A realy cool cd player deesign

[knirfie]

Apart from doing retinal surgery with reflection from the laser. St-o-o-o-pid!

A CD player uses something like 10mW for the laser. Far from damaging levels.


Nice design, but I see issues with having a lot of scratched cd's after use...

[Umfriend]

I quite enjoy listening to tube equipment though, yes I know it is less accurate and doing a side by side listen on my bros highened kenwood or yamaha equipment against some handmade valve stuff (older quality design but using new valves) you would almost immediatly say the solid state equpiment sounds better initially but after listening to the valve stuff for a few hours you enjoy it more (less ear stress?..weird?)

I too have compared my solid-state class-A integrated amp with my friends valve-pre and class-A SS power amp and found the tube/SS setup to be far nicer to listen to.

One explanation offered sometimes is that the harmonics (=distortion) introduced by valves are all of even order whereas from SS they are odd orders and the latter would be far more noticable. Of course, the magnitude of these harmonics have been far far smaller for SS for quite some time now.

Another possible explanation might be that my amp was euro 700 wheras his setup was euro 4,000. Still, actual distortion on his setup is measurably larger.....

[az]

Even-order Harmonic Distortion can actually sound nicer than sound without those.

[Brian Ellis]

The absolute power is not the criterion as to what can or cannot cause damage, but the energy/unit area. If a 10 mW laser has its beam focussed on an area of 1 µm diameter (roughly correct for a DVD, a little more for a CD) then this has a power intensity of ~637 kW/m², which is far from negligible. This is why they carry a warning label "Class 1 Laser Product to IEC 60825-1. Caution: Invisible Laser radiation when open, avoid direct exposure to the beam." Furthermore, the wavelength (780 nm) is such that absorption by the retina would be very high.

OK, I agree that light reflected from the CD is not likely to remain coherent and the risk may be attenuated, but an open mechanism is not a good idea.

[az]

Brian, that laser is also focussed to be that size at the distance of the data layer, it will disperse at longer distances. Furthermore, nobody can hold still enough for a laser to continuously hit the same retina spot for even a tenth of a second.

I wouldn't want to accidentally touch the edge of a CD rotating at 500 revolutions per minute (more for modern players which have large buffers to fill, so make it 1000), though.

[Tjalfe]

well one thing this thread has done is scare away our most recent active member..

[az]

I guess that I could be seen as one of the ones responsible for that. That was not my intention at all. I didn't want to pick a fight (actually, I didn't think I did), and it was nothing personal anyway. I just think certain firms could use a little more morals and that customers in general are too gullible.