Hi, I am not overly technical, nor an expert on balanced, but I have done a fair amount of research on this topic, so I'll take a shot at parsing this for Heaf-fi applications. I will also respectfully defer to contributions from Lavry owners or engineering types...
The balanced output of the DA 10 is optimized for line level connections which means it needs to be able to drive fairly long cables with the associated capacitance and other issues in a stable manner. In order to do this, the design has a higher output impedance than the Headphone output.
Most headphone amps have very low output impediance (some close to zero ohms). The Lavry must have a fairly high output impedance (which is also the case with many 2ch preamps, because the designer assumes that the next link in the chain (the power amp), will have an input impedance between say 10K - 100K ohms.)
Without doing research, I assume that the Grados are a very low impedance phone, so the Lavry engineer is stating the DA 10 was not built with Grado-level impedance in mind.
The headphone output is optimized to drive headphones, including low impedance headphones like the Grado GS-1000. You are welcome to try either approach. I think you will find the headphone output gives much better results with low impedance headphones than the XLR output.
He indicates you can try running it balanced, but does not hold out assurance that -- using G1000s -- the balanced outs will sound as good or better than the single end plug.
The only consideration is that the DA 10's XLR outputs are actively balanced, so any wiring that grounds or connects output pins from two channels together will result in significantly higher distortion in the output. There are internal jumpers to configure the output for unbalanced operation.
He states here: 1.) You must use the internal jumpers in order to run the balanced outputs, and 2.) that balanced outputs require separate grounds for both the L & R channels (i.e. the grounds from the balanced outputs should not be shared, contrasted with the fact that the standard 1/4" phono plug is a shared ground.
If you are going to use the headphone output, you can take advantage of the balanced wiring of the headphones by only connecting the "low" side of the two channels together as close to the 1/4" headphone as possible. The best way to do that would be to make a "Y" cable that has one 1/4" stereo plug to which two cables are soldered. Each cable would then have a separate (XLR) connector for the headphone at the other end.
He states that if your phones are wired for balanced (with XLRs), you can make an adaptor that will allow the balanced jacks to be connected to the standard 1/4" phono plug. Doing so would drive the headphones as single end. Your other option of course would be to have the cables re-terminated in a standard 1/4" phono plug. [Bottom line: He saying drive your phones unbalanced, even if they're currently wired for balanced.]
Headphones and speakers are by nature "floating" loads (not referenced to ground), so the only difference between operating them "balanced" or "unbalanced" is when the "low" side of the unbalanced signal is not a perfect ground. This happens when the connection between the speaker/headphone terminal and the ground of the amplifier driving them has impedance greater than "zero ohms." If the impedance is purely resistive,
the level will be reduced the voltage division of the cable resistance and driver resistance. For example, if they are equal (say, both 32 ohms), the signal will be divided equally between the two resistances and half of the signal that is coming out of the amp will appear across the headphone.
What can happen in "classic" three wire headphone wiring is that the finite impedance of the ground connection to both drivers causes a voltage drop that, in effect, modulated the "low" side of the driver. This results in "out-of-phase" signals being mixed with the signal coming from the amplifier.
By wiring the cable connecting to the "unbalanced" headphone output of the DA 10 the way I have suggested, you can gain 98% of the benefit of having balanced headphones without compromising the performance by using an output that is designed for other applications.
This last one is a bit over my head. I'm also not sure why you would get 98% of the benefit of balanced by using a Y cable from the unbalanced jack.
Summary:
1.) If you already have balanced jacks for the phones, I believe he indicates you can try it. He also indicates it may not sound better.
2.) He indicates you can make an adaptor that would allow an existing set of balanced phones to be used from the single end jack.
3.) You also have the option of using higher impedance phones from the balanced outs (like HD650s), or using the balanced outs from the Lavry to drive a balanced headphone amp, in turn to drive the G1000s.
Hope this helped
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