Annnnd...done. As
@Lysander said the difference is
staggering. The hiss is gone. Ok,
technically there's still some hiss but I have to put my ear to the tweeter to hear it. For all intents and purposes, it's silent.
The mod took me about 2 hours total I think, with most of that from building the three 1604/SOIC assemblies a couple days ago. Today the YIHUA solder sucker arrived. I pulled the preamp out of the FR-12, desildered the stock TL084s, installed the new opamp assemblies, and reinstalled the preamp all in under an hour.
When I went to test it and flipped the power on it was so silent I was concerned I messed it up. Nope. It's just that quiet.
The mod itself is fairly simple
if you have the right tools. The YIHUA solder sucker as recommended by
@aflynt and
@roy is incredibly handy. Removing the stock opamps would have taken
at least triple the time without it. Awesome tool for this work.
Also I'm using a nice
Hakko soldering station, some
Kester solder, some handy
soldering tips, and some
magnifying glasses.
If you are handy and not intimidated, and either have the right tools on hand or don't mind buying them, it's really pretty easy and not expensive. Also, you'll want pretty steady hands--I could see it being significantly more difficult if your hands shake because the parts are very small.
Great work figuring this out Lysander, and also thanks to WKSmith on the Fractal Forum.
So yeah...I now have extra parts for 3 more of these mods.