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How do/can DACs and amps change sound signature?

post #1 of 60
Thread Starter 

I've been wondering this for a while, but I can't find any description for how a DAC or amplifier can change the nature of the sound. I hear descriptions like "warm", "bright", "transparent", essentially the same things we use to describe sound coming from speakers and headphones, but for the life of me I can't wrap my head around how a DAC or an amp can alter the timbre and quality of the sound. Wikipedia is unhelpful in this because the authors for the pages on DACs and amps assume prior knowledge of terms and principles.

 

This really breaks up into several questions. What makes the ODAC so much smaller than the Schitt Bifrost or Anedio D2? Why is it 1/3 and 1/14 the cost, respectively? How do any of these color sound as opposed to translate a digital signal into an analog signal? The same questions exist for me about amps. I do not understand why the FiiO E6 can be as small as a 6Gen Nano, but the Lyr the size of a home theater PC case an an order of magnitude more expensive. I don't know why such a fuss is made about tube amps versus solid state. Are these devices not supposed to simply amplify the power of a signal, meaning what comes in should also come out (just louder)?

 

Adding PMPs and smartphones to the mix makes me understand even less the relationship between size, cost, performance, to speak nothing of how different devices will influence sound quality.


Edited by BBEG - 11/12/12 at 9:42am
post #2 of 60

They shouldn't affect the sound signature. Many of those descriptions are BS.

People think tube amps sound warmer because the tubes literally get warm and glow. Seriously. This is how our stupid brains work.

 

"Transparent" is the only sound descriptor one wants in an amp, IMO. This just means the amp has low distortion, and has a flat frequency response (e.g. they are designed correctly). 

 

You are thus correct, the only purpose of an amplifier is to amplify the sound. People here and elsewhere seem to think that amps magically affect the sound in ways that aren't explained by the specifications. If you gave these people two electronically identical amplifiers house in different enclosures they would never conclude that they sound the same. The one housed in a wood case would most likely sound more organic, and the other housed in a metal case would sound more analytical and accurate.

post #3 of 60

One DAC tends to sound worse than another due to factors such as jitter. Too much jitter and the sound will tend to be congested and unmusical. How well the dac drives whatever follows it and how well it is driven by whatever preceded it matters. A dac that receives a weak and dirty signal from a PC will normally give poorer sound than a dac that is fed with a strong clean signal. Some USB DACs take all their drive from the source (they do not have their own power supply) and in that case clean power is especially important.

 

I think amps sound different due to distortion, damping and power. Some people like certain tube amps because they introduce a "warm" kind of distortion. This will often make harsh recordings and sub standard equipment upstream nicer to listen to. Damping is related to the output impedance of the amp and the impedance of the device it is driving. If the amps output impedance is too high it will struggle to control speakers and headphones resulting in bloated bass. The opposite is also true. Amps will also sound bad if they are asked to perform beyond their power envelope, resulting in clipping that is not nice to listen to.

 

Why is one component smaller and cheaper than another? That is a huge can of worms. Just remember, smaller and cheaper does not always equal poorer performance. Fancy boxes and big names cost $$$.


Edited by Hooster - 11/11/12 at 1:35am
post #4 of 60
Quote:
Originally Posted by Eisenhower View Post

They shouldn't affect the sound signature. Many of those descriptions are BS.

People think tube amps sound warmer because the tubes literally get warm and glow. Seriously. This is how our stupid brains work.

 

Many descriptions of sound are pure BS, but tube amps often produce a sound often referred to as "warm." It's a fact:

 

  http://en.wikipedia.org/wiki/Tube_sound

 

I agree that the notion it's due to heat or light is stupid. Those are simply two more artifacts of how tubes work.

 

Quote:
Originally Posted by Eisenhower View Post

"Transparent" is the only sound descriptor one wants in an amp, IMO. This just means the amp has low distortion, and has a flat frequency response (e.g. they are designed correctly). 

 

Some people want a warm-sounding amp. Some people don't. Myself, I'm in the more-transparent-is-better group.

post #5 of 60

I used to like tubes, but the coloration they introduce gets old. I am just into enjoying music these days and I want equipment that does not draw attention to itself. So, put me in the transparent is best camp too.

post #6 of 60
Amplifiers should amplify the sound, but it's a fact that different DACs and amplifiers may sound different than others, not because of "magic" or that i.e tubes get hot and glow.
post #7 of 60
Quote:
Originally Posted by HamilcarBarca View Post

 

Many descriptions of sound are pure BS, but tube amps often produce a sound often referred to as "warm." It's a fact:

 

  http://en.wikipedia.org/wiki/Tube_sound

 

I agree that the notion it's due to heat or light is stupid. Those are simply two more artifacts of how tubes work.

 

 

 

Some people want a warm-sounding amp. Some people don't. Myself, I'm in the more-transparent-is-better group.

 

Nothing on that wikipedia page provides a sound technical explanation as to what make tubes sound "warm". Hi-fi tube amps still attempt to have low distortion, which wouldn't make sense if distortion was as desirable as you say.  

post #8 of 60

Audio quality:

In the real world, we make stuff out of real-world parts (building blocks like transistors or even vacuum tubes have nonlinear electrical characteristics; other parts do too to some extent) and have to deal with things like thermal noise; it's impossible to build an amplifier or anything with ideal properties.  You can't have 0 noise, 0 distortion, perfectly flat frequency and phase response, and more.  You proposed something that just multiplies the input—that doesn't happen.  However, people can use a wide variety of techniques to make that very close to a reality.  How close?  This is a matter of contention with audiophiles (in my opinion, without much merit), though for many other purposes and electronics applications, there are not the same kind of objections.

 

Some designers, constrained or motivated by cost, size, weight, ideals / philosophy, or goals, do not intend to get it as close as possible.  There are a number of reasons why some amps (less commonly and significantly, for DACs) may sound different from one another, when driving certain headphones or IEMs.

 

Ex1) have a noisy amp and sensitive IEMs, you can hear the background noise.

 

Ex2) amp has high output impedance and headphones have impedance varying with frequency -> the amp no longer can be considered like an ideal voltage source because it is dividing the output voltage among its own output impedance and the headphones, resulting in an effective frequency response shift for the headphones.

 

As for some of the descriptions of sound for some of these devices?  Listening impressions are valuable, but take everything with a grain of salt, especially if the listener knows what they're listening to.  Often times, the perceived difference in amps is more a result of a difference in expectations or the way one is listening (or order effects, or many other factors) rather than the difference in signal produced.

 

 

Audio device size:

For desktop audio, the size of the enclosure may be significantly larger than that of the electronics.  Often times, the jacks (the internal part you don't see) and thickness of the enclosure may be larger than you realize.  The size is often dictated by usability and visual impression / handling points of view, rather than by the electronics.  That said, there are some factors based on the electronics, detailed in the rest of this section.  What takes up a lot of space are transformers, if one wants to do a linear internal power supply.  The higher the power consumed by the device, the larger the transformers need to be.  Likewise, the size of the capacitors needs to be larger as well.  For amplifiers, some devices are a lot more powerful than others, and some are a lot less efficient than others, so more waste heat is produced.  Class A amplifier operation is less efficient but has lower distortion to begin with, so don't consider low efficiency a bad thing (aside from using more power, arguably unnecessarily).  Whenever there is relatively high power consumption, it is almost all going to waste heat, so space for heatsinks to dissipate the heat is necessary.  Often times, the chassis itself is used as a heatsink.  Also, keep in mind that high temperatures are bad for the longevity of components, so for example, a larger design might be a good idea to physically separate hot components from temperature-sensitive capacitors.  At least, that would be a good practice for long-term reliability over many years.  Through-hole components on a PCB take more space than small surface-mount components; the surface-mount components can be automatically soldered into place by machine.

 

Ex3) ODAC filters and regulates USB power, so it doesn't need transformers, and power consumption well under 1W so power circuitry can be miniscule; components are small and surface mount; only USB input and only one output, so little space required by jacks.

 

Ex4) E6 has low power consumption, high efficiency, low output power levels.  It runs off a small battery and uses a low-power, highly integrated output chip which does amplification, volume control, and negative power supply rail generation all by itself.  Compare this with the much more powerful and less efficient Lyr, which needs much larger components.  It's possible to have a much more efficient design than the Lyr with similar output levels, but that's not their priority.

 

 

Audio device cost:

High costs mostly come from the relatively low volume of production—not many units are sold.  Manufacturing costs can be high, even if the cost of materials is relatively low.  In many designs, the cost of the chassis is higher than that of the electronics.  The rest of the cost goes to profits and to pay for the R&D.  


Edited by mikeaj - 11/11/12 at 8:08am
post #9 of 60
Quote:
Originally Posted by Eisenhower View Post

Quote:
Originally Posted by HamilcarBarca View Post

 

Many descriptions of sound are pure BS, but tube amps often produce a sound often referred to as "warm." It's a fact:

 

  http://en.wikipedia.org/wiki/Tube_sound

 

I agree that the notion it's due to heat or light is stupid. Those are simply two more artifacts of how tubes work.

 

 

 

Some people want a warm-sounding amp. Some people don't. Myself, I'm in the more-transparent-is-better group.

 

Nothing on that wikipedia page provides a sound technical explanation as to what make tubes sound "warm". Hi-fi tube amps still attempt to have low distortion, which wouldn't make sense if distortion was as desirable as you say.  

 

You can do such further research as you feel will help you understand.

 

It won't help to misinterpret my remarks. I didn't say and have never said distortion was desirable.

post #10 of 60
Quote:
Originally Posted by HamilcarBarca View Post

 

You can do such further research as you feel will help you understand.

 

It won't help to misinterpret my remarks. I didn't say and have never said distortion was desirable.

 

I've built two tube amps, so please don't patronize me just because you can't defend your claims.

post #11 of 60

Higher nonlinear distortion, particularly 2nd harmonic products, may be attributed to sound warm.  Kind of.  Some amps containing vacuum tubes have very low distortion though.  It mostly just has to do with the design and intent.

 

The main thing is higher output impedance.  Higher output impedance means less control over the driver and a frequency shift towards the impedance spike in the midbass that many headphones have.  Tilted FR towards midbass will make the sound warmer.  However, it's mostly just OTL tube amps that have the significantly higher output impedance, and some solid-state options have high output impedance as well.  And many headphones don't have such a feature.

 

Many tube amps that are sold are not really intended to be "hi-fi" in the sense of actual high fidelity, particularly the cheaper ones that some may be more familiar with.  (That's a bad overgeneralization when applied to all tube amps, but fair enough for some.)

 

 

 


Quote:
Originally Posted by HamilcarBarca View Post

I agree that the notion it's due to heat or light is stupid. Those are simply two more artifacts of how tubes work.

 

No, I think this could be a main contributing factor as well.  Senses are linked; expectations change perceptions.  Warmth (temperature) and light can impact the perception of sound, not to mention the time waiting for a tube amp to warm up.

post #12 of 60
Quote:
Originally Posted by mikeaj View Post

Higher nonlinear distortion, particularly 2nd harmonic products, may be attributed to sound warm.  Kind of.  Some amps containing vacuum tubes have very low distortion though.  It mostly just has to do with the design and intent.

 

The main thing is higher output impedance.  Higher output impedance means less control over the driver and a frequency shift towards the impedance spike in the midbass that many headphones have.  Tilted FR towards midbass will make the sound warmer.  However, it's mostly just OTL tube amps that have the significantly higher output impedance, and some solid-state options have high output impedance as well.  And many headphones don't have such a feature.

 

Many tube amps that are sold are not really intended to be "hi-fi" in the sense of actual high fidelity, particularly the cheaper ones that some may be more familiar with.  (That's a bad overgeneralization when applied to all tube amps, but fair enough for some.)

 

Don't you think that if tube amp designers could make their amps have 0.0% distortion, they would? And wouldn't people still claim those amps to be warmer sounding? I've used quite a few tube guitar amps that have are extremely bright sounding when distorted. 

 

The tilted FR theory does make more sense. Of course, one could easily EQ a solid state amp to achieve the same effect, or use headphones with the sound signature they desire, rather than rely on inherent flaws in an expensive output transformer...

post #13 of 60

i haven't noticed a significant change in sound signature from a DAC really. 

But amps can sound  different.  Some are warm, some are flat and sterile others are somewhere inbetween.

Tube amps tend to be in that warm vein.  I believe it comes from ever so slightly rolled off highs, and a little midrange presence

post #14 of 60
Quote:
Originally Posted by Eisenhower View Post

Quote:
Originally Posted by HamilcarBarca View Post

 

You can do such further research as you feel will help you understand.

 

It won't help to misinterpret my remarks. I didn't say and have never said distortion was desirable.

 

I've built two tube amps, so please don't patronize me just because you can't defend your claims.

 

Assembling kits isn't electronic engineering. I posted a link for you to a Wikipedia article to help get you started. Good luck.

post #15 of 60
Quote:
Originally Posted by HamilcarBarca View Post

 

Assembling kits isn't electronic engineering. I posted a link for you to a Wikipedia article to help get you started. Good luck.

 

And linking to wikipedia articles is???

 

You still haven't defended your claims. Seems to me that you actually know nothing about electronic engineering or the scientific method.


Edited by Eisenhower - 11/11/12 at 10:48am
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