At the risk of stating the obvious, make sure the Pianoteq's volume is as high as you can go without clipping, too.

If you can get the volume high enough, but it still doesn't sound the way you want it, you could always try EQing to taste.

If you end up needing an amp, the one I'd try at the moment, for full sized headphones, would be the portable FiiO A5. (I haven't ever tried it, but that's the one I'd try out first)

I've contacted Focusrite in the past about the specs of the headphone output, and I remember thinking it would probably be loud enough for most full sized headphones.

Greg.

Schiit Magni headphone amplifier at Schiit.com
https://www.schiit.com/products/magni-3

—

Strange... what model of Focusrite interface are you using?

A Scarlett 6i6 1st gen.
The sound is +/- ok but I have to put the volume at 3-4 o'clock to have enough power and even at this level, the sound is not full, generous... With an old Roland headphone the sound was heavier at 12 o'clock, but lower in quality.

That is why I am ready to go for an amp at max 200 euros.

Thank you for the explanation. Sadly, as you can understand, that is totally out of my budget.

However, these small headphone amps have good reviews...

<..>

EDIT: Maybe Joe's older AKG are the 300 ohms ones? that would explain everything...

Good point, Gilles.

Cheers,

Joe

EDIT: Maybe Joe's older AKG are the 300 ohms ones? that would explain everything...

For almost all of the twelve+ years I have owned my AKG K702's, I plugged them directly into my Apogee Duet Audio interface.  I "thought" the sound was very satisfying, although a little lacking in extreme dynamics and in the lowest bass.  Interestingly, even when the Duet's volume control was set to its maximum value, I wish there was more gain available. I thought I heard everything through the AKG-Apogee Duet combination, but there was some musical information that I had been completely missing through these very revealing headphones. 

Four months ago, I acquired a used Anthem Statement D1 preamp/processor whose retail price was $5000 USD (and its most current model retails for $9500USD) to use with my main sound system.  One of the benefits of this preamp is that it contains a separately controlled- and powered headphone amplifier of very high build quality and circuitry.  Well, Sir, let me tell you:  now these AKG's sound as though they have been given a new lease on life!  The sound is punchier, much more dynamic, and if I choose to emphasize the bass using the D1, one can dial in too much bass in these 'phones.

I had missed the AKG's true potential because I did not use a headphone preamp of high enough build quality, componentry and current/amperage capability. 

So back to your original question, if we would choose between two headphone preamps, each very small and each retailing for less than $200USD, I think you would be missing the boat regarding the sound quality these AKG 702's have the potential of providing you.

Cheers,

Joe

P.S.  "More Expensive" is not necessarily better, but a piece of equipment of build quality and current handling capability costing 25X to 50X more -- "Will" make a difference.  Restated, if you are serious about exploiting the capability of your 702's, a $200 headphone amp is insufficient to satisfy you for any length of time.

The sound coming from the headphones output of my focusrite soundcard lacks of punch on my headphones (AKG K702)

I think to put a heaphone amp to increase the power and to improve the sound quality.

Now, I have 2 options:

1° An HIFI type amp that is qualified as "audiophile", like this one:
https://www.amazon.fr/Micromega-Myzic-A...mega+myzic

2° A "Studio" amp, like this one:
https://www.thomann.de/fr/art_headamp_4_pro.htm

Technically (power, impedances....) which one do you think suits the best to be plugged on the outputs of a usb soundcard?

Thanks,
SK