Why my headphones sound better out of my integrated than my Headphone amplifier?

[kokono]

Ok, I don't use my headphones as much as I like, and I just have a pair of old Sennheiser HD650, with no dedicated amplifier.
I just plug them whenever I can, but I have some good dacs with headphone amplifiers, and one has been reviewed here, The Sabaj 2023 Dac and it should be very good.
Well it drives the HD650 effortlesly good volume and details, but still lacking a bit in bass and soundstage, which may very well be a limitation of these headphones.

The problem is that when I use the headphone out of my old JVC integrated, late 80s heavyweigh, they transform in 2 small speakers with bass and soundstage, the microdetails are a bit better on the Sabaj though, but still I much prefer the sound out of the integrated.
I know that there is not a headphone amplifier inside of JVC, just some big resistors that go to a small pcb, but they do the job.
Is this because of the relatively high impedance of the Sennheisers? Will smth with 600ohm impedance sound even better on the integrated?

 

[oleg87]

Bass "enhancement" caused by the JVC's high output impedance, I would guess. Adding a relatively wide bump around 100hz with PEQ would approximate the same effect.

 

[jjk1]

I’m experiencing the same thing with a Marantz pm8006 - I’ve had a few dedicated headphone amps. An Oppo ha-1, a few 4v balanced dongles, and a Fosi Zh3. I’m thinking of buying a dx5ii to get uca2 hardware volume control back.
Well It seems to me that with the Hd 650s I get better, or at least more bass response at very low volume with the Marantz integrated when compared to the dedicated headphone amps I’ve got. So much so that I was going to pose the same question..
In fact the Marantz is making me wonder why I keep buying headphone amplifiers - I’ve read that it should be less than ideal being a speaker amp.
JJK

 

[sofastreamer]

two words: output impedance

 

[Overseas]

Same thing with my Yamaha As1100 vs dongle amplifiers, I prefer Yamaha hp out.

 

[multiformous]

 

[usern]

Is this because of the relatively high impedance of the Sennheisers? Will smth with 600ohm impedance sound even better on the integrated?

It's because of _variable_ impedance of Sennheisers AND impedance of headphone amplifier output socket