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Old 10th January 2012 | Show parent
 
The EMI Abbey Road Line Input Bypass Mod

I just had some time to play around with my a77 last night and figured out the line input bypass mod, and since it doesn't seem to be publicly posted anywhere, I wanted to share it for any other a77 owners.

It's REALLY simple. And the end result is you're not even using those input amplifiers built into the a77 anymore! So more pure sound and no more clicking when you hit "0" on the tape, saturation is possible AND awesome on this machine!

On the back of the input level pots there's 4 pins each. a black wire goes to pins 1 and 4, pins 2 and 3 are red and orange (i forget which is which off the top of my head - doesnt matter). Solder the ground wire to either 1 or 4, and the hot lead to the same pin as the red wire (nothing needs to be disconnected from the pots - as a matter of fact everything should stay in case you do want to still use the regular inputs for any reason)

Now, with my board setup, the input was HOT! I was hitting 0 at almost no gain on the controls even with a -10db unbalanced output, and I did have a load happening on the board - lost most of my signal going to my master fader - my VUs dropped from 0 to around -20. A 10k resistor in line with the hot lead on each channel brought it back. I'm reading "0" on the VUs at around the 3 on the inputs of the tape machine now. At max gain the needle drops back a little on mine (almost looks what happens when you do bias adjustment). I don't think there's ever a situation when you would even begin to hit that threshold so it doesn't matter to me. Maybe a 22k would be a little more accurate, but no worries, i'm happy.

This machine can achieve BEAUTIFUL saturation - i just tested with 468 tape. Wow. I'm stunned how buttery and rich it is. Bypass those mic/line inputs pronto! You don't know what you're missing if you don't!

Nick