Originally Posted by OmarF
Originally Posted by Bob Pariseau
^ OPPO UK handles all of Europe.
I've not heard anything through Beta Tester channels here in the US which contradicts that tech note published by OPPO UK.
Well, why not just call OPPO yourself and ask?
Sorry to be a bit slow getting back on this; the fellow I asked at OPPO Digital was traveling.
What follows is from Jason Liao, CTO of OPPO Digital here in the US. As you'll see there are considerations which different engineers might weigh differently. For example, it makes sense to me to pad the recommended input impedance for the amp to give some safety margin against the variability of impedance vs. frequency as pointed out by Rich B., above.:
The technical specification information on the OPPO UK site is correct except for the output impedance of the 7.1ch. I believe that all channels have 100-Ohm output impedance, and there is no difference between the front and surround channels. I need to double check this when I return to the office. The general recommendation for input impedance is that the input impedance should be at least 10 times the output impedance, so a 47K-Ohm input impedance power amplifier should work fine, but it does not need to be that high. People drive tube amps with 1k-Ohm input impedance using the 105 without any problem.
The BDP-105 was not designed to be or to replace a pre-amp. I would not call it “well suited”, not because the performance of the BDP-105 is not good enough, but because the lack of some pre-amp features such as no physical volume knob. There is also the danger of very high output volume if the user is not careful when resetting the player.
Although we do not recommend using the 105 as a pre-amp, some users do it anyway. Some other users connect it to active speakers. In order to help these users, we recently added some features such as maximum volume level so a spouse or child does not accidentally set the volume too high. We also added the feature of remembering the last used input. These “pre-amp like” features do not mean that we encourage using the BDP-105 as a pre-amp. Our intention is to help the users who have already decided to use the 105 this way.
If you do not consider room correction or other “enhancements” a full featured pre-amp can provide, from a sonic quality point of view, a direct connection to the power amp will have less distortion and interference for sure. Introducing a pre-amp in the signal path adds a source of distortion and interference. If the pre-amp is a quality one, this impact should be minimal and usually cannot be heard. If the pre-amp is not so good, the signal can be degraded. This is why our customer service technicians sometimes tell users that if their pre-amp is a quality one, there is no need to take it out, and removing the pre-amp should only be considered if the pre-amp quality is not that good. The answer is not always black or white. It depends on the entire system configuration. Sometimes people are willing to trade convenience for performance; sometimes the opposite can happen.
Another more important factor that complicates the decision is the sensitivity of the power amp and speakers. We found some users were using the BDP-105 with volume set to 1 or 2 in order to get a comfortable listening level. This severely under-utilizes the dynamic range of the player. In this case, the player’s normal output level is too high for the power-amp, and a pre-amp should be used to reduce the level. If there is no pre-amp, passive attenuators should be used instead. If the player’s volume level can be set to anywhere between 70-100, the result should be good.
So here's MY take on this: A key factor is whether the output level and output impedance of the 105/105D happen to be well matched for your amp and speakers. If not, having a quality preamp in the Analog signal path CAN improve audio quality simply because it acts as a buffer and/or attenuator in the signal path. I.e., it provides a convenient way for you to adjust for that mismatch. Obviously if the preamp is not a good one the degradation from that alone may outweigh such benefits of having it in the signal path.
If your amp and speakers ARE well matched for the output levels and output impedance of the OPPO then putting a preamp in the signal path (and with no audio processing engaged) can not improve the audible quality. The signal can't be made any better than what is already present on the outputs of the player. It can only be made worse. (I.e., the preamp, no matter how good it is, can not magically re-create information which is not in the player's Analog output signals to begin with.)
Reaching for that "perfect" rendering of the signal on the player's Analog outputs does not come without cost. At the very least you lose the ability to play other, Analog sources since the player has no Analog inputs. And then there are the convenience factors, such as the lack of a physical Volume knob as mentioned above.
You also have to be careful about how the Analog outputs of the player render different types of content to make sure you are not falling into a configuration trap. When using the Asynchronous USB DAC Input, or when playing DSD files with DSD-Direct-to-Analog conversion engaged for example, no audio processing is possible in the player, since that processing is done digitally, and those two types of playback bypass the digital processing and head straight for the DACs. Which means you lose Crossover processing, among other things. Which can change the amount of Subwoofer boost needed external to the player to match the Analog Subwoofer output to the other Analog outputs. For folks who want to do this type of playback, the benefits outweigh such complications, but the complications do have to be kept in mind.
And if you add back in the value of audio PROCESSING, then there's a whole additional set of considerations. I use the OPPO players with an Anthem Statement D2v pre-pro. My speakers are chosen to require support from a subwoofer, and thus there's a premium on the quality of that blending. I use Anthem Room Correction (ARC) in the D2v to do that and it sounds great. But that means Analog input from the OPPO has to be re-digitized prior to that processing and then converted back to Analog in the D2v for output. I love the result, but it does mean that trying to bypass the D2v to try a pure Analog path comparison is a problem, because I'd have to redesign my bass solution to be as good as what I get from ARC.
In general then, including a preamp or sound processor is valuable because:
1) Additional types of inputs (e.g., Analog) and convenience features are included
2) Adjusts for inherent mismatch between amps/speakers and player, and
3) Addition of "value added" audio processing options, when you choose to use them.
The better the quality of the preamp the more likely you will be able to keep it in the signal path without degradation of the Analog audio.
If you hear better audio with a preamp included in the signal path, then the simplest explanation is that the preamp is providing benefit #2, above.