the sort of device that you want: http://www.rdlnet.com/product.php?page=25 It isn't $10.00 but it works and not only will repeat but also convert. Steve  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-28-2009 06:20 AM                     Last year I went to a cinema, and after the show went up to the box to see the chief. I hadn't been up there since the digital equipment was installed. They were also running live shows, but I don't think it was Met. Opera. Sitting on top of some other equipment was the receiver which had been installed as part of the package. It was a horrible thing, flimsy plastic case which didn't even fit together very well, poor quality connectors, d.c. power input socket with a plug which was so loose that it fell out if you knocked it. Only outputs offered were HDMI, Toslink and a SCART, which presumably carried a SD output. There was a power on/off button, which felt like it would break at any time, and all other functions could only be accessed via an IR remote control, No RS-232, 422 or 485, or even connections for control by dry contacts. It was connected by some of the nastiest cables that I've ever seen, which presumably came with it. We have a similar problem at the college, where some of the older ceiling-mounted video projectors in classrooms, and also the signal sources in a language lab have no remote control inputs, and are controlled by an IR LED stuck onto the front panel, and which generally falls off after a few months. We are now using a different installer, which provides a much better system. Contrast this with the other equipment installed in the cinema, Kinoton 35mm, old but still good, Irem rectifier, Fumeo 16mm, digital cinema projector, Christie Cine-IPM 2k, Dolby CP-65, decent amps, good quality D-A converter, though it wasn't a Dolby DMA. All decent kit, so why the horrible receiver? 'It is what was supplied with he package' was the answer which was given. It seems to me that some of the equipment being supplied to cinemas for these live shows is not really fit for its purpose, and (I hate to use this word, and have avoided it before but I will use it now) something more 'professional' should be installed. Something where you don't lose power if you touch it, which isn't about to fall to bits, which is safe, which can be controlled by standard interfaces, which provides outputs which can go a reasonable distance on decent quality connectors, and if it can be rack mounted, so much the better. The Toslink repeater which Hordur is using also seems barely fit for its purpose, though we don't know yet if that is part of the cause of his problems, and his receiver is somewhat lacking in outputs; why no AES, or at least co-ax S/P-DIF, which given that he has the original DMA8 might be better in his case, outputs? Nobody would think it reasonable to supply a cinema with $50 Radio Shack speakers, so why do they supply such poor quality receivers as the one which I saw? Is nothing better available? Is it because most cinemas are unfamiliar with this sort of equipment, and basically don't know what they are getting? Any comments?  |  IP: Logged Mark Hajducki Jedi Master Film Handler Posts: 500 From: Edinburgh, UK Registered: May 2003 posted 12-28-2009 04:53 PM                     Have you used any other satellite boxes in the past, and did they have the same problems?  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 12-29-2009 02:27 AM                     quote: Stephen Furley Nobody would think it reasonable to supply a cinema with $50 Radio Shack speakers REALLY?? Don't be so sure about that! OK Here in the UK we only have Maplin Electronics these days, but it's the same difference. The horrors I have seen and heard, all in the name of 'cheap'  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 12-29-2009 05:50 AM                     When Maplin first started they were quite good, certainly far better than Tandy (Radio Shack). However, since the demise of the latter in the UK Maplin have really gone downhill. Actually, they're not so bad if you order from them by post, but that brings in the problem that I'm not at home when the post comes. The shops however are almost totally useless, and if you leave out the 'almost', that would be a fair description of many, possibly most, of their staff. There are exceptions; I was recently served in one of their shops by an Indian lady, significantly older than their typical staff, who was very good, but sadly she's the exception. Apart from the fact that most of the staff are useless, the shops seem to keep hardly anything in stock, other than disco equipment and gimicky items. If you're looking for components, forget it. Last year I needed some small PCB mounting relays, six of them. After visiting several branches I finally found one that had some in stock, two of them. The young man behind the counter said he could order me some, or there was another branch, far away, and difficult to reach by public transport which also had one. He said he could order me another two. I told him that I needed another four. He couldn't order that many; it was higher than his stock level. I pointed out that he wasn't putting them into stock, he was selling them to me, but he insisted that he couldn't order that many. These things cost about 60 pence each, and are about 18x8x5 mm; hardly something that it's difficult to keep in stock. I tried another branch, who had none in stock, but said they could order six, but didn't know when they would be in. Two weeks later they still hadn't arrived, so I canceled the order, and ordered them on-line; they arrived the next day.  |  IP: Logged Hordur Valgardsson Film Handler Posts: 25 From: Reykjavik, Alfabakki, Iceland Registered: Oct 2009 posted 01-04-2010 08:42 AM                        Hi all we have now moved the satellite receiver to the same spot as the DMA8, since we were not able to reproduce the errors we will just have to see if it keeps happening. thanks alot for all your advice i´l keep you guys posted weather it was in fact the DMA8 that was faulty  |  IP: Logged

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