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Sunday, February 12, 2012

The Modular Preamplifier, Part 7 : completed phonostage


The phonostage with E55L tubes is complete.

Separate power supplies for the input and output section on the left. Input and output sections in the middle and external MC step up transformer and LCR EQ unit on the right.
A six chassis phonostage! It will later be complemented by an active linestage. So this will end up as a 8 chassis preamplifier. It can be reduced to a more modearte 5 chassis by integrating MC step up transformer and LCR EQ into the phono input stage and by using it with a passive volume control as shown in earlier posts. However if the sytsem needs more gain, an active linestage is required. Which will be two chassis (external power supply). Two versions are planned using directly heated and indirectly heated tubes. Also in the planning stage are phono sections with directly heated triodes. These will be more extreme and require even more chassis. Initially 841 and 801A tubes are planned for these. Calculations and simulations are in progress for a variable LCR EQ unit for this combination. It will fit into one of the longer chassis, same size as the active stages and PSUs. Initial measurements of the phono gain stages are done and things look good. Before listening could start the phono stage had to go out on the terrace for the photo session. It will have to proove it's sound capability against the EC8020 LCR phono stage. This preamp will require quite a lot shelf space. But the stackability should make it a bit easier.

Don't hesitate to contact me if you are interested in such a phonostage or if you want to build one yourself. I can provide all the parts and schematics needed and will also help during the building phase.

Stay tuned for the listening report and the completion of the linestages in the same style.

Best regards



  1. The set looks very nice, Thomas.

    I am curious how E55L sounds compared to your standard 8020 phono. I do not have any 8020 but have some E55L tubes form a few years ago when I was thinking about using it for a spud amp.

    I am very tempted to build a variable EQ LCR phono stage for quite a while. I hope it could fix a number of thin sounding LPs.



  2. Thanks Tony!

    I still need to do the listening comparison. First listening is promising. Need to do some adjustemnts since the gain is a bit low. I will report when I had the chance to compare it to the EC8020 phono. But that will take another week or too.

    Best regards