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AV8/P7 Sound Cut out

Discussion in 'Arcam Owners' Forum' started by luddite2, Apr 19, 2004.

  1. luddite2

    luddite2
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    Has anybody come across P7 cutout with Master and Commander at 12 and half minutes approx?Occurs at 45 on db panel readout (not loud).Using DV89 as source.Arcam investigating just wondering if anyone else had similar with same kit or different arcam kit?Cheers.
     
  2. BigAl217

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    Had to try this out and mine does the same at around 12mins 40 secs.

    I have to say it is bloody loud on my system though and i'm sure its some sort of safety cut out, all channels shut down go red except stereo / front r & l, which start to flash green. According to manual this is a DC offset fault and amp needs to be powered off and back on to reset.

    Im feeding my AV8 P7 with a DV27 would be interested to know what Arcam come back.

    Regards
    Alan
     
  3. luddite2

    luddite2
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    Yep that's the same fault they are aware of.Any other dvd high action scene will not trigger the same fault at considerably higher level-I think "THX" is at 53 on db scale.This level and louder ok with other source material but as I said 43 will trigger fault with M and C.I'm sure Arcam will figure it out.Cheers.
     
  4. mightyoakbob

    mightyoakbob
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    The same thing happened to me on Easter Sunday with my AV8/P7 when watching M&C. I contacted Arcam last week about it and I was a little relieved when they told me they were already investigating the problem and mentioned Pirates of the caribean as another disc with the same issue.

    Apparently there is some DC offset recorded on the DVD to add to the sound effects, I'd love to know what effect that has.

    Now for some pure conjecture on my part. The implication of the above is that the AV8 and P7 are in the most part DC coupled so it is difficult for me to see an easy solution. Fitting series capacitors into the interconnects would not be popular I wouldn't think. So is it a case of making the P7 less sensitive about small quantity, short duration DC? Maybe that could be done as software rom change in the P7 or possibly a resistor value modification. It will be interesting to see what they manage to come up with.

    Cheers,

    Bob.
     
  5. luddite2

    luddite2
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    I guess from limited response to this problem there are less of these machines owned by forum readers than I thought!!
    I have no prob with "Pirates..." at high volume.I saw another thread about someone using P7 with Tag Processor-if you happen to read this does Master play ok on your setup as if it does it will be AV8 that causes problem for AV8/P7.I'm trying to trouble shoot as nothing from Arcam yet.Has the same problem reared it's head with any other releases yet?Cheers.
     
  6. mightyoakbob

    mightyoakbob
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    I'm not sure about your suggestion that if the tag-processor/P7 doesn't give the problem it is therefore the AV8 that is the cause of the problem. It *could* mean that the tag is not dc coupled and just not as good as the AV8.

    Seems to me that both the AV8 and P7 are DC coupled so as to remove capacitors from the signal path for sound quality reasons. Knowing this would sound good but at the same time make the P7's life more stressful they decided to detect any DC offset in the output and shut it down. If quality of sound is your goal it sounds spot on to me.


    They clearly didn't expect CDs and DVDs to have DC deliberately encoded on the discs. There may at some time be a fix available for the AV8 and/or P7 but I'm not sure that proves either to be at fault as such. My money is split because on the one hand, the AV8 looks to be doing a perfect job with a dodgy signal so therefore the P7 needs a tweek on the other hand, it is much easier to change the software on the AV8. Time will tell.

    Speaking of software upgrades is everyone using version 3.0 I seem to be on version 2.4. Has anyone done an upgrade themselves? My dealer says he has no problem with me doing it.

    Cheers,

    Bob.
     
  7. luddite2

    luddite2
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    How do you know which software the machine(s) are using?As for the technical side of this problem I am way out of my depth.In a nutshell I want my system to play DVD's-simple as that-and so am trying to find the "problem" from my point of view and cure it or get rid of it as we (my family) do not want to end up with a bunch of DVD's that don't work (as I assume M and C is just the first) in the interests of sonic excellence.That's just me-cheers.
     
  8. mightyoakbob

    mightyoakbob
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    I don't think there is any great secret about finding out what software you're using although I can't understand why this information is not in the user manual. On the AV8 simply hold down the OK,CD,DVD buttons on the front panel simultaneously. You then step through each item of software for its version. I assume that the first one, "AV8 version" is the most significant.

    The P7 is a different matter. I wouldn't think there is any way for a user to obtain this information.

    Your position about wanting your system to play every DVD as apposed to absolute sound quality is perfectly resonable. For me, it would depend on the degree of sound quality loss - given the choice.

    Cheers,

    Bob.
     
  9. luddite2

    luddite2
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    "mightyoakbob"-it worked!!!!!My AV8 is using Version 2.4 same as you.Cheers.
     
  10. ANDY_DUTTON

    ANDY_DUTTON
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    Hi,

    I have checked the Master and Comander DVD here it has a period of about 400mS arround 12:40s that has a significant DC bias. About 0.5V on the preamp outputs (i.e a significant parts of the available range has been taken up by DC as the outputs are 2V rms)

    As has been mentioned here before both the AV8 and P7 are DC coupled with servos to remove any DC offset. This is to preserve the bass timing and improve sound quality by removing electrolicitc capacitors from the signal path.

    For this to work we rely on CD and DVD manufactures not to record DC on their disks. It has no benifit as you cannot hear it all it does is make the drive units cones flap about, so there is no reason to record it on the disk.

    We cannot change the DC detector time in the P7 as it is a hardware feature and to AC couple the AV8 all the time would compromise the sound quality.

    However you can solve this problem by creating a preset configuration using the THX or THX EX settings in Speaker Sizes menu. This will create a speaker setup using all small and direct all of the base to the subwoofer (or you can manualy set all speakers to small with sub present if you prefer) . This effectively AC couples the AV8 in the digital domain and your subwoofer will almost certainly be AC coupled so will not have the same problem.

    This preset can then be used whenever you have a disk that has been incorrectly recorded with DC on it. I would recomend using your standard configuration for other disks (unless you have a THX type sub sat set up in which case you should not have seen this problem anyway) as you will get better sound quality.

    Best Regards,
    Andrew
     
  11. warrj

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    Hmm. I just watched M&C at the weekend using an AV8 and Roksan AV5 Power-Amp. I didn't experience any problems. I'm actually considering an upgrade of power amp and the P7 is on my shortlist. However, I wouldn't feel confident about buying one knowing that there were issues with it.

    I must admit I don't understand the technical issues involved and I believe that I shouldn't need to. However I was (erroneously it would seem) under the impression that power amps were (relatively) simple beasts and all they do is amplify a line-level signal - a task which they've been performing without too much trouble for decades. Is there really more to it than that?

    Regards,

    Jules.
     
  12. John Dawson

    John Dawson
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    Jules -

    There are no issues with the AV8/P7 in normal use - what I believe we have here is a disc recorded with a stupid amount of DC on it at one point. This is wholly inaudible and really should not have happened. To the best of my knowledge we have not come across this issue before so we can be pretty confident it is not normal mastering industry practice. The amount of DC Andrew found is equivalent to a 12 Volt (!!!) DC offset at the output of the power amplifier at full drive and is sufficient to bottom the cones on ported (reflex) speakers which is wholly undesirable. If it were me I would complain to the makers of the DVD concerned so that it can be fed back to their mastering house.

    We fit DC offset protection to our power amps to prevent such things damaging your speakers - you never see it in action unless it needs to be!

    We have suggested a simple workaround which is in many cases exactly what a customer would already be using in his normal setup anyway - i.e to redirect really low bass to the subwoofer. It is only when you have some of your main speakers set to large that this erroneous disc triggers the system protection, and for good reasons.

    So you can buy that P7 with confidence!

    HTH

    John Dawson (Arcam)
     
  13. Urotsukidoji

    Urotsukidoji
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    Would it not have more impact if Arcam themselves contacted the makers of the DVD?
     
  14. luddite2

    luddite2
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    John and Andy thanks for the information.Sounds like it should be "fixable" but I'll re-read tomorrow when London Pride has subsided and then go play with the knobs and menus and see if we can get past the dreaded "12:40--Ah the seven has stopped and the point one is lonely!!!!"Cheers.
     
  15. mightyoakbob

    mightyoakbob
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    I would like to thank the guys from Arcam John and Andrew for both looking into the problem and taking the time to come and talk to us on the forum.

    I have to agree with their opinion that neither the AV8 or P7 is in any way at fault. They were both designed to get the very best out of any sensible source. The problem here is that this disc is not a sensible source. If another processor/amplifier combination does not suffer the safe (or worse) problem, it is very likely that that system has a much more restricted performance.

    Going back to Andrew's solution. I do not have a subwoofer and therefore I would like to know what cut-off frequency is applied when the speakers are set to "small". I would also like to know if there is only one burst of this problem on the disc. If so, I would just drop the volume or skip that period on the disc. I've not been near that disc since it nearly gave me heart failure. :)

    Cheers,

    Bob.
     
  16. John Dawson

    John Dawson
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    Bob - I don't have the manual in front of me but from memory 40 or 50Hz is the lowest cut off frequency - you can choose it over quite a wide range. That won't IMO make a huge difference to the sound as most even quite large full range speakers are already falling away at that kind of frequency. However I am not much into trouser flapping or chest rattling bass!

    You could pick the "small" speaker setting just for that movie if you liked, or even the offending chapter. Please try it and let us know what you think.

    Does anyone on here know of any other places on the DVD where this DC effect happens?

    John Dawson (Arcam)
     
  17. luddite2

    luddite2
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    Yep picking THX EX in speaker set-up (with seven spkrs) cured the problem as I presume would setting small in the size menu.I don't think we ran the film through after 12:40 at a level which would have triggered the same problem if there had been any more recorded on to the disc so can't help John there as to "is there any more".Ditto with thanks for tech input here as it's a lot easier and quicker.Cheers.
     
  18. LarryCable

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    I am having real problems with my new AV9/P7 combi cutting out at arbitrary time(s) ...

    Seems like the P7 is tripping a cutout ...

    not the behavior I expect from any amp never mind such an expensive one ...

    anyone got any clue as to the probable cause(s)?
     

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