The upgrades discussed below are in addition to my replacing the
Beyer input transformers with Reichenbach RE-115K-E units,
presumably the equivalent of Jensen JT-115K-E.



> Tell me a bit about installing proper shielding in an MX-10.

I soldered a thin piece of mumetal to the chassis, between C13 and R32 
(the ch. A level set control).  After listening to the thing's hum and 
buzz via headphones, and noting that ch. A was worse than ch. B, I 
decided to experiment.  I attached a clip lead to a piece of mumetal 
about 2" square, wrapped the square with electrical tape, clipped the 
other end of the lead to the chassis, and gingerly moved the mumetal 
square around some of the power supply components.  Apparently C13 was 
"radiating" 60 Hz harmonics, and the R32 level control was picking up the  
buzz.  So I installed the mumetal in the best location (determined by 
listening), with the electrical tape wrapped around it.



>Until several years ago, I used one in some location recording
>going direct to DAT and liked the sound.  Of course, I had
>already replaced all of the transformers with the very Jensens
>you mentioned and changed out all of the pots and coupling
>capacitors, etc, so it was virtually rebuilt.

I didn't change any pots because they remain quiet.  It appears that my 
unit has had very little use.  But I did change many (but not all) of the 
caps, as well as some of the EF86 plate dropping resistors in the mic 
input stages.

Yes, I replaced the 2-section selenium rectifier (CR3) in the DC filament 
supply with some silicon diodes that I already had on hand:  Radio Shack 
276-1661.  These are 6A [!] 50 PIV, so they are over-rated, but there is 
plenty of room for them.  There was less room to install a 15 mH choke in 
the filament supply, but I did, and it helped.  I simply used the one out 
of the electronic assy. of my 354 parts machine.  The filament voltage is 
now a bit high (I don't recall the actual measurement), and one of these 
days I'll install a dropping resistor.

I also paralleled one each 33 uF 350 V Radio Shack electrolytics with C 
12a, b, & c (in the B+ supply) as well as a 4700 uF 35 V cap. in parallel 
with C18 in the filament supply.

All of these measures helped, so they stayed.

Also, I am now using premium Amperex 6084 tubes in the 4 EF86 mic input 
stages.  They are gold-pin and taller than conventional EF86s (same glass 
envelope as a 12BH7).  The original tube shields don't fit, but those for 
12BH7s will, of course.