[cloudbaseracer]

I have being doing a lot of research and posting on a lot of forums to determine if the Oppo 105 will work as a good preamp due to it's volume control. Many on here, including Dan of Modwright, have stated that it is not good because it looses information.  Quite a few on other forums say that yes it works good and one in particular provided this....

    "The volume control for the BDP-105 is for the analog and headphone outputs and happens inside the 32-bit ESS DAC. It has plenty of dynamic range to preserve all 24-bits of data."

More info here: http://www.esstech.com/PDF/digital-vs-analog-volume-control.pdf

Which was then followed by....

     "This issue has been discussed and addressed many times in the BDP-105 forum on AVS: http://www.avsforum.com/t/1439524/official-oppo-bdp-105-owners-thread/510#post_22636549

And that lead to:


    "The BDP-105 headphone amplifier has a great dynamic range. Your volume setting of 80 is actually very good. This is because the built-in headphone amp on the BDP-105 works very differently than other standalone headphone amps.

A standalone headphone amp takes a line-level input signal and amplifies it to drive headphones. Since the input level can vary greatly from one device to another, the amplifier is usually designed to work with a big range of input level. It is possible that when the input level is too high or the volume is set too loud, the output can clip, causing significant distortion. For this reason, standalone headphone amps are normally operated at a low volume control setting (below 50%) to preserve the "headroom" in case a high level signal comes in.

The headphone amp in the BDP-105 is connected directly to the ESS Sabre32 Reference DAC. Its input level is fixed. The highest input level is called 0dBFS and that is the maximum level a digital audio sample can represent. The amplifier is designed to take this 0dBFS input and amplifies it to drive headphone, at the maximum output level (volume control at 100), without clipping.

Volume control in the BDP-105 is implemented in the DAC chip as a 32-bit floating point multiplier. When the volume is set to 100, the digital audio signal is not attenuated at all. The headphone amplifier gets the maximum input level and drives the headphones at the rated output (depending on the impedance of the headphones). If volume level 100 works for your headphones, that's the best. If it is not loud enough (unlikely though), then the headphone amp in the BDP-105 is not suitable for your headphones - you will need to use an external headphone amp.

It is most likely that volume level 100 is too loud. You will need to reduce the volume. Will that hurt the sound quality? The answer is no. Thanks to the 32-bit volume control in the DAC, the performance is as good as an analog volume control but without the statics and wear. ESS has a nice presentation about the volume control mechanism in their DAC chips, which are used in the BDP-105.

The second to last slide says, "A digital volume control with access to the DAC internal data path will behave just like the analog one until it reaches the noise floor of the analog components of the DAC." The noise floor is at -135dB in the ESS Sabre DAC. It is nothing if you reduce the volume 20dB or so, which is volume level 60 on the OPPO BDP-105.

So the conclusion is that the headphone volume level on the BDP-105 is "Bigger is Better". There is no need to worry about the dynamic range or headroom because the headphone amp is a non-clipping design."


In particular, the pdf file in the previous post was referenced in the AVS forum post in November of last year. "[/color]

Reading the pdf it seems that as far as ESS is concerned the volume control is fine.  Why is it that many on AC say it does not provide full resolution? Dan, can you comment?

Cheers,
James

[ryno]

http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/dacs-preamps-number-bits-and-volume-control-15110/
More info

[mfsoa]

I guess I don't have nearly the engineering background to understand how you attenuate digitally without losing information.

Seems more accurate to say "Since the bits that are lost are so far down as to be inaudible, no sonic degradation occurs" rather than "The digital volume control in component X doesn't loose bits".

Let's say you turn a digital volume control from dead flat silence to the very tiniest signal that can be heard. If a system "doesn't loose bits" then that teeny tiny signal would have to have every speck of information that would be present if there was no attenuation at all - Just seems like this is not possible. 

Can anyone explain to me what is happening when a 16 bit redbook signal is played back on, let's say the 35 bit NAD player.  Do the 16 bits get spread out over the now-available 35 bits?

-Mike

[Elizabeth]

I guess I don't have nearly the engineering background to understand how you attenuate digitally without losing information.

Seems more accurate to say "Since the bits that are lost are so far down as to be inaudible, no sonic degradation occurs" rather than "The digital volume control in component X doesn't loose bits".

Let's say you turn a digital volume control from dead flat silence to the very tiniest signal that can be heard. If a system "doesn't loose bits" then that teeny tiny signal would have to have every speck of information that would be present if there was no attenuation at all - Just seems like this is not possible. 

Can anyone explain to me what is happening when a 16 bit redbook signal is played back on, let's say the 35 bit NAD player.  Do the 16 bits get spread out over the now-available 35 bits?

-Mike

OK how the 35 bits can mean the device does not lose any information.
Say you start with the standard 16 bits. Now you zoom this up to 35 bits by adding a pile of zeros behind the bits with information;
So say 5555666655556666 is the instantaneous bit at the moment direct from the Cd as 16 bits of info..
The you add on a lot of zeros.
55556666555566660000000000000000000. (these extra zero are tinier and tinier levels of information way way below the lowest level of info on a CD)
Now we cut the volume a tiny bit
((but for this example it magically is an integral of the 35 bits)).
So the new volume cut is 05555666655556666000000000000000000
See no information bits are lost! but the volume is lower.As the computer chip can extrapolat down to the very least bit of the 35 bits.
So say the person cuts to volume much further to:
000000005555666655556666000000000 Still have perfect total information at a much lower volume.
Make sense?

Now in real life the numerical number probably will change, but the simple experssion here is the main idea. With the increase of smaller and smaller bits extending down way beyond the 'least significant bit' the least significant bit can now move well below what could otherwise be done, with no loss of info in the digital domain.
(now if you lower the volume enough the analog portion of the circuit may lose some information to below it's threshold, but that happens all the time anyway in all analog circuits.)
The magic of big numbers...

[Stu Pitt]

The Oppo doesn't loose bits.  It may or may not lose bits, but that debate is beyond my technical knowledge. 

[Russtafarian]

The older 16 bit digital volume controls did sound pretty bad when attenuated because "music" bits were being crunched to reduce level.  So the prejudice against digital volume control is well deserved.

The 24 bit VCs, like the one in my Squeezebox are better.  The SB VC had little to no impact on sound quality that I could tell except at the lowest levels.  But the output stage of the SB or any DAC I used with it was not robust enough to drive my power amps and sub crossover, so it was best to use an analog preamp and keep the digital VC all the way up.

With newer 32 bit DAC chips, there are enough bits for the DSP to handle VC without getting into the "music" bits of a 24 bit file.  My Benchmark DAC2 is like the Oppo 105 in that volume control is handled in the ESS DAC chip.  The DAC2 has a robust output stage that can drive my amps and sub XO directly and that's how I use it.  I've tried it with and without a preamp (Sony TAP9000ES), and the Benchmark direct to the amps is the cleanest, clearest, most resolving and most musical digital I've heard in my system, at any volume level.

As always, listen for yourself and make your own decision.  But my guess is that if you like the sound of an analog preamp VC better than digital VC direct, it's probably because the output stage of the digital component can't drive the amp properly, or you prefer the sonic character that the analog preamp adds to the music.  There's nothing wrong with that preference, but it's probably not the fault of the digital volume control.

Russ

[tenantman]

I find that the Oppo 83SE digital volume control is more "alive" and does seem to have more detail information when used as opposed to the volume on the Integrated Virtue Audio Sensation. The trade off occurs at full volume output.  When the Sensation (passive preamp) volume is set to maximum and the Oppo 83SE volume is used as the primary control,  the sound is not as musical. The Virtue Audio Sensation preamp volume control is more musical.

I find the best balance to be half and half depending on the gain level of the recording which is another subject in itself.

[cloudbaseracer]

The Oppo 83SE is a different animal than the 105.