I have a problem with blanket statements like this. First, YOU may hear differences that others may not. I know two people that can hear cap differences (proven in double blind tests) that no one else could hear. You may fall into that group. Second, did you measure the caps to verify they had the same value and then compare frequency response and dB levels? Third, did you go to the effort of doing a double blind test?
I’m not trying to attack you and I’m sure you hear a difference. But it’s also possible it was due to cap value differences or confirmation bias. The trouble is I can find similar blanket statements about using wooden risers to lift cables off the floor. And those people are just as sure as you are. Like they say, sometimes it's hard to tell the wheat from the chaff. And until I see some supporting data I consider it all chaff.
The bits fit loosely on mine too. I think they're just poor quality and yours might be stripped.
After reading some recent discussion here about the BRZHiFi amp, I wanted to post the minimal modifications that I think should be done to the input section. As it is, the non-inverting and inverting op-amp halves are in parallel, making the input impedance way lower than it needs to be. This will raise the input impedance and allow using the input film caps without a low end response penalty.
Yellow - jumper
Red - remove
Orange - replace with 100-200k, value isn't too critical
Blue (optional) - remove resistors and replace the 50k linear taper pot with a 20k or 50k log taper. This will get rid of the increased noise and scratchiness around mid volume range.
Yellow - jumper
Red - remove
Orange - replace with 100-200k, value isn't too critical
Blue (optional) - remove resistors and replace the 50k linear taper pot with a 20k or 50k log taper. This will get rid of the increased noise and scratchiness around mid volume range.
Neither of the tools you mentioned work on any of the screws. They all grip to a point and then start slipping. None budged at all. I really believe they're gluing the screws in now, even though that sounds ridiculous. So I guess the only way I can open this thing is to drill out all the screws. Frankly I think the amp sounds fine the way it is so I might just leave it. I have it matched to some very efficient high-end focal bookshelf speakers. The only thing that has bothered me so far is a mushy sounding low mid range on certain recordings 20 or 30 years old. But on most of it sounds great. Thanks for the minimal input upgrades with photos, really wonderful information to have.
Thank your post is really informative and well imaged, thank you for sharing without denial!
This chip is very interesting.... but compared to the SAbAJ A20A.....200 euros, the price is almost divided by 10....
Congratulations in any case, for making unimaginable things easy!
I got in! Turns out a 1/16" allen wrench worked with extra force. I'd tried one before, that spun, tried another from the garage and it worked. Couldn't loosen one screw holding the bottom half on. So did all the mods from theAnonymous1 above except the input caps and and pot replacement. Wish I could get at those caps. It sounds big. I'm surprised I got away with my messy fix- these 70 year old eyes are almost not up to microscopic work. Thanks again.
Good use for the parts if you aren't someone that gets bothered by using ceramics or just don't want to try and shoehorn larger caps there.'could stack the left-over 2u2 to the chip input coupling caps
Ah, I see an oversight in my original mod suggestions. Once you jumper the 2u2 ceramics you must remove the [blue] 22k resistors that are used to "law fake" the linear taper pot. It isn't optional at that point unless you want to cut the trace on the signal side of those resistors and add jumpers to the input side of the film caps. I removed them and put in a 20k log taper pot.
That was the first thing I tried. My 1.5mm had no traction. Couldn't break the seal before it just spun. Could be that since these are such small sizes they are not all alike.
I had the same problem on one of my Units.
I opened only the back unscrewed the nut of the pot and pulled the circuit board out.
May I ask what 20k log pot you've used? I only find 10k Alps RK09 in the EU region that would fit right in.