Hi guys.
If it was not clear in the release notes, I will work to make it clearer.
There is one reason and one reason only for the RevE board existence. It is the singular fact that ST Micro abruptly discontinued the production of 2 critical devices used in the RevD board, the 2N3439 and the 2N5416 transistors. Although we tried to quickly get in on the last time buy through distribution, it seems that ST had a very short window, produced one last batch and then quit forcing this move. It is sad that it had to come to this because the RevD board was the culmination of customer input and performance/reliability improvements up to that point. While hard to find, the 2N1304/5 pairs are still locatable. The RevE remedies that availability problem as well. Both Lee and I have retained repair buffers of these EOL parts.
Every feature that is in the RevE is in the RevD board right down to the exact pinout locations on the board. None of these were moved even a smidgeon to ensure total backward and forward compatibility.
The only thing that will require a change at the backplane level is the PL400 emitter resistors. The typical PL400 emitter resistors are 0.22 ohms, the ones desired for the SOA protection of the output devices with the RevE board are 0.33 ohms. Given that the RevE is only just completing beta at the moment, I have considered and alternate population that will support the 0.22 ohm value as well. This has not been fully thought through yet but is on the list of things to do prior to production release of the board.
We will be working to standardize the build of both the 400 and 700 backplane kits around the 0.33 ohm value sometime in the future. That along with unifying around 150 ohms as the base-emitter resistor on the pre-drivers in both the 400 and 700 application instead of the 180 ohms currently packaged in the PL700 backplane kits. The long term goal is to have the only real difference being the number of output drivers used on each backplane, 3 on the 400 and 5 on the 700 on each rail. Not big changes and they will have no effect on the performance or sound but will make it more uniform.
Hope this helps. Transitions are tough...
If it was not clear in the release notes, I will work to make it clearer.
There is one reason and one reason only for the RevE board existence. It is the singular fact that ST Micro abruptly discontinued the production of 2 critical devices used in the RevD board, the 2N3439 and the 2N5416 transistors. Although we tried to quickly get in on the last time buy through distribution, it seems that ST had a very short window, produced one last batch and then quit forcing this move. It is sad that it had to come to this because the RevD board was the culmination of customer input and performance/reliability improvements up to that point. While hard to find, the 2N1304/5 pairs are still locatable. The RevE remedies that availability problem as well. Both Lee and I have retained repair buffers of these EOL parts.
Every feature that is in the RevE is in the RevD board right down to the exact pinout locations on the board. None of these were moved even a smidgeon to ensure total backward and forward compatibility.
The only thing that will require a change at the backplane level is the PL400 emitter resistors. The typical PL400 emitter resistors are 0.22 ohms, the ones desired for the SOA protection of the output devices with the RevE board are 0.33 ohms. Given that the RevE is only just completing beta at the moment, I have considered and alternate population that will support the 0.22 ohm value as well. This has not been fully thought through yet but is on the list of things to do prior to production release of the board.
We will be working to standardize the build of both the 400 and 700 backplane kits around the 0.33 ohm value sometime in the future. That along with unifying around 150 ohms as the base-emitter resistor on the pre-drivers in both the 400 and 700 application instead of the 180 ohms currently packaged in the PL700 backplane kits. The long term goal is to have the only real difference being the number of output drivers used on each backplane, 3 on the 400 and 5 on the 700 on each rail. Not big changes and they will have no effect on the performance or sound but will make it more uniform.
Hope this helps. Transitions are tough...
