Is dedicated PreAmp with Oppo 105 needed?

@ noble100: Thank you for your consideration & reaching out to help.

There are multiple reasons why I haven’t jumped yet: 1.) I’ve limited knowledge. I came across very few multi-channel analog audio PreAmps/ PrePros (online) and even lesser number of comparison reviews/ opinions. 2.) I had some financial difficulties due to job loss & other factors. And I do recognize my budget is limited for what I’m expecting to achieve 3.) I’m extremely picky & would like to do things right the first time.

From what I’ve read, the sound straight from Oppo 105 can be very digital or clinical. That’s why, I’m looking for a Tube or Tube like sounding Pre/Pros that is good for both Stereo & HT (multi-channel) listening.

Not sure how a 2-ch stereo preamp with a HT Bypass works. But ideally I should be able to connect Oppo’s Stereo XLR/ RCA for music & 5 out of 7.1 RCA Audio for movies to my Parasound A51. Regularly toggling the "Input Select" switch is not an option. https://www.parasound.com/a51.php

Hello Hits,

    No problem, I'll help you out as much as I can.
    I actually use an Oppo 105 in my system, too. I use my system about 60% for HT (TV and movies) and 40% for 2-ch stereo music. I currently use the Oppo as the preamp without a separate 2-ch stereo preamp but previously used a VTL tube preamp with a HT Bypass switch to add a bit of warmth, texture and dimensionality to music. Here's how a 2-ch stereo preamp with HT Bypass works:
    For preamp connections, the Oppo's stereo XLR/RCA left and right outputs would be connected to the preamp's "processor" inputs. The preamp's left and right "processor" outputs would be connected to two of the Parasound A51's input channels.  The Oppo's rear left/right rear surround and center channel rca outputs would remain connected to three of the A51's rca inputs.
    The final step required is using the Oppo's remote and going into the "SETUP" menu, selecting "Audio Processing", scrolling down and selecting "Stereo Setting" and then selecting "Front Left/Right". This just instructs the Oppo to send any 2-ch stereo info on a disc, such as a CD, to its Stereo XLR/RCA left and right outputs.
    For music, you leave the HT Bypass switch in the 'OFF/OUT' (not engaged) position and only the left and right stereo channels are played back on your main speakers.
    For TV and movies, you leave the HT Bypass switch in the 'ON/IN' (engaged) position and only the front left and right surround channels are played back on your main speakers along with the center and rear left + right surround channels being played back.
    As I mentioned earlier, I originally used a VTL 2.5L preamp, that utilizes four vacuum tubes and has a HT Bypass switch, in my system for music playback and its ability to quickly be switched to playing back the front left and right surround channels for HT. At the time, I also used a set of four expensive Mullard NOS (new old stock) replacement tubes in the VTL preamp and a Parasound AVC-2500 surround sound processor.
      Several years ago, in an effort to streamline my system, I decided to compare the performance of my system with and without the VTL preamp and Parasound surround sound processor. I found that my music sounded just as good to me without the VTL/tubes and that the 5.1 surround system actually sounded better to me decoded by the Oppo's internal ESS Sabre dac chips and with the Oppo's audio outputs connected directly to my amps. I attribute this excellent performance mainly due to the Oppo 105's exceptionally high quality audio section, dac chips and design.
      My main intent of describing all of this to you is to stress that you're unlikely, in my opinion, to find a better performing preamp than the one already existing in your Oppo 105. The VTL 2.5L tube preamp I formerly used is a very well reviewed and high quality preamp that costs about $2500 new with the standard Chinese or Russian tubes and another $200 for the aftermarket set of four Mullard NOS tubes I believe further enhances its performance.
      I've proven to myself that using a separate high quality tube preamp is definitely capable of altering or flavoring the sound of all the source content played through it and that the specific tubes utilized are also capable of further tailoring the sound to match one's preferences.           However, I ultimately discovered that the combination of a high quality music recording, played through a neutral high quality solid state preamp (like the Oppo 105 represents by adding or subtracting nothing from the inputted signals) and amplified by a neutral high quality solid state amp (like a high class D amplifier represents by adding or subtracting nothing from the inputted signals), is a more honest and simpler alternative method of achieving extremely good sound quality performance in my system.
    So, my question for you is what direction would you prefer to take? Would you like to buy an expensive new or used tube preamp and prove what I discovered for yourself? Or would you rather take the more honest and simpler alternative path of utilizing neutral high quality components, such as a more neutral high quality multi channel amp, to achieve extremely good sound quality performance in your system?
    I should warn you that an honest and neutral high quality system will not hide or mask anything. Optimum results require very good quality music recordings and any of your music that's not well recorded will suddenly become painfully obvious to you. But good recordings will sound extremely good and you'll also more clearly notice the sonic effects of any changes to your system, even smaller changes such as upgraded power cords or cabling.
    I'll stop here and await your impressions and questions thus far before continuing any further with my assistance.

Thanks,
  Tim

Not sure how a 2-ch stereo preamp with a HT Bypass works. But ideally I should be able to connect Oppo’s Stereo XLR/ RCA for music & 5 out of 7.1 RCA Audio for movies to my Parasound A51.

You don't actually need a HT bypass switch. You can use any preamp with a home theater processor. If there is no HT bypass you simply set the volume control to a particular position and let the HT processor handle the rest.


Since the Oppo and your amp are balanced, it makes sense to use a balanced preamp. I don't agree with Tim's assessment above though- a good tube preamp will give you a more neutral/natural presentation than solid state and will be less irritating in the high frequencies.  This is because solid state in general has higher ordered harmonic distortion that is more audible than it is with tube gear. I don't like the 2nd harmonic 'warmth' coloration that is often blamed on tubes but if your preamp is fully differential and balanced that harmonic will be absent. In general though tube preamps have far less of that sort of thing than amps so its not a big deal.

What might be a bigger deal is how the preamp handles balanced lines. There is a standard for balanced operation called AES48 (Audio Engineering Society file 48, although the standard was around long before the AES itself). Very few home preamps with balanced operation (tube or solid state) support this standard! The standard is quite useful as the interconnects used with the preamp won't impose any sonic footprint (that is part of the reason the standard was devised)- you won't have to audition cables to get the system to sound right and be neutral. When the gear does not support the standard all bets are off. So its a good idea to check with the manufacturer to see if their preamp supports the standard. When asked, it should be simply 'yes' or 'no'; if the answer gets much longer than that there's a pretty good chance that the manufacturer doesn't support the standard and may not even know what you are talking about (FWIW our gear does support the standard). One of the aspects of the standard is the input impedance of your amplifier will not be an issue- any device that supports the balanced line standard should be able to drive a low impedance line which might be only 600 ohms, so the typical 10K to 47K input impedance of most solid state amps will be a breeze.


If the preamp you select employs an output transformer then you will have to pay attention to loading the transformer for optimal bandwidth. I mention this because in the balanced standard, the output of the preamp floats with respect to ground; each side of the output signal (pins 2 and 3 of the XLR) reference each other to complete the circuit rather than ground. This is done to prevent ground loop problems. A transformer is one way this is accomplished; the only other way I know of is the method we patented, which is direct-coupled.

Hello atmosphere,

     Thank you for pointing out accurately that a HT Bypass switch is not technically necessary on a preamp since using the proper unity gain position on the preamp's volume control can be used as a substitute.  I was trying to keep the ease of use and concept understanding as high as possible because I wasn't sure of Hits' technical knowledge and audio experience.
      I've always really enjoyed listening to music played back via a high quality completely tube based system even though I realize it's not completely accurate and is imparting a 2nd harmonic warmth or coloration to the music.  Years ago, I understood that tube distortion tends to become audible on even ordered harmonics, that sounds much more pleasant to us than solid state distortion that tends to become audible on the odd ordered harmonics.   But I was building a combination stereo music and 5.1 surround HT system and knew that an all tube system was impractical.
      So,  I originally added the VTL tube preamp and swapped the standard tubes for NOS Mullard tubes in an effort in my system to attain the 2nd harmonic 'warmth' coloration that's often blamed on tubes, and that I liked, because I thought it was the only method to add that characteristic to my system's sound on stereo music playback at the time. 
     I began by pairing a good quality tube preamp with various good quality class AB solid state amps.  I never considered utilizing an amp to attempt to improve the sq performance of my system until I purchased an inexpensive Class D Audio SDS-440-CS amp that was a revelation to me.  This amp had extremely low measured distortion levels and the most accurate and neutral quality that I'd ever experienced in an amplifier, like the audio ideal of 'a straight wire with gain' with nothing added or subtracted from the inputted signals.  I considered the stunning neutrality of this class D amp a revelation and it began my thinking of the possibilities. 
     I only discovered a while later, through personal experimentation, about the alternative method of using very well recorded music sources played back via high quality and very neutral components along with very detailed and revealing speakers.  I found out that this type of system would also reproduce music in my room that possessed the warmth, detail, texture and three dimensional palpable qualities I really enjoyed experiencing when listening to music.
      It only required the combination of a neutral high quality preamp (the Oppo 105's preamp section), a neutral high quality amp (the Class D Audio amp and subsequently a pair of D-Sonic M#-600-M class D mono-blocks) and detailed and revealing speakers(a pair of Magnepan 2.7QRs) to achieve the sound qualities I previously thought only a tube preamp could provide.  
     Now it's just a matter of whether the recording is of a sufficiently high quality level to have captured the natural music qualities of warmth, detail, texture and other palpable characteristics. I think I couldn't achieve these results using my VTL tube preamp because it wasn't neutral enough but I realize you may have good ideas of how to accomplish these sound characteristics using a combination of more neutral tube components.     
     It's a bit of a compromise that the better the quality of the recording, the better the music sounds but I consider this prerequisite completely natural, logical and acceptable given the outstanding sound quality results. 

Thank you,
   Tim
  

Based on @atmasphere & several others suggestion, I've dropped the idea of getting a HT PreAmp. 

For a while, I explored the idea of getting 60s & 70s Fisher Tube receiver/ amplifier. However, since I don't have experience troubleshooting (I can do soldering), I would not like to get stuck with a set of expensive, dead equipment that I cannot use. The repairs on this can go upwards of $500 + Parts + S/H. 

Instead, I'm thinking of spending extra upfront & getting a used tube Stereo PreAmp or an Integrated for around $3000. It will sit in-between the Oppo 105/ Nakamichi Cassette Deck & Parasound Halo A51 Amp. 

Based on all the positive reviews, Atma-Sphere would be my first preference. However, they're very hard to come by used & definitely haven't seen anything in my budget. Apart from that, I've also read positive reviews about PrimaLuna, VAC, Conrad-Johnson, Audio Research, McIntosh, Cary Audio, Stanely, etc. They all have some good & some products to avoid. 

Any recommendation on Brand or a specific model over others?