Posted by Lew on November 18, 2002 at 13:48:38:
In Reply to: M1s annd Atmasphere MA1s and best internal wire and caps posted by sandy on November 16, 2002 at 16:18:56:
I use M1s with my Atma-sphere MA240 amps, which supply a little more output power than the "14-tube" version of the MA1. First, I highly recommend that you get the optional backplate for OTL or other tube amps, the one that includes an inductor in series with the resistor in the hi-pass filter. Second, you probably ought also to get a pair of Zeros or the Atma factory impedance matching transformers. (Even with the modified backplate, I found that use of the Zeros set at only 2X impedance multiplication helps prevent me blowing fuses on my output tubes, although the sound is just as good with or without the Zeros.) Third, I do recommend ditching the factory-supplied Solens metallized film caps in favor of any number of alternatives. I am using 2uF polystyrene/tin caps made by Southern Electronics, and I was able to make 12 of these caps fit into the power supply box neatly. However, Southern no longer makes these caps. Apparently, they still make them in 1uF values, as Al or Roy mentioned. A less space-taking alternative is to use REL MIT PPFX-S (polypropylene and tin) Multicaps. These are available in 4uF and 8uF values, so you would need either six of the former per side or three of the latter. I used these in my former pair of U2s, and they sounded great. Hovland is another admittedly costly alternative (but not costly compared to the cost of the M1s themselves). After all of the above, THEN I would still worry about the resistors in the hi-pass filter BEFORE worrying about wire. I would change the sand-cast resistors supplied by the factory for either Caddock hi-power resistors or Mills 12W resistors, wired as per the factory (so that you need 8 resistors per side). I am using Cardas 15-ga wire internally, but this is not a recommendation. I think silver ribbon would be better, but that's just me.