The 717 is rated at 450v RMS which means it reaches 600v P-P easily but the final voltage the phones see is tied to the volume level. Now whether or not this is a problem depends on the cap and the circuit. The piece of tape hides part of the circuit though and I couldn't make out the colors on the small resistor which is above the tape.
To save bandwidth, why don't you just upload the pictures here? The site accepts 4kx4k pictures up to about 8mb.