I just got my D4 topkit, plus a bonus OPA2227 and have been playing around with them for the last hour. My very first opamp rolling experience. Does this mean I've lost my audio virginity?
First off: WOW, I'm impressed. I was expecting changing opamps to make a difference, but I wasn't expecting such a visceral and obvious difference.
HiFlight suggested the OPA2227 when I said I wanted warm and bassy. He warned that it with the bypass buffers was 'too bassy' for the JH16's. Frankly I didn't think such a thing was possible, but in this case it was. The sound was better than the stock kit, but the bass was so powerful as to distort the JH16's at a moderate volume level. This made some kinds of Electronic music sound pretty nice, the sound isn't well suited to rock/indie stuff.
Moving on I tried the topkit OPA1161 with the bypass buffers. While others have described this as 'perfect' and 'neutral' I found it a bit cold (I like my music like I like my men: hot), but the clarity was amazing. The difference between this and the stock opamp was stunning - I was already tripping over my new JH16's and how many little details I'd never heard in favorite tracks, but with this opamp I'm hearing even more subtlety than I was before. The bass has impact AND detail, and the midrange is downright visceral.
I tried putting the stock buffers in with the OPA1161 and am going it set up like that. The stock buffers add a touch more warmth to the sound and suits my tastes perfectly. The bass and midrange impact/detail are the same as with the bypass buffers, and the highs seem a bit less piercing. This setup was perfect for both booming electronic music (50% of my listening) and rock/indie stuff (the rest).
While I was expecting the difference between this setup and the stock setup to be perceptible, perhaps a 5% difference in perceived sound, I was really honestly surprised to find it made a marked difference, in the 25-30% 'different' range. Given a blind A/B test I wouldn't have believed that the same amp made both sounds. Then again - did it? Isn't the opamp what does the amplification itself? So hard to seperate the device I can hold from the chip in my mind.