Rewire cans for balanced input? How?

Oct 11, 2004 at 8:40 AM Thread Starter Post #1 of 9

gaboo

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Amps like PIMETA & PPA use 3 separate (amped) circuits, one of which is dedicated to the return current improve the ground quality etc.

Balanced equipment, already has 4 amped circuits: there are two separate circuits for the return (reverse phase) current. Isn't this better in theory than using the same wire (actually the shield for unbalanced cables) for the return current, even if it has its own circuit?

So, question for the gurus: does it make sense to rewire cans to use the 4 amped circuits, i.e. separate return current for each driver? Would this improve anything? Since cans have no earthed ground, what should the ground (pin 1) from a balanced wire be connected to in a can?
 
Oct 11, 2004 at 6:53 PM Post #2 of 9
Ok, so it is relatively simple to rewire cans as dual mono, giving you separate return currents. Actually, one can be more creative an use a "backwards-compatible" (to common ground that is) interface: http://headwize.com/ubb/showpage.php...alanced;input;
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But there doesn't seem to be a way to use signal on a balanced cable without additional receiver circuitry in the cans. It looks like it would take at least one dual op amp http://sound.westhost.com/project51.htm, or two for a better circuit: http://sound.westhost.com/project87.htm. Then one would need to power those amps. With phantom power, it's getting too complex to be worthwhile. Any owner of balanced cans around here volunteering to open them and see what's inside?
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Oct 11, 2004 at 7:43 PM Post #3 of 9
All I did was chop off the standard 3 conductor 1/4" phono plug and put on a 4 conductor XLR style plug. Since the cable was 4 conductor all the way to the plug on my HD600s. If I want to connect to a standard single ended 3 conductor source, I use an adapter I also made.

You totally lost me on the last part. Receiver circuitry? Phantom power? These are headphones, not microphones.

With a differential output (aka balanced), the amplifier drives both wires leading to each headphone driver. With single ended output, the amplifier only drives one wire to each headphone driver. The other wire, often shared between the headphone drivers, goes to ground. That's it. There is nothing added to the headphones at all.
 
Oct 12, 2004 at 12:04 AM Post #4 of 9
Quote:

Originally Posted by DCameronMauch
All I did was chop off the standard 3 conductor 1/4" phono plug and put on a 4 conductor XLR style plug. Since the cable was 4 conductor all the way to the plug on my HD600s. If I want to connect to a standard single ended 3 conductor source, I use an adapter I also made.


Cute. I hope my cables are 4 conductor as well.

Quote:

Originally Posted by DCameronMauch
You totally lost me on the last part. Receiver circuitry? Phantom power? These are headphones, not microphones.

With a differential output (aka balanced), the amplifier drives both wires leading to each headphone driver. With single ended output, the amplifier only drives one wire to each headphone driver. The other wire, often shared between the headphone drivers, goes to ground. That's it. There is nothing added to the headphones at all.



Yeah, I was way off.
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I now realize that I can drive the dual mono cans using the differential signal. This was discussed before in this thread .

The only concern I still have is whether the halved impedance will cause any problems. But that's another thread .

Thanks DCameronMauch. Much obliged!
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Oct 12, 2004 at 2:03 AM Post #5 of 9
The halved impedance thing is generally not a problem. Wether single ended or differential output, the total power delivered to the headphones is the same. You will just need less voltage per phase. But the same current. I used a Neutrik 4 conductor XLR style plug. They also make a matching panel mount locking jack which looks very similar (exact same mounting requirements) as the 1/4" locking jack.

You could go ahead and chop off the plug. See how many wires you have. Worst case, and you have only three conductors, just solder back on a regular 1/4" photo plug. Exactly which headphones? I only know for certain about the Senn HD580/600/650s and all Grado models having 4 wires to the plug.
 
Oct 12, 2004 at 3:21 AM Post #6 of 9
Quote:

Originally Posted by DCameronMauch
The halved impedance thing is generally not a problem. Wether single ended or differential output, the total power delivered to the headphones is the same. You will just need less voltage per phase. But the same current. I used a Neutrik 4 conductor XLR style plug. They also make a matching panel mount locking jack which looks very similar (exact same mounting requirements) as the 1/4" locking jack.


Thanks for the tip. I'd rather attach two 1/4" TRS plugs. The immediate plan is to plug them straight into the sound card (1212m).

Quote:

Originally Posted by DCameronMauch
You could go ahead and chop off the plug. See how many wires you have. Worst case, and you have only three conductors, just solder back on a regular 1/4" photo plug. Exactly which headphones? I only know for certain about the Senn HD580/600/650s and all Grado models having 4 wires to the plug.


ATH-A900 (40ohm) and Senn HD-280 (64ohm). These have single sided cable so I'm not so hopeful. HD-280 should be easy to open, so I can check that way. People did it to mod the cup with blue tack.
 
Oct 18, 2004 at 7:46 AM Post #8 of 9
Quote:

Originally Posted by DCameronMauch
Exactly which headphones? I only know for certain about the Senn HD580/600/650s and all Grado models having 4 wires to the plug.


4-wires:
Beyer DT770/880/(990? probably), DT531 (probably)

3-wires:
Senn HD500/570/590 and 515/555/595
Ultrasone HFI650
AKG K240/K271S
Sony CD3000
 

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