JahJahBinks
Headphoneus Supremus
- Joined
- Nov 22, 2002
- Posts
- 3,306
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- 11
oh no! it looks like my laptop only supports 48k, so is USB better in my case?
I've never seen the output impedance of the headphones ouputs being posted anywhere but I would suspect it to be low. Maybe you could try asking one of the sellers or Yulong.
Got mine yesterday.
I analysed the circuit and can say that the output impedance is very low.
When you leave the DAC section, you pass a signal cap (wima), go thru a potentiometer and reach an op amp that feed a push pull emitter follower. Transistor stage are included in feedback loop. So the op-amp control everything.
In closed loop, the opa2134 datasheet state about 0.01ohm. with the wire+ connector resistance, maybe 0.4ohms.
the low impedance output is just a serial resistor of 47ohms that feed the 2nd headphone jack. If you want to loose dynamic, that is the output to use...
As for the class A, it's a real joke.
the output stage have a iddle current of about 11mA.
On my 45 ohms orthodynamic (he-6. the 45 ohms is measured with my Fluke DMM)
it mean that I can reach 1volt peak-to-peak in pure classA
translate in 0.34V rms
do the math and the result is a whooping 3.8mW of class A before going to class AB
I want to raise the bias voltage but the transistors are surface mount and no heatsink are present. the transistor will blow if I crank the current. they are stated at 300mW maximum dissipation. (they are already at about 165mW, so not more room)