Has anyone tried the Koss PRO4AA with Crack?

[Pfenning]

Any opinions on these? I was looking through the headphones on Musicians Friend and came across the Koss PRO4AA. At 250 ohms, it should match up good, but how is the sound quality? I read a couple online reviews that claim good sound quality, but nothing reviewed on a tube amp. $99 seems pretty cheap if they are decent, and maybe with a cable upgrade or some other mods, they could be a good bang for the buck.

Pfenning

[earwaxxer]

wow - I remember the Koss Pro4AA! Great cans in the day.

[Grainger49]

Late to this, I had a pair of Pro 4AAs when the first came out.  Loved them.  But I have no idea what the impedance was.

[Wanderer]

I recall "olde" Koss Pro 4AA from when they were intro'ed in the 1970s. I recall heavy, hot on the ears. and some what "murky" sound. Once I heard/wore Sennheiser HD 414 (2000 ohm on mine) I never looked back.

I have not heard current production Koss Pro 4aa or the current 4aa Titanium.   

Have you heard 'em and like them??   

       

[4krow]

I also owned the AA. They sounded like headphones. I sold them and bought Koss HV-1A open air headphones. Wow! what a step up. Had them for a few years.

[Adrian]

I know this is a very old thread but I wanted to keep information regarding the Koss Pro 4AA under one "roof".

I have a pair of original '70s vintage 4AAs that had been my go-to cans for three decades plus.
I used these in the studio back in the day and they used to be the phones many audio engineers used for mixing.  I also used these at home through my trusty workhouse: a Marantz 2325 receiver of the same vintage (still in use today).
Given the many changes in audio engineering these have been replaced by others for many reasons.  One reason is that the 4AAs are heavy cans.  Once I got used to them this was never a problem.  They seal very well, making them a good choice for studio work.  They came stock with the coiled cable necessary for use in the studio where it would not get caught or in the way while moving around.
These cans have what some may call a "dark" sound.  They are bass heavy but I don't think they boom or become muddy.  The bass boost these cans have can make the mids and highs fade somewhat into the background.  When using them I would commonly cut or buck the bass 1-3 dB and boost the mid/treble eq 1-3 dB depending on the source material.  Nevertheless I always found them to be quite enjoyable.  I added some more damping inside the cups which smoothed out the sound (I think?).
I currently listen to HD600s through my Speedball Crack and will occassionally use the 4AAs.  After some valve (tube) rolling I found a respectable combination that will brighten up the 4AAs (I don't use EQ adjustment anymore).  This pairing is a GEC 6AS7G with an RCA 12AU7A Cleartop.  The beautiful presentation of the 6AS7G and the "sparkle" from the Cleartop helps to bringout the mids and treble while keeping the prominent bass frequencies.  This valve pair also works well with the HD600s, lifting the "veil" associated with the HD600s.  They have become more resolving throughout the wonderous mid range while adding some needed sparkle to the treble.  The HD600s have become brighter but not too bright.
I cannot comment on Koss' current version of the 4AA.
For the record, the Koss 4AA are 250 ohm headphones.
Here a couple of pics of both the 4AAs and the HD600 with the GEC 6AS7G and RCA 12AU7A CLeartop: