[fzman]

Hello all. I have been comparing several headphone amps lately, using my Alpha Prime, Utopias, Nighthawks, and borrowed HD800.......
In the conjunction with listening-test comparisons the Violectric 280, Phonitor X (and E), and the new Luxman P-750u, I discovered the following power specs- and they don't make too much sense to me--HELP!!!????

In balanced mode, the Luxman does 8Wpc into 16R, 4Wpc into 32R, and 213mWpc into 600 ohms. This seems to imply a stable 11.5-ish volts output. OK- I thinkI get that (and the calculations bear that out.

The Violectric 280 manual quotes the following:
> 32,9 Veff in 600 ohms = 1800 mW
> 28,2 Veff in 300 ohms = 2650 mW
> 23,0 Veff in 100 ohms = 5300 mW
> 12,4 Veff in 50 ohms = 3100 mW
> 9,1 Veff in 32 ohms = 2600 mW
> 4,9 Veff in 16 ohms = 1500 mW

How does it do that, rather than "doubling" the wpc as load impedance is halved? Why, e.g., is the 100R output the highest?

The Phonitor:

Max. Output Power (at +30 dBu @ 1 kHz)

• 2 x 1 W at 600 Ohm impedance
• 2 x 2 W at 300 Ohm impedance
• 2x 3.7 W at 120 Ohm impedance
• 2x 2.9 W at 47 Ohm impedance
• 2x 2.7 W at 32 Ohm impedance

For the Phonitor, why isn't the power at 32 ohms more like 11-12 wpc?

Do these amps vary their voltage swing depending on the output load? I am really confused....

HELP!!!!????

 

[technobear]

They are probably limited by their 'current' capability.

A high voltage coupled with a low impedance would cause more current to flow than the output stage is capable of passing. As impedance rises you pass a point where the current is always less than the maximum available so the maximum power is dictated by voltage. As impedance falls, greater current is required for a given voltage until the current limit is exceeded. From then on down only successively lower voltage may be used according to the maximum current available so the maximum power is dictated by current.

 

[fzman]

Thanks technobear! That's a huge help. What also threw me was that the highest output levels were in the middle, not the bottom (or top) of the range of load impedances. I know enough to get myself in trouble, but not always enough to get myself out of it.

 

[gimmeheadroom]

I know enough to get myself in trouble, but not always enough to get myself out of it.

We must be cousins or something