DIY CMOY: First Experiences; Finally Successful
Dec 11, 2008 at 12:11 PM Post #16 of 38
Quote:

Originally Posted by dgbiker1 /img/forum/go_quote.gif
1. Use as little resistance as you can stand for R5, the higher R5, the lower the SQ.


higher R5 actually improves sound quality (lower distortion, better able to drive long cables, prevent accidental shorts, etc.). but it does lower the loudness, which is another way to cure the high gain in cmoy.
 
Dec 11, 2008 at 12:12 PM Post #17 of 38
Quote:

Originally Posted by Fred_fred2004 /img/forum/go_quote.gif
Unplug the headphones can you still hear a faint hiss if so its the same hiss you hear when you hold a seashell to your ear.


that could also be the sound of some ceramic decoupling caps.
 
Dec 11, 2008 at 12:58 PM Post #18 of 38
higher R5 actually improves sound quality (lower distortion, better able to drive long cables, prevent accidental shorts, etc.). but it does lower the loudness, which is another way to cure the high gain in cmoy.
This isn't fair to new people stop talking rubbish
 
Dec 11, 2008 at 1:03 PM Post #19 of 38
Quote:

Originally Posted by Fred_fred2004 /img/forum/go_quote.gif
higher R5 actually improves sound quality (lower distortion, better able to drive long cables, prevent accidental shorts, etc.). but it does lower the loudness, which is another way to cure the high gain in cmoy.
This isn't fair to new people stop talking rubbish


don't worry, fred. anyone graduating from a half decent highschool should have no problem understanding it.
 
Dec 11, 2008 at 10:21 PM Post #20 of 38
Then why don't you explain it

or is that beyond you
 
Dec 11, 2008 at 10:32 PM Post #22 of 38
Quote:

Originally Posted by millwood /img/forum/go_quote.gif
higher R5 actually improves sound quality (lower distortion, better able to drive long cables, prevent accidental shorts, etc.). but it does lower the loudness, which is another way to cure the high gain in cmoy.


http://www.tangentsoft.net/audio/cmo...angent-sch.pdf
R5 is inside the feedback loop, and most people do not use it, but short it. In my experience going above 100 ohms (by mistake; 470 ohms to be specific) caused massive distortion. I don't see how increasing the resistance (47k???)would achieve any of the items you list (other than perhaps tolerance for shorting the output). Please explain...
 
Dec 11, 2008 at 10:35 PM Post #23 of 38
He can't he's what we used to call a Troll he spouts rubbish and pretends to know stuff in when reality he is just an attention seeking pratt. Trying to sound important
 
Dec 11, 2008 at 11:09 PM Post #24 of 38
Quote:

Originally Posted by Pars /img/forum/go_quote.gif
http://www.tangentsoft.net/audio/cmo...angent-sch.pdf
R5 is inside the feedback loop, and most people do not use it, but short it. In my experience going above 100 ohms (by mistake; 470 ohms to be specific) caused massive distortion. I don't see how increasing the resistance (47k???)would achieve any of the items you list (other than perhaps tolerance for shorting the output). Please explain...


is it possible that the tangent version isn't what I was talking about?

HeadWize - Project: A Pocket Headphone Amplifier by Chu Moy

there are many reasons NOT to put that resistor inside the feedback loop; and there are many reasons why using a high value there would cause distortion.

and there are also many reasons to put that resistor OUTSIDE the feedback loop and having a high value there would help.

Anyone having a highschool degree will know that.

But if you need me to elaborate, I am happy to help,
smily_headphones1.gif
.
 
Dec 11, 2008 at 11:09 PM Post #25 of 38
Quote:

Originally Posted by Fred_fred2004 /img/forum/go_quote.gif
He can't he's what we used to call a Troll he spouts rubbish and pretends to know stuff in when reality he is just an attention seeking pratt. Trying to sound important


fred, you did such a wonderful job describing yourself.

a job well done!
 
Dec 12, 2008 at 1:04 AM Post #26 of 38
Quote:

Originally Posted by millwood /img/forum/go_quote.gif
is it possible that the tangent version isn't what I was talking about?

HeadWize - Project: A Pocket Headphone Amplifier by Chu Moy

there are many reasons NOT to put that resistor inside the feedback loop; and there are many reasons why using a high value there would cause distortion.

and there are also many reasons to put that resistor OUTSIDE the feedback loop and having a high value there would help.

Anyone having a highschool degree will know that.

But if you need me to elaborate, I am happy to help,
smily_headphones1.gif
.


The vast majority of people here build a CMoy from Tangent's tutorial. But yes, discussions of placing it outside the feedback loop and its benefits have occurred here as well as on headwize. A large value (actually any value) inside the FB loop will effect the gain. Outside the feedback loop is as you say a different story.

What I am interested in is your reasoning about why a large value outside the feedback loop would help. Values in the range of 47k (as you had mentioned) would absolutely kill most headphone response, as you would be dropping virtually all the output across R5. Since you're so happy to help, why don't you
popcorn.gif
 
Dec 12, 2008 at 1:16 AM Post #27 of 38
Quote:

Originally Posted by Pars /img/forum/go_quote.gif
A large value (actually any value) inside the FB loop will effect the gain.


I believe even a dropout from a half decent highschool would disagree with that statement.

Quote:

What I am interested in is your reasoning about why a large value outside the feedback loop would help.


I am happy to help on that. But first please tell me why a high value inside the feedback loop would hurt,
smily_headphones1.gif
.

you don't get anything for nothing in return.

Quote:

Values in the range of 47k (as you had mentioned) would absolutely kill most headphone response, as you would be dropping virtually all the output across R5. Since you're so happy to help, why don't you
popcorn.gif


you are absolutely right on that. The discussion where the 47k firgure came up was on interference and I was thinking about R2 but typed R5 - it is the resistor that terminates the non-inverting end to ground.

a typo on my part, sorry for that. I think I mentioned somewhere else that R5 typically is in the 11 - 120ohm range and I have used as high as 1k in one case.

yes, a 47k will basically attenuate the signal to the point where there is virtually no output on the headphone.
 
Dec 12, 2008 at 1:57 AM Post #28 of 38
Millwood, all you had to do was explain your reasoning for the modification. When someone ask you why you are suggesting a modification, responding by saying even a high school dropout would recognize why makes people think you are a smart ass, or an idiot. People are reading on here to learn, not to be insulted by you.
 
Dec 12, 2008 at 5:02 AM Post #29 of 38
Quote:

Originally Posted by millwood /img/forum/go_quote.gif
Quote:

Originally Posted by Pars
A large value (actually any value) inside the FB loop will effect the gain.


I believe even a dropout from a half decent highschool would disagree with that statement.<snip>


Actually, it will effect the gain at the opamp output pin, but not at the output as drawn. R5 is in series with R4 as far as the opamp is concerned, so...
 
Dec 12, 2008 at 7:02 AM Post #30 of 38
Guys, please ignore millwood. He is so full of it he sees brown. His intention is to illicit response for his own enjoyment. I have yet to find one post of his where he was helpful and non-combative.

There is absolutely no advantage in using a resistor greater than 100ohm for R5. The purpose of it is to help the amp drive low impedance phones. 22-50ohm should be enough for 32ohm phones. You should use as low a value as possible to attain the desired effect.
 
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