Responses from dinov

McIntosh MC20 - 1960's - No Left Channel
There is a McIntosh forum that is more tech oriented in audiokarma.org that may be more helpful but +1 @mwood for the Audio Classics recommendation. I use them for all my vintage gear. Good luck.    
JJ preamp tubes - repeated problems
Yes they do test them but current tubes aren’t what they used to be quality wise. McIntosh is very easy on tubes, so the problem is definitely the JJs. That’s why I use NOS. I use Amprex Medical 12 ax7 s in my C2300 and have well over 10000 hours.... 
vibration control - cd player
Use Isoacoustics footers under the component I use them under all mine and my speakers. They not only protect against vibrations, knocks etc but improve sound.  
Neat "Tweaks" to improve the SQ of your streamed music!!!
+1 @upshift I did this a couple of years ago. Adding a fiber optic ethernet connection before the streamer is the best bang for the buck upgrade you can do in my opinion.  
Ways to make your digital streaming sound better
Fiber optic Ethernet! With Finisar SFP modules. Makes a big difference in sound.    
20 Years?
Happy anniversary!  
Signal tube versus power tube, sound impact?
Usually power tubes first then signal tubes in an amp. Also it’s the first signal tube in the series for a particular channel that has the most impact. For instance, if you have 3 -12 ax7s  for each channel, the first one in the series has the mos... 
Bananas rule, spades drool. End of discussion.
+1 @erik_squires totally agree. I used to be a bare wire advocate but after going to banana connectors I’m a believer.   
Value of a preamp?
+1 @soix also it gives you the ability of various inputs, sound level balance, and control of your system components.  Ideally, it should “get out of the way” in terms of sound and noise but it’s personality can add quite a bit to a system given t... 
Qobuz Issues?
It was down yesterday on the 8th for about an hour.   
What qualities stand out in really good solid state preamps?
Quiet, absolute silence!  
Clock vs Streamer advice
Used Lumin, absolutely!  
Mcintosh pre amp pricing
That’s part of buying a McIntosh. Among many other reasons, they will hold their value, even for you should you purchase one.    
Does a turntable mat make any difference?
+1 @baylinor   
Did I damage my new amp
Amp probably not, speakers ie tweeters maybe.