Seasonic Platinum Series 860W - Platinum without the Fuss

Probably the Best PSU Ever!

The Seasonic Platinum 860W is the best current Seasonic product, and very probably the best power supply available at this time. The delivery contents and the number of connectors are at least above average. The internal design, the fan, and the excellent measurements surpass all current solutions from their competition. Clever ideas like the switch for active or semi-passive cooling operation are welcome extras and work without any complications.

Inside Seasonic uses a powerful variation of the well known resonant converter. As usual, the manufacturer implemented the latest silicon carbide diode in the primary circuit and very good MOSFETs. With a mains filter and further components for EMI filtering the PSU is very well equipped. Other manufacturers tried to cut components here in order to improve efficiency, but here Seasonic still includes passive surge protection and inrush current limitation. As expected, Seasonic uses high-quality Japanese capacitors and very good PCB materials. However, even Seasonic is not safe from problems. We saw ferrite beads on two Gate connectors (part of a MOSFET).

Perhaps the PFC control circuit should get a multi-layer design, since some conducting paths are used for different circuits. This might be a source for differential mode interferences and the reason why ferrite beads are necessary. Apparently Seasonic seems to have no problems with the frequency range of their buck converters used for 3.3V and 5V—some engineers bet on HF litz wires on the storage inductors or reduce the frequency with an external circuit. In addition the ESL (Equivalent Series Inductance) of capacitors gets more and more important. Regardless, Seasonic integrated well chosen components and the soldering quality is impressive.

As noted on the previous page, the Platinum 860W showed no significant weaknesses, only the usual strengths of Seasonic. The ripple and noise voltage is never higher than about 30mV at 12V, and the smaller outputs show even lower results. Moreover there is no significant voltage drop at higher loads; all output voltages are very well regulated. Only the chirping of the PFC inductor becomes noticeable if you are close enough; in a closed PC case the noise should not be audible. Right up to higher loads the fan is quiet—or even inaudible below 40% load if the semi-passive mode is activated. Up to 93% efficiency can be achieved with this design and even at 10% load efficiency is still very good. At very low load the regulation effort is usually high—measured against the operating current. This causes high power loss during low load.

Seasonic has no problem with these power losses and even passive components such as filtering coils can't stop Seasonic from reaching and exceeding the 80 Plus Platinum requirements. That might sound strange at first, but FSP for example changed the input differential-mode choke into two single wires with a ferrite core. The lower inductive reactance opens the doors for differential mode interferences. Other manufacturers try to remove important parts such as OCP to reduce power dissipation. The solution from Seasonic is a major advance, which makes the power supply the flagship in its class. A high efficiency should always be compatible with constant quality, which doesn't mean other solutions wouldn't be acceptable as well. FSP tried to make low prices for their Platinum PSUs—an understandable step.

The larger Platimax models (>1000W) from Enermax might have more extras than the Platinum 860W, but Seasonic includes plenty of extras as well and at least matches what you get with the Platimax 750W. The 60 to 65cm motherboard and GPU connectors are extremely long, and the Platinum 860W can support up to four PEG, eleven SATA, and eight HDD connections. In particular, the number of SATA connectors is very satisfying, and the high quality cable sleeving is another reason to buy this product.

The direct competitors include the already mentioned Enermax Platimax 750W / Platimax 850W and the Golden King Platinum design (Kingwin LZP-750) from Super Flower. The latter offering isn't just questionable in name, but the missing overcurrent protection and MOV are also a major drawback. As such, we wouldn't put that particular unit in the same category as the Seasonic; Super Flower products in general use cheaper quality. In price and quality Enermax Platimax is close to the Seasonic Platinum, but Seasonic clearly demonstrates better soldering quality and uses extensive EMI filtering. The Seasonic Platinum 860W is currently available for $220, which is $20 less than the best price we can currently find on the Enermax Platimax 850W. Given all of these factors, there is only one possible ending: the Seasonic Platinum 860W deservedly earns our Gold Editors' Choice Award for being as good as one's word—and in some cases, even better.