Topping headphone amp preferable to integrated amp with 100 ohm output?

[WillW]

I listen to music & TV mainly through headphones these days, connected to my old Arcam Alpha 9 integrated amp. This amp has headphone output impedance of 100 ohms, whereas my headphones have impedance of 32 ohms. The Arcam volume control barely needs to move - less than a quarter volume would be deafening. I'm wondering whether my headphones would perform better / be happier/safer with a dedicated headphone amp - something like a Topping L30. I would pair this with Topping E30 DAC for optical TV input & co-ax from FLAC player.
If the Arcam is doing them no harm then all well and good, but I'm told I should be running these headphones from a much lower impedance output. Is this the case? Please don't deluge me with tech & numbers, I'm just not made that way.
Thank you,
Will

 

[DVDdoug]

The Arcam volume control barely needs to move - less than a quarter volume would be deafening.

The output impedance together with the headphone impedance makes voltage divider and a higher output impedance actually reduces the signal into the headphones!

The "real problem" is that headphone impedance isn't constant over the frequency range. For example, where there is an upward "bump" in impedance, relatively-less voltage is lost across the amplifier's internal resistance and you get a bump in frequency the frequency response.

With a low "source impedance" (relative to the headphone) the signal doesn't vary with frequency and headphone frequency response is independent from output-impedance. Headphones are tested & specified with a low-impedance (AKA "constant voltage") source.

This amp has headphone output impedance of 100 ohms,

Are you sure that's the output impedance? Sometimes it's the recommended headphone impedance... It's the same with speaker outputs... They specify 4 or 8-Ohm speakers but the amplifier's output impedance is much lower.

 

[WillW]

 

[WillW]

So... Is the Topping going to be a better idea than the Arcam..?

 

[Robin L]

I've got the Topping E/L 30 combo, I'm real happy with it. Having a very "hot" signal for the headphones from the Arcam indicates that the potentiometer is operating in the range [from silence to low levels] with the worst performance. One of the virtues of the L30 headphone amp is that there is a three position switch to adjust volume range. It's best to have the volume control 2/3 open---something like 2:00 on most volume controls. The background noise level with the Topping stack is inaudible, and I'd bet that if you were to compare the sound of the Arcam headphone output to the Topping output, you would hear low-level noise with the Arcam that you don't hear with the L30.

The impedance mismatch might alter the EQ of the headphones, but I don't think that would be as big a concern as the potentiometer issues.

 

[WillW]

There is certainly a quiet hum in the headphones from the amp at zero volume, but I don't notice it otherwise. It usually drives a pair of Dynaudios, but I can't really use speakers any more, or not as wound up as I'm used to, due to now having neighbours for the first time in decades..
Thanks for input. Looks like a change of set-up is on the cards..