Dell Precision M3800 Owner's Review

Yeah dude, what's up with the low res cam? It's almost 2014 already. Not able to afford a good camera even though you have 2 2k super high end laptop?
I'm just kidding Thanks for the videos of the xps and m3800 anyway. Will never buy (need) them but still enjoying looking at beautiful handicraft anyway. Thumbs up!

 

thanks for the test.

 

The Intel 525 is worth consideration there as well, although probably pricier than the other options at the given size. Performance on the Crucial is going to be slower than either the Intel or the Samsung if your workload is write-heavy, but the prices on the Crucial certainly tend to be great and for a lot of things the read speed is plenty.

 

As an EE i feel compelled to reply here. PS: sorry in advance for being a stickler on terminology.
It is true that the Laptop is fed with DC (ca 19V is common) but nothing inside the PC runs at that supply voltage.
The battery (if 6-cell) will have a charge voltage of around 12.60-13.05 V.
The Optical drive (if present) at 12V and 5V.
SSD/HDD at 5V
The RAM and CPU are fed by the motherboard which in turn (generally from the 12V rail) generate ca 0.75-1.35V (CPU) and ca 1.0-1.65 V (RAM).

So how does the computer make all these voltages?
Answer: A DC-DC buck-converter!
This is a small circuit comprising of an oscillator, a transistor, a comparator and some sort of filter. The high voltage DC is fed through a power transistor (Switched by the oscillator). If the duty-cycle is 50% (half the time OFF and half the time ON), the resulting voltage will be 50% of the input voltage. This switched power needs to be filtered to give the receiving equipment a nice delicious, smoooooth DC, free of ripple. To prevent filters from getting HUGE, the switching frequency is usually quite high (often in the kHz range, where we find high-pitched sounds).
The comparator is generally placed after the filter and monitors the output voltage and compares it to a set reference, allowing it to manipulate the duty cycle to achieve a regulated output voltage (that doesn't swing if the input should vary).

The filter generally consists of a coil-and-capacitor (aka LC) circuit (forming a low-pass filter).

To the M3800:
What you could be experiencing is a number of things, but I believe that "Coil whine" (again, sorry for nitpicking) is a misnomer. Coil HUM is prevalent in unregulated transformers, as the high current fed through the coil makes a strong oscillating magnetic field. For some high-power/high-frequency application this can also be experienced as a whine (Laptop powerbricks is an example). I believe what some are hearing is a "capacitor whine". Solid state capacitors (ceramics in particular) have piezoelectric properties. This means that as the voltage over them change, they physically change shape (expanding/contracting). This can be experienced even in fairly low-power circuits.
As the capacitor changes shape, it displaces the air around it and this is transmitted through the air as high-/low-pressure zones. Or "soundwaves" as we generally call them.
Other caps that share this property (although not through piezoelectrics) are electrolytic capacitors.

Usually, there are several/large caps at the power inlet to "smoothen" any ripple that may come from the powerbrick and/or be picked up through the cable (RF noise) to avoid disturbing the signaling inside the device. Also to avoid the "switching noise" of the transistors in the DC-DC circuits to "leak" out on the power inlet cable (to the power-brick or to radiate through the power cable). In high-end designs, these are Film (Polyester, Polystyrene, etc) or Tantalum. However, generally you'll find 'lytics or ceramics (or a combo).

I believe that it is very likely that the sound is generated by a capacitor (so it is a "Cap-whine") placed in one of the following places:
a) directly on the power input (also called a "smoothing" cap) - Symptom: The pitch (frequency) will be the same as that from the powerbrick (put your ear against the powerbrick to check)
b) On the DC-DC circuit feeding the battery-charging circuit (a filter cap) - Symptom: The frequency will vary with charge cycle (louder and different pitch when battery is discharged, than when full. No/little sound when battery is removed/full)
c) On another DC-DC circuit in the system (like 12V system power or 5V USB-power). - Symptom: Pitch changes with load (on USB-port) or voltage (PC power state).

Generally there is very little to do with this other than to:
1) change the capacitors for higher-quality ones (film, tantalum, better electrolytics)
2) "potting" the capacitors in a suitable material (Epoxy, Polyurethane, Latex, etc)

As for the severity of this "whine":
If it is an electrolytic capacitor then it is very unfortunate (as it could "blow" after some time). This is symptomatic of under-dimensioned electrolytic capacitors (too high ripple current).
If it is a ceramic capacitor then it is not as serious (at least in the forseable future). The contraction/expansion could place some stress on the solder points as the solder work-hardens (basically a form of annealing) but for this to lead to a component failure would probably take many years.

Nevertheless, it can be quite annoying..
If the whine comes from case "a", then a different PSU may give better results (or worse). If anyone has an older Dell 130W it could be interesting to see if it fixes the problem.
If the whine comes from any of the other two proposed cases then I believe we'll just have to wait and see what happens and if DELL performs any component changes or not...

 

What an outstanding explanation! Thank you very much for taking the time to write this up!

On my system the whine seems to change volume (and maybe pitch) with workload, and it seems to happen more while playing games, so I believe it's coming from circuitry handling the GPU(s), though possibly not EXCLUSIVELY from GPU circuitry. But since the fans come on when I'm playing games anyway, causing my laptop to make more noise overall (plus there's the game audio itself), it doesn't really bother me in the least.

EDITS: Someone else mentioned in the XPS 15 thread that the whine only happens while under load AND with a fully charged battery. Since my laptop is constantly plugged into AC power, mine could be the same.

Additionally, I do actually have BOTH of the older generation 130W AC adapters (the 2007 and 2011 versions pictured in the very first post of this thread). I haven't tested with them, but I suppose I could if needed.

 

Interesting.. If you have time (and the plug adapter) then it would be great to hear if the symptoms are similar with a different PSU.

Sent from my Nexus 7 using Tapatalk

 

There is an app for Android called AudioTool this is capable to do a spectrum analysis:
For example I can see the 15KHz peak that a my old CRT TV emits when it's on.
Unfortunately is an App very pricey 6€, maybe there are others apps that do the same thing for free.


https://play.google.com/store/apps/details?id=com.julian.apps.AudioTool

 

I don't know much about this, and I don't have an EVO SSD, but just in case it is useful to someone, apparently a couple of firmware upgrades have been released in the last few days:

- Support advanced data security features(TCG/Opal and IEEE 1667)

Samsung SSD (Solid State Drive) 840 series | Samsung SSD Website

 

Well, that's just the point (note the words in bold): What good does that resolution do me if there's no way for me to see individual pixels even in FHD? Just to be clear, I have seen MB Pros side-by-side with high-quality FHD displays, and I can't see a difference, with my reading glasses on, mind you. In simple words, all other things (color, brightness, viewing angles) being equal, I do not perceive any difference between FHD and QHD screens. So what's the point?

Oh, and, sure, I've been younger once myself, and had no problem immediately spotting individual bad pixels on 15" FHD screens. Maybe in those days, QHD would have made a difference. But those days are gone.

See above: It makes no difference whatsoever to me. 4k on a 30+" display? Sure, I can see that. On a 15" screen? I repeat, I don't see what good that would do me.

 

Tried all 3 130W adapters: the one that ships with the unit, an older 2011 version, and a 2007 version. The whine is the same in pitch and volume with all 3 (my battery was at 100% when I performed this test, if that matters), though I noticed that the whine goes away when NO power adapter is connected.