AKG1000s - What Amp? - Page 2

Well, they arrived! I hooked them up and upon first listen, I decided they needed to break in, so the wife and I went to dinner while the diaphragms flexed and the electrons flowed... Noise is no problem with this amp given sensitivity of the cans. Quite a different listening experience. Almost sounds like there's a suck-out in the mid bass region, but more likely, I so used to hearing a mild lift in that region on the Senns and Grados that the absence of it sounds different! This is goint to take time to break in. I do believe it's a trifle better already since dinner. Well, I'll just close the door to the office tonight and let 'er run, and in the mean time, it's fun to listen... It's going to take a lot of iteration around to dial in the sub. I'll let them break in without it first. Greg, thanks for the suggestion about running the sub in nearfield configuration. I will definately give that a try when the time comes. I can't wait to try these out with a Rel sub once they're broken in!! Hey, you know, I think these things are growing on me...

Comfort level isn't too bad. AT this point, they do strike me as peaky in the upper mids. I'm going to let them break in for a while before I make up my mind.

If you look at the published response curve of a Senn HD580 or HD600, you'll see what looks like maybe some phase cancellation in the high end, and particularly with the HD600, a broad accentuation in the low end from 60Hz through 500Hz. Both the 580 and the 600 show a small peak around 1.7k, then a dip around 2.5-3kHz and both rolling off starting around 6kHz. They're actually almost 10db down @ 20kHz relative to the broad rise in the mid bass. The 580 plots look better than the 600.

The Grados show a somewhat similar characteristic curve.

The AKGK1000's however plot flat as a ruler (+-2db) from about 50Hz through 20kHz. I've never seen anything like it in a headphone before.

One issue to consider is that normally the combination of your pinna and air distance from sound source typically produce similar dips in frequency response of your ear. When you move a sound source close to your ear so as to eliminate the attenuation effects of both the pinna and air distance, the same sound source would sound perceptually bright. So, I'm not entirely clear as to how much interference your pinna causes with a near field sound source such as the K1k's.

All this theory aside, I hear grain that I don't like and it's probably the lousy amp I'm using. Drat! Now I'll have to look for a good amp before I can finish evaluating these critters.

Well, things are looking up this morning. After letting them break in overnight, the grain seems to be reduced this morning. Not sure why. The low level linearity seems quite impressive. Linearity at higher levels still seems compressed, probably due to amplifier being used. I like the soundstaging. It reminds me a bit of my VIP-1000, a headphone system from Sony circa 1994. It has its own DSP and amplifier system. There is some sort of gyro built into the cans so that when you put them on and press the centering button, which ever way you're facing is front and center, then as you turn your head, the front and center stays put where you told it to be, just like in "real" life. Kind of a cool effect. The Sony cans are physically (drivers in the air away from your head like the F1's) open, much like the K1000s. The amp built into the Sonys is fairly lousy with very limited dynamic range. The limits sound hard and I suspect the major limitation is the dynamic range of the DSP and not the analog system. Too few bits. Anyway, this K1000 is a much better kettle of fish. Not as much intra-aural crosstalk as I was hoping for in a soft room, so the K1000s would still benefit from some form of cross-feed processing aka Headroom or Corda. The Sonys (VIP1000s) do that part right (via DSP). The acoustic image is fixed firmly in front of you and not in your head. Well, I hope these K1000s continue to improve. At least it sounds like I will be able to live with the current amp after all, until I find something better. Cheers!

Well, the K1000s have been breaking in all day and they are continuing to sound better. I find that some program material sounds pretty good on them and other stuff, not so good. Acoustic guitars sound nice. Nice pluck. Acoustic basses sound good also. Some male voices. I like the low level detail.

Well after about a week of break in there was no more discernable change in the sound of these cans, so all I could do was to await the arrival of the SAC K1000 amp that was coming. It arrived today. I was full of anticipation of improved sound. Guess what? It sounded absolutely terrible!!!!!
After about 2 minutes of listening I discovered at least part of the problem... The left and right channels are 180 degrees out of phase with one another! Can you believe it? Does anyone else's SAC K1000 have this problem? I popped the hood and rewired the right channel output after determining that it was the channel that was inverting absolute phase. The sound was immediately 1000% better. Much fuller, proper imaging, sobstantially better bass, etc. But... This amp still sounds cold compared to the Kenwood Class A amp I was using. The SAC sounds a little bit faster than the Kenwood and exhibits better dynamics, but still one cold sucker sound-wise. Temperature wise it runs hot as a pistol. The surface temp of the top of the case is 116F+ degrees after an hour of "on" time. So please somebody help me here. What are your collective experiences with this SAC amp??

Thanks!!

A few more observations:

• The temperature at the surface of the case seems to have topped out at 122F. So I raised the amp another 0.25" off the base upon which it was sitting and now the case temp is around 115F.
• The amp is on even when it's off. What does the on/off switch really do??
• The sound seems to have warmed up a bit.
• The power supply looks like it is supposed to put out + and - 18vdc. I measure + and - 23vdc. Is this supply module supposed to be a regulated supply? Maybe this amp would benefit from a better power supply.
• Does anybody have any specs/manuals/schematics for the SAC K1000?

Thanks everybody!!

Things are improving sound quality wise as I sit here and listen and the amp runs in. The gentleman I purchased it from said he used it so little, he doubted it would even qualify as having been broken in. Judging from the cosmetic condition I would have to agree. Judging from the sound quality out of the box I wouldn'thave been able to listen to it for more than a few minutes before taking it back off the shelf and putting it back in the box for good. There are yet a number of areas where I see further potential for improvement, but as it is, it's begining to sound as Jan Meier described in his review on Headwize. I have now been able to "open" up the earspeakers to their fully extended position to obtain the most neutral response with this amp. The sound is full and very detailed and delicate. Still plenty of punch, although still missing the very bottom octave. If I can find specs/manuals/schematics for this thing, that would help me with the tweaking. Cheers!

A side note: My wife just ducked her head in the office and got a look at me and started laughing She saw me for the first time with the K1000s "flaps" fully extended. She said it qualified for the geekiest thing she'd ever seen. But honey, it's the sound, it's the sound...
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