the 49720 is just a relabelled 4562-- neither of which are bad opamps. the metal casn version, which is a to-99-8, and costs about $16 at digikey, sounds better than the dip versions. they can be placed in dip sockets if you carefully bend and trim the leads. the tab identifies pin 8, and they are in sequence. if you hold the can with the tab pointing to the left, and carefully bend pin 8 and the three immediately to its right (counterclockwise, on the circualr pattern) away from you, the other 4 pins are then 1-4 in order.)
what i did was to bend them that way, and used extra dip sockets i had, and conformed the leads so they would sit in the sockets. they stick up too far this way, but that wil give youa guide for how much of the leads to trim off, so they sit closer to flush.
i recommend trimming a bit at a time (remember the old adage "measure twice and cut once"!), so you do not trim too much. they will not sit completely flush, but excess lead-length will introduce rfi problems (listen for vast but vague soundstage/imaging, and edgy artifacts).
also, the metal can is connected to V-, so make sure you don't bend the pins so much that they touch the can.
once you've got them trimmed and bent into position on the spare sockets,they should remember their positions fairly well (i left them in the spare sockets for about a day (actually i cheated and put them into the essence along with the extra sockets, and leared about the rfi/stray capacitance ill effects from too long leads and the cans being electrically connected when they touched the card's shield and also bent to much -- i have no patience!!!!)
anyway, they were easy to slip into the card's sockets once they'd gotten use to their new shapes in the spare sockets, and they sound wonderful after many days of continuous play.
i loved the warmth and rich natural tonality of the stock sound, but wanted more snap, resolution, and dynamics than the stock sound could provide.
i have it now, and i am prety much done opamp rolling (i know, famous last words). what's in their now is 49720 metal cans in the i/v spots, and a pair of mono 49710 metal cans, on a browndog adaptor in the output position.
the singles have a slight edge in terms of stage, but are a pain to get seated correctly as the box caps surrounding the socket prevent the browndog from seating completely.
my audio pc is an antec fusion htpc case, so the opamps are sideways, not upside down like they would be in a tower case, so i've made it work. the shield will not fit back on with this arrangement. i have not had time yet to put back the metal 49720 instead, and see how much the shield effects the sound.
to finish the story a bit, i have a dedicated audio pc, running xp sp2 in cics cmp2 mode, using winamp as the player, with a recompiled asio exe plug in that was done by a guy in audioasylum. playing with the asio and winamp config setting, mainly thread and process priorities and buffers makes a musically significant impact on sonics. i run the volume sliders in the xonar panel all the way up, and the rotary volume at abut 50-75%. full up it sems to overload my preamp (i am running analog outs to my two channel speaker based system via magnan silver-bronze ics.
sound card and player settings, along with killing unneeded processes has a major impact on sound -- do experiement with these as you swap opamps, and take notes so you can go back to prior settings. opamps are not simply plug and chug, and some like the 6172s, i believe, may not really be compatible with the card without some circuit tweeks.
happy hunting!
mark
