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Sunday, May 8, 2011

Making of a EC8020 LCR Phono Preamplifier, Part 2: Wiring

Hi!

In this article I will show the process of the internal build up and wiring.



After the basic mechanical construction of the phonostage was done, wiring and internal built up could proceed. Let's start with photos of the PSU. This is much simpler than the phonostage itself. Here a photo of the initial internal wiring: Mains connections, socket wiring and the B+ capacitor bank. The heaters get a separate DC supply. The heater transformer is mounted inside:


The chokes and some additional capacitors are mounted inside the chassis on a second tier made from aluminum profiles. Here a shot of the completely wired and tested PSU, 3 B+ chokes for good filtering of the high voltage and even a choke for the heater supply:


Next the signal chassis itself. First a ground bus is laid out and some initial wiring to the sockets, heater wires, and connection to the signal input RCA jacks, an additional capacitor bank is mounted inside for separate B+ decoupling of each stage:



Some more wiring: signal wires all done with teflon insulated solid core silver wire. Where necessary additional sleeves are pulled over the wires for extra insulation and mechanical protection:


Each stage gets it's own B+ choke for decoupling. Also the interstage and output transformers are mounted inside, again all signal relevant wiring is done in silver. Here a shot of the completed internals of the phonostage:


Ready for the first test run! Measurements look good and the initial sound is as expected compared to an exisiting EC8020 phonostage. Some extended burn in still to be done and fine tuning. Then the plates will be mounted in wooden frames.

Best regards

Thomas

2 comments:

  1. Wonderful construction, as usual, Thomas. Are grounding wires from the suspended socket aluminum plates to the main chassis needed only in low signal chassis like the phono preamp, or should they be used in all your preamplifiers?

    Thanks,
    Matt

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  2. Hi Matt,

    all metal parts of a chassis should be solidly grounded. In a phonostage this is especially recommended to avoide any hum issues. But I'd do this as a general practice.

    Best regards

    Thomas

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