I just finished restoring rajacat's SB3 to life. He had a very nasty power spike through it that took out a lot of the DC line protection.
He also sent me a SC transformer to install in the digital line. I just did that and compared it to two other modded SBs that I have on hand.
First off, the SB is compatible with the digital mods. If you have the Full mods, as did Rajacat, there is not a lot of room left to work with to install the transformer. With the digital only mods, there is a bit more room, but it is still very tight.
I did run a ceramic cap from the shield on the transformer to ground for isolation.
I compared Rajacat's modded SB3 with transformer to a prototype "Statement" SB3 (most of the work on this one has gone into the analog section) and a modded SB2 with a copper Bybee Purifier in the digital output. All three were run off an Ultimate PS into a BOLDER digital cable into a Monica 2 DAC run off a SLA battery.
The transformer coupled digital output seem to be a bit "quicker" than the straight digital mod. In listening to Ahmad Jamal's "Ruby" the acoustic bass fingering was clearer. With the straight digital out, it was a bit "boomy". In it's defense, the "Statement" SB3 is still breaking in. Some of the "boom" could be attributed to many BlackGate caps that have only about a week of use on them.
In comparing the digital out from both of the units to the analog sections, the digital (at least through the Monica 2 DAC) did not have much in the way of extended highs or really sharp attack and transients. Bass was not as extended or as tight.
When I put in the SB2 with a Bybee Purifier, it was a lot closer to the sound of the analog section. The upper midrange was clearer, highs were extended and the bass was deep and clear.
In this comparison, to me, while the transformer may help with some isolation, it is not as dramatic a difference as using a Bybee Purifier in the digital line.
This comparison was NOT an apples to apples one. I did not have two units with the exact same mods done to them that were fully broken in. The differences between the "Statement" SB3 and the transformer coupled SB3 could be attributed to the new caps in the internal power supply.
The SB2 has been used for about a year and a half and is fully broken in. It also has a Silver WBT digital output jack vs the copper/gold on the other two.
While not a careful, DBT, everything exactly the same except for one difference, comparison, I thought this information may prove worthwhile to some.
This was the only time I could do this comparison. Rajacat's unit is going back to him this week.
