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Skeptico Saloon: An Objectivist Joint - Page 8

post #106 of 820
Quote:
Originally Posted by OJNeg View Post

 

Correct me if I'm wrong, but most valve amps don't use NFB because it's not plausible in the design. Tying the feedback loop to the output with an OPT would introduce phase shift and all sorts of other problems. Rod Elliott wrote about this a little bit. Maybe there are a few designs out there that manage to do so, but I'm not aware of them.

 

Also, since most valves are constricted to fairly low gain, trading it in with NFB doesn't make sense. There's no need to use NFB to stabilize the circuit like you would with an op-amp (infinite gain). Saying that valve amps need "adequate negative feedback" is a bit misleading methinks.


Yeah, I would say you are incorrect in the idea most valve amps don't use NFB.  Most have a small amount of global NFB.  You can't use too much or the circuit will oscillate due to phase shifting.  Of course in the last 20 years many triodes SE, and PP have been put forward without global feedback due to the idea NFB is always bad.  Even so I believe most you encounter do have NFB.  The NFB used in tube amps is normally not a large amount.  This will lower distortion a bit, extend bandwidth a bit, and lower output impedance some.  It helps to have quality OPT's.

 

This page has pertinent formulas for designing tube feedback circuits. Very near the bottom of this long page are two graphs of response for an amp with and without feedback. In this case 12 dB feedback.  One shows it without phase compensation in the feedback path and one with phase compensation. 

 

http://www.turneraudio.com.au/basic-tube-3.html


Edited by esldude - 7/4/13 at 12:50pm
post #107 of 820

Hello friends.

 

If you had to choose one of those IEMs by looking at it's measurements, which one would it be?

 

http://www.innerfidelity.com/images/LGQuadbeatHSSF420.pdf

http://www.innerfidelity.com/images/SteelseriesFluxInEar.pdf
 

post #108 of 820
Quote:
Originally Posted by Kaffeemann View Post

Hello friends.

 

If you had to choose one of those IEMs by looking at it's measurements, which one would it be?

 

http://www.innerfidelity.com/images/LGQuadbeatHSSF420.pdf

http://www.innerfidelity.com/images/SteelseriesFluxInEar.pdf
 

assuming that's the sound signature you want, I would go with LG

post #109 of 820

LG

post #110 of 820
LG - "Life is Good"
Yeah the measurements for the LG look better unless you prefer the darker sound of the SteelSeries.
post #111 of 820
Quote:
Originally Posted by jcx View Post

triodes have V feedback built in - the mu parameter

 

its difficult to build any amplifying circuit of any utility without feedback - but it may be local feedback, not global - certainly global feedback around output transformers is limited by the transformer bandwidth/phase shift

 

some marketing "no feedback" amplifiers try to deny that local or internal feedback is exactly that, negative feedback


Local feedback for sure. When people talk NFB, I generally think of a global loop from the output tied back to an inverting input.

post #112 of 820
Quote:
Originally Posted by miceblue View Post

LG - "Life is Good"
Yeah the measurements for the LG look better unless you prefer the darker sound of the SteelSeries.

LG used to be lucky goldstar XD

post #113 of 820
While an objective approach to this hobby seems like a sane one, the fact of the matter is that that stuff doesn't sell. And in the end, it's about the dollar. And if enough people run around telling others that the 50 dollar China no name amp/dac simply does the exact same thing as a 1000 dollar woo audio firefly, then this hurts business.

I mean, who would buy an audio magazine with titles on the cover like:

Big amplifier test: They all sounded the same!
Audio myths revealed: Those high end racks could be made of bricks no sonical differences found.
Interview with dre: My headphones sound like crap but they have dat thug life yolo factor!


So, I always try to educate, but not flame. I know it's hard and I miss a step once in a while and go postal on a cable guy.

I feel that the above woo audio IS worth the money, just not purely following rational thinking and measurements. A WA2 is just plain porn in my eyes. It looks sexy as hell and is built really nicely out of good looking aluminum et cetera.

It's just when some 16 yo spends a bunch of his hard earned paper boy cash on, lets say a cable upgrade, that I feel the need to jump in with facts.

Why is it that in other industries these things are considered plain and real fraud but in the audio industry sell like hot cakes without remorse? And should I start making "audiophile products" too?
Edited by ev13wt - 7/6/13 at 3:59pm
post #114 of 820
Quote:
Originally Posted by ev13wt View Post

I feel that the above woo audio IS worth the money, just not purely following rational thinking and measurements. A WA2 is just plain porn in my eyes. It looks sexy as hell and is built really nicely out of good looking aluminum et cetera.

 

I look at it this way... If I'm going to spend a grand on a good looking, sexy hunk of metal, I think I'd like it to be a bronze of a female nude.

post #115 of 820
Quote:
Originally Posted by bigshot View Post

I look at it this way... If I'm going to spend a grand on a good looking, sexy hunk of metal, I think I'd like it to be a bronze of a female nude.

But, does she have tubes that glow? no. smily_headphones1.gif
post #116 of 820
Quote:
Originally Posted by ev13wt View Post


But, does she have tubes that glow? no. smily_headphones1.gif

 

She might...

"Danger!  High Voltage" by Electric Six:

https://www.youtube.com/watch?v=2a4gyJsY0mc

post #117 of 820
Quote:
Originally Posted by Don Hills View Post

She might...
"Danger!  High Voltage" by Electric Six:
https://www.youtube.com/watch?v=2a4gyJsY0mc


hahaha nice one. I actually listen to the whole song too. smily_headphones1.gif
post #118 of 820
Quote:
Originally Posted by KamijoIsMyHero View Post

 

assuming that's the sound signature you want

 

biggrin.gif

post #119 of 820
Thread Starter 

So this program by Harman was posted in another forum here; it's called How to Listen. It offers examples of different types of distortion that users can classify. Legit or no legit? It seems like it could be a very helpful tool.

post #120 of 820
Quote:
Originally Posted by gnarlsagan View Post

So this program by Harman was posted in another forum here; it's called How to Listen. It offers examples of different types of distortion that users can classify. Legit or no legit? It seems like it could be a very helpful tool.

Very legit!
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