Both the A and D versions are accurate representations of what the 1176 was supposed to be (insert endless conversations regarding wide component tolerances and what is a "real" anything vintage). This applies to the A version. If you read the thread for the Rev A build, you will find posts regarding how the compression kicks in very quickly, but this is how the original version operated. There is a resistor change that can be made to make compression threshold similar to the Rev D on that same thread. You'll have to do some investigating as I don't remember the details.
As for needing a 20dB pad for the Rev D, that is silly talk. More than likely such a discussion arises because all the kids on all the other forums gain stage everything to +18dBu (maximum output on most all converters) and when this circuit was first built +4dBu was generally the target on tape machines. A 20dB pad on a super hot signal would accomplish "response more similar to original units."
Since you have both a Rev A and D Hairball unit, what do you think when you use them? I think they sound awesome. If you are of the same opinion, are you concerned about how original units sounded? I ask this with all sincerity.
Thanks!
Paul
