I was going to start a new thread on my laptop PSU build, but this seems as good a place as any as it was made to try and get the most out of a laptop based .wav file ripping and playback setup at my desk.
As I was drafting info on it, rather than edit it to fit better here, I might just post it as is if that’s OK....
A warning though, I got carried away just a little and it’s trifle VERBOSE….
Hi Guys,
Following on from Alex’s work on linear-JLH enhanced supplies for his external BR writer and HDD, here is my attempt at an all-in-one box linear supply for my laptop, and external LB BR writer and 1Tb Samsung HDD.
Some background, since using cPlay for playback and reading about the cMP2 media player implementation, it seemed folk were getting SQ benefits by reducing all unnecessary services in Win XP and by using low power consumption CPUs that allowed the use of passive heat sinking (no fans to avoid unnecessary noise) and thus also the use of linear power supplies, which for whatever reasons generally sounded better. Obviously things have moved on since then, with many of principles of the cMP2/cPlay concepts being applied in apps such as Fedilizer and jPlay and the like.
More on cMP2 /cPlay here.
www.cicsmemoryplayer.com/www.diyaudio.com/forums/digital-source/141451-cmp2-diy-mods.htmlAnyway, to make an office laptop-based ripping and playback system, I looked for a laptop with eSATA sockets and Express Card slots to allow extra eSATA connections, thus avoiding the need for slower and possibly noisier USB connections to the HDD and BR writer, but with USB to DACs of course. A Toshiba Satellite Pro A300 Core2Duo (CPU is now getting on a bit) fitted the bill for this ~18 months ago, but some the newer low-power consumption i3-CPU-based laptops would be what I’d probably look for now.
I always had a plan to try and power these with linear power supplies but … I move at a snails pace and most things I’d like to do I don’t get to do. However, in support of Alex’s investigations here, which seem positive to “most” folk, including me, who listened to some of his .wav files ripped from his new external BR writer using a linear-JLH enhanced PSU, or from his Corsair USB pen drive powered by a linear PSU, I thought I’d make a concerted effort to try and replicate this, hopefully supporting his findings independently on differences in SQ with wav files ripped from a BR writer supplied from a linear-JLH enhanced PSU, and of course allowing me to rip the best sounding .wav files possible. (Please.. any believers of the power supply quality cannot possibly affect .wav file sound refrain from being critical, I enjoyed the challenge of building an getting this linear-PSU working and I learned a lot..... so from that perspective alone its been a success for me, plus I hope it will allow me to investigate this phenomenon first hand with each component being able to run from its stock SMPS or the linear supply). The only USB cable in use will be one to my NFB12 USB-DAC and with this I’ve taken out the 5V Vbus wire by placing a thing sliver of magi-tape over the pin in the USB plug at the laptop end, so no potential for this power wire to impart any nasties in the digital lines. BTW, this USB cable is from Musicaly (eBay) and they're hand built using sold sliver wires, nice made too.
So what bibs and bobs have I used for the PSU
1. A 300VA 9-0-9 toroidal transformer with secondaries connected in series for 18V. Needed this for 19V DC supply to my laptop and hoped it would be OK for 12V with the 5A LM388K PSUs, with fingers crossed that their heat sinks would be able to burn off those additional (non-ideal) volts.
2. Linear IC based regulator PSUs designed to deliver a reasonable amount (5A) of current. I choose these LM338K-based units on eBay that looked to have sufficiently rated rectifiers and enough heat sinking to cope.
3. For the 5V supply needed in addition to the 12V supply for the BR writer, I used a little eBay Audiowind PCB with AC or DC inputs, using DC fron a 12V supply
4. The dual JLH PCBs were the Greg Erskine designed beauties easily usable for dual +V supplies on the same PCB and were a generous gift from Alex. 2 x 4700uf 10V low ESR were used for each JLH, J506 constant current diodes have been fitted to each 5V JLH output, and the 0V and +V tracks were beefed up with extra wires
5. As I was concerned about inrush current at turn on with the 3 PSUs wired in parallel, I also purchased a Soft Start V3 circuit from Connexelectronic.com (the same place I purchased my SMPS500R being used to power my Class D Audio amp), both of which I’ll put in a plug for because both work great. Sorry Alex.
6. A case (always a hassle) but I found a few old record keeping card draws at work earmarked for the tip that were not too big might fit all in a pinch, and with lots of ventilation hole drilling and a spray paint, it worked out to be OK.
www.altronics.com.au/index.asp?area=item&id=M5509www.ebay.com.au/itm/LM338K-DC-AC-6V-30V-Out-DC-4-5V-28V-5A-Converter-/300553684555www.ebay.com.au/itm/Voltage-Regulator-PCB-LM317-78xx-Series-IC-/130579769451?pt=Vintage_Electronics_R2&hash=item1e6729286busers.tpg.com.au/users/gerskine/greg/default.htmconnexelectronic.com/product_info.php/cPath/43/products_id/49?osCsid=rusni65077hl0gm5d2srtc85t1www.connexelectronic.com/documents/Power_SoftStart.pdf.
Firstly, the LM338K 5A PSUs were modified, the trimmer resistors to set voltages were bypassed with 10uf-22 uf 50v electrolytic caps and protection diodes were added accordingly.
Initial testing of the laptop with one of these LM338K 5A PSUs wasn’t too successful. Basically it ran out of regulation, voltage would drop from 19V to 17-18V periodically in concert with loud buzzing of the transformer and with this, the 2SC5171 connected to the BC639 on the JLH got scorchingly hot very quickly. Because of this, I added substantial heat sinking to the 2SC5171s on the JLH supplying the laptop as a safeguard against it self destructing. However, this was a bandaid and the solution to the problem was adding extra bulk capacitance before the LM338K regulator. I used 2 x 10000uf 35Vcaps on a little vero board with wires connected under the PCB to the DC output pins of the rectifier for 22200uf total capacitance. With this additional capacitance, the regulator now seems to cope fine and I have not noted any substantial heating up of the JLH 2SC5171 whatsoever. So LM338K regulation seems fine with normal laptop loads and although the PSU heat sink can get hot, I can’t see there being any melt downs. Checked after extended use with a thermometer, the heat sink settles at ~55C.
I have the ability to select “Power Save” mode for laptop with reduced performance (designed for extended use on its battery), but as the PSU copes OK with the default “Balanced” mode selected, that’s what I’ve been testing it with. The heat sink will be staying on the JLH 2SC5171 though for ‘just in case’ safety reasons.
Because of the experience with the requirement for additional bulk capacitance on the laptop PSU, with caps available I included and additional 6800uf off board to the other 2 x 5A LM338K PSUs and an additional 9400uf off board to the 5V Audiowind PSU. The LM338K PSUs all have a 2200uf cap onboard and the 5V PSUs has a 4700uf cap onboard, so 9000uf and 14100uf totals.
For the BR writer 12V and 5V supplies, I’ve run 12V DC from the PSU to the 5V PCB fitted with a LM338T TO220 regulator so this 5V is double regulated. I also fitted additional heat sinking to the std TO220 heat sink, as in the picture, but as my connection method for this wasn’t as efficient as it could be, even though the onboard heat sink seemed to be coping OK, I’ve since replaced this with another attached directly to the LM338T with fins above the other heat sink at conducts much more efficiently. The heat sink on the LM338K PSU supplying 12V to the 5V board as well as 12V directly to the BR writer cops OK and stabilizes at ~55C, in fact similarly as the other 2.
I cut a whole in the back panel of the BR writer case to fit a molex-SATA power adapter to allow molex cable connection to this, thus bypassing the on/off switch and associated circuitry in the case. This allowed direct connection by a SATA-eSATA cable from the laptop to the BR writer with also bypassed whatever USB/eSATA circuitry was used in the case.
The 5A PSU 12V supply for the external Samsung 1Tb HDD was tested before additional bulk capacitance was and it worked fine, so current draw from the HDD must be low, and with the extra 6800uf of capacitance, it don’t expect any problems.
So……… this is where I’m at, and seeing I’ve gone to this trouble, I’d better do some comparison .wav rips soon. I’d like all the PSU and JLH well formed first but will get to this soon enough. Initial testing of even the laptop playing .wav files through its speakers suggests the linear supply adds some niceness to the sound, so I’m looking forward to more little surprises like this.
More reports on this soon.
cheers.. jeffc
PS. I still have to drill holes in the front panel of the PSU case for neat exit of laptop, HDD and BR writer supply wires and add a well ventilated top, and I will get to that....... eventually.