A week or so ago I was able to spend a small amount of time with the new SABRE 9018 based, Eastern Electric DAC. Alex has designed a unit with both tube and solid state outputs. It uses the 12AU7 tube.
It offers multiple inputs including RCA, BNC and Toslink S/PDIF, USB and AES.
You can switch on the fly between tube and solid state and can also switch phase.
I was able to make some small changes to both the analog section and digital input while the unit was here. The owner of the unit wrote to me that the soundstage had become very 3D and definition had improved.
I contacted Bill @ Morningstar and Alex, the designer. I have received semi-official permission to offer mods for this unit.
In fact, Bill is sending me his personal unit for me to work on. There are quite a few things that can be done to this unit. Alex designed it to a price point. Once you remove that restraint, many options can be offered.
The tube circuit can be modified a bit. The output coupling caps can be changed for a different "flavor". The op-amps used in the I/E section and the output section can also be changed and the circuit optimized for different op-amps. The voltage regulators for the DAC chip, while very good, can also be upgraded. The options for this can get very expensive but I do intend to install some Paul Hynes regulators in some of the sections.
The input switching can be disabled along with the output volume control to eliminate some mechanical contacts from the signal path. A more expensive volume control may be able to be used or the gain of the circuit can be adjusted to whatever would meet your needs. The input switch might be able to be changed out to a MUX type circuit.
I hope to get another unit to work on in the next week or so. I will try to keep this thread updated with the mods I might be able to offer and pricing. I have found the unit is stock form to sound fantastic. I hope that a modded unit will only improve on that sound.