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Are amplifiers worth it - Page 15

post #421 of 429
Quote:
Originally Posted by runnin' View Post

Arny, I don't quite understand that graph, or most of what you were trying to say, but let's stick with the graph. Why does it measure power losses in db's? Normally power loss is measured in watts, or something of that nature.

Different authors make different choices. In this case there can be an isomorphic transformation between watts and dB so the choice of one over the other is in some sense arbitrary.
Quote:
Also, since I've got you on the horn, you as well as everyone else who bothered, ignored the diode effect I had mentioned. Would you mind sharing your views on that as well?

There are several diode effects related to wire. In the end, if they were significant they could at least be measured.

Commercial speaker and interconnect wire is usually carefully made so that diode effects are pretty much avoided.

Copper and other materials used in fabricating wires and connectors are themselves highly linear stuff.

Over a period of time corrosion by oxygen, sulfur and other contaminants can lead to the creation of chemical compounds on the surface that are nonlinear. In my experiments highly corroded copper wire remains highly linear, even if finely stranded and heavily corroded, provided you make a good electrical connection to the actual copper core.


In some of my experiments I took heavily corroded (literally green-blue) stranded copper wire, cleaned up the ends with fine sandpaper, soldered the wire to electrical contacts, and tested it for linearity. The wire remained linear to well below the -110 dB level. That is something like my local measurement limit.

I've seen tests that claim to have found non linearity in copper wire somewhat below the -140 dB level but those experiments were questionable simply because audio measurements at that level are inherently flaky. At that level the thermal air currents in your living room are magnified so that they are more like a hurricane.

The threshold of human hearing for nonlinear distortion under very ideal conditions is more like -66 dB. Under typical conditions it may be has poor as -20 dB or even poorer.

So whether tests show nonlinearity 100 dB down, 110 dB down or 140 dB down its all sonically moot.

OTOH make a inadequate connection with corroded cables and you can have large amounts of measured distortion: 30% or more. Corrosion can simply mute the signal.
Edited by arnyk - 12/19/12 at 7:41am
post #422 of 429
1% distortion is -40 dBV or -20 dBW and I bet most can't hear that if it happens to musical peaks whilst listening to a CD (record, tape, whatever). Most speakers set the distortion floor of the system, not the electronics let alone the wires.

Arny has done an excellent job of discussing skin effect, along with good insights from others. It is often very misunderstood by audiophiles, in part due to misapplication of the concepts by some cable manufacturers. I can't recall specifics off-hand (and don't care enough to look any up) but there have been some very "interesting" white papers posted. It can be a huge issue for me in my work (which has ranged from 10 to 100+ GHz); it is something I don't worry about in my stereo.
post #423 of 429
Quote:
Originally Posted by runnin' View Post

Arny, I don't quite understand that graph, or most of what you were trying to say, but let's stick with the graph. Why does it measure power losses in db's? Normally power loss is measured in watts, or something of that nature.
Also, since I've got you on the horn, you as well as everyone else who bothered, ignored the diode effect I had mentioned. Would you mind sharing your views on that as well?

Quote:
Originally Posted by JHAz View Post

Why is a football field measured in yards, not inches?
dB is more relevant in audio, so it's pretty common to see things measured (and in the pro world specified) in dB. Also, I can't give a hard and fast answer in watts, because it depends on what the power input is. You could, as Arny does above, convert dB to percent . . .

It is presented in dB because dB is a ratio and as such makes the chart universal. If the y-axis was based on watts you've need to have a different chart, or at least different y axis scale, for every wattage discussed. With dB, the ratio is the same regardless of the watts so you just use the dB (ratio) to calculate based on the watts in the specific application.

Just for an example, the -0.1dB @ 100kHz would be about -0.023W relative to 1W and about -8.6W relative to 375W.
Edited by whoaru99 - 12/19/12 at 10:55am
post #424 of 429
Quote:
Originally Posted by kbarnes701 View Post

Perhaps you would care to reply to post No 375?  GP4 hasn't, so maybe you can help... thanks.
Yo KB; did you read Quantum Studio's earlier post? He ANSWERED your Q about post #375 before I got to it & and he answered WAAAY better than I could have. Thank you QS! I'm w/ya, QS buddy on many other points in that post, my fav, the one on our Creator.

T
post #425 of 429
Quote:
Originally Posted by arnyk View Post

I agree that the project looks nice. Very nice. Been there, done that. But we have to pinch ourselves and realize that DIY projects like this are more about craft, art and personal satisfaction than any actual improvement or difference in sound quality.

Don't forget that DIY you get more for less. As mention, the main benefit is you can fine tune the amp gain to match your pre-amp or receiver. I think this is a part where it will influence the SQ plus knowing your speaker power requirement. Also need to mention I listen at close to reference level around -2db to -5db. In my situation, I don't think Denon 4311 alone can drive all 7 channels at reference level. If you don't listen at such level + high efficiency speaker, I agree you might not need an external amp.
post #426 of 429
Quote:
Originally Posted by Johnny2Bad View Post

SNIP

This was a nice read, yet disturbing at the same time, because now I see that the FTC is freaking aware of this, yet like many government bodies simply does nothing about it. A very similar issue takes place with computer PSUs and everyone savvy knows about it, it seems unbelievable that it has been allowed to go on for over 3 decades now. It seems to me that by now they should have come up with a pretty simple universal power rating because it only serves to confuse the consumer even more. Just like in HT, in computers people are often duped into buying new PSUs that are way more powerful than they need because the companies that make say video cards have learned that most PSUs are so over rated they in turn must way over rate what the requirements of their video card are to play it safe.
post #427 of 429
Thread Starter 
Well in speaking about the amps in avr's I can say I hear a noticeable difference now that I have a different one. I had a Denon 1611 and when I listened close to reference I would have to turn it down because it was painful. Now that I have the Onkyo 805 I can listen at or close to reference without any issues and the system sounds nice with a punch.
post #428 of 429
Thread Starter 
Quote:
Originally Posted by runnin' View Post

I just think it's not worth adding a lot of upgrades when you have ceiling speakers.

For the most part maybe not however, I upgraded av's from the Denon 1611 to the Onkyo 805 and the sound is night and day even with the in ceilings. The bass is for sure very noticeable and clean.
post #429 of 429
Changing AVRs changes a lot more than just the amps in the box...
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