Differences in sound: DAC vs. DAC + Pre-amplifier

[CG]

18 hours ago, barrows said:

Sorry, i guess I was not clear.  In no way do i mean to suggest that those who design preamps are trying to add colorations.  What I am saying is that any component addition (like a preamp) can only result in loss of fidelity; by adding a preamp, where one was not present before, the only possible result is that doing so adds more distortion and noise than there was before.  If one then prefers the sound with that preamp in place, what that person is preferring is the coloration added by that preamp's noise and distortion profile.

 

Actually, that's not entirely true.  It is in regard to thermal noise, but not necessarily with regard to the rest.

 

Distortions can cancel.  This is the basis for feedforward used in amplifiers as well as the use of predistortion.  (Too much to cover here!)

 

In addition, common mode disturbances are often defined by the size and shape of the current loops of the system configuration and the interconnections, including powering and stuff like network connections.  (Again too much for here - try searching on the term "Henry Ott")

 

And, most amplifiers are sensitive to the source impedance at their input.  That affects not only amplitude response over frequency, but also actual distortion.  This is true with opamp configurations, which are the dominant topologies in use today, whether in integrated circuit form or not, as well as open loop configurations.  (Again...  Walt Jung has authored some articles on the subject that are pretty easy to digest.  But, there's loads of others.)  

 

This isn't voodoo or any other form of magic.  

[CG]

It's more complicated than whether the DAC or preamp can drive the amplifier input impedance.  The source impedance is actually part of the circuit.

 

Here's just one example:

 

https://www.pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Jung_W/ADI_1992_2002_Audio_Seminars.pdf

 

Look at page 8-70.

 

Distortion cancellation isn't really common, because of the gain structures in audio systems, but is not as rare as you might think.  It's actually possible to cancel distortions created in the original source (aka recording) and this does happen in communications systems.  The problem is that unless you carefully control the distortion cancellation process, the result will be selective and will be all over the place.  Anyway, I only brought that up as one example.

 

To me, a much bigger question is the system topology with cables of various lengths connected in various ways in all sorts of combinations, that often are additionally coupled to other nearby electronics gear.  That could be due to electromagnetic coping or plain ole direct connections.  Amazing, but true.

 

Or, you (generic YOU, not Barrows specifically) plain may not care.  that's ok, too.

 

[CG]

23 minutes ago, Miska said:

On my DAC designs, the output buffer stage has cable capacitance compensation circuits and such, to ensure that for example square wave outputs don't end up having overshoot or other unwanted effects. This also applies to design of the analog reconstruction filter.

 

Very good!

 

Too bad you can't do that for the rest of the system...

 

Most people don't realize that the input and output impedances affect the performance.  Basically, almost every amplification device is unstable at some point.  Fundamentally, that's because the gain drops over frequency for a bunch of reasons.

 

Dennis Feucht is no quack:

 

http://audioworkshop.org/downloads/AMPLIFIERS_OSCILLATION_BJT_CIRCUITS.pdf

[CG]

2 hours ago, Miska said:

 

And this is related to what? And relation to this topic is?

 

Preamplifiers essentially look exactly the same input and output wise as any other line level device. Or these days you should actually call it preattenuator, because it provides only negative gain.

 

 

I guess the situation is already perfect then!  Great!  

 

No point in even discussing the matter.  Farewell, then.

[CG]

1 hour ago, barrows said:

may be what @CG was referring to earlier in this thread which he referred to as distortion cancelling.

 

But I would suggest that we now can have electronics which have no audible distortion at all, so there is no distortion which needs to be masked anymore.  

 

I've finally seen the light and have learned that audio electronics are perfect now.  So, I wouldn't be frequenting this website any longer - what's the point? - but I received an email informing me that Barrows had asked a question of me.  It only seems fair and reasonable to answer his question.

 

There's far too much information available on this subject.  If you go to your favorite search engine and type in "distortion cancellation mechanism series amplifiers" you'll get "About 3,140,000 results".  You probably don't need to go through all of them.  But, even on the first page of results, there are some names you probably are familiar with.

 

Have fun!