Now for the final mods that I made to the 708B. This mod put this amp well over the top, especially after a healthy, constant 92 hour burn-in time.
Resistor & Diode Upgrades:
I replaced every single resistor on the audio board that has to do with the sound getting from the input jacks to my ears, which means the ONLY stock resistors left on the audio board are the two very small, blue ones all the way in the back of the board going to the pre-amp outputs, one for left and one for right channel, which are disconnected anyway.
Almost all of the resistors used on the board are PRPs. There are three exceptions. For the anode load resistors, I used a pair of Kiwames. For the input resistors, I used a pair of Audio Note Tantalums. I also used another pair of Audio Note Tantalums for the outputs which is mounted directly on the headphone jack.
I also upgraded the stock cheap PS rectifier diodes with Vishay-Telefunken ultrafast soft recovery diodes.
Here's a few pics of the entire process.
I'm not sure what kind of sound improvement the diodes made, if any. But as far as the resistors are concerned, WOW! This amp has totally transformed into something special, leaving my LDM+ and my brother's LD II++ lightyears back in the dark ages!
This is what I wrote dcheming in a couple of PM's...
This one was only a few hours after performing the resistor and diode upgrades.
"And as for an update on the amp... Man, this thing is blowing me away! Especially when you have a good quality recording spinning! This MH cdp is excellent also, but just to be safe, I reconnected the Sony cdp for a couple of hours tonight after work. These improvements I am hearing are definately coming from the amp itself. All I can say is "WOW"! And then when I put the MH back up to it, it's another "WOW" all over again! I'm telling ya, you need to upgrade all of those resistors when you get a chance. They really make this little amp come to life."
And then this morning.
"BTW, on a side note, I have had this amp and MH cdp playing constantly since Wed afternoon (4pm) when I finished the last batch of mods and installed the opamps. I now have roughly 89 hours on both the amp and cdp.
All I can say is WOW! Everything is working flawlessly, everything sounds excellent, and I am just loving this entire setup. For a couple hours last night, I had the Sony player on the amp again and I couldn't get over how excellent that little cd/sacd player sounds now. The amp was definately the weak link, but not anymore! However, once I reconnected the Music Hall cdp, I could certainly hear another huge improvement in sound.
So I can safely say that the mods to the amp are definately worth it, especially replacing all of those resistors. You'll see what I'm talking about whenever you get your resistors upgraded.
Imaging, soundstaging, air, space, depth, detail, bass... Now I can finally see (hear) what everyone has been raving about with these K701 cans!!"