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The CAPI 2-Stage Line Amp Rev B card is a custom made PCB for line amplification and utility type functions. The circuitry is based on my vintage API recording console. The first stage is a -6dB balanced receiver using a 2520 style opamp. This stage is implemented in exactly the same way as the line receiver of my console's input modules. The output of this stage is unbalanced. It can be balanced off-board with a 2623-1 transformer wired 1:2. This will provide a balanced unity gain signal. In my console, the first stage's output would feed the channel's EQ slot. If using this card as a console channel, the output of the 1st stage (or EQ slot) would drive a 1k fader. This is not mandatory but if used would be a slide type audio taper fader or rotary style like this fine Elma switch. The 2nd stage of the 2S-LA card is a 2520 booster amp with variable gain that can be trimmed and/or preset with the on-board trimmer. If following a typical build, there will be +6dB of gain built into this stage. The output of the 2nd stage is unbalanced. It can be balanced off-board with a 2623-1 transformer wired 1:2. This will provide +12dB of gain in relation to the card's input signal. The unbalanced output can also feed multiple summing bus resistors and/or a pan pot network with bus resistors. In that case, the extra 6dB of gain would be made up in the 2-ACA-Bo circuitry. Designed for Molex .156" KK headers Simple daisy-chain power to adjacent boards Standard 2520 footprint with .09" plated thru holes to accept Mill-Max #0322015013427100 sockets to makes for easy swap of different discrete opamps Board is 4.4" long by 2" wide ***Please note: CMRR calibration must be carried out exactly in the same way as our ML2 and 500 series EQ modules. ***Please note: At this time, we are not offering complete parts for this build. The pic below is of the green proto boards that were initially produced for testing. The production boards are blue but no other changes were made. Hairball 990 opamp kits were also used on the proto board. I used this configuration as receiver and makeup gain for vintage Langevin EQ-252-A graphic equalizers.

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Proto Built