[plyr]

I pretend to buy a mini-amp that is 100ohms unbalanced, to my HD650, i know that 100ohms isnt enough, but at the manual of the mini-amp there are listened 600ohms phones that can be used, so im

...

 

[ephemere]

A 100 ohm output impedance is very high for consumer headphones. Many solid-state "audiophile" amps have output impedances of less than 1 ohm.
The output impedance shouldn't be the same as the headphone impedance, it should ideally be much lower.

 

[Buster Sword]

That answers questions for ohms, but what does the original question mean?
I don't know either.

 

[ephemere]

Oh, you mean balanced/unbalanced?

An unbalanced signal has a single active channel, whose voltage is relative to ground. So an unbalanced signal typically needs two wires: ground and signal.

A balanced signal has two active channels, positive and negative, still relative to ground. So a balanced signal typically needs three wires: ground, signal+, and signal-.

Headphones are typically wired for unbalanced outputs and need three wires: a common ground, left signal, and right signal. But they can be rewired for balanced outputs. In that case, they need four wires: left signal-, left signal+, right signal-, right signal+, with ground discarded (or possibly used as a cable sheild).

So that's technically what it is, but I cannot explain why a balanced amp should sound any better than an unbalanced one in audiophile circles. I think pro audio equipment uses balanced signals for much more mundane reasons, to deal with ground loops and so forth.

Someone should correct me if I got any of this wrong.

 

[SennFan]

In terms of stereo/multi-channel setups, there really isn't a significant difference between single-ended and balanced XLR unless you have incredibly long cable runs (50 ft). In many A/B comparos, I have found there to be little or no intelligible differences between the two to justify the often pricey difference between the two options. I personally prefer single-ended connections using Eichmann terms.

 

[plyr]

So you say that Stock HD650 should came unbalanced them?


Here are the specs and the headphone recomendation list:
S amp Specifications
Input Impedance: 100K Ω unbalanced
Max Input Level: +19 dBV
Input Connectors: Stereo 1/4” TRS phone
Outputs: (4) 1/4” Stereo 1/4”
Output Impedance: 100 Ω each output
Max Gain: 20 dB/Channel
S/N Ratio: >90 dB
THD: <.005%
IMD (SMPTE) <.005%
Power: 18 VDC adapter


OTHER MANUFACTURER'S HEADPHONES
Manufacturer Model Impedance Sensitivity /mW
AKG K-141 600 ohm 98 dB
AKG K-240 600 ohm 88 dB
Beyer DT-150 250 ohm 114 dB
Beyer DT-801 250 ohm 114 dB
Fostex T-10 50 ohm 91 dB
Fostex T-20 50 ohm 96 dB
Fostex T-40 50 ohm 98 dB
Sennheiser HD-450 (original) 70 ohm 94 dB
Sennheiser HD-450 Series II 60 ohm 94 dB
Sony MDR-7502 45 ohm 100 dB
Sony MDR-7504 45 ohm 103 dB
Sony MDR-7506 63 ohm 106 dB


When you say that the output impedance should be much lower, i realy dont understand...

 

[gpalmer]

Quote:

Originally Posted by ephemere So that's technically what it is, but I cannot explain why a balanced amp should sound any better than an unbalanced one in audiophile circles.

Typical designs have four times the power and twice the slew rate (they can change voltage twice as fast) compared to unbalanced versions. You also don't have a shared ground which could potentially allow cross talk between channels. (NOTE: most designers go to considerable lengths to prevent this unless it's a very poor design, so in actual practice it probably isn't that big a factor).

 

[quackattack]

Quote:

Originally Posted by plyr So you say that Stock HD650 should came unbalanced them?

Yes, you would know if they were balanced. The cord looks completely different and requires a special amp.