Post by solderdude on Feb 9, 2017 20:34:59 GMT
The adapter will always provide a load of around 35 Ohm to the amplifier.
(Almost) regardless of how high- or low-Ohmic the connected headphone is.
Even when you short the headphone (make it 0 Ohm) the load the amplifier 'sees' is still 33 Ohm.
For the headphone things differ.
When you have an amplifier with say 30 Ohm output R the 'source resistance' that drives the headphone will be around 3 Ohm
When you have an amplifier with a 120 Ohm output R the 'source resistance' that drives the headphone will be around 3.2 Ohm
When you have an amplifier with a 0 Ohm output R the 'source resistance' that drives the headphone will be around 3 Ohm
It attenuates around 20dB for all headphones when connected to an amplifier with an output R below a few Ohms.
It attenuates around 26dB for all headphones when connected to an amplifier with an output R of around 30 Ohms.
It attenuates around 33dB for all headphones when connected to an amplifier with an output R of around 120 Ohms.
How about the loudness issue.
The HD650 needs 0.2V to reach 90dB (acc. to Tyll)
The HD662-EVO is rated at 98dB with 1mW power and is around 35 Ohm in impedance (32 Ohm is just a 'standard' number)
This needs to be converted to a voltage. Ohms law comes in handy.
1mW = 0.001W
To reach 0.001W in 35 Ohm you need 0.18V
In this case it produces 98dB.
We need 90dB to compare.
The difference is 8dB
I will spare you the calculations but this means a factor 0.398 in voltage.
Let's make it 0.4x
0.18V x 0.4 = 68mV.
So.... HD650 needs 200mV to reach 90dB
the HD662-EVO needs 68mV to reach 90dB.
When both headphones are connected to a low Z amp (V200) the HD662-EVO will play 9.4dB LOUDER.
Now, when the HD662-EVO is connected through a 20dB attenuator it will play 20dB softer.
So when the HD650 is connected directly and the EVO via the attenuator the HD650 will play 20dB-9.4dB = 10.6 dB louder than the HD662-EVO.
When you realise about 10dB is a (just about) doubling in percieved loudness then it is clear that when both are connected directly the HD662-EVO will play about 2 times louder than the HD650
But when the HD662-EVO has the attenuator inline the HD650 will be about twice as loud as the EVO
(Almost) regardless of how high- or low-Ohmic the connected headphone is.
Even when you short the headphone (make it 0 Ohm) the load the amplifier 'sees' is still 33 Ohm.
For the headphone things differ.
When you have an amplifier with say 30 Ohm output R the 'source resistance' that drives the headphone will be around 3 Ohm
When you have an amplifier with a 120 Ohm output R the 'source resistance' that drives the headphone will be around 3.2 Ohm
When you have an amplifier with a 0 Ohm output R the 'source resistance' that drives the headphone will be around 3 Ohm
It attenuates around 20dB for all headphones when connected to an amplifier with an output R below a few Ohms.
It attenuates around 26dB for all headphones when connected to an amplifier with an output R of around 30 Ohms.
It attenuates around 33dB for all headphones when connected to an amplifier with an output R of around 120 Ohms.
How about the loudness issue.
The HD650 needs 0.2V to reach 90dB (acc. to Tyll)
The HD662-EVO is rated at 98dB with 1mW power and is around 35 Ohm in impedance (32 Ohm is just a 'standard' number)
This needs to be converted to a voltage. Ohms law comes in handy.
1mW = 0.001W
To reach 0.001W in 35 Ohm you need 0.18V
In this case it produces 98dB.
We need 90dB to compare.
The difference is 8dB
I will spare you the calculations but this means a factor 0.398 in voltage.
Let's make it 0.4x
0.18V x 0.4 = 68mV.
So.... HD650 needs 200mV to reach 90dB
the HD662-EVO needs 68mV to reach 90dB.
When both headphones are connected to a low Z amp (V200) the HD662-EVO will play 9.4dB LOUDER.
Now, when the HD662-EVO is connected through a 20dB attenuator it will play 20dB softer.
So when the HD650 is connected directly and the EVO via the attenuator the HD650 will play 20dB-9.4dB = 10.6 dB louder than the HD662-EVO.
When you realise about 10dB is a (just about) doubling in percieved loudness then it is clear that when both are connected directly the HD662-EVO will play about 2 times louder than the HD650
But when the HD662-EVO has the attenuator inline the HD650 will be about twice as loud as the EVO