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Tuesday, November 19, 2019

The Differential Digital to Analog Converter


In a previous post I showed some of the latest DA-Converters I built. Among those a fully differential all silver version. In this post I will present that one in more detail.

While previous versions of the DAC used a single ended output stage with ELROG ER801A directly heated triodes, this one doubles up the number of tubes for fully differential operation.

The output stage follows a similar circuit topology as my differential 10Y line preamplifier.

It follows the same approach as the other DACs with separate power supplies for the output stage and digital sections.

In addition it uses an even higher precision clock, which comes from a separate 'SuperClock' module from eXD. Here we see some construction steps. The Clock module is mounted directly on the underside of the top metal plate.

Then silver output transformers and silver plate chokes on the next level. And finally the DAC boards:

There are two DAC boards mounted on top of each other one for each channel for  fully differential operation. The finished DAC:

The receiver board is mounted to the back plate and receives two clock signal from the Clock module through coaxial cables.

The High voltage and filament supply are similar to that of the differential line preamplifier.

The classic full wave bridge configuration with 4 TV damper tubes.

The digital supply chassis:

This now houses 3 independent power supplies, one each for the receiver, Clock Module and DAC sections.

The power supplies can be placed separately.

Or stacked.

The digital supply receives a switched mains voltage from the analog supply which acts as the master.

Digital and Analog supply voltage are fed via separate umbilicals to the DAC chassis.

Which has both XLR and RCA outputs. Inputs are Coax or USB, selectable via the switch at the front.

The DAC with the tubes lit up.

This DAC will be on demo at next years High End show in Munich.

Best regards


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