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Old 10th January 2011, 09:32 PM   #1
IanAS is offline IanAS  England
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Default A Discussion on Headphone Driving and Wiring Schemes

For those people who feel that using push pull has no effect, here are two graphs from headphone.com that shows a difference.

It's an interactive applet that allows to you select and compare plots for the many head phones in their list.

You'll need to copy and past the whole string, not just click on it.

http://www.headphone.com/buildAGraph.php?graphID[0]=853&graphID[1]=583&graphID[2]=&graphID[3]=&graphType=0&buttonSelection=Compare+Headphones

http://www.headphone.com/buildAGraph.php?graphID[0]=863&graphID[1]=2321&graphID[2]=&graphID[3]=&graphType=0&buttonSelection=Compare+Headphones

One one, 'balanced' increases the bass and reduces the treble, on the other it's the opposite. Apart from the 5 to 8kHz peak which is further peaked with both.
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Old 15th January 2011, 09:58 PM   #2
IanAS is offline IanAS  England
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Owen, a further question.

Did you go straight for the LME49990 or try the other LME49 series chips first?

I've been using the LME49710HA for a year and a half or so.

I tried the plastic 8pin DIL then the metal can TO99 version, the 49710HA. The latter was MUCH better. Ran them both in for three months before comparing in a very revealing system.

Audioman54, ex National engineer and the original specifier of the LME49713 (current feedback) said he prefered that chip's sound to the others. But is the 49990 is newer that his time as he was laid off at maybe the end of 2009?

Either way, did you try LME49713's as the input buffers?

Also, as mentioned many times on this site, a 0.1uF to 0.5uF cap across the pins of each chip can make a nice difference. I ran in for several months 5 x 0.1uF and 2 x 0.33uF Arcotronics R46 series caps and then compared them across a pair of TO99 LME49710HA which I'd crafted into the dual op-amp socket as the subtractors for the two sets of differential outputs of an Auzentech X-Meridian soundcard.

Only needed to use one cap (or bank of) fitted under the board for both single op-amps due to them being in the one dual socket.

The best by a wide margin was the 0.33uF. One to 5 of the 0.1's and combinations with a 0.33 all made a sizeable change, above 0.33 was going away from improvement making the sound a bit dull and confused. One 0.33 was MUCH better than 3 x 0.1uF.

The effect was to bring up the volume from male vocal downwards and clean and sharpen the transient response everywhere.

I already had a well run in 100uF @ 16v Nichicon Polymer cap, similar to what you used, from each socket supply pin to the ground plane.

Then I fitted a 22nF polystyrene FSCEX 1% across the 0.33uF yeilding another great cleaning and sharpening.

Did you try any of this?

Thanks,

Ian

Last edited by IanAS; 15th January 2011 at 10:06 PM.
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Old 16th January 2011, 06:52 PM   #3
qusp is offline qusp  Australia
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Quote:
Originally Posted by IanAS
There are significant disadvantages with balanced; double the output impedance, double noise, perhaps double the distortion, double components in the signal path, half the damping factor, cancelling the even order harmonics and leaving all the odd order possibly making it sound harsh. Does doubling the slew rate and deleting the ground reference really outweigh? Many people and reviewers say that to their ears it does. Are they enjoying the extra distortion?
ermm i'm not quite sure what to say to that, I think perhaps you are regurgitating this from somewhere, because the majority of these statements are completely untrue or redundant when talking about truly balanced gear vs much modern SE output gear and only most of them partially untrue if talking of the 'balanced' implementations. i'm guessing you yourself havent got any balanced headphone gear and i'm guessing you havent actually built any balanced headphone circuits.

extra distortion??....... pretty much any modern dac these days has balanced outputs, so to get a single ended headphone output, in general the signal has gone through a conversion stage and removed these harmonics and distortion anyhow, so all you get at the end is half or sometimes all of that signal but with some noise from interference from the point of the conversion. and if not, you have mostly chosen to use only half the DNR performance by grounding the negative phase. there are some rare exceptions to this

Last edited by qusp; 16th January 2011 at 07:04 PM.
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Old 16th January 2011, 10:24 PM   #4
IanAS is offline IanAS  England
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Thanks for your reply qusp.

Correct, I've used headphones for TV and music for only about a month due to breaking one of my monoblocks which I haven't repaired yet. For a year I've used some 5 headphones to watch news clips and stuff on the PC if the HiFi was not powered up, for much of the 15 years prior to that, the Hi-Fi was never switched off. Three weeks ago I bought some better headphones as I was disappointed with the lack of bass, treble and dynamics compared to the HiFi, HD600's, and this week I bought some HD650's. Last night I fitted my own brand of solid silver wire via the Cardas connectors. They are actually the interconnects from the soundcard to the front pair of amps, I changed the amp end plugs. Just wanted to see how they sounded, they are unscreened with about 4 twists per foot. (I've been making and selling solid silver leads since about 1994.) No hum or hiss here with my equipment, so screening would appear to be superfluous in this speaker cable application to a 300 ohm drive unit. I wonder why all the aftermarket cables I've seen are screened? I did hear the physical impact noise carried so well into the ears, so that might need to be addressed, or maybe just lived with for the sake of sound quality. This is not a portable set-up after all.

Regarding push pull amplification; Perhaps you could point me to some circuitry that doesn't follow those engineering facts? I do know some stuff about amplifiers and have professional amplifier design engineer friends who know quite a lot more. I took a bit of time to read up on push pull for myself.

None of us use headphones so I looked on the www to try and find a very good circuit I could throw together to drive my new phones until my main system is functioning again. And possibly beyond that as nowadays I need to keep the volume down at night when watching film or TV and it's been good to be able to have normal listening level again through the headphones. Though I still prefer surround sound from the 4 corners and bass I can feel.

Do you mean some manufacturers have taken measures to ameliorate or negate these facts of physics and electronics? I expect they have, but I've read reviews from people who've been only disappointed with the industries offerings which does not surprise me at all. There's hardly a single item of Hi-Fi, even super high end, that I / we have not been able to improve the sound of for friends and customers. And I can't just pop out to the shops and unload 4000 on another amplifier just for my headphones especially when I think it might cost me a tiny fraction of that to make up something as good, or maybe better, myself, with the help of people on the www. It might mean buying some item and modifying it.

Have you built your own electronics? What did you find best? Ah, I just recalled another thread or forum where you'd posted you have two of those units mentioned early in this thread.

I think I don't need that. Just a better output stage for the X-Meridian might do for now. It plays 24/192 and uses the AK4396 DAC and for the subtractor chip I've fitted an LME49710HA and other stuff, so not too bad.

Something like the subject of this threads group buy might be suitable and I could graft it on. But I could do it push pull if I could find a very good push pull circuit and solid evidence that that was actually better rather than better in the way a lot of people like euphonious valves with their 0.1% distortion that can give a full and big sound and can make up for deficiencies in the tonal balance, as distortion often sounds louder and more fat with more bass and treble.

Just changing a metal film resistor to a Vishay bulk foil changes some distortion, I presume by getting rid of it, but maybe it's also adds some. I've never seen any graphs but it's easy to hear as wooly mush is taken away.

Last edited by IanAS; 16th January 2011 at 10:52 PM.
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Old 16th January 2011, 10:51 PM   #5
IanAS is offline IanAS  England
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Quote:
Originally Posted by qusp View Post
extra distortion??....... pretty much any modern dac these days....
To me a DAC is a chip, not a box of chips. I've haven't used one (as in a box of) I didn't massively modify for, er, well, ever, back to the early '90's. Many of the DAC chips have internal I/V, dual differential outputs and a subtractor to combine them, often with the HF digital noise shaper filtering around that one chip. I'm guessing you're not into electronics at this level? This does not end all distortion, just reduces common mode distortion, and better if all the components are particularly well matched which in commercial equipment they are usually not so as to save money. The chips I use have very low noise indeed, but that's not really an issue as the gain is so low after DAC chips, a gain of 2 or 3. It matters for phono cartridges as the gain is huge, I forget now, maybe 200 for moving coil, so the chips noise is 200 times amplified.

I guessing you can't really help me with my quest to find a decent push pull circuit topography that I can assemble myself? But I'd be pleased if you can explain to me the sonic benefits of push pull over earth referenced?

Thanks.

Last edited by IanAS; 16th January 2011 at 11:01 PM.
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Old 17th January 2011, 12:27 AM   #6
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Hello IanAS,
From one point of view I do not care or need to know the the magic going inside the amplifier balanced or not.
Inspired by the 307A SET amplifier by Pete Millett. I built a single end triode amplifier. The SET drives a custom Electra-Print center tapped output transformer. The center tap is grounded for safety and the headphones, HD600’s, are driven by the balanced output of the transformer. There is no canceling of even harmonics, doubling of noise or any of the other things you said, by the way.
If you want to go balanced cheap try a pair of these connected to the output of the Wire. EDCOR Electronics Corporation. XSM150/150
Ground the center tap at the output. Remember you will need a 4 wire cable to the headphones.
DT
All just for fun!

DT
All just for fun!

Last edited by DualTriode; 17th January 2011 at 12:51 AM. Reason: oops
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Old 17th January 2011, 12:54 AM   #7
IanAS is offline IanAS  England
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DT, thanks for that.

There's no magic going on, just science

I was talking about solid state as in the context of this thread. No output transformer is used.

For each channel, two amplifiers are used, one for each wire to the headphone voice coil. Hence the doubling and halving.

I guess a Tx as mentioned here could be driven by one single solid state amplifier. Does anyone do that?

Last edited by IanAS; 17th January 2011 at 01:22 AM.
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Old 17th January 2011, 02:55 AM   #8
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Quote:
Originally Posted by IanAS View Post
DT, thanks for that.

There's no magic going on, just science

I was talking about solid state as in the context of this thread. No output transformer is used.

For each channel, two amplifiers are used, one for each wire to the headphone voice coil. Hence the doubling and halving.

I guess a Tx as mentioned here could be driven by one single solid state amplifier. Does anyone do that?
Hello,
When my eyes are closed and the music is dancing all around it is magic to me. It is a transitive vs. substantive sort of thing.
For science the exception is the rule. Sometimes rules can be broken. That is where the magic comes back in.
If you recall I ask the question if the next iteration of The Wire would retain balanced through to the output!
Among other tricks transformers are impedance matching devices. The load reflected to the amplifier is the load impedance times the square of the transformer turn ratio. In the case I presented the turn ratio is one, the load the headphones present to the amplifier is 300 ohms or the impedance of the 300 ohm Sennheisers. The reason for the transformer is to provide the output center tap and allow balanced output.
Are transformers used to go from single end to balanced and the other way about. There after market transformers to convert single end to balanced and the other way around sold for the person mixing consumer and professional gear. Take a look at the Rane Balance Buddy.
Tube amplifiers commonly use transformers as phase splitters.
DT
All just for fun!
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Old 17th January 2011, 10:47 AM   #9
qusp is offline qusp  Australia
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Quote:
Originally Posted by IanAS View Post
Thanks for your reply qusp.

Correct, I've used headphones for TV and music for only about a month due to breaking one of my monoblocks which I haven't repaired yet. For a year I've used some 5 headphones to watch news clips and stuff on the PC if the HiFi was not powered up, for much of the 15 years prior to that, the Hi-Fi was never switched off. Three weeks ago I bought some better headphones as I was disappointed with the lack of bass, treble and dynamics compared to the HiFi, HD600's, and this week I bought some HD650's. Last night I fitted my own brand of solid silver wire via the Cardas connectors. They are actually the interconnects from the soundcard to the front pair of amps, I changed the amp end plugs. Just wanted to see how they sounded, they are unscreened with about 4 twists per foot. (I've been making and selling solid silver leads since about 1994.) No hum or hiss here with my equipment, so screening would appear to be superfluous in this speaker cable application to a 300 ohm drive unit. I wonder why all the aftermarket cables I've seen are screened? I did hear the physical impact noise carried so well into the ears, so that might need to be addressed, or maybe just lived with for the sake of sound quality. This is not a portable set-up after all.

Regarding push pull amplification; Perhaps you could point me to some circuitry that doesn't follow those engineering facts? I do know some stuff about amplifiers and have professional amplifier design engineer friends who know quite a lot more. I took a bit of time to read up on push pull for myself.

None of us use headphones so I looked on the www to try and find a very good circuit I could throw together to drive my new phones until my main system is functioning again. And possibly beyond that as nowadays I need to keep the volume down at night when watching film or TV and it's been good to be able to have normal listening level again through the headphones. Though I still prefer surround sound from the 4 corners and bass I can feel.

Do you mean some manufacturers have taken measures to ameliorate or negate these facts of physics and electronics? I expect they have, but I've read reviews from people who've been only disappointed with the industries offerings which does not surprise me at all. There's hardly a single item of Hi-Fi, even super high end, that I / we have not been able to improve the sound of for friends and customers. And I can't just pop out to the shops and unload 4000 on another amplifier just for my headphones especially when I think it might cost me a tiny fraction of that to make up something as good, or maybe better, myself, with the help of people on the www. It might mean buying some item and modifying it.

Have you built your own electronics? What did you find best? Ah, I just recalled another thread or forum where you'd posted you have two of those units mentioned early in this thread.

I think I don't need that. Just a better output stage for the X-Meridian might do for now. It plays 24/192 and uses the AK4396 DAC and for the subtractor chip I've fitted an LME49710HA and other stuff, so not too bad.

Something like the subject of this threads group buy might be suitable and I could graft it on. But I could do it push pull if I could find a very good push pull circuit and solid evidence that that was actually better rather than better in the way a lot of people like euphonious valves with their 0.1% distortion that can give a full and big sound and can make up for deficiencies in the tonal balance, as distortion often sounds louder and more fat with more bass and treble.

Just changing a metal film resistor to a Vishay bulk foil changes some distortion, I presume by getting rid of it, but maybe it's also adds some. I've never seen any graphs but it's easy to hear as wooly mush is taken away.
Quote:
Originally Posted by IanAS View Post
To me a DAC is a chip, not a box of chips. I've haven't used one (as in a box of) I didn't massively modify for, er, well, ever, back to the early '90's. Many of the DAC chips have internal I/V, dual differential outputs and a subtractor to combine them, often with the HF digital noise shaper filtering around that one chip. I'm guessing you're not into electronics at this level? This does not end all distortion, just reduces common mode distortion, and better if all the components are particularly well matched which in commercial equipment they are usually not so as to save money. The chips I use have very low noise indeed, but that's not really an issue as the gain is so low after DAC chips, a gain of 2 or 3. It matters for phono cartridges as the gain is huge, I forget now, maybe 200 for moving coil, so the chips noise is 200 times amplified.

I guessing you can't really help me with my quest to find a decent push pull circuit topography that I can assemble myself? But I'd be pleased if you can explain to me the sonic benefits of push pull over earth referenced?

Thanks.
wow you like the sound of your own voice even more than I do....... thats a feat

apparently you know everything already, so what could I possibly have to say that could tell you something you didnt already know? apparently you design dac chips too to 'be into it on such a stratospheric level'? or you just do lots of reading?

ohh I get it, you are being facetious... clever...

and yet you do not have any actual experience of what you speak. perhaps the main benefit might be following the fully differential and in my case dual differential signal path from start to finish. and given competent component choice and construction the balanced design goals are met

plus it appears you totally missed my point, if you convert a fully dual diff signal to SE for the headphones or headphones amp, you have already done what you seem to be trying to avoid. you either throw away half the output and only use one leg, or you sum the outputs before the amp and remove the beloved 2nd order harmonics. seems kinda redundant does it not?? this dac has FAR better output if a balanced current output is used, so this would seem a good reason to me and if the channels are summed you lose (as far as you are concerned) and if they arent you lose (as far as myself and the dac chip designer is concerned). you could of course use a cct to invert the inverted phase and then add it to the positive phase to retain DNR, but then you may have timing issues.

this amp was VERY specifically designed for a particular dac and this dac is capable of outputting SE, dual diff, balanced, 8 channel or fully mono depending on internal logic settings. and although this amp has SE output, the cancellation has already occurred and yes for it to be nearly all of it component matching is key; of course (so condescending).... part of the reason I use SMD 0.02% matched Zfoils for the IV and headamp in my portable rig (also a sabre dac running on 26V A123 LiFePo4 battery pack capable of putting out enough current to vaporize pretty much anything attached to it) which as far as digital circuits and headphone amps gives up nothing to home headphone amps IMO; hell many home amps do not have that much power

I guess PP guys and SE guys will never see eye to eye, why would I bother to justify my liking for balanced headphones, the reply above is only to attempt to put my post above in words you might understand.

Last edited by qusp; 17th January 2011 at 11:17 AM.
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Old 17th January 2011, 02:11 PM   #10
qusp is offline qusp  Australia
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sorry for the mess opc, I spent too long editing the above post and when I decided straight after it was saved that I could not be bothered carrying this on as it is fruitless to argue about something without one party being willing to try it out, but more interested in arguing about the theoretical technical merits or flaws. I asked admin to delete it, but probably it will be pointless by the time they see it; I guess no admins were on duty. so I have taken steps so that I will not have to reply to the undoubtedly long reply coming.

so IanAS, do not bother to carry this on expecting a reply. it seems you are not interested in the amp and I do not wish to make more mess in Owens thread

DualTriode: WRT driving headphones with a phase splitting TX; i'm unsure how you are able to have a balanced signal to your headphones without CMRR cancellation, you may not have done it inside the amp circuit, but does it not just happen at the headphone driver? real question as i'm always keen to expand my understanding and will try it out
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