X-bit labs

ATX Power Supply Units Roundup: Part II (page 11)

Category: Other

by Oleg Artamonov

[ 04/25/2005 | 03:45 PM ]

The build quality of this PSU is high. I would like to draw your attention to the panel with the connectors on the front panel of the PSU which gave me cause for complaints in the Ryanpower2 section of this review. This panel is as neat as everything else in the OCZ ModStream: the wires are not soldered to this panel, but are attached with neat clips, sleeved in transparent insulating pipes (the clip of the +5V rail is visible in the snapshot above).

The load capacity of the +12V rail is somewhat lower than that of the typical 400W ATX12V 2.0 PSU, but the allowable load on the +5V rail is impressive. The purpose of such a high load capacity remains obscure to me because modern systems rely mostly on the +12V rail and the capabilities of this PSU will most likely remain underused.

Alas, the kinship with the PSU from be quiet! shows up not only in the design, but also in the characteristics. The BQT P4-450W couldn’t boast stable output voltages, and the ModStream OCZ-520 cannot, either. I think it’s already clear that this PSU doesn’t have any auxiliary regulators, like the models of the PowerStream series.

The pulsation of the output voltages might have been better, too. The amplitude is about 70 millivolts on the +12V rail, which is lower than the acceptable limit. But on the +5V rail the pulsation approaches the limit: the high-frequency pulsation of 50 millivolts combines with the low-frequency 100Hz pulsation with an amplitude of about 10 millivolts. This is observed only at full load (the oscillogram is taken at 500W load). When the load is lower, the low-frequency pulsation vanishes, while the level of the high-frequency pulsation diminishes (for example, to 25 millivolts on both rails at 300W load).

The PSU works very quietly, and its fans don’t practically change their speed. The speed is only increased at highest loads, but only to 1250rpm at maximum. And there are no overheat-related problems even at full load.

It is the excellent efficiency of 89% at full load that helps the PSU to keep the fan speed low. The power factor is about 0.7 because this PSU has no power factor correction circuitry (we tested the American version of the PSU; the European version is equipped with PFC).

So, the power supply from OCZ leaves a most pleasant impression with its highest build quality, attention to various details, detachable cables and quiet operation. I think that the OCZ ModStream deserves to be called an “open platform for modding” more than the Ryanpower2 from A.C. Ryan (these two PSUs can be considered competing products, at least in terms of functionality and target user groups). The latter company should follow the example and improve the quality of manufacture of its PSUs. On the other hand, the OCZ ModStream is inferior to the Ryanpower2 in the actual parameters, first of all in the stability of the output voltages. So, OCZ should also make some improvements – to the electronics of the PSU. I think that a PSU of the PowerStream class, even without the manual voltage control but with the functionality of the ModStream series, would be a highly successful solution. So, if you’re going to buy a power supply with detachable wires – and this is really a helpful feature – then you’re facing a difficult choice: the Ryanpower2 is more stable, while the OCZ ModStream is better in terms of build quality and user-friendly design. If you’re going for a PSU from OCZ Technology, I would recommend to you to pay attention to models from the PowerStream series instead.