Seventeam ST-550P-AM Power Supply Review

[Hardware Secrets Team]

There has been a new article posted.

Title: Seventeam ST-550P-AM Power Supply Review
URL: http://www.hardwaresecrets.com/article/727

Here is a snippet:
"ST-550P-AM is a 550 W power supply from Seventeam where you can manually control the fan speed – and can even disable it – a feature called "ASM" by the manufacturer. We've already tested another mode..."

Comments on this article are welcome.

Best regards,
Hardware Secrets Team
http://www.hardwaresecrets.com

[Olle P]

My list of comments.

Page 1:
1. "[The housing] ...being only 5 ½” (14 cm) deep."
This means the size is compliant with the ATX/PS2 standard and will fit in all ATX cases (as opposed to many longer PSUs). That's a plus in my book!

2. "With the knob ... you can control the fan speed. ... shut it down completely ... if the temperature there goes too high the fan starts spinning even if you turned it off."
Very interesting feature! Would love to read more about how it works!

3. "... the presence of only two SATA power connectors. Since nowadays you will have at least two SATA devices – the hard disk drive and the optical drive – you will have trouble installing a second hard disk drive."
A bigger problem is that the two connectors are on the same cable, only 15cm apart! Installing two SATA HDDs is thus easy, but one HDD and one optical drive will be far more difficult.

4. "The second problem is that this power supply has only one power connectors for video cards, while all competing products have two."
I suppose an additional connector on the 12V1 line could do.

Page 6:
5. "Today a typical PC pulls more current/power from the ATX12V/EPS12V and video card auxiliary connectors, and all these outputs are concentrated on the same rail, while +12V1 has only components that do not demand a lot of current/power."
Video card connector: max 7.5A
Motherboard: 8A for the PCIe alone, plus integrated graphics, integrated sound, NB, SB, network, fans, etc. = max >10A?
CPU, 100W: 10A?
With 20A available on the 12V2 rail the EPS/ATX can count on at least 12.5A (150W). Shouldn't be a problem, right?

Page 7:
6. What fan setting was used? How does different fan settings effect stability, ripple, noise (electrical and acoustic) and efficiency?

Page 8:
7. "...the label states an 18 A limit for each rail."
The label on the picture states an 20A limit for each rail.

8. "Maybe the value is too high on purpose, since the +12V2 rail is connected to the CPU ... and to the video cards at the same time, what would shut down the power supply under normal working conditions."
As noted under point 5. that doesn't compute unless you run an overclocked Prescott and/or have the graphics connector split to supply two inputs.

General:
9. I'd really love to see some more info on the variable fan feature.
- How does it behave with various settings and load?
- How does it effect the electrical properties?

Cheers
Olle

[Gabriel Torres]

Hello Olle P,

See below my answers for your questions.

Originally Posted by Olle P

2. "With the knob ... you can control the fan speed. ... shut it down completely ... if the temperature there goes too high the fan starts spinning even if you turned it off."
Very interesting feature! Would love to read more about how it works!

It works as described on the text. What you want to know exactly?

Originally Posted by Olle P

Page 6:
5. "Today a typical PC pulls more current/power from the ATX12V/EPS12V and video card auxiliary connectors, and all these outputs are concentrated on the same rail, while +12V1 has only components that do not demand a lot of current/power."
Video card connector: max 7.5A
Motherboard: 8A for the PCIe alone, plus integrated graphics, integrated sound, NB, SB, network, fans, etc. = max >10A?
CPU, 100W: 10A?
With 20A available on the 12V2 rail the EPS/ATX can count on at least 12.5A (150W). Shouldn't be a problem, right?

Yes, however our comments on this part of our reviews is on the theoretical side; we always want to see CPU and video cards on separated rails, if possible.

Originally Posted by Olle P

Page 7:
6. What fan setting was used? How does different fan settings effect stability, ripple, noise (electrical and acoustic) and efficiency?

Thanks for pointing this out. The setting used was with the fan manually put on its maximum speed. I updated the review to include this information.

Originally Posted by Olle P

Page 8:
7. "...the label states an 18 A limit for each rail."
The label on the picture states an 20A limit for each rail.

Fixed, thanks.

Originally Posted by Olle P

8. "Maybe the value is too high on purpose, since the +12V2 rail is connected to the CPU ... and to the video cards at the same time, what would shut down the power supply under normal working conditions."
As noted under point 5. that doesn't compute unless you run an overclocked Prescott and/or have the graphics connector split to supply two inputs.

Removed, thanks.

Originally Posted by Olle P

General:
9. I'd really love to see some more info on the variable fan feature.
- How does it behave with various settings and load?

We decided to review the power supply at a fixed fan temperature so results wouldn't be biased with the use of several different fan configurations.

Originally Posted by Olle P

- How does it effect the electrical properties?

Technically speaking the higher the temperature, the lower the current semiconductors can deliver. This characteristic is called derating and you can read more here:

http://www.hardwaresecrets.com/article/181/8

This way, having a better ventilation system can help the power supply to deliver more current.

I hope I have answered all you questions.

Cheers,
Gabriel.

[Olle P]

Regarding variable fan settings.

The reason for having this feature in the first place is obviously to provide the user with an option to make the PSU more quiet. Using this PSU with the fan on maximum by default therefore seems like a last grasp to use only if/when the room temperature is very high.

The interest therefore is much more in how the fan behave under different temperatures at different settings.
Top interest is of course what happens when the fan is set to "off". Does it go directly from no speed to high speed at the threshold level, or is it a smooth transition? What is the threshold temperature(s)? And how does it effect performance, not in broad terms but in actual values?

Testing with the fan at maximum show how well the PSU can perform under favourable conditions. Testing with the fan "off" show how well it will perform under normal conditions.

Cheers
Olle

[Gabriel Torres]

Hello Olle P,

I understand what you mean. However we don't have the manpower to do more than we usually do -- which is already a lot... I hope you will understand.

Cheers,
Gabriel.

[Gabriel Torres]

The results from this review were updated today to reflect AC power and efficiency measured by our new precision power meter. The updated results did not affect our conclusions or recommendation about this power supply.