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My experiences with new M-60 Mk.3.3s, good and not-so-good

Posted by jeffreybehr on April 23, 2016 at 14:28:07:
1. First, sound quality--resolution/transparency and smoothness (= nonedginess)--are excellent, even with brand-new everything.
2. Have had some problems with lack of good contact with tube sockets. Had lots of trouble getting one amp to null its DC offset. Thought it was mismatched output tubes or even bad frontend tubes. Played with 16 output tubes (hereafter OT or OTs) and several frontend tubes (FETs)--original Chinese and old Tung-Sol roundpates. Sometimes the cathode follower's filaments wouldn't glow. Eventually worked out a sequence of loading input tubes into the amp and then pairs of OTs, and all has been well in both amps for a couple days. (I experienced the problems in only one amp, I experienced NO OT-internal-fuse blowings, and Ralph was very helpful.) My lesson learned--TY, Ralph--is that the Chinese tubes have slightly larger pins, and sometimes the socket's contacts don't make good contact with my old tubes.
3. Have installed new Cardas CCGR bindingposts, new solid-silver wires to the cap terminals, new Furutech FP-901(R) RCA jacks, two 1uF SoniCap Platinum output-stage-PS bypass caps in each amp, and three strips of SoundCoat the thicker...see link...on each bottom cover. IMO the chassis rings too much, and I'll be adding more of that stuff. (IMO vibrating resistors, capacitors, wire, vacuumtubes, etc., do NOT add to the sound quality, they all diminish it.)
I applied SoundCoat inside the VERY-highly-ringing transformer cover of the 2nd amp.

This cover is now DEAD!
4. I THINK the first serious improvement project I'll do is to replace the inexpensive 100/350 'lytic caps in the frontend's powersupply with BlackGate VK-series 150/350s*, bypassed with 0.47uF Platinums. ... But that's a big project, and probably it'll take me weeks to start that. Then I'll replace the output-stage PS caps, and for that I have a bunch of BlackGate 470/160s*.
I've removed the feet from my amps; I'm using the 2"-square Wagner antivibration pads...

...two-high. They seem to work just finely on my carpeted concrete-slab floor.
* that I've been saving for many years