What would be your source(s) for headphone listening? When you say it will be separate, do you mean that the headphone rig will have its own dedicated source(s) or will use the same sources as listed above?
Your thinking is sound - a decent headphone setup will take you farther down the road of "audiophile" listening for considerably less money than chasing other incremental upgrades elsewhere in your system. The HD600s paired with any number of dedicated headphone amps will yield huge dividends in listening pleasure. Spend some time on www.headfi.org. My experience with the 600s is all positive - great sound and very comfortable. The HD580s are very near the same performance for a little less.
FWIW - keep the NAD and KEF gear. Really good values! I assume that the Technics is sound (is it a 1200?) and the cartridge is an m97xe - there is room for improvement with your phono pre without too much of an additional expenditure. Search www.audioasylum.com (vinyl) for recommendations.
Depending on how much you listen to digital, there are many different directions to go (standalone player, DAC, server) - but suffice to say that there is better than a Sony PlayStation for not alot of moolah.
Good luck and happy listening!
Your 501s will benefit a ton from a good headphone amp. I've got the K701s, Audio Technica W5000s and Ultimate Ears Triple.fi 10 Pros, all driven by a Woo Audio WA6 with a Holland GZ34 rectifier tube.
Lots of people love the Senns, so you'll be in good company. I haven't heard the ASL amp. If it's up in the $600 range, then you need to consider the Woo also. If you buy some Senns and an amp, then keep the 501s for a while to see if the new amp doesn't smooth them out.
Also, AKGs and most cans need 100-300 hours of break in. Use your cheap Headphone Out circuit to break them in, if you haven't already done so. The character will totally change in many cases. My Audio Techicas sounded like pure crap until I got over 100-hours on them. Most people say the AKGs need up to 300-hours.
Your ultimate goal will be to get your speaker system up to the standard of your headphone rig. Most of us think that speakers are superior, but a price point of up to 10X for equivalent performance.
Thanks for your responses. To fill out my options as I'm seeing them now: I agree, Dave, that ultimately getting my speaker setup up to the quality of the headphone setup might wind up being my goal. And from what you both say I suspect I might be best off buying the tube headphone amp first (the Woo is new to me, but I just checked out the website and it sure LOOKS great) and getting the most out of my AKGs, with an upgrade to the Sennheisers later. I've given the AKGs at least a hundred hours, but I'm certainly willing to believe that the right amp and some more break-in could fill them out.
Soulbrass: My plan at this point has been to set up the headphone amp in another room with its own dedicated digital source. I'll probably start with the Playstation since I have it on hand. My feeling about the NAD and KEF combo has been generally the same as yours, and I especially found myself surprised at the capability of the amp and speakers when I got into vinyl--that they were able to convey its character so well. My Technics is the SL-D2 model, but the Shure is the M97xE. You may be right that the phono pre and digital source might be my biggest limiters just now--so though I know I'm on the speakers forum maybe I can ask you for the budget digital sources you'd suggest. I heard the ASL amp and Sennheisers with a Pioneer Elite DVD player, though I'm not sure of the model or price, and it impressed me as a part of the combo. Source might be the second or third step if I do decide to pursue the headphone rig. Were I to use the new source in my main rig instead, could I then hook up the headphone amp to the tape monitor loop?
Oppo is a very reasonable digital source for under $200.
Some of don't consider Senns and upgrade from AKGs. ;-)
Make sure you break in those AKGs for at least 100 more hours. I like the Senns ok, but think they're euphonically distorted and they hide details that pop with the 701s. Most of the AKGs DEMAND high quality amps, while the Senns are much more forgiving of the source and amp.
If you want to listen for hours and you like your sound a little laid back, the Senns are a very good choice. The MG is also a pretty decent HP amp. You can run it off the tape outs of your pre-amp and get all of your sources available to you. I've never heard the AKG 501s, but if they are very detailed you may start to hear the limitations of your source. You can get a lot of advice on headphone and hp amp combos at head-fi.org.
The good news is that very good digital sources are much more common and affordable than in years past! I'd look for a well regarded player that is 2-4 years old (e.g., Arcam, Rega, Creek, Musical Fidelity, Rotel, Denon, Marantz, etc. ). Are you into hi-rez? Really nice universals from Denon and Marantz are available here on AGon for not alot of dough. Cambridge Audio and Music Hall both have nice sounding, entry-level CD players. You can always upgrade later using your choice to supply a digital signal to an outboard DAC.
A good position to be in if you're looking for digital playback... : )
Hey Soulbrass, do you play trumpet or 'bone in a soul/funk group? I did so for years in Dallas. I was lead trumpet with the funk/rock/soul group The PitPops. We had a blast. Alas, my move to Denver forced me out of that. I don't miss the late nights of tearing down, but the gigs were a trip.
Thanks again to everyone here for responding. I was lucky enough just now to snag the ASL amp on a classified posted today, so it looks like that's my first step into more serious headphone listening--it does seem to be the place where my dollars will stretch the farthest to get true high-end sound. My plan is to start with my AKGs and the Playstation as a source with a switch to the Sennheiser HD600s and an upgraded source soon to come. The Oppo's looking attractive, with the option of a DAC at a later date. Soulbrass: that 2-4 year old range for something swankier is good thinking--I hadn't realized there'd be some Musical Fidelity players at reasonable cost. Since I'm on the speakers forum after all I'll wrap it up with this: the Totem Model One Signatures I fell in love with will just have to wait till my income swells--it's 'phones for now!
I went that route with my first born, removed the second system from the extra bedroom and turned it into a baby's room.
Our music taste is roughly the same with focus on jazz. I just cannot stand listening to jazz with headphones. These days, my headphone rigs are just collecting dust in the study room except the occassional use when I need to do some heads down work.
ASL is a good starting point, but I would not have suggested it for amp. HD600 are good. I have a pair w/ Cardas headphone cable. I also have a pair of HD650 w/ Zu Mobius cable. After doing some comparisons with several other cables side by side, I felt these are the best combos in my system. I have not tried many of the new offerings. I actually prefer HD600/Cardas when listening to my turntable than the HD650/Mobius combo.
As other have suggested, before shelling out any more money, check out www.head-fi.org and read! Good thing is the folks in the headphone community get together quite often, so you get to try things out first before you buy.
My alias there is "gundam91" as well. You can check out my headphone rigs there, and also some reviews I have posted in regards to headphone amps.