Notes on Setting Up for Analog Output
For folks new to the OPPO players, these notes may help save you some head scratching.
As mentioned in my post above regarding direct connection to a Power Amplifier, the "normal" way to wire Analog out of the OPPO is to connect to the inputs of a pre-amp -- which also includes the Analog inputs of an AVR since they always have a pre-amp in those.
When doing so, the USUAL Volume setting for the OPPO is the maximum value of 100 -- or setting Output Volume to FIXED, which does the same thing.
However, depending on the headroom designed into the inputs of your pre-amp, a Volume 100 output signal may possibly "clip" the inputs of the pre-amp in the loudest audio passages you play. The symptom would be a sense of "harshness" in the loudest audio passages, which cleans right up if you lower the OPPO's Volume a bit.
If you hear that, what you should do is test a selection of your loudest audio content and lower Volume on the OPPO just enough to insure you don't have clipping. It will usually only take a few steps reduction of Volume: -1dB to -3dB, meaning Volume 99 to 97. If you DON'T hear clipping in your loudest audio passages, that simply means your pre-amp has enough headroom designed in to prevent it, and you can leave Volume in the OPPO at 100.
Once you have found the Volume setting in the OPPO which insures against clipping of your loudest audio passages that is a "set and forget" setting. I.e., use that same Volume for everything you play. (Of course while using the Volume control in your pre-amp to achieve a comfortable listening level.)
NOTE 1: If you hear "harshness" which does *NOT* go away when you lower output Volume in the OPPO just a few steps, then that's some other problem. For example you may be overdriving your speakers or you may even have a damaged speaker.
NOTE 2: As mentioned in my post above, it is also best practice to set your individual speaker Volume Trims in the OPPO so that none of them are in positive dB territory. If after doing a check you discover that one or more speakers needs a +dB trim, simply lower ALL the trims the same amount so that the largest trim is 0dB and all the rest are -dB trims.
The Analog Subwoofer output of the OPPO carries both LFE channel content (the .1 of 5.1 or 7.1 tracks) and bass steered from the main speaker channels due to Crossover processing. Bass steering happens for speakers you have set to SMALL in the Analog Speaker Configuration settings in the OPPO. The Crossover frequency can also be set.
NOTE 1: Crossover is not a sudden change. It rolls into effect over the span of about an octave -- a factor of two in frequency. So if you set a Crossover frequency of 80Hz, that means the main speakers are carrying audio in their individual channels above 80Hz, and that between 80Hz and 40Hz the audio is carried by a mix of the speaker and the subwoofer outputs. Below 40Hz the audio in that speaker channel is carried almost entirely by the subwoofer channel. The upshot is that you should pick a Crossover at last twice as high as the lower frequency limit for good quality audio from your speakers. If that's 30Hz then the Crossover should be 60Hz or higher. It is also wise to not set the Crossover too high, as that steers, for example, male voices into the subwoofer. In addition, the audio from the subwoofer becomes "localizable" at higher frequencies, which means you hear audio coming from the direction of the sub instead of from the direction of the speaker where it is intended. Low bass frequencies on the other hand are not "localizable". The Sub produces low bass by "pressurizing" the entire listening space -- setting up "standing waves". And so that low bass appears to come "from everywhere" -- with no set direction. In particular, not from the location of the sub. The bottom line is that when using Crossover at all, the Crossover frequencies between 60Hz and 90Hz are your best bet. Pick the one that sounds best given your speakers and the "bass response" characteristics of your listening room.
NOTE 2: The industry standard nomenclature of SMALL vs. LARGE is unfortunate. It has nothing to do with the physical size of your speakers. It is simply a way to specify whether you want Crossover processing to happen (SMALL) or not (LARGE).
The LFE channel just mentioned is special in that it is a channel designed to carry *LOUD* bass. *ALL* the speaker channels are unlimited in how low they can go in frequency. You can put the lowest of the low bass in any or all of them. But the energy necessary to hear (or more likely, feel) very low bass is pretty significant. And if you put *LOUD* bass like that in the normal speaker channels you would clip those channels.
So the LFE channel is recorded -10dB down from the normal speaker channels -- giving it 10dB additional headroom to carry *LOUD* bass.
The rules of authoring multi-channel audio are that the mixers can not assume listeners will have a sub. So all "critical" bass in the sound design also has to be in the main speaker channels. But *LOUD* bass has its home in the LFE channel.
The Subwoofer output of the OPPO preserves that recording level for LFE. That is, the signal that comes out on the Subwoofer RCA jack is at least -10dB below what comes out on the main speaker RCA jacks. This is so that you can feed the Sub signal through a multi-channel pre-amp (like the multi-channel inputs of an AVR) without clipping that Sub input jack on the AVR.
But before the audio goes to the speakers, "Sub Boost" has to be applied. I.e., that signal from the Sub output jack of the OPPO has to be raised +10dB so it is back up to the same level as is authored into the main speaker channels.
By default, almost all AVRs apply +10dB Sub Boost automatically. If you are using different electronics -- perhaps running the Sub output of the OPPO directly to your Subwoofer - you need to arrange for that Sub Boost yourself. For example by raising the Volume knob on the Sub itself.
An important concept here is that Sub Boost should be applied *EXTERNAL TO* the player. That is, it is not a good idea to try to achieve the needed Sub Boost by raising the Subwoofer Volume Trim in the OPPO. Why? That clipping I just mentioned.
If Crossover processing is engaged in the OPPO, there's more audio than just LFE going out on the Analog Subwoofer output jack. You now also have that jack carrying bass "steered" from the channels of speakers you have designated as SMALL.
To accommodate that, whenever Crossover is active in the OPPO an additional -5dB of attenuation is applied to the Analog Subwoofer output jack -- again to prevent "clipping" of that input of a pre-amp. That means the Sub Boost you need to get it back to the level of the main speaker output is now +15dB. To summarize:
1) If no Crossover happening, external Sub Boost should be +10dB.
2) If Crossover happening, external Sub Boost should be +15dB.
How do you achieve that additional +5dB? Well some AVRs and pre-amp processors will have an adjustable Sub Boost setting. Simply change that from +10dB to +15dB.
Otherwise, achieve the additional +5dB by raising the Volume knob on the Sub itself.
NOTE: If you are doing Analog "pass through" in your AVR, raising the Volume on the Sub to achieve the right level of Sub Boost may result in too MUCH bass when you are playing content via digital connections. The solution to THAT problem is to first set Volume on your Sub as needed to get the Analog connection to work. Then in the digital audio settings of your AVR or pre-pro, REDUCE Sub output the same amount to compensate. In most cases, that adjustment will not affect the Analog "pass through" levels and so you now have achieved correct Sub levels both for Analog "pass through" from the OPPO and for Digital content played through your setup.
There is a gotcha here for folks who want to play multi-channel DSD content using DSD-Direct-to-Analog Conversion. When the player is set to send DSD directly to the DACs for Analog output (i.e., without first converting that DSD to LPCM) no processing of the audio is possible. No down-mixing, no speaker distance adjustment, and in particular no Crossover processing. All you can do with DSD-Direct-to-Analog Conversion is Volume control.
And that means even if you have some speakers set to SMALL in the OPPO, they are treated as LARGE when you have DSD going directly to the DACs.
And THAT means the required Sub Boost is now +10dB -- because no Crossover is engaged.
NOTE 1: For those familiar with the design flaw in SACDs regarding LFE level for multi-channel tracks, suffice it to say the OPPO compensates for that automatically. That is when you play a multi-channel LFE track the .1 channel is treated exactly the same as the .1 channel of normal content. This is true regardless of whether you are sending DSD or LPCM to the DACs for Analog output of that multi-channel SACD track. The same -10dB level is produced on the OPPO's Analog output path, meaning the same, default +10dB Sub Boost is needed for both types of content -- plus the additional +5dB if the Crossover is engaged.
NOTE 2: If you screw this up and apply +15dB Sub Boost during DSD-Direct-to-Analog Conversion instead of the correct +10dB you may not actually hear any problem! Why? Because of that design flaw in the SACD spec I just mentioned. It has caused so many headaches that many studios author their 5.1 SACD tracks with *NOTHING* in the .1 channel! I.e., they author ALL the bass into the 5 main speaker channels. So it is actually 5.0 content packaged as a 5.1 track. So with nothing in the LFE channel -- and no Crossover happening from the main speaker channels -- the Subwoofer output of the OPPO is silent. Meaning there's nothing for the incorrect Sub Boost level to screw up. In the alternative, you may hear WEAK bass (instead of too much). That's because you've gotten used to Crossover processing supporting your main speakers by sending their lowest bass to the Sub. But that doesn't happen when you use DSD-Direct-to-Analog Conversion, so you are now totally dependent on the low bass output characteristics of your main speakers.
All of the above is complicated to read, but checking whether you've got things set up CORRECTLY is actually pretty easy. Simply play a calibration track and check!
For checking your non-DSD setup, I recommend the LPCM 5.1 or 7.1 Channel ID tracks on AIX Audio Calibration, Blu-ray (available direct from OPPO).
For checking your DSD setup, I recommend tracks 43-48 -- the speaker level tracks -- found on the 5.1 content of "Stay in Tune with PentaTone", SACD, available on Amazon. Important note: Do NOT use the speaker ID tracks found earlier on that disc for this. Even though those sound the same, the LFE channel for those has an artificial +10dB increase "to make the subwoofer easier to hear". Use tracks 43-48 instead.
It is best to check this using a Sound Pressure Level (SPL) meter. Set that to Slow response and "C" weighting, and point it straight up towards the ceiling while held at seated ear height at your normal, center seating position. Adjust Volume so that the test tracks are producing roughly 75dB SPL.
If things are set correctly, the main speakers *AND* the Subwoofer will all produce the *SAME* SPL reading with these test tracks. It doesn't matter HOW you have achieved the correct Sub Boost; if you get the same SPL from the Sub as from the main speakers then things are set correctly.
Even set to Slow response, the readings will bounce around a bit, particularly for the Sub. So just do a mental average of them as you check.
ETA: Things Change!
In the Official 0922 firmware for the 205, released September 25, 2017 in the US, the implementation of the Volume control was changed. See this post:
The new Volume control attenuates at -0.5dB per step below Volume 100, instead of the -1.0dB per step used prior to this.
In the discussion above, I mention some equivalences which now have to be adjusted. So for example, reducing output -3dB (if needed) to eliminate Clipping would have equated to Volume 97 before. It now equates to Volume 94 (six steps of -0.5dB per step). Please adjust what you read above, accordingly.