Official OPPO BDP-105 Owner's Thread - Page 343 - AVS Forum
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Old 04-24-2014, 07:23 AM
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Originally Posted by OmarF View Post

COUGH COUGH COUGH :-)

Omar

Play nice! biggrin.gif

You discovered a problem, and your insistence that there WAS a problem was a key factor in getting this sorted out.

But Dan actually found the bug -- i.e., what needed to be fixed.
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Old 04-24-2014, 07:45 AM
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LOL

I've no intention of minimizing his part...just claiming my own :-)

Omar
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Old 04-24-2014, 07:45 AM
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As long as were are talking long-standing bugs with Analog output, I might as well re-mention my other fav.

The Crossover setting incorrectly attenuates high frequency bass from LFE content.

That is, if you have a Crossover set to 40Hz, the LFE content sent to the Sub is rolled off above 40Hz. LFE runs up to 120Hz, although the meat of LFE is found in the 40-80Hz range (with additional energy below 40Hz in some tracks that's more felt than heard). So with a typical Crossover of 80Hz, the modest rolloff between 80 and 120Hz would usually not be noticed because there's not much LFE above 80Hz to begin with. But if you set your Crossover low because you believe (perhaps mistakenly) that your main speakers can really handle things that low all on their own, then LFE content you SHOULD hear in the Sub gets lost.

That's "lost' -- not "steered" to the main speakers.

Note that the bug only affects LFE content. The apportioning of bass coming in as main speaker content between the mains and the Sub (i.e., normal Crossover processing) works correctly for all Crossover frequency settings. Bass that's attenuated from the main speakers is mixed into the Subwoofer output -- not lost.

I fear the reason this one has not been fixed is that it is baked into the hardware design.

The upshot is that you should not use a low Crossover setting in the OPPO if you intend to play multi-channel tracks with content in the LFE channel via the multi-channel Analog outputs.

(This bug has no effect on Digital audio output such as HDMI Audio.)
--Bob

I'm trying to make sense of this. Does this mean, if for example I set my crossover for 40 and my rears to small, that all the info from the rears below 40 will correctly be sent to the sub, but all the LFE information going to the sub will be attenuated above 40 Hz at the same time?

Does this only come into effect when some speakers are set to Small? Or should I always have my crossover set at the highest point, even though all my speakers are Large?

Omar

If all speakers are LARGE there is no issue. There's also no issue if you are using digital audio output (e.g., HDMI Audio), regardless of speaker settings in the OPPO.

If you are using the multi-channel Analog audio outputs, have the Subwoofer enabled for those, and have ANY speakers set to SMALL then this issue affects you.

My recommendation, in that case, would be to set the multi-channel Analog output Crossover in the OPPO no lower than 60Hz.



The meat of LFE is in the range 40-80Hz (with additional energy from 15-40Hz in some tracks -- bass that is more felt than heard -- which can be reproduced by better quality Subs). The Crossover is not a brick wall. It rolls into effect over a span of about an octave -- a factor of two in frequency. So a 60Hz Sub Crossover will start to roll off LFE to the Sub above 60Hz, but it doesn't cut it off suddenly. The upper end of LFE is 120Hz, but a 60Hz Crossover will have only a few dB attenuation at 80Hz, and so you are still OK since there's not much LFE above 80Hz in the first place compared to what's BELOW 80Hz.

And of course this only affects playback of tracks that actually include content in the LFE channel. Stereo tracks don't have an LFE channel, so no issue. And it is often the case that multi-channel music tracks, even though packaged as 5.1 or 7.1, don't actually have audio in the LFE channel. The main speakers channels are fully capable of carrying bass as low as the authors want to go. The LFE channel is special in that it is configured to carry LOUD bass. This is particularly true about SACD discs due to a screwup in the way Sony spec'ed LFE for SACD way back in the year dot. So you'll find studios (e.g., PentaTone) which have a policy of not putting content in the LFE channel of their SACD discs

As for the regular speakers, if you set your Crossover as low as 40Hz, what you are actually saying is that you believe your speakers are capable of quality output -- at VOLUME -- down as low as one octave below that -- i.e., all the way down to *20* Hz! It's a rare speaker that can do that. If your speakers don't have powered woofers (which basically means a sub built into the speaker cabinet) it's unlikely they can do that.

If your speakers are rated down to 30Hz (a not uncommon number), and you BELIEVE that number (given that speaker specs are often, umm, optimistic), then you should set the Crossover at 60Hz or higher to insure the speaker can continue to contribute its share of quality bass for a full octave below the Crossover.

There is no issue as regards the steered bass from the regular speakers. Whatever Crossover you pick, bass below that will be steered out to the Subwoofer.

Again, all of this only applies to the multi-channel ANALOG outputs.
--Bob

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Old 04-24-2014, 07:47 AM
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^ Okay, so just using the multichannel outs and having the sub activated is not enough. I'd have to set one or more of my speakers to Small. Cool...
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Old 04-24-2014, 07:49 AM
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^ CORRECT.
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Old 04-24-2014, 08:01 AM
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Quote:
Originally Posted by OmarF View Post

Quote:
Originally Posted by DanF8500 View Post

By the way, how does your multi-ch system sound now? biggrin.gif Is it a clearly different listening experience than before? It's remarkable that no one on the 10x forums, aside from Omar and Process, had noticed there was something strange going on. I know most were quick to judge and say something must be wrong with their home systems. Heck, even if this bug was introduced in the last release, that was in February. Two months ago. eek.gif

Dan, I noticed this all the way back with my 95, before they took away ISO processing. It's been pretty endemic. I would think someone at Mediatek was pulling an all-nighter trying to get his code done for a chip release, and no one ever bothered to verify his numbers. And I'm willing to bet that most OPPO users do their distance processing in an AVR of some sort.

Omar

The current scheme for speaker layout controls was introduced into the 93/95 a few months after the 95 was released -- in the 46-0428B Public Beta firmware released May, 2011, which became Official firmware in July, 2011. That would be a likely point for the bug to have appeared, but that's not been confirmed yet. If true, that would mean the later, ISO-capable firmware for the 93/95 *DOES* have this Speaker Distance Adjustment bug.

Countering that is tester memory that this stuff was checked out and used to work. Another likely point for the bug to have appeared is when the A/V Sync setting was introduced. That will be sorted out later -- after the fix gets released.
--Bob

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Old 04-24-2014, 08:10 AM
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^ Since we are talking Crossovers, I might as well complete the picture and point out it is ALSO a problem to set the Crossover frequency too HIGH!

First, of course, your Sub might not even be able to reproduce those higher bass frequencies.

But that aside, a high Crossover will send things to the Sub that are not really good to ask the Sub to reproduce -- such as the low end of male voices.

The Rule of Thumb to avoid this is to keep the Crossover no higher than 100Hz -- 90Hz or below is even better.

But of course a 90Hz Crossover means you believe all your regular speakers (including the Surrounds) are good for a full octave below that -- i.e., down to 45Hz -- which could be a problem for bookshelf speakers.

Sometimes you have to make a compromise choice.

And we haven't even gotten into how bass from each speaker/Sub couples with the room geometry (Room Response for bass). Bass configuration is a complicated topic. See the Audio Theory and Subwoofer forums here to learn more about this than you probably care to know.
--Bob
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Old 04-24-2014, 08:34 AM
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Folks I believe this was like this for some time. I could never figure out why it sounded so discombobulated. I tried directly to amp about 8 months ago and thought the same thing.

I agreed with most of you that it shouldn't sound as bad as I thought it did. Directly to amp should take all the noise out of an additional component. Now I know why it did. wink.gif
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Old 04-24-2014, 08:57 AM
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Quote:
Originally Posted by OmarF View Post

COUGH COUGH COUGH :-)

Omar
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Originally Posted by Bob Pariseau View Post

Play nice! biggrin.gif

You discovered a problem, and your insistence that there WAS a problem was a key factor in getting this sorted out.

But Dan actually found the bug -- i.e., what needed to be fixed.
--Bob
It was the butterfly effect. biggrin.gif If Omar had not brought his concerns/listening experiences to the forefront on the forum, I would never have bothered to want to test distance processing on my 105, thus nothing would have been resolved. If I had not been so adamant to share with Bob and the forum that the outcome of my 2-ch distance testing was amiss, the probing would have stopped, and again nothing would have been resolved. And if Bob had been a complete disbeliever that what some of us were hearing was simply a problem with "our" systems, and just shrugged us off (like some folks did), we all would have been back to square one, and this bug would have never been caught. I'm glad I continued to "press" him for answers. biggrin.gif We'd still have a few owners posting from time to time that something just didn't "sound" right in their home systems, but we may never have provided the real solution for them. As is obvious, there was a lot more probability for the distance bug to remain hidden like it has for quite some time, but it all worked out in the end for the better!! That's what matters the most.
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Old 04-24-2014, 09:05 AM
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It was the butterfly effect. biggrin.gif If Omar had not brought his concerns/listening experiences to the forefront on the forum, I would never have bothered to want to test distance processing on my 105, thus nothing would have been resolved. If I had not been so adamant to share with Bob and the forum that the outcome of my 2-ch distance testing was amiss, the probing would have stopped, and again nothing would have been resolved. And if Bob had been a complete disbeliever that what some of us were hearing was simply a problem with "our" systems, and just shrugged us off (like some folks did), we all would have been back to square one, and this bug would have never been caught. I'm glad I continued to "press" him for answers. biggrin.gif We'd still have a few owners posting from time to time that something just didn't "sound" right in their home systems, but we may never have provided the real solution for them. As is obvious, there was a lot more probability for the distance bug to remain hidden like it has for quite some time, but it all worked out in the end for the better!! That's what matters the most.

Perfectly said, Dan!
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Old 04-24-2014, 09:49 AM
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These are $200 K (plus lens) JVC professional projectors.
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Old 04-24-2014, 09:59 AM
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^ Well, sure. You can't expect them to throw in a lens for only $200K. biggrin.gif
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Old 04-24-2014, 10:10 AM
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Cool so you are using the audio analog from the OPPO? Is it the true 4K from JVC or their e-shift pseudo 4K ?

$200K (plus lens) JVC 4K professional proctors.
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Old 04-24-2014, 10:12 AM
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^ Well, sure. You can't expect them to throw in a lens for only $200K. biggrin.gif
--Bob

Not for 40' planetarium dome. My guess that the lens are around $30K each.
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Old 04-24-2014, 05:57 PM
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Again, all of this only applies to the multi-channel ANALOG outputs.
--Bob

Analog is beginning to seem as treacherous as HDMI.  ;)

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Old 04-24-2014, 06:00 PM
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Analog is beginning to seem as treacherous as HDMI.  wink.gif
Are you referring about the bug? Didn't find anything odd with the hdmi yet,what have you notice?
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Old 04-24-2014, 06:03 PM
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Are you referring about the bug? Didn't find anything odd with the hdmi yet,what have you notice?

Note the smiley.  I was referring only to the general criticisms of HDMI complexity compared to the long-familiar analog connections.


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Old 04-24-2014, 06:39 PM
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Quote:
Again, all of this only applies to the multi-channel ANALOG outputs.

--Bob
Analog is beginning to seem as treacherous as HDMI.  wink.gif
I've always thought so! biggrin.gif

My usual comment is Analog is Not for the Faint of Heart!
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Old 04-24-2014, 06:58 PM
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What's this about clipping of frequencies above the xover frequency? I thought a poster said something about it...

 

 

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Old 04-24-2014, 07:20 PM
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What's this about clipping of frequencies above the xover frequency? I thought a poster said something about it...

Yes, this is for the LFE channel when using analogue and bass management. Apparently it's part of the Dolby spec, and Oppo want to stay certified so won't change it. I've attempted to email Dolby to ask why, and let Oppo "fix it".
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Old 04-24-2014, 08:35 PM
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Yes, this is for the LFE channel when using analogue and bass management. Apparently it's part of the Dolby spec, and Oppo want to stay certified so won't change it. I've attempted to email Dolby to ask why, and let Oppo "fix it".

You can ask Roger Dressler who wrote the Dolby spec for an explanation.
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Old 04-24-2014, 09:37 PM
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What does it mean anyways? Are they talking about sharply filtering above the xover frequency? Clipping the amplitude of frequencies above the xover?


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Old 04-24-2014, 09:52 PM
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What does it mean anyways? Are they talking about sharply filtering above the xover frequency? Clipping the amplitude of frequencies above the xover?

The numbers Oppo gave me were, if the crossover is set to 80Hz then by 92Hz there's nothing left. The LFE channel is specced to 120Hz.
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Old 04-24-2014, 10:04 PM
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^ I think you've misunderstood what they said. Crossover filters are typically -12dB per octave. 80 to 92hz is only a small fraction of an octave. For a filter to leave "nothing left" over that span would be highly unusual.
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Old 04-24-2014, 10:06 PM
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Bob, here is the email text from Oppo copied and pasted:

For example, if LFE goes up to 120Hz, but the Crossover is set to 80Hz, then anything over 92Hz will be completely lost (92Hz since we use a 12dB octave/slope, with the nominal output being at 80Hz).
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Old 04-24-2014, 10:14 PM
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The description and the math don't match. An octave above 80 Hz is 160 Hz. An attenuation of -12dB/octave would mean only slight attenuation at 92Hz.
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Old 04-24-2014, 10:31 PM
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^

So this means never to listen to movies or other LFE-containing-content using MCH analog outputs if your xover frequency is less than 120Hz as it would be truncated. If this is Dolby spec, is this limited to analog only and not digital sources?


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Old 04-24-2014, 10:35 PM
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Wrong. I gave the correct information above. Please reread my post.
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Old 04-25-2014, 07:49 AM
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Quote:
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Bob, here is the email text from Oppo copied and pasted:

For example, if LFE goes up to 120Hz, but the Crossover is set to 80Hz, then anything over 92Hz will be completely lost (92Hz since we use a 12dB octave/slope, with the nominal output being at 80Hz).
That person is completely insane. As a hint for anyone with little-to-no audio engineering background, a basic understanding of general science and math will do. He talks about a 12dB/Octave slope on the crossover, but then is talking about frequency in Hz. He then proceeds to alter the crossover frequency by 12Hz, not 12dB, and gives you that number. THAT ALONE should be enough for you to have serious questions about the overall statement.

While understanding the meaning of the phrase "the crossover for the subwoofer is -12dB/octave" takes some audio engineering knowledge, seeing that the statement made above is complete tosh requires only moderately competent knowledge in math and science. Our grade-school eductions tell us that additions and subtractions, to be meaningful, have to be done using the same unit of measure. So here is the key: when thinking about frequency in the phrase "12dB per octave" - guess which 'word' has more to do with frequency. Hint - "dB" is about volume and "per" probably is not it ;-) He talks about a 12dB/Octave slope on the crossover, but then is talking about frequency in Hz. He then proceeds to alter the crossover frequency by 12Hz, not 12dB, and gives you that number. (He even manages to use "-12" and ADDS, as though he can somehow be even MORE wrong). The failure to use units properly should be enough for you to have serious questions about the overall statement, even if you are not an audio engineer.

Finally, as a reminder, dB is a ratio. It has not units, so can be applied to anything...but it represents a ratio. In our circles, however, it can be only loosely though of as a unit of volume. -12dB is half volume, not "completely lost." And an octave is a doubling (up) of halving (down) of frequency. So the net of this statement

"the crossover for the low-pass for the subwoofer is -12dB per octave"

means this
1) It is a low-pass filter, which means that lower frequencies pass through unharmed (hopefully ;-) and higher frequencies are reduced as follows:
2) A crossover at 80Hz means that frequencies at or around 80Hz are reduced by 3dB. (-3dB in mathematical notation, sometimes also called the '3dB down point')
For reference, 3dB represents, in most real-world settings, a reasonable minimum audible change in volume - i.e. anything smaller and you probably can't hear it
3) -12dB per octave means, for each doubling (in this case, because it is low-pass and not high-pass) of frequency (an octave) the volume will be reduced by 12dB. This puts you at about -15dB at 160Hz for an 80Hz crossover. (12dB down from where it was at 80hZ, which was already 3dB down, for a total of 15dB down) That is noticeably more quiet, but still quite audible in most listening situations. Similarly, the 320hZ band will be at -27dB.

So a good heuristic (rule of thumb) for understanding the phrase "low-pass at 80hZ and 12dB/octave" is to think "at a little over twice 80hZ (160hZ), the volume coming from the subwoofer is about half what it would be for frequencies below 80Hz."

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Old 04-25-2014, 08:38 AM
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Laird,

 

Thank you for the education. For those that are scrambling to find what it was that Bob said, it is pasted below. It seems he may be privy to something other than that -12db/octave filter. Either that or I still don't understand today's lesson. Perhaps Bob can clarify.

 

Quote:

Originally Posted by Bob Pariseau View Post


If all speakers are LARGE there is no issue. There's also no issue if you are using digital audio output (e.g., HDMI Audio), regardless of speaker settings in the OPPO.

If you are using the multi-channel Analog audio outputs, have the Subwoofer enabled for those, and have ANY speakers set to SMALL then this issue affects you.

My recommendation, in that case, would be to set the multi-channel Analog output Crossover in the OPPO no lower than 60Hz.
 

The meat of LFE is in the range 40-80Hz (with additional energy from 15-40Hz in some tracks -- bass that is more felt than heard -- which can be reproduced by better quality Subs). The Crossover is not a brick wall. It rolls into effect over a span of about an octave -- a factor of two in frequency. So a 60Hz Sub Crossover will start to roll off LFE to the Sub above 60Hz, but it doesn't cut it off suddenly. The upper end of LFE is 120Hz, but a 60Hz Crossover will have only a few dB attenuation at 80Hz, and so you are still OK since there's not much LFE above 80Hz in the first place compared to what's BELOW 80Hz.

And of course this only affects playback of tracks that actually include content in the LFE channel. Stereo tracks don't have an LFE channel, so no issue. And it is often the case that multi-channel music tracks, even though packaged as 5.1 or 7.1, don't actually have audio in the LFE channel. The main speakers channels are fully capable of carrying bass as low as the authors want to go. The LFE channel is special in that it is configured to carry LOUD bass. This is particularly true about SACD discs due to a screwup in the way Sony spec'ed LFE for SACD way back in the year dot. So you'll find studios (e.g., PentaTone) which have a policy of not putting content in the LFE channel of their SACD discs

As for the regular speakers, if you set your Crossover as low as 40Hz, what you are actually saying is that you believe your speakers are capable of quality output -- at VOLUME -- down as low as one octave below that -- i.e., all the way down to *20* Hz! It's a rare speaker that can do that. If your speakers don't have powered woofers (which basically means a sub built into the speaker cabinet) it's unlikely they can do that.

If your speakers are rated down to 30Hz (a not uncommon number), and you BELIEVE that number (given that speaker specs are often, umm, optimistic), then you should set the Crossover at 60Hz or higher to insure the speaker can continue to contribute its share of quality bass for a full octave below the Crossover.

There is no issue as regards the steered bass from the regular speakers. Whatever Crossover you pick, bass below that will be steered out to the Subwoofer.

Again, all of this only applies to the multi-channel ANALOG outputs.
--Bob
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