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Many AV Receivers/Stereo Integrated amps do NOT use opamp powered headphone jacks - Page 6

post #76 of 215
Quote:
But after testing the 7200 in Harvey, it was so quiet and clean sounding using the CD3K, even at full volume, that honestly, I did not care a little bit about what was behind it...
BTW many vintage receivers also have that solution and they offer very good sound, the main problem is how good and clean sounding the amp is...
I've been trying to get to some truth around this issue in the last couple of days. I have a vintage Harmon Kardon that sounds great with my HD580s. I picked up a 70s Kenwood receiver for my dad at a garage sale a couple of months ago and it sounded good with the 580s as well. Still, it seems that some of the better manufacturers use discrete headphone circuits in their best integrated amps (You heard it from Marantz, I got it yesterday in a conversation with folks at Yamaha about their high-end A-S1000 and A-S2000...). The drawback, from what I've gotten so far, with the resistor method is with low impedance phones. These systems tend to have high impedance output compared to discrete, op amp based headphone jacks, and evidently that can seriously effect the frequency response of low impedance phones.

Or so I'm hearing. I haven't heard enough of anything to be sure yet.

Tim
post #77 of 215
FWIW, later this week I'll be taking ownership of the Onkyo A-9555 integrated amp. I'm anxious to hear how it's headphone out compares to my GS-1 (provided my current bout of tinnitus clears up shortly).

Slighty OT, why do you think that reviewers of major publications rarely discuss the capabilities and specs of headphone outs on amps and receivers? When The Absolute Sound and Stereophile reviewed the Onkyo, both failed to mention the headphone out other than that it included one.
post #78 of 215
Thread Starter 
Quote:
Originally Posted by tfarney View Post
The drawback, from what I've gotten so far, with the resistor method is with low impedance phones. These systems tend to have high impedance output compared to discrete, op amp based headphone jacks, and evidently that can seriously effect the frequency response of low impedance phones.

Or so I'm hearing. I haven't heard enough of anything to be sure yet.

Tim
The theory is actually quite sound for this. There have been instances where line noise was virtually undetectable with high impedance headphones and absolutely horrible with low impedance headphones.

To throw some hard evidence into answering this question, I tried a Denon-D2000(25 ohms), ATH-AD900(35 ohms), and SR-225(32 ohms) with a Sherwood integrated that was fairly old. I don't know what was powering the headphone jack. All of them sounded fine. No distortion or anything that seemed very off. The person who owned the system is a musician and a former music teacher. He had been listening to the receiver with some Yamaha reference monitors for years. He liked the AD900 and just loved the D2000. We listened (rock, opera, classical) to a wide range of music and he didn't seem to have any complaints apart from not liking the SR225 all that much.

Quote:
Originally Posted by zotjen View Post

Slighty OT, why do you think that reviewers of major publications rarely discuss the capabilities and specs of headphone outs on amps and receivers? When The Absolute Sound and Stereophile reviewed the Onkyo, both failed to mention the headphone out other than that it included one.
Probably because headphones are even more of a niche product than high end audio. I know somebody who has $100,000 worth of "critical listening" speakers in one room. He has other setups around his house. When I asked about headphones he said he had of pair of electrostatics he hadn't used for a while. They were in a box somewhere

zotjen - You seem to have a few low impedance headphones. Do you have a integrated or AV receiver? Could you try those headphones with the receiver and report back here what you find? If you do have one, could you tell us the model number. Also let us know how you like the Onkyo - I already know how the headphone jack is powered but I won't tell you yet!

We already have evidence that resistor powered headphone jacks work well with high impedance headphones. It would be nice to have some reports on low impedance headphones.

Anybody with a resistor powered headphone jack want to head over to their local store and pick up some headphones and see how it sounds? The MDR-7506 is available at Guitar Center!
post #79 of 215
Quote:
We already have evidence that resistor powered headphone jacks work well with high impedance headphones. It would be nice to have some reports on low impedance headphones
I wouldn't expect low impedance phones to distort with the resistor method. Based on what I've heard, the high impedance output will change the frequency response of low impedance phones. You might actually like what you get, who knows?

Very sensitive phones, which are often of the low impedance variety, will reveal noise in any amp where it is loud enough. I have no reason to believe that a well-implemented resistor-type headphone section will be noisier than a discreet circuit built around op amps.

Tim
post #80 of 215
Quote:
Originally Posted by odigg View Post

I know nothing about frequency measurement. .
Well then maybe you should learn a bit about it, before saying that something is amiss... If they where measurements for speakers, they would not sound great, but when the driver is in a headphone....
post #81 of 215
I can't imagine using low impedance phones with my NAD. I'm listening to my 250 ohm DT831 right now. The volume knob is at 8:00, 8:30 is too loud, and 6:30 is no sound. I don't think I could get the volume low enough.

Edit: Just tried the KSC75 and they needed the same level on the volume knob I wonder what the sensetivity of the DT831 is. BTW, the KSC sounds like crap compared to the Beyer, regardless of the hype the get here
post #82 of 215
Thread Starter 
Quote:
Originally Posted by tfarney View Post
I wouldn't expect low impedance phones to distort with the resistor method. Based on what I've heard, the high impedance output will change the frequency response of low impedance phones. You might actually like what you get, who knows?

Tim
I should have elaborated on my earlier comments on the three headphones out of the receiver. I had a chance to also run them through the DAC/AMP of the Total Bithead. Now, people do say the D2000 and SR225 more than a simple portable amp, but the ATH-AD900 is sensitive enough to run out of most anything. People have reported little to no improvement amping them. With that in mind I say the following comments.

It's been a couple of months since I did the comparision, but I don't recall any major tonal shifts between the Total Bithead and the Sherwood headphone jack. The Bass was a little flabby with the Sherwood, but that seemed to be the general character of the amp rather than a tonal shift. As said by scompton, it didn't take all that much to go from nothing to deaf on the volume dial.

Nick 214-As I don't know anything about frequency measurement, perhaps you could explain more about what you said. Are you saying that headroom's measurements accurately represent what people are hearing? I do know that speakers *should* have a flat measurement and headphone are looking for something else.
post #83 of 215
Quote:
Originally Posted by tfarney View Post
I wouldn't expect low impedance phones to distort with the resistor method. Based on what I've heard, the high impedance output will change the frequency response of low impedance phones. You might actually like what you get, who knows?

Very sensitive phones, which are often of the low impedance variety, will reveal noise in any amp where it is loud enough. I have no reason to believe that a well-implemented resistor-type headphone section will be noisier than a discreet circuit built around op amps.

Tim
That is true, but do not forget that what they use most of the times is not a simple series resistor to just attenuate, but a resistor network, that combine both series and parallel resistors, to compensate for the differences that you may get, and try to preserve the original sound of the amp...of course in some cases depending on the values and hepadhones to be used, you will get better or worst results, in the Marantz I have tried both, high and low Z and both sound about the same...I prefer the headphone amp by far, of course, but with the lack off, and in an emergency, I could easily live with it...
post #84 of 215
Thread Starter 
After billbillw's comment I emailed replied to Denon's email. I was more insistent about details with their answer. Apparently their previous answer was not accurate. Turns out, in their AVR line, models above the AVR-788 and AVR - 1908 use a dedicated headphone circuit. Keep in mind that the AVR - 788 and AVR -1908 are the same receiver with a different case design.

So, it turns out they use a dedicated circuit in their more expensive amps, perhaps where there is more money to create a decent design. I guess somebody would have to test it to make sure.
post #85 of 215
Quote:
Originally Posted by odigg View Post
After billbillw's comment I emailed replied to Denon's email. I was more insistent about details with their answer. Apparently their previous answer was not accurate. Turns out, in their AVR line, models above the AVR-788 and AVR - 1908 use a dedicated headphone circuit. Keep in mind that the AVR - 788 and AVR -1908 are the same receiver with a different case design.

So, it turns out they use a dedicated circuit in their more expensive amps, perhaps where there is more money to create a decent design. I guess somebody would have to test it to make sure.
Aren't most AVR amps multi channel? I'd think all multi channel amps would need a dedicated op amp circuit. I don't really know anything about circuit design, so it may be relatively simple to combine multiple channels in to 2. But it can't be as simple as a stereo amp.
post #86 of 215
Quote:
Originally Posted by scompton View Post
Aren't most AVR amps multi channel? I'd think all multi channel amps would need a dedicated op amp circuit. I don't really know anything about circuit design, so it may be relatively simple to combine multiple channels in to 2. But it can't be as simple as a stereo amp.
I don't think it combines multiple channels into 2 but, rather, each channel has a separate amp, so if you wanted to feed a headphone out through a nest of resistors, you would only use two of the amps. I know my 7.1 channel digital Panasonic uses two amps to each front speaker when running in 2-channel mode, unless you bi-wire, in which you can set it to feed two amps to each woofer and one to each tweeter.

The really interesting thing about all of this is that the discrete headphone circuit, built around op amps, is emerging, not as the cheap-o compromise it has been positioned as here on Head-fi, but as the preferred method that some of the best companies (well, Marantz, Yamah, Nuforce...) use in their best integrated amps and receivers, regardless of whether they are AV or not.

It really should come as no surprise. Some really great dedicated headphone amps are built around op amps. Op amps in an of themselves are not a problem. The surprise is that here on Head-fi we've had it wrong all along. Oh and by the way, my old Harmon Kardon, with it's nest of resistors, still makes my HD580s sound great.

Tim
post #87 of 215
Quote:
Originally Posted by scompton View Post
Aren't most AVR amps multi channel? I'd think all multi channel amps would need a dedicated op amp circuit. I don't really know anything about circuit design, so it may be relatively simple to combine multiple channels in to 2. But it can't be as simple as a stereo amp.
I was wondering the same question. I wouldn't be surprised to learn that OPAMP based receiver offer virtual headphone, dolby headphone, silent cinema, surround headphone or whatever you call it... And that resistor based don't offer this feature...
post #88 of 215
Thread Starter 
Quote:
Originally Posted by scompton View Post
Aren't most AVR amps multi channel? I'd think all multi channel amps would need a dedicated op amp circuit. I don't really know anything about circuit design, so it may be relatively simple to combine multiple channels in to 2. But it can't be as simple as a stereo amp.
As far as I know, AV receivers use multiple amp sections. One for front, one for rear, one for center, etc. If you take something like the Cambridge 340A (stereo) vs 340R(5.1), I'm guessing the 340R has the equivalent of 2 340A'a and a one channel amp for the center. So from there it shouldn't be too hard to just resistor off the one main amp for the fronts. I was looking at a discontinued Yamaha 5.1 amp schematic and this is exactly what they have done.

Also keep in mind that a lot, if not all, amps tend to split all channels and amplify them individually. So even a stereo amp is two one channel amps.

As for using opamps for Dolby Headphone, I think that depends on how the signal processing is done. If all the DSP is done on one chip then perhaps the resistor method will work. If there are two DSP sections (one for main amp, one for headphone jack) then the opamp solution is more likely(I think).
post #89 of 215
OK..correct me if I am wrong, but I think all the previous discussions have been wasted by not discussing the purpose of headamp and the related formulas.

Purpose: headamp is designed to do 2 things: 1) perserve small complex signals, and 2) provide enough driving power to the headphone

Problem with integrated amps with R divide: 1) by having an extremely high output Z, the amp, the power amp is effectivly restricting voltage output as its necessary since most integrated are at least 30dB in gain. Now when your Zload >> Zoutput, you are making the load less sensitive to the input voltage and therefore you lose alot of the fine detail and you also loose control. If you look at damping factor (DF), you will see that in a R divide headamp, you have a very very tiny DF; and a tiny DF means lack of control, sloppy base, and loss of details.

Another more damaging problem with integrated amp is the DC offset at the output, while they are sufficently low for speakers, even a few mV can do damage to your headphone should you decide to leave it plugged in all the time.
post #90 of 215
Quote:
Originally Posted by FallenAngel View Post
It's a matter of "properly implemented". Single resistors to drop current will set the output impedance and create a voltage divider with the headphones altering their frequency response (changing how they sound).
are you sure? I don't recall being able to create a filter with just linear elements; a filter requires atleast a 2nd order circuit.
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