[warnerwh]

when it comes to layout of components?  What I'm trying to ask is what affect can having large caps next to say resistors have?  For example could two amplifiers that have exactly the same components and design sound different due to the layout?

Lastly: Do parts such as caps, inductors etc change from their rated values when in a circuit?  Is this something that can be accounted for?

IF these are too complex to answer to a layman such as myself don't worry about it.  I'm just wondering why two amps that would measure nearly the same would sound different assuming they're both very load insensitive and measureable distortions are below what is considered audible.  

I've read too many times that specs don't matter. What makes me wonder is that how the heck else can you design something without having design parameters that must be dealt with.  You couldn't make anything because parts specs etc don't matter. It sure as hell ain't magic.

Thanks

[JohnR]

"Specs" provide a very limited view of what the thing actually does. It's a bit like buying a car based purely on the amount of horsepower produced by the motor. A more sophisticated shopper might look at power and torque vs rpm curves. You might get really involved and try and characterize its handling in terms of spring rates and damping. But most likely, you would be better off just taking the thing for a drive.

Layout does make a difference. I'm sure someone more expert than me will comment. You may find a read of Doug Self's blameless amplifier interesting.

[Tweaker]

I was just about to ask almost a very similar question. What makes an amp sound good, or bad?
It seems to me that it should be fairly simple to design and build a great sounding amplifier. That does not seem to be the case. Some designers talk about extensive listening tests to different component selection and argue it is why they use "audiophile" grade parts. Others like Van alstine feel that is rubbish and tout their innovative circuit design. You can't argue with the results Mr. Van Alstine gets as his amps are great sounding. (But I have to wonder if they couldn't taken to yet another level if he were to use, for example, Wima resisters, Hovland polypropylene caps, etc. It would sure jack up the cost but many would no doubt gladly pay the extra money if it meant an improvement in sound). But I'm like warnerwh in that I can't totally understand why two very similar designs with good specs can sound so different. There are a lot of very mediocre amplifiers out on the market that spec out very well. So, yeah. Just what the heck is it that makes an amp sound good whatever type, class, brand it might be? Or is that an unanswerable question? Is it like a Stradivarius? No one has ever been able to figure out what made his violins so special and they have been analyized to death. Maybe it's the ears of the designer. Perhaps some just hear better and keep fussing with circuit design or component selection- whatever, untill it sounds right. Others may be satisfied with the bench performance. If it tests good, meets all of the design criteria  it's good.
  If I recall right, I think Van Alstine was the victim of plagarism some years back when B&K came out with an amp that was apparently an exact copy of an existing design of his. It was a very good sounding amp but did it sound exactly like the model it was copied after?

[Dan Banquer]

You could write a book on this, but unless you are thoroughly familiar with the priciples involved, such as biasing, feedback, compensation, reactive load handling, grounding, shielding, filtering, etc.etc. then one can only speak in very general terms that may only confuse the issue more.
My apologies,
        d.b.

[avahifi]

Don't confuse a musical instrument, which is designed to produce music, wirh an audio component, which is designed to reproduce music.

For example, good sounding wood would be important for a violin, but certainly not for a speaker cabinet, where any "sound" from the cabinet walls themselves would be all wrong.

Parts layout can certainly be an important design aspect.  For example B&W's design blunder with the 801 series II loudspeaker that we discovered and fixed for them. They located the largest iron core inductor in the crossover board (one for midrange, one for bass) next to and in line with each other.  Of course this accidently formed one large transformer.  We measured 100 percent cross coupling between the bass and midrange at 200 Hz. To make matters worse, they then made other crossover parts value corrections to try and fix the overlooked mistake.

Our .pdf file explaning the problem in detail and the fix is still available from us.

Most passive parts likely have little physical interaction.  Heat can be an enemy though, power resistors certainly can cook other nearby parts.

Microphonics are important too.  For example, many large soft spiral wound film capacitors (typically audiophile grade good sounding parts) are simply microphonic.  Adding them to a circuit actually can be the same as adding little "reverb" machines.  The added ambiance is nothing more than a series of reverb generators you cannot turn off.

Be careful what you start changing. What you hear and what you are really doing may be something completely different.

Frank Van Alstine

[Occam]

.... Lastly: Do parts such as caps, inductors etc change from their rated values when in a circuit?  Is this something that can be accounted for?
IF these are too complex to answer to a layman such as myself don't worry about it.  I'm just wondering why two amps t ...

Yup, inductors, and to a lesser extent capacitors, act in non-linear ways. An inductor behaves differently, depending on its bias voltage, current... because the various permable materials act squirrelly on its journey over the B-H curve. Similarly, non COG ceramic caps change capacitance significantly with frequency and voltage.
Both inductors and capacitors have parasitic characteristics, a capacitor has equivalent series resistance and inductance, ESR & ESL, while an inductors has ESR and ESC (capacitance).  Because resistance and the frequency dependant reactances, inductive and capacitive, all contribute to the total impedance, these comonents vary characteristics non-linearly with frequency.
I believe that much of what we call tweeks, is our subjective seach to ideally optimize those non-linear characteristics. An engineer might approach the problem with a network analyzer and non-linear gradient seach programming. They might also draw on their knowledge of those second order charateristics and use the proper tools for the proper tasks, like what cap is appropriate for that use, or an awareness of the source and load impedances. Then again, many of our tweeks might well be a search for that meliffluous distortion  

Indeed, the problem is too complex for the layman, but its also too perplexing for most engineers, who only answer with edjimacated opinions. Whether engineer or tweaker the one defining rule is -
 
First, you steal 2  identical stereo amplifiers...

[JoshK]

Its like what one of my math professors at the U of Chicago use to say, "...if only the world were linear, homogenous, stationary and gaussian..."

IMO, a good engineer is someone who understands the limitations of their model and some empirical understanding of how things behave outside the realm of there model.

[warnerwh]

Thank you guys for the responses. This helps to some degree. I know nothing about electronics but have been curious about this. I would never mod any of my electronics as I don't have a clue what I'd be doing.
The fact alot of modding is going on had been part of my reason for asking.

I see people keep modding things and wonder what makes them think they're smarter than the guy who designed it. Then the mods can cost so much that you probably should have just spent more on that component in the first place.

[Occam]

.....I see people keep modding things and wonder what makes them think they're smarter than the guy who designed it. Then the mods can cost so much that you probably should have just spent more on that component in the first place.

So the troll finally comes. Here is a great discussion, without the preamble -
http://www.audioasylum.com/scripts/t.pl?f=general&m=431712
from a like minded individual.

[Dan Banquer]

Well: I see a lot of "tweakers" who don't appear to put much thought into what they do, and there appears to be a an all too rare few who actually think about and research into what they are doing.
I am extremely pleased when I hear someone say: " I need to peruse the data sheets". I'd like to hear that more often.
I guess all too often I see knee jerk reactions when a serious view of the application is required.  
That's my 2cents.
                  d.b.

[avahifi]

One other little known fact is that when you install capacitors in parallel, you reduce their series inductance.

So if you have a 100uF speaker crossover capacitor, for example, and want to replace it with some "audiophile grade" part, but you find that your pet brand only comes in 10uF max value, then you will need ten of them in parallel to get that 100uF needed value.

Now you listen and things sound better.  You think it was because of the high priced new brand you used  Likely it was just because you reduced the circuit inductance with all the caps in parallel.

Sometimes a little knowledge is useful, and saves money too.

Frank Van Alstine

[Occam]

Dan -
A guy walks into his doctor's examining room, says -
'Doc, it really hurts when I do this', He rolls up his sleaves and proceeds to stick his arm up his arse all the way up to his shoulder.
The doctor mulls this over for a bit and says - 'Do you have to stick it up ALL the ways? and don't you think you should take your Rolex off first?'

FWIW,
Paul

[amplifierguru]

Hi warnerwh,

To answer your original question "does layout matter?" I have to say VERY much! Good layout of circuit board , lead dress and chassis layout are crucial to realizing the potential of a design!

An Example: In 1988 I was contracted to a prominent CT High End amplifier manufacturer, to design a range of mid-fi products. While I was working on my prototypes, their 'chief' engineer was prototyping the latest new model amp a few metres away. When he started scratching his head and cursing the ST analyser, I asked what the problem was. Way too much distortion 0.6% - the original design which he was reworking into a more modern style/product was much lower apparently. I quickly glanced over the prototype board. "Cut that arc shaped track and re-route it away from the input stage" I said. He did - and the THD dropped two scales to ~0.03% .

"I didn't know layout mattered!" he exclaimed. "How do you do the layouts now- fit?" , "Yes, MY DRAFTSMAN does them based on fit" . This was a company that espoused the need for reg supplies for their $10,000 amps...

I proceeded to teach him about designing layouts.

Cheers,
Greg

[warnerwh]

amplifierguru: This is just exactly what my main curiosity had been aimed at.  Thank You.

I've got a friend who does work for the military and apparently tolerances aren't tolerated much.  Layout is apparently critical but they are working in a very tiny area and mistakes and failures aren't allowed.  It just seemed to make sense that this could be the reason for the different sound we hear from very similar amps where the specs would indicate otherwise.

[Dan Banquer]

Dan -
A guy walks into his doctor's examining room, says -
'Doc, it really hurts when I do this', He rolls up his sleaves and proceeds to stick his arm up his arse all the way up to his shoulder.
The doctor mulls this over for a bit and says - 'Do you have to stick it up ALL the ways? and don't you think you should take your Rolex off first?'

FWIW,
Paul

Did he get that Rolex down in Battery Park? If so, no wonder it hurt  so much.    
           d.b.

[Dan Banquer]

From Amplifier Guru:
"I didn't know layout mattered!" he exclaimed. "How do you do the layouts now- fit?" , "Yes, MY DRAFTSMAN does them based on fit" . This was a company that espoused the need for reg supplies for their $10,000 amps... "

As I explained earlier in another thread, there are reasons for regulated supplies that are not specifically related to board layout. If you are under the misconception that board layout replaces certain advantages of a regulated power supply than I sugeest you read on further. It appears you have a problem understanding the theory here, so if you are having trouble, and I assume you are, then please feel free to ask an appropriate question.
d.b.

"I think there is another issue to be considered here, and that is with more capacitance you will better regulation of the supply. As with most of audio and the post quoted above the concept of better regulation is dismissed.
I beg to differ.
When considering better regulation one must look at the gain bandwidth of the transistors in the amp and how that relates to supply voltage. If one reads the transistor data books carefully you will find a spec for gain bandwidth at a certain supply voltage. That spec holds for that supply voltage but not other supply voltages within x amount of volts.
Now that initially sounds like a lot of techno babble but consider the following: An unregulated supply's voltage will vary under load so by definition at higher loads the voltage across the amp will sag. We also notice that when we do distortion measurements we find that the distortion increases as the load increases for amps with unregulated supplies. Now lets add some real world conditions and put the amp under reactive load (like a loudspeaker) and we are now faced with voltage and current that are out of phase at the output transistors.
The distortion can go even higher under these circumstances because the feedback that is applied to the amp was based on a relatively stable supply voltage. If that supply voltage goes outside the parameters set by the feedback loop then the gain bandwidth has changed due to supply voltage changing and the feedback loop is no longer "correct".
In short: Change that supply voltage too much and your feedback loop is not working for the initial parameters it was set for and you can get anything from instability to upper order distortion.
There is a penalty for the lack of regulation, and it goes right back to classic analog design rules. "

[amplifierguru]

Hi Dan,

Regarding your quote -

"I think there is another issue ................classic analog design rules. "

I love this 'stuff'.    Where did you get it?

Cheers,
greg

[Dan Banquer]

Hi Dan,

Regarding your quote -

"I think there is another issue ................classic analog design rules. "

I love this 'stuff'.    Where did you get it?

Cheers,
greg

In College, and over twenty years on the job in electronics. Beats the crap out of ignorance, and pays the bills.
             d.b.

[amplifierguru]

Hi Dan,

Sorry, but I'm just trying to identify the source of the quote. Was it from college notes then?

I once attended a lunch-hour lecture while working at the Uni, postgrad in Physics, being given by a EE lecturer on... wait for it ... the new distortion - TIM! Yes uni lecturers were taken in by this @#^ and spouting it , as gospel, to a room full of eager EE ugrads!   They have a lot to answer for.

Cheers,
Greg

[Dan Banquer]

There is reason why no amplifier outside of audio uses just an unregulated power supply, and use regulated supplies. The reason is outlined twice: both in this thread and the thread on power supply capacitance.
                         d.b.