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Many AV Receivers/Stereo Integrated amps do NOT use opamp powered headphone jacks - Page 8

post #106 of 212
7/1/08 at 5:54pm
Thread Starter 
Quote:
Originally Posted by Headdie View Post
Thanks for your answer. I'd say that I'm still confused period, by that thread and more, but I don't give up So a 1-headphone can be played without a dedicated amplifier, the sound level will be ok, but the sound quality won't be very good, because the amp won't have enough grip on the drivers (not enough damping factor remaining at headphone out)...
I think the idea was that a "1" headphone doesn't need a dedicated amplifier and you will get most or all of it's "goodness" without an amp. I take the example of the ATH-AD900. An amp improved the "sound quality" by nothing at all to my ears.

The 3 is at the opposite end (or it is supposed to be). Without a dedicated headphone amp it's going to be rather flat - or so they say.
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post #107 of 212
7/1/08 at 6:02pm
Quote:
Originally Posted by odigg View Post
Thanks!
That is assuming the A449 headphone jack is resistors off the main speakers. How old is that amplifier? I've been trying to find info on it but haven't had much luck.
It's an early 90s amplifier, and I have always assumed that it uses resistors off the main speakers since there is only one voulme control for the entire item. It was hard to see more clearly with the lid off too.
( Pictures of the inside of the amplifier (I have hi-res photos but head-fi won't allow large attachments) http://www.head-fi.org/forums/f5/fix...5/#post4406501 )

Quote:
Originally Posted by odigg View Post
Just so we have more information regarding that bass behind the noise section in the second track, how does it sound through speakers? Do you get that same feeling, that the bass is hidden? I'm trying to figure out if that is the character of the amp or if we are talking about issues only with the headphones.
I'll have to try that later because if I power on my Infinity Alpha 50s now in the middle of the night I will cause some trouble that will be hard to explain....
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post #108 of 212
7/1/08 at 6:18pm
Thread Starter 
Quote:
Originally Posted by DefectiveAudioComponent View Post
It's an early 90s amplifier, and I have always assumed that it uses resistors off the main speakers since there is only one voulme control for the entire item. It was hard to see more clearly with the lid off too.
( Pictures of the inside of the amplifier (I have hi-res photos but head-fi won't allow large attachments) http://www.head-fi.org/forums/f5/fix...5/#post4406501 )

I'll have to try that later because if I power on my Infinity Alpha 50s now in the middle of the night I will cause some trouble that will be hard to explain....
Only having one volume knob doesn't indicate things either way and a picture probably won't help either. A lot of times the resistors are on the board with the rest of the parts so it's hard to figure out what is going on.

If you look at the headphone jack in those pictures, do you see resistors on or connected directly to the jack?

Let us know what you think in the morning. Go to sleep (by order of odigg)
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post #109 of 212
7/1/08 at 6:41pm
I don't think there is anything inheretly wrong with liking int amp and find the sound satisfying. Subjective like and objective performance are interconnected, but then they are not porpotionally varied with one another...my data poinst is PS1..measure like crap..sounds like wonder.

Have fun with your int, but you all should keep in mind that there are limitations and there are better stuff out there, and int amp is no where near the top.
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post #110 of 212
7/1/08 at 6:52pm
Quote:
Originally Posted by chesebert View Post
volume control (attenuation) happens at the Vinput NOT Voutput.
I still don't get it. Perhaps it's because I don't know what the "V" is. But I get input and output. At either end, the signal from the source is running through a nest of resistors. If that sucks out detail what is the difference. And talk real slow and kinda loud. I'm dumb and I don't hear so good.

Tim
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post #111 of 212
7/1/08 at 7:10pm
I think he's saying that the potentiometer is before the amp circuit. It's essentially part of the preamp section, so it doesn't effect the output impedance. I assume it's isolated somehow from the actual input or it would effect the input impedance which I think I've read is not a good thing.

I'm not sure how all of this works. I just started reading a book on Electronics that was recommended in the DIY forum, so I can get some type of handle on it.
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post #112 of 212
7/1/08 at 7:14pm
Quote:
Originally Posted by tfarney View Post
I still don't get it. Perhaps it's because I don't know what the "V" is. But I get input and output. At either end, the signal from the source is running through a nest of resistors. If that sucks out detail what is the difference. And talk real slow and kinda loud. I'm dumb and I don't hear so good.

Tim
hmm...let's see if I can explain this in the most basic way.

attenuation at input (Vin) reduces the signal level, but does not reduce the detail of the signal (fast forier transform (FFT)will still reveal all the frequency components of the composite sine waves) such that FFT of the source output == FFT after the attenuator, only reduced in amplitude. But having a resistor divider at the output is not like atten at the input, wherein the output is driving a load resistor or load imp. The effect of a high output Z driving a low load Z is that the signal does not transfer well from the output to the load, such that the load is only sensitive to the higher signal sine wave components, whereas the lower signal sine wave components are left out. As a result your FFT at the out put of the driving stage but before the resistor divider != FFT measured after the resistor divider (assuming amp and load have formed a complete circuit).

It might be helpful to have another EE verify my explanations.
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post #113 of 212
7/1/08 at 7:23pm
Quote:
Originally Posted by scompton View Post
I think he's saying that the potentiometer is before the amp circuit. It's essentially part of the preamp section, so it doesn't effect the output impedance. I assume it's isolated somehow from the actual input or it would effect the input impedance which I think I've read is not a good thing.

I'm not sure how all of this works. I just started reading a book on Electronics that was recommended in the DIY forum, so I can get some type of handle on it.
headphone amp IS a special preamp with enough power to drive low imp loads (normal preamp drive imp in the kohms), so most great headamp can be used as preamp; and some preamp can be used as headamps (benchmark DAC1 for example)
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post #114 of 212
7/1/08 at 7:32pm
Thread Starter 
Quote:
Originally Posted by chesebert View Post
It might be helpful to have another EE verify my explanations.
Dude. I don't mean to be mean, but are you really talking about fourier transforms to somebody who just said he needs things spelled out for him? Even a second year EE student would have cried at your answer. I'm not an EE, but I do have a fair bit of technical knowledge and your answer is confusing. If I got the gist of your explanation right, it can be explained in a simpler language. I'll let you do it because you have far greater knowledge of electronics than me.

Bring it down a few levels.
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post #115 of 212
7/1/08 at 7:44pm
Quote:
Originally Posted by odigg View Post
Dude. I don't mean to be mean, but are you really talking about fourier transforms to somebody who just said he needs things spelled out for him? Even a second year EE student would have cried at your answer. I'm not an EE, but I do have a fair bit of technical knowledge and your answer is confusing. If I got the gist of your explanation right, it can be explained in a simpler language. I'll let you do it because you have far greater knowledge of electronics than me.

Bring it down a few levels.
Here is a great little claculator (better to see it in action

Voltage Bridging - Zout - Interconnection of two units - sengpielaudio

honestly inadequate damping is only a theory...audio is strange enough of an animal that I have given up mostly on finding any plausible explanation for why certain circuit sounds a certain way....

if you judge by your ear you can't be wrong
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post #116 of 212
7/1/08 at 8:13pm
Quote:
Originally Posted by chesebert View Post
Here is a great little claculator (better to see it in action

Voltage Bridging - Zout - Interconnection of two units - sengpielaudio

honestly inadequate damping is only a theory...audio is strange enough of an animal that I have given up mostly on finding any plausible explanation for why certain circuit sounds a certain way....

if you judge by your ear you can't be wrong
Well, I'm doing that and you're telling me I either have no taste or can't hear, so I thought I'd try a different angle. FWIW, I don't doubt for a moment that we hear things differently.

Tim
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post #117 of 212
7/1/08 at 8:18pm
A voltage divider is a voltage divider whether it be at the front or the rear. However the issues with it at the rear are 1) likely to dissipate some heat and hence be chosen as a chunky low precision part that may change value slightly as it heats, 2) the 'upper' resistor in the divider is in series with the amp output impedance and hence raises the effective ouput impedance resulting in a very significant decrease in damping factor. In practice these things may or may not be important or noticeable.
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post #118 of 212
7/1/08 at 8:25pm
Quote:
Originally Posted by Leny View Post
A voltage divider is a voltage divider whether it be at the front or the rear. However the issues with it at the rear are 1) likely to dissipate some heat and hence be chosen as a chunky low precision part that may change value slightly as it heats, 2) the 'upper' resistor in the divider is in series with the amp output impedance and hence raises the effective ouput impedance resulting in a very significant decrease in damping factor. In practice these things may or may not be important or noticeable.
Or may be prefereable. It's been my experience that non-dedicated amps generally have a fuller bass--not necessarily flabby but just fuller, giving more foundation to the sound. Someone has posted here that this often gives a better subjective balance whether totally accurate or not, and so I've found. It's interesting that one or two of the better Cmoys on Ebay are now offering switchable bass boost (eek!).
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post #119 of 212
7/1/08 at 11:09pm
Quote:
Originally Posted by Leny View Post
A voltage divider is a voltage divider whether it be at the front or the rear. However the issues with it at the rear are 1) likely to dissipate some heat and hence be chosen as a chunky low precision part that may change value slightly as it heats, 2) the 'upper' resistor in the divider is in series with the amp output impedance and hence raises the effective ouput impedance resulting in a very significant decrease in damping factor. In practice these things may or may not be important or noticeable.
But according to the linked Meier article, if you put a resistors in parallel you can lower the impedance. He was saying to build an adapter outside of the amp for amps like my NAD, that for all I can tell just has 470 ohm resistors in series. It doesn't make a difference which side of the headphone jack you put the parallel resistors does it? The article said the output impedance is (R1*R2)/(R1+R2) where R1 is the resistor in series and R2 is the resistor in parallel. So if I make an adapter that has 220 ohm resistors in parallel, I'll end up with 150 ohm output impedance which I believe is more normal.

I do like the way it currently makes my DT831 sound. From what I've read in the Ortho thread, output impedance makes no difference to orthos which is what I usually have plugged into the headphone jack anyway. And Stax on the speaker outs.
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post #120 of 212
7/1/08 at 11:35pm
Quote:
Originally Posted by scompton View Post
But according to the linked Meier article, if you put a resistors in parallel you can lower the impedance. He was saying to build an adapter outside of the amp for amps like my NAD, that for all I can tell just has 470 ohm resistors in series. It doesn't make a difference which side of the headphone jack you put the parallel resistors does it? The article said the output impedance is (R1*R2)/(R1+R2) where R1 is the resistor in series and R2 is the resistor in parallel. So if I make an adapter that has 220 ohm resistors in parallel, I'll end up with 150 ohm output impedance which I believe is more normal.

I do like the way it currently makes my DT831 sound. From what I've read in the Ortho thread, output impedance makes no difference to orthos which is what I usually have plugged into the headphone jack anyway. And Stax on the speaker outs.

Here is an article of how to do it....hope this helps...
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