The majority of 610s in the UK were powered by a 3VA transformer housed in a 3 pin plug top box. Most people with earlier 610s choose to replace the dry cell PSU or rechargeable battery PSU with this plug top type. The class 2 rated transformer transformer was specified at 20V (x2 in parallel) on full load. There was thermal fuse adjacent to the transformer in the mains primary circuit rated at 102C. The preamp rectified and smoothed this 20V supply to create 28V DC as well as rail splitting the PSU and smoothing it to millivolt noise levels. The splitting was done by onboard TL431 shunt regulators, see below.
There was a flaw in the concept of this PSU. It had a 3 PIN DIN plug at the preamp end. Unfortunately the 5 pin DIN for the Phono input also has a DIN plug (5 pin). It is possible to put the PSU into the 5 pin phono DIN which then fries the MC section of the preamp. All 610s with this error should have the PSU plug changed to a 4 pin DIN and the matching socket on the 610 changed to 4 pin also.
The preamp feeds this 28V via a 100R resistor in each rail to two TL431shunt regulators. The TL431s are set to give +/- 10V on the PCB.
610 PSU with a 4 pin DIN plug fitted. Background is Crimson 710.
This PSU need to be as far from the preamp as possible if the MC input is in use.
These UK PSUs are still available via Crimson Products as of 2024. A replacement Euro type PSU has also been available in 2024.
Since July 2024 610 PSUs have been fitted with simple mains noise suppression components.