Letz pile on qusp while DC offsets hurt hizHead
Could this partly be because the noise reduction of balanced can be measured electrically but those of bridging are only detectable experientially?
Could this partly be because the noise reduction of balanced can be measured electrically but those of bridging are only detectable experientially?
Important Data
As regards my pondering the need for balance from bitz thru canz, I would argue that SE up to the headamp is probably adequate. I now believe the bulk of my quest as having been directly related to keeping the Senns satisfied.
I am planning to carefully listen to a pair of SE-SE 'wire's bridged across the Senns and fed by my Roland Edirol. Fed thru the BAL-BAL it sounds remarkably good (incredibly good for a portable). It is less than what an audiophile might wish for as h(is)er 'primary listen' but . . .
Note that this still requires 'balanced' cables, the topic of this thread.
As regards my pondering the need for balance from bitz thru canz, I would argue that SE up to the headamp is probably adequate. I now believe the bulk of my quest as having been directly related to keeping the Senns satisfied.
I am planning to carefully listen to a pair of SE-SE 'wire's bridged across the Senns and fed by my Roland Edirol. Fed thru the BAL-BAL it sounds remarkably good (incredibly good for a portable). It is less than what an audiophile might wish for as h(is)er 'primary listen' but . . .
Note that this still requires 'balanced' cables, the topic of this thread.
Adequate, perhaps, but I think it would be a waste if the DAC is one of those with balanced outputs and you don't maintain the balanced signal all the way to the headphone amplifier. Such fully balanced circuits allow cancelation of much of the DAC noise, power supply noise, etc.
Of course, if your chosen DAC has SE output, then it makes sense to simply run SE until the headphone amplifier.
Agreed
There is a middle ground that still allows push pull buffers bridged so as to get common noise cancellation at the cans. By using one SE-SE for left and another for right, one need only invert the signal on one side of each 'wire'. I will be using lower voltage rails (+-12v) but the cans, because of the inverted signal, will see 80% of the swings of a full BAL-BAL. These will be frankenWires built on rework boards.
Certainly I plan to continue my efforts with the dual mono WM874x as a possible replacement for the quad BB1704s. The Edirol is not even in the same class but for a 24/96k recorder/player that fits in your palm and boasts 20Hz-40kHz +-2Db it is a heavy duty iPod upgrade
This also will provide a data point in my ongoing effort to sort bridged from balanced. My conclusions will in no way be generalizable. All my testing has been with Senns and I now believe they have been a significant part of my difficulty in reaching nirvana.
For anyone interested in the inversion, read adgr on his High(er) Wire using LME49860's rather than LME49990's for the rework. The 860 is a dual
There is a middle ground that still allows push pull buffers bridged so as to get common noise cancellation at the cans. By using one SE-SE for left and another for right, one need only invert the signal on one side of each 'wire'. I will be using lower voltage rails (+-12v) but the cans, because of the inverted signal, will see 80% of the swings of a full BAL-BAL. These will be frankenWires built on rework boards.
Certainly I plan to continue my efforts with the dual mono WM874x as a possible replacement for the quad BB1704s. The Edirol is not even in the same class but for a 24/96k recorder/player that fits in your palm and boasts 20Hz-40kHz +-2Db it is a heavy duty iPod upgrade
This also will provide a data point in my ongoing effort to sort bridged from balanced. My conclusions will in no way be generalizable. All my testing has been with Senns and I now believe they have been a significant part of my difficulty in reaching nirvana.
For anyone interested in the inversion, read adgr on his High(er) Wire using LME49860's rather than LME49990's for the rework. The 860 is a dual
An inverted signal is completely unnecessary with regard to common-mode noise rejection.
se
Only the noise needs to be present on both polarities, not the signal.
When the headphone cable picks up noise, it is presumably equal on both wires (especially for twisted pair), and thus the speaker driver ignores any voltage that is identical on both terminals because no additional current flows as a result of adding the same voltage to both terminals.
Similarly, any power supply noise injected equally onto both terminals would also be canceled out at the speaker driver.
Whether the signal appears inverted on the second terminal wire is irrelevant with regard to noise cancelation. You can, however, improve signal to noise by 6 dB if you include the inverted signal on the second wire.
"alone" should be "along" in previous
The confused may include Wolfsin :-( One thing of which he was unaware is the following from opc:
"If you want to use an SE input as you mentioned, keep in mind that the gain is different for an inverting and a non-inverting op-amp setup. You'll have to account for this and make sure the total gain of each leg is exactly the same. If you run each side of the bridge with a gain of 1, you will have a total system gain of 2. Otherwise, it should work."
The confused may include Wolfsin :-( One thing of which he was unaware is the following from opc:
"If you want to use an SE input as you mentioned, keep in mind that the gain is different for an inverting and a non-inverting op-amp setup. You'll have to account for this and make sure the total gain of each leg is exactly the same. If you run each side of the bridge with a gain of 1, you will have a total system gain of 2. Otherwise, it should work."
SE as good as BAL only in absence of common noise
Oh, Steve, you meant SE. The problem there is that SE provides no common noise rejection since groundIzground and the amplified signal plus common noise appears on one side of the can. In the case of bridged, the amplified inverted signal plus common noise appears in place of the ground and the cans see the difference, i.e. ampd_signal - (-ampd_signal) = 2 x ampd_signal with NO common noise.
For the first couple years of working with bridged cans I was repeatedly confused and repeatedly got DC offsets that worried me (as they should). All this was with discrete stereo SE headamps driven with honest to goodness balanced signals, + connected to L and - connected to R so that the outputs connected to each side of one can, i.e. bridged. The BAL-BAL wire is an honest to goodness balanced headamp that cancels common noise electronicly before the outputs (but the outputs are still bridged across the cans, providing additional common noise reduction). BAL-BALs are in limited supply but I have several SE-SEs that need rework. An SE-SE with, say L and -L applied to the stereo inputs, achieves common noise cancellation at the can bridged across the outputs but is not quite as good as a BAL-BAL. Note that 'not quite as good' depends primarily on the quality of the power supply, assuming it is common to both channels and that the gain is exactly equal.
I hope this helps. Many think that SE is as good as BAL. Where there is no common noise to be cancelled, i.e. a pristine common power source, or entirely separate (battery driven?) power supplies, SE may be very nearly as good as BAL.
Oh, Steve, you meant SE. The problem there is that SE provides no common noise rejection since groundIzground and the amplified signal plus common noise appears on one side of the can. In the case of bridged, the amplified inverted signal plus common noise appears in place of the ground and the cans see the difference, i.e. ampd_signal - (-ampd_signal) = 2 x ampd_signal with NO common noise.
For the first couple years of working with bridged cans I was repeatedly confused and repeatedly got DC offsets that worried me (as they should). All this was with discrete stereo SE headamps driven with honest to goodness balanced signals, + connected to L and - connected to R so that the outputs connected to each side of one can, i.e. bridged. The BAL-BAL wire is an honest to goodness balanced headamp that cancels common noise electronicly before the outputs (but the outputs are still bridged across the cans, providing additional common noise reduction). BAL-BALs are in limited supply but I have several SE-SEs that need rework. An SE-SE with, say L and -L applied to the stereo inputs, achieves common noise cancellation at the can bridged across the outputs but is not quite as good as a BAL-BAL. Note that 'not quite as good' depends primarily on the quality of the power supply, assuming it is common to both channels and that the gain is exactly equal.
I hope this helps. Many think that SE is as good as BAL. Where there is no common noise to be cancelled, i.e. a pristine common power source, or entirely separate (battery driven?) power supplies, SE may be very nearly as good as BAL.
No, I didn't mean SE. I meant a balanced bridge as you originally described.
There needn't be a signal on the second channel for common-mode noise rejection. You can simply tie its input to ground if you'd like.
se
SE-BRGD
You guys asked questions that made me see the problem in slightly different ways. I now plan to build the SE-BRGD in two ways. The one I described above requires trivial rework. But by adding a single opa1632 on a tiny adapter and leaving off both 49990s requires no rework at all. It has even fewer blue wires, but a slightly thicker profile. A pair of 12v 5Ah lead acid batts should allow a pair of these to play for 24hrs into HD600 Senns with +&-12v rails.
Thanks all.
You guys asked questions that made me see the problem in slightly different ways. I now plan to build the SE-BRGD in two ways. The one I described above requires trivial rework. But by adding a single opa1632 on a tiny adapter and leaving off both 49990s requires no rework at all. It has even fewer blue wires, but a slightly thicker profile. A pair of 12v 5Ah lead acid batts should allow a pair of these to play for 24hrs into HD600 Senns with +&-12v rails.
Thanks all.
Since you leave me little alternative, and dueling is illegal (and dangerous), I'll take it back. Extremely sorry, I was in a bad mood (as usual). Where can I purchase some balanced headphones and amplifiers so that I can try this for myself? (then I'll curse it as nonsense again, most likely)
bad mood? no worries **** happens.
headphones are non-denominational, being a 2 terminal floating device they are balanced by nature, but really dont care one way or the other. easiest way to try is with headphones that have removable cables so you can make your own cable or buy any number of places. I believe Beyer have recently started selling their pro range with optional balanced termination, but its 2 x 3 pin XLR, which is pretty impractical. its not available at their custom manufaktur shop which is a pity, but then i'd replace it knowing me anyway.
as for amps; there are numbers of them several designs in this part of the forum, just steer away from the types that are simply 2 bridged single ended amps, which is the most common.
headphones are non-denominational, being a 2 terminal floating device they are balanced by nature, but really dont care one way or the other. easiest way to try is with headphones that have removable cables so you can make your own cable or buy any number of places. I believe Beyer have recently started selling their pro range with optional balanced termination, but its 2 x 3 pin XLR, which is pretty impractical. its not available at their custom manufaktur shop which is a pity, but then i'd replace it knowing me anyway.
as for amps; there are numbers of them several designs in this part of the forum, just steer away from the types that are simply 2 bridged single ended amps, which is the most common.
I have put these headphone on a large sofa arm to stretch the head band. To my surprise IT WORKS! IT WORKS WELL. It took a few days of using them then keeping them stretched really good overnight and after a few days they are quite comfortable and have stretched out and seem to be staying that way. Now five star headphones. They are all I use and all I would want in a headphone. now.
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