# Do I need external preamp?



## Dwight Angus (Dec 17, 2007)

Greetings

I am new to this forum & looking for your opinions.

I am using an OPPO 105d directly connected to Bryston 4bsst with xlr cables so no external preamp. The Bryston is driving Goldenear Triton Ones. I usually play high resolution flac music in pure direct mode & I am happy with the sound but looking for ways to squeeze out more performance. Do I gain anything by adding a quality 2 channel external preamp? I have heard differing opinions regarding digital volume control vs analog volume. Digital has the potential to lose resolution because it throws away bits in order to change the volume. Also heard that a better pairing with an external preamp will yield better impedance matching. I am not a techy type just telling you what I have heard.

In my mind the argument against adding an external preamp is 1)shorter signal chain is probably better. 
2)The OPPO ESS Sabre DACS perform very well & hard to beat.

Trying to convince dealer to give me a 2 channel preamp for a few days to test it out.

Some background

My room pulls double duty ie HT plus 2 channel music. I have treated the room with acoustical panelling/bass traps. So that work is done. I am currently testing with different speaker positions.

Appreciate any input/opinions you may have


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## Wayne A. Pflughaupt (Apr 13, 2006)

You’re new with over 800 posts? Who are you trying to fool? :laugh:

Seriously though, I doubt you will hear a difference either way, but if you do trust your ears.




Dwight Angus said:


> I have heard differing opinions regarding digital volume control vs analog volume. Digital has the potential to lose resolution because it throws away bits in order to change the volume.


 I think they probably mean that LSBs are lost (quantization). 

If that’s the case it’s nothing to worry about. It’s generally accepted in the professional recording field that once your AD/DA converters are at 16 bits or above, the human ear can no longer detect quantization errors at low levels. This is because a 16-bit waveform, which has 65,536 amplitude or quantization “steps,” is considered the threshold of what is acceptable for hi-fi sound. While there may be some debate about that in audiophile circles, a 24-bit converters have over _*250 times*_ more amplitude “steps” - 16,777,216. 

It should be obvious that a 24-bit system has sufficient resolution to perform well above the 16-bit threshold, even with reduced input voltage due to digital attenuation. LSBs (e.g. loss of quantization) can’t possibly contribute to a reduction of an AD converter’s bit depth. As you can see from the picture below, LSBs are merely a single step - the lowest step - in the voltage “ladder” that is quantization. _Bit depth_ is what determines quantization (resolution), not the other way around. Therefore a loss of LSBs, even a large number of them, cannot possibly downgrade a converter to a lower bit-depth (lower-resolution) device. A 24-bit system in particular can shed several hundred thousand LSBs from its 16,777,216 quantization steps and still be comfortably above – _miles_ above - the 65,536 quantization resolution of a 16-bit system.










*Least Significant Bit in a 3-Bit System*​

Indeed, we can go even further: Each bit in a 24-bit system will contain 699,050 quantization steps (i.e. 16,777,216 ÷ 24). Now - compare that figure to the mere 65,536 quantization steps of a 16-bit system. It’s not much of a leap from there to determine that you can attenuate the signal levels of a 24-bit system to the point that, even if only _one_ of the original 24 bits “remains,” you will still have more than _ten times_ the resolution of a 16-bit system. 

Thus I’m not sure I’d take such claims seriously. Besides, any HT pre-pro has digital attenuation for adjusting all the various speaker levels, so if that’s the concern then you’re no better off with a pre-amp unless it’s straight-up analog.

Regards, 
Wayne


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## Lumen (May 17, 2014)

Dwight Angus said:


> ...I am happy with the sound but looking for ways to squeeze out more performance. Do I gain anything by adding a quality 2 channel external preamp? I have heard differing opinions regarding digital volume control vs analog volume. Digital has the potential to lose resolution because it throws away bits in order to change the volume.


Page 30 of the User Manual states the Oppo's volume control only affects analog signals. I've been unable to determine if the control itself is analog or digital, but my bet is on digital. 

Post #7 of this thread gives a description of analog vs digital volume by a well-respected authority:

_


AudiocRaver said:



*No* reputable designer would control gain by dropping bits.

It is a multiplication function, and in a processor like the DDRC-88A it is mixed in with thousands of other types of DSP math operations done in 32-bit precision math, so it has 256x better resolution than the 24-bit audio being processed, in terms of creating or adding distortion. Yes, the signal to noise ratio SNR decreases as the volume is reduced, but when you consider that the volume setting that most listeners use on their DAC is probably never lower than 20 dB from their normal listening level, if that, the SNR is reduced from, say, 125 dB - about the practical SNR limit for any DAC regardless of bit depth, unless one resorts to cryogenics - to 105 dB, still an excellent number. If that number was getting reduced to 80 dB or less, then there might be reason for concern.

Now, one might feel better about the analog ladder's better spec emotionally, or just want it because they like the idea of it, and that is perfectly fine, but expecting to ever hear a difference (noise &/or distortion) is a big stretch, unless I am missing something obvious. A lot of us buy components that operate 10x or 100x or whatever better than what we are likely to ever be able to hear, just because we can and we like the idea of it - and why not? No harm done if we can afford it.

In this case, I like the idea of the resistive ladder DAC, but do not see there being an audible difference under even extreme conditions.

Click to expand...

_


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## Lumen (May 17, 2014)

Wayne A. Pflughaupt said:


> Seriously though, I doubt you will hear a difference either way, but if you do trust your ears....


Much better said than I! You the man! :R


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## Dwight Angus (Dec 17, 2007)

Wayne A. Pflughaupt said:


> You’re new with over 800 posts? Who are you trying to fool? :laugh:
> 
> Seriously though, I doubt you will hear a difference either way, but if you do trust your ears.
> 
> ...


Many thanks Wayne. Wow a very detailed thorough explanation. I get it thank you. Your response has confirmed my suspicions. I must admit had to read it several times before it registered as I am not very technically minded but at a macro level I get it.


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## Dwight Angus (Dec 17, 2007)

Lou

Yes its a digital volume control. For 2 channel music I only use analog signals.


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## Dwight Angus (Dec 17, 2007)

Wayne

Just caught your last comment in your response to me earlier today. Are you saying an analog preamp would be a noticeable improvement?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Didn't mean for it to sound that way. The thought was that it’s the only option you want to avoid digital volume adjustments.

Regards, 
Wayne


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