Using a Prodigy HD2 DE (VIA driver 188.8.131.5256, no VIA software), I went from an old configuration of (2)AD797BR and (1) 627AU to new configuration of (2) LME49990MA and (1) 627AU. or without the 627AU LT1028ACN8 in the output (needs this adapter). Listening with either ATH AD700 (open) or ATH A900X (closed).
For a point of reference, listened to Donald Fagen - Morph The Cat - Mary Shut The Garden Door - 2006 in FLAC Wavpack via Media Player Classic and The Very Best Of Fleetwood Mac - Everywhere - 2009 remastered from the original tape but well done for back in the day (1985-1987), Hummin' To Myself - Linda Ronstadt - Hummin' To Myself - 2004 and a recent movie with Pitch Perfect (2012) Blu-Ray (DTS) 24bits, 48KHz sampling.
To my ears: LME49990MA beautiful on the mid and esp. high end. Lacks a bit on the low end but I prefer the detailed highs as there is much going on in that range. Compared to the old configuration the AD797BR has more low (bass) range and is missing an area between the upper mids and high range. LME49990MA covers the entire mid to high range with very good separation, details and clarity, bass is in the background somewhat but maybe the new chips will break-in, both headphones are broken in already.**
Because of LME49990MA clarity, I prefer listening with my AD700's staging and highs response, Most ATH always have good voice range, so no problems there.
Through my Klipsch Ultra 5..1 sub, the bass is very clean. So the jury is still out if the LME49990MA is producing a more natural clean bass sound versus the AD797BR coloring the bass or highlighting it to much. Having the open headphones on with the sub on pumping out the bass is a real plus.
** Bass only slightly highlighted. More bass showing up after 10 - 20 hours of breaking in the LME49990MA chips, can't really explain it but just starting booming better but still has the cleanness in bass sound that I am not use to. Turned my AD700 into a well balanced headphone. My A900X are turning out to be very capable phones minus some staging of course.
Because the LME49990MA is my first opamp that was specifically tailored for music [Discrete? (according to the literature)] that I have used versus opamps that had other uses (ex. MRI machines or phone banks) but also worked with music and human hearing ranges, I am finding the LME49990MA a great sounding opamp, very clean sounds throughout even the bass range being clean is something different to my ears.
The following opamps are all used on their appropriate dual adapter boards. LME49990MA stayed on-board and I only exchanged in the output socket. Because of the LME49990MA the output opamps I tried below have a great signal to work with and give good benefits depending what you prefer...
*OPA627AU in the output seems to add a little unnecessary color to the sound,
sounds better without them/it.
*AD797BR in the output, more highlighted bass now with the highs slightly more pronounced (owing to more hiss present in poor recordings) maybe a hair tinny in the highs.
*AD8066AR in the output favors the bass, not in bad a way but colors/puts its tone even on a hum of a bad recording. Nice if you like your bass sounds.
*LT1028CN8 in the output makes the bass sound a bit more believable but the very highs suffered (purchased this model by mistake).
*LT1028ACN8 in the output gives clarity and separation throughout the ranges causing great staging, favors the highs, lows slightly hidden in the background (my favorite output chip so far).
Some dual channels chips that didn't require an adapter board...
*NE5532N in the output makes no changes to the signal other than enhancements like turning up the volume across the entire range at once, very very clean sounding.
*LT1364CN8 in the output favors the highs and enhances the clarity along with staging with a little bass boost. Very clean as well (like its brother LT 1028CN8 above).
*AD827JNZ in the output favors the lows to mids, brings them forward and puts the highs in the background. Very strong and realistic lows with a trade off of losing some detail in the highs. (So far best at handling lows)
Listened with, AD700 and A900X headphones.
Edited by razzz42 - 5/21/13 at 5:40pm