[some1x]

Doesn't have to be exactly 2V. Anything between 0.5V and 2V is fine for home audio gear.

I can't remember for sure, but I the highest it will output is 9V, which is intended for studio/pro gear.

 

[lowmagnet]

Quote:

Originally Posted by yanfeng /img/forum/go_quote.gif Maybe they should add some words around that hole: "unconventioal headphone out, HD6XX only!" I don't see this as terribly bad idea.

I do, Benchmark is not an audiophile company. They do everything they do for professional reproduction, and they just happen to do an amazingly good job of it. Putting in tweaks that nobody will use has a low return in their core market.

Also, with -100, -125, -130 dB crosstalk at 20 kHz, 1kHz, and 20Hz, do you really need to worry about isolating your lines? That's the only thing I'd think you could gain by going balanced (especially since headphones can't be balanced without a ground, technically)

 

[schaqfu]

Quote:

Originally Posted by lowmagnet /img/forum/go_quote.gif Also, with -100, -125, -130 dB crosstalk at 20 kHz, 1kHz, and 20Hz, do you really need to worry about isolating your lines? That's the only thing I'd think you could gain by going balanced (especially since headphones can't be balanced without a ground, technically)

Oh man, somewhere in Bozeman a HeadRoom engineer is crying his balanced eyes out and the only reason his colleagues haven't joined him is they haven't read this yet.

 

[lowmagnet]

Quote:

Originally Posted by yfei /img/forum/go_quote.gif XLR is better than RCA is only when a) transfer distance is long and b) XLR is used to transfer signal from one 'electrical' instrument A to another electrical instrument B. A put positive to pin 1, ground to 2 and negative to 3. B receive the three signal, then 'flip' the negative, and add to positive. In this way the noise picked up by the long signal cable has been removed. If you use XLR for simple device as headphone, headphone don't have the circuit to remove the noise. and for such as short distance it is really not needed.

x1000. This is what I came across the other day (the reason behind balanced in the studio) and after reading it, I now know that balanced headphones is just an expensive gimmick the hardware doesn't have circuitry to discriminate signal from noise by reading the balanced signal and subtracting said noise.

But this isn't the end of 'balanced' headphones. Louder = better for people. Sigh.

 

[schaqfu]

Quote:

Originally Posted by lowmagnet /img/forum/go_quote.gif x1000. This is what I came across the other day (the reason behind balanced in the studio) and after reading it, I now know that balanced headphones is just an expensive gimmick the hardware doesn't have circuitry to discriminate signal from noise by reading the balanced signal and subtracting said noise. But this isn't the end of 'balanced' headphones. Louder = better for people. Sigh.

I really, really don't think it's just about the noise reduction from elimination of common ground crosstalk. That's one advantage, but I think the reason people experience noticeably different sounds on some headphones (HD650s) more than others (Grados) is the doubling of slew rates. Bass in particular will be driven with more articulation because you've got two people standing on either side of the see-saw, pushing both forward and backward, rather than just forward.

Balancing headphones isn't for one second about making them louder. It's about changing the tonal quality. Some headphones, almost always high impedance, show marked change; others, typically low impedance, show almost no change at all.

 

[lowmagnet]

Quote:

Originally Posted by schaqfu /img/forum/go_quote.gif Balancing headphones isn't for one second about making them louder. It's about changing the tonal quality. Some headphones, almost always high impedance, show marked change; others, typically low impedance, show almost no change at all.

That's another reason to not re-wire grados, since they are all in the 32 ohm range.

Like I said, if I had a cable to try with the DAC1, I'd attempt this. I just have my doubts regarding sound quality.

 

[lowmagnet]

Quote:

Originally Posted by schaqfu /img/forum/go_quote.gif ...I think the reason people experience noticeably different sounds on some headphones (HD650s) more than others (Grados) is the doubling of slew rates.

I looked up the whole issue on slew rate and came up with this article by Bryston. They sell amplifiers with balanced inputs. They do, however, take umbrage with certain of the claims people made about the effect of balanced cabling on a particular environment. Luckily the whole thing was summarized by a nice conclusive list at the bottom.

Quote:

Originally Posted by Bryston IN CONCLUSION: balanced-line technology; Will: Reduce any system noise caused by ground loops, RF, power lines etc. Allow shorter speaker leads by permitting the amplifier to be placed adjacent to speakers without extra noise. Will Not: Increase the slew rate of an audio system. Affect the given cable properties. Improve distortion characteristics in an otherwise well designed audio product. Improve on the individual audio component noise.

Note that balanced headphones don't provide 1 or 2 in the 'will' list since they are both ungrounded and contain no circuit to remove noise. Your claim that balanced modifies slew rate of the amplifier is also put out here. Also, since the 650s are an 'otherwise well designed audio product' I don't see the point of doing it, however willing I am to try the balanced cables.

 

[schaqfu]

Again, I'm not the source, but my sources tell me:

"Often called “fully balanced” designs (fig.3), this type of amplifier has completely separate and matching electronics circuits for all four (left normal and inverted, and right normal and inverted) audio signal paths. The advantage of this design is that there are two power amps driving each coil; each amp effectively drives half the coil, with a virtual ground or zero voltage point halfway into the coil. Since each amp is only driving half the load, a significant improvement in control can be achieved, and because the voltages are in opposition, an effective doubling of slew rate (volts per second the amp can swing) is realized compared to the normal slew rate of either amp by itself. In other words, by doubling the amount of electronics circuits, a two-fold performance increase in some critical areas can be achieved with only a 50%-70% increase in cost." http://www.headphone.com/products/fa...-vs-fully-bal/
part 2 of 4, starting here: http://www.headphone.com/products/fa...vs-unbalanced/

I don't think there's all that much variation in how balanced amps work. I guess some could introduce a real ground if they wanted, rather than the zero-point virtual ground halfway up the wire. I see this stuff written in excruciating detail too much to believe it's completely hype.

 

[lowmagnet]

Unless Headroom will publish their slew rate, along with their other specs or if someone will measure their balanced amp's output of a square wave to measure it, I'm not going to continue this conversation.

BTW, the DAC1 is driving my HD560 (just got them) quite well from the front. Really amazing cans.

 

[cotdt]

The balanced line output will certainly not increase slew rate, but a balanced amp will. The tighter bass of balanced amps comes from the much lower output impedance and this can be detectable by measuring the frequency response. You'll get tighter, deeper bass, especially for open headphones. Balanced is definately the way to go, for both solid state and tube amps. The increased slew rate makes solid state amps warmer from lower distortion, but would probably not do anything for tube amps which don't suffer from such problems. The bass on balanced tube amps I expect to be something special. Simple mathematical calculations can easily show why.

Besides, what's not to like about 4x the power output =)

 

[lowmagnet]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif The bass on balanced tube amps I expect to be something special. Simple mathematical calculations can easily show why.

You made some claims above. Care to show your math to prove it?

 

[cotdt]

Quote:

Originally Posted by lowmagnet /img/forum/go_quote.gif You made some claims above. Care to show your math to prove it?

If you have to ask, would you guys be able to follow it? The basic idea is that the output impedance of balanced is half of the unbalanced (i want to say single-ended, but that would be reserved for the amp topology) amp, since each amp channel is only driving half a transducer whereas in unbalanced mode, it would be one amp per transducer. With half the output impedance, you get double the damping factor:

The 'damping factor' is the speaker impedance (ZL) divided by the amp's output impedance, for example 60 ohm headphone driver and 2 ohm amp output impedance:

DF = ZL / Zo = 60 / 2 = 30

With a balanced amp, the damping factor would be 60. What does this mean? Well if you know what Thiele-Small Parameters are, there is this factor called Qes, which is the electrical Q, and this value effects the bass response and varies depending on output impedance. High damping factors usually mean that the bass response will be well defined ("tight"), whereas a low damping factor will result in a loose sounding bass. If you have a high output impedance, the voltage delivered by the amp is reduced at lower load resistance, while it remains constant at high load resistance. This is true even with low output impedance, but the change in voltage in the circuit is much smaller.

From http://www.audioholics.com/education...ked-questions:

Slew Rate: This is a term used to describe how quickly the output of an amplifier can track its input. Slew Rate is usually measured in V / usec. The higher the value (up to a point), the better the amp is at potentially reproducing the subtle nuances and dynamics associated with music reproduction.

Damping Factor: This is a quantity which defines how quickly the amplifier can stop a reproduced frequency such as a bass note. The higher the damping factor, the better the amp will control the woofer and help reduce overhang distortion (again to a point). The damping factor of an amplifier is mostly dependent on the output impedance of the power amplifier and the ability of the power supply which feeds the power amp.

 

[lowmagnet]

Quote:

Originally Posted by cotdt /img/forum/go_quote.gif DF = ZL / Zo = 60 / 2 = 30

Based on the above formula calculations, from the specs of the DAC1 and the Sennheiser HD650:

From the HPA2: 300Ω / 0.11Ω = 2727
From the Balanced XLR: 300Ω / 60Ω = 5, but since it's balanced, we say 10

Of course, I just did the math, and I'm afraid I don't know if 2727 is too high a damping factor or not. The chart on Audioholics stopped at 2000, and at that end, it seems to have minimal effect.

 

[cotdt]

Quote:

Originally Posted by lowmagnet /img/forum/go_quote.gif Based on the above formula calculations, from the specs of the DAC1 and the Sennheiser HD650: From the HPA2: 300Ω / 0.11Ω = 2727 From the Balanced XLR: 300Ω / 60Ω = 5, but since it's balanced, we say 10 Of course, I just did the math, and I'm afraid I don't know if 2727 is too high a damping factor or not. The chart on Audioholics stopped at 2000, and at that end, it seems to have minimal effect.

Yeah that's the problem with driving headphones out of DACs, the damping factor is too low. Ideally the higher the damping factor the better, but beyond a certain number it no longer makes any difference. It's not fair to compare an amp and a DAC's analogue output, because the amp is specially designed for the purpose of driving headphones/speakers, while the DAC is designed to drive an amp.

 

[schaqfu]

Wow, good stuff. Haven't seen this explanation before.

So if the damping factor is 10 coming straight out of the balanced line output to the HD650s, and it's 2727 coming out of the headphone jack, how and why is it that so many people are reporting significant improvement in quality when going through the balanced outs from the DAC1 directly to their HD650s? Virtually everyone reports significant improvements in bass handling, tightness and articulation -- all the things one would typically expect from a balanced amp versus unbalanced.

Why are the numbers lying?