Friday, June 3, 2011

Ampex MM-1200 Repro EQ Card Upgrade

So, I had some down time at the studio and I decided to upgrade and modernize the reproduce eq cards on my MM-1200. I bought some Wima capacitors and Dale CMF55 resistors and installed them on all 24 repro eq cards. I did a "test" one first and A/B'ed it to the original and the test one was noticeably better both in sound and in ease of alignment.

With the old cards, I had the low eq pot cranked up all the way and it was still half a db under "0" with a 50Hz tone and not much better with 100Hz, even with brand a new Flux Magnetics playback head. Now the low eq pot is just above half way or so and the sound is a bit more "rich" sounding, and has a hair more clarity, although that could be only in my mind, ha ha. I didn't notice much difference in the high frequencies during a quick listen, but it seems like frequency response is more flat according to the meters during set-up. Those 35 year old carbon resistors had definitely drifted out of specs!

During this overhaul, I discovered that I have 16 revision -03 cards, and 8 revision -02's. There isn't really any information out there on the -03 version and my manual only goes up to the -02 version, so if anyone out there knows anything about them, please let me know. They definitely seem to align my machine for NAB, and CCIR in 15ips, and AES 30ips no problem, but I'm curious to see what they actually are.

On my 440 2-track machine, I replaced every component in the entire record and reproduce cards, and I do mean EVERYTHING! This is not a 440 B or C, this is an original 440, probably from the late 60's...we're talking almost 50 year old carbon resistors, capacitors, and transistors in this machine! Amazingly (when you put it like that), the machine sounded fantastic to begin with, but this upgrade made this thing sound like the best thing I've ever heard in my life and I wish I could listen to everything in life off of it! I feel like the change was so dramatic that even a "regular" person could notice.

For any of you out there with an old Ampex 440, or MM-1000, do yourself a favor and put new parts in your cards! I wonder if this is how the machine sounded when it was new, or if the metal film resistors, and modern capacitors do indeed sound better than their brand new original counterparts. In any case, I'm glad I did this, and if I ever want the original "dirty" sound, I have a box full of untouched original cards I can swap in.

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