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Many AV Receivers/Stereo Integrated amps do NOT use opamp powered headphone jacks - Page 5

post #61 of 215
Wow, I had to check my calendar to see that this really started 2 days ago.
Just get a good headphone amp and you won't care about these arguments anymore
post #62 of 215
Quote:
Originally Posted by pp312 View Post
There are some interesting points here. As you doubt the manufacturer's emails, I doubt that the NAD C320BEE uses op-amps. I don't contradict, I just doubt, and would like confirmation from elsewhere.
I checked again, and I was wrong.

The NAD 317 definitely use opamps, but the C320BEE uses the main amp with resistors. I feel like a heel. I was just glancing at it earlier and there is an opamp shown in the schematic right near where the headphone output is, but when I went back and looked closer, it is part of the protection circuit, not the headphone.

I can say that most of my experience is with older designs. Stuff from the 80s and 90s mostly. Most of them used opamp circuits. Some were good, some were not. I know this, because I targeted them for upgrades almost every time.

Perhaps this trend of using resistor networks is fairly new and is a sign of cheapening products.

Ok, I've buried myself deep enough. I'm out of this conversation now.

BTW, the distortion I was hearing with my Senns when hooked to the Denon was mostly during highly dynamic scenes. Gunshots, loud bass hits, etc. To me, it was a clear sign that the circuit was running out of steam.
post #63 of 215
Quote:
Ok, I've buried myself deep enough. I'm out of this conversation now.
Don't worry about it. There seems to be a ton of misinformation on this subject going around. I've done a bit of digging today and I've had some correspondence with a couple of good manufacturers and some non-affiliated technical people. I think either method can probably deliver really good results, but it seems that most headphone sections are the speaker amps stepped down through resistors, but the very best, in the most expensive equipment are separate circuits from the main speaker amps, built around op amps. At least that's what I'm getting so far. Of course this is exactly the opposite of what we have all believed here, where the conventional wisdom said that op amps were the cheap route and resistors went away with the golden age of SS in the 70s. I intend to keep digging. Op amps or resistors, I don't care. But if I can get a good headphone amp and upgrade my speaker rig with the same money and desk space, that sounds smart to me. I intend to find out. And I intend to find expertise and confirmation elsewhere.

Tim
post #64 of 215
My audiolab integrated amps sound quality character on the headphone is the same character the amp imposes on the speakers which sort of say they are just using resistors right? Anyway, My hd600s are awesome from my audiolab 8000a's headphone jack. No veil. The time I had a meier headfive, I did a comparison with the ad2000s and the audiolab was less dry and analytical yet more accurate and punchy. Bottom line is it might be pointless to get a budget headphone amp if one has a decent integrated amp. You would have to spend much more to get better than my audiolab I think.

Anyway, I'll compare the next amp I get with my integrated using the hd600 to see what the fuss is all about with more expensive headphone amps
post #65 of 215
Quote:
Originally Posted by pp312 View Post
Incidentally, I'm not sure what you mean when you say your Senns sounded distorted plugged into a Denon receiver. Distorted? Surely you'll only get distortion when there's a fault.
I have some very hard to drive headphones. If I plug them into a wimpy headphone jack, they clip so bad that the music is unrecognizable. There's no fault, other than the amp not having enough guts to drive difficult headphones.
post #66 of 215
what headphones are these?
post #67 of 215
It's happened 4 times for me.

Pioneer SE-700 is a piezo electric headphone. It requires a lot of juice. When I got it, I was at work and only had a portable amp available. I plugged it in and thought I had bought a blown headphone it sounded so bad. Literally none of the music was recognizable. The amp is a XM4 run with a wall wart, not a battery.

The next one was a Yamaha YH-3 ortho, plugged into the same amp with almost as bad a result. The music was vaguely recognizable.

The third, was not really fair to the amp. I bought an Audio Technica AT-706 electret that both the headphone and adapter were converted to TRS. For grins, I plugged it into portable amp, and what little could be heard sounded bad.

All three of these sound as good as they can sound plugged into the headphone jack of my NAD 3155 at home. Although the electret requires about 80% volume.

The last time it happened, I was listening to my iPod with an Audio Technica ATH-2. Normally, this is a fine combination. But some electronica came up with a heavy bass line and it clipped the bass really bad. The music was recognizable, just unlistenably distorted.
post #68 of 215
Quote:
Originally Posted by scompton View Post
Pioneer SE-700 is a piezo electric headphone.
I think I had one of those. Isn't it from the early 70s?
post #69 of 215
All of them are from the 70s I believe. I know the Pioneers and AT-706 are from the 70s. The ATH-2 and YH-3 may be from the early 80s. The Pioneers and YH-3 aren't great headphones, OK but not great. The AT-706 and ATH-2 are very good.

The like to the Meier article, especially the graph of the effects of output impedance, prompted me to do a test. The graph showed the extreme tilt down towards the treble of the response of the DT931 at 470 ohms.

Since I think my NAD is 470 ohms and I own a pair of DT831s, I decided to get them out and give them a listen. I haven't listened to them for over a year, before I got the NAD, and they had very little bass.

Out of the NAD they are bass monsters. Although the treble doesn't sound as bad as the graph lead me to expect.
post #70 of 215
Quote:
Originally Posted by scompton View Post
Out of the NAD they are bass monsters. Although the treble doesn't sound as bad as the graph lead me to expect.

Graphs are tricky little things. If headphones really sounded like their graphs there'd be nothing to do but stamp them into the carpet. Fortunately there's only the vaguest correlation between graphs and perceived sound.
post #71 of 215
Quote:
Originally Posted by odigg View Post
Not too long ago I came across this thread. http://www.head-fi.org/forums/f5/usi...ed-amp-329395/

More than anything else, it prompted me to finally get some evidence to either support or disprove a statement that has been made repeatedly for years. "With receivers/integrated amps the headphone jack is an afterthought. They use a cheap opamp circuit."

I decided to just email different manufacturers to ask them if opamps powered the headphone jacks or if they used resistors connected to the main amp/speaker out. I contacted Denon, Yamaha, NAD, Cambridge, Onkyo, Marantz, Harmon Kardon, and Pioneer. For the sake of full disclosure, most of the emails started out by asking a general question about if their receivers/stereo integrated amps used resistors or opamps for the headphone jack. Then I said that while I was looking for an answer about all their equipment, I would provide them some specific models if they needed them. I wandered around the websites and picked models at random, making sure to include at least one of their less expensive models. The exception to this email format was HK and NAD. For them I only asked about specific models although NAD gave me an answer about all their amps.

Here were the replies to my questions.

Email Responses

Denon - All headphone jacks are powered via resistors off the main amp.

Marantz - All headphone jacks are powered via resistors off the main amp.

Yamaha - All models powered via resistors connected to the main amp.

Nad - All models powered via resistors connected to the main amp.

Cambridge - More expensive models use opamp circuit. All others (340A, 340R, 540A, 540R) use resistors off the main amp.

Onkyo - No reply yet.

Pioneer - VSX-818 ($250), VSX-1018AH-K (both AV receivers) - resistors. A-35R ($200, stereo integrated) - resistors. SX-A6-J ($650 stereo receiver) - dedicated opamp circuit.

HK. AVR-146 uses opamp. HK-3390 uses resistors. This makes sense as people have reported the AVR headphone out is not very good but the stereo amplifiers have good headphone jacks. They provided the opamp used and a quick search suggests it isn't very good.
Mainly all of them indeed uses resistor networks to acomplished the taskt, that is true...But do not trust blindly all those answers.
Unless you talk directly with any really knowledgeable person inside the firm, mainly all customer service reps that will answer the emails has no clue of what they are talking about, and will give you a book answer, specially Marantz. For sad expereince I know that, you have to be really enquisitive to get an straight answer.
Now for example I know for sure that one recent Marantz models do have a dedicated headphone jack, and you got the opposite answer from them....
post #72 of 215
Thread Starter 
Quote:
Originally Posted by pp312 View Post
Graphs are tricky little things. If headphones really sounded like their graphs there'd be nothing to do but stamp them into the carpet. Fortunately there's only the vaguest correlation between graphs and perceived sound.
I agree. Have you ever compared headphone graphs on headroom? Look at the K701 and HD650. It looks completely different from what you would expect after reading reviews/comparison on this site.

I know nothing about frequency measurement. But I am confident that there is some mismatch between many graphs and human ears.
post #73 of 215
Thread Starter 
Quote:
Originally Posted by Sovkiller View Post
Now for example I know for sure that one recent Marantz models do have a dedicated headphone jack, and you got the opposite answer from them....
Which model are you talking about?
post #74 of 215
Quote:
Originally Posted by odigg View Post
Which model are you talking about?
While I was trying to get my PM7200, one of the technicians at Marantz that I spoke off, to find out the main differences between the PM7200 and the upcomming PM7001, one of the points he discussed with me was about the heapdhone jacks. According to him, and he asured me that, the PM7001 has a dedicated circuit behind the jack, while the PM7200 (that I ended getting) had only a resistor network. But the 7200 was Class-A while the 7001 was a current feedback amp...
I do not have schematic, so I could not tell you for sure, but the guy was really knowledgeable, and this was one fo the strongest points of our discussion, as I was really concerned about the quality of the jack as well, as sometimes we get no amp around, due to upgrades and so, and still we could use them.
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...
post #75 of 215
Thread Starter 
Quote:
Originally Posted by Sovkiller View Post
According to him, and he asured me that, the PM7001 has a dedicated circuit behind the jack, while the PM7200 (that I ended getting) had only a resistor network. But the 7200 was Class-A while the 7001 was a current feedback amp...
That's good to know. I've heard other reports that the PM7001 has a opamp powered jack.

If we exclude the high end amps that can afford to use well implemented headphone opamp circuits, there seem to be a number of current day models that use resistor outs. With that in mind a question would be, why go with the cheap opamp method when a resistors would be cheaper and work better?

Based on other posts in this thread, I suspect that some designs (class D for example) don't easily lend themselves to sharing a ground between speakers (or drivers) and this is why the resistor route does not work. Perhaps there are other amplifier designs that will also sound bad with a resistored off headphone jack.

Which brings me to an interesting experiment. The HK AVR-146 (perhaps all models in the AVR series) use a opamp headphone jack. If somebody was to connect a DIY headphone adapter to the speaker terminals, would it sound bad? Based on my paragraph above I predict it would. Anybody want to try it?
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