After reading some of Slimdevices CEO Sean Adams tests on jitter in the SB2
here , I have decided that all future mods will have the second oscillator removed. All previous units modded can be sent back to have this rev done at no charge.
I will be trying out a pulse transformer on the digital output soon. If that makes an appreciable differnce, I will add it as an option to the mods.
I will also be trying out some additional power supply mods. I will be building an upgraded outboard unit that will have three regulated supplies. It will have the main 5 volt input that would run the computer end of the SB2. There would then be a separate 5 v and a 3.3 v supply that would just go to the DAC chip. Internally, the SB2 DAC would be completely isolated from all the switching power supplies.
This may be offered as an upgraded package. Anyone who ordered the "basic" power supply and/or mod can have it upgraded to the "deluxe" version. The SB2 would have to be modded to use the new power supply.
As a final option to the new unit, the DAC supplies can be run off a 6 volt SLA battery for complete and total isolation from the computer supply. This will require a separate charger for the battery, so two things will have to be plugged into the wall. There will be one switch to change between the battery driving the DAC and AC. The switch will also allow the battery to be recharged.
Having the battery just powering the DAC chip will not draw very much current. I expect quite a long life for each charge.
This is not going back on my thoughts in another post about battery power. I still feel that a straight output from a SLA battery does not sound as good as when a cap bank is used. Having a battery power regulator circuits with big caps on the output should work out fine. I am not sure yet as to any audible difference between a pure AC powered version and the partial battery version. I will build one and listen and report. If all goes well I will have this ready for the listening session during RMAF.
