DIY power supply for squeeze box

krikor · « **Reply #40 on:** 12 Apr 2007, 01:46 pm »

Quote from: JoshK on 10 Apr 2007, 03:14 pm

At this point, I don't know if it is worthwhile, but if there is min orders or other impedances to ordering the tx's, do any of you guys want to get together for a mini-groupbuy on these transformers. I am willing to pick one up to test out.

Thanks JoshK!

I'm in for one of the transformers ... provided installation is not too difficult. I'm OK with a soldering iron, but there are some tiny components on that SB3 board. Anyone know just how tough this mod might be?

BTW: Regarding the previous discussion about the amount of capacitance in the power supply, I'm messing with an Elpac WM220-1950 and WM220-1 that I picked up on Ebay for $30 for both (they are essentially the same, but the 1950 seems a bit beefier). After opening them, I found that the 1950 comes stock with 20,000 mfd (2x10k) on the 5v section. Seems like quite a bit! I hope to have them up and running as soon as I disable the 12v sections, add a connector and perhaps do a few other tweaks (caps, diodes).

WM220-1950 on the left, WM220-1 on the right (with some of the 12v components removed).

tanchiro58 · « **Reply #41 on:** 12 Apr 2007, 05:27 pm »

Quote from: JoshK on 12 Apr 2007, 01:32 pm

Tan, toroids have a lower magnet field generation (not quite the right terminology) but they are not what I call 'low noise' meaning they pass all the noise that is on the line much more readily than a comparable EI. This is because they are wideband, which really isn't a benefit in power supply noise.

Plitron makes what they call a low noise toriod and in essense it is a narrower band toroid. Toroids also typically have more interwinding capacitance between the primary and secondary, so filtered crap gets back into the supply more readily as well. I have Occam to thank for my brief education in transformers.

JoshK,

Thanks for the explanation about the application between toroids and EI transformers in the PS.

If I want to add a filter choke at the IEC to avoid RFI and EFI from AC get into the transformer of PS what values would I choose (H or mH, mA and DCR)? I also connected two Auricap .47uF/630V caps from the fuse (hot) to the cold of IEC. Do you think this would help?

Thanks in advance.

Regards,
Tan

jrebman · « **Reply #42 on:** 12 Apr 2007, 06:44 pm »

Quote from: F-100 on 10 Apr 2007, 06:17 pm

I'm also in the hunt for a bigger chassis to house the SB3 too but still haven't found one that I like yet.

Have a look at these:

http://www.lansing-enclosures.com

In particular the GrayBox series -- I have a 2U, half-rack (8" wide x 8" deep "B" style box for a phono stage I'm building. If you get one of these, order the captive screw option for the top and bottom covers -- much nicer than fussing with tiny little nuts and washers.

Further notes: they aren't cheap, but they are sturdy and very nicely finished. The side panels each have 4 holes designed for bolting multiple boxes together, but to me they look like a nice way to fasten some nicely finished wood end panels. The front and rear panels are recessed -- i.e. they have a bezel surround about 3/32 deep. On the front anyway, I plan to set another nicely finished wood insert into this recess.

Lansing has a zillion options for these things including vented side panels, lots of stock sizes, etc., and as I mentioned, they are finished very well with nice smoothe surfaces all the way around.

-- Jim

Audiovista · « **Reply #43 on:** 12 Apr 2007, 07:01 pm »

From Plitron's website - they are top of the line toroidal transformers manufacturer.

http://www.plitron.com/advantages.asp

One way to fight interwinding capacitance is by inserting a shield between primary and secondary windings.

JoshK · « **Reply #44 on:** 12 Apr 2007, 07:42 pm »

Quote from: Audiovista on 12 Apr 2007, 07:01 pm

One way to fight interwinding capacitance is by inserting a shield between primary and secondary windings.

In fact that is exactly what I did with my UcD amp tx's. I ordered Plitrons with an electrostatic shield. Kevin at DIY Cable also provides his tx's with a shield.

jhm731 · « **Reply #45 on:** 13 Apr 2007, 04:32 am »

My SB3 linear(cost $30.)

68,000uf cap on the 5 volt rail.

Stock SB3 PSU shown next to the cap for scale.

crooner · « **Reply #46 on:** 16 Apr 2007, 05:37 am »

I put my "MKIII" power supply together this weekend. It's based on a 12A medical supply. I used an enclosure from DIYenclosures.com. I have some HEXFREDs and upgraded caps on order so it still needs some "fine tuning". Right now it's sounding good, with superb bass but midrange is a little harsh. Once it's broken-in and with the upgraded parts, this thing is going to rock baby!!

JoshK · « **Reply #47 on:** 16 Apr 2007, 04:32 pm »

crooner,

love your work, very cool.

let us know how you like it when it settles in.

i think i should split the group buy posts off from this thread so the power supply ideas can continue uninhibited. it also might avoid confusion.

so look for a new thread for the sc947-02 group buy. here

crooner · « **Reply #48 on:** 16 Apr 2007, 09:33 pm »

Thanks Josh!!!
I guess it two at least two previous tries to get to this level. The very first PS I built looked like a homebrew low cost unit, which it was. The second one was not too shabby, but this one is the ultimate. Approx 65,000 uF of filter capacitance!

I've just returned from work and checked the unit. It's barely warm to the touch. The blue LED is rather bright, so I will have to increase the series resistance value to dim it down.

Nick77 · « **Reply #49 on:** 16 Apr 2007, 11:52 pm »

http://i59.photobucket.com/albums/g295/mrnick_2006/Picture272.jpg

I stole this off an elpac cord I had laying around, can anyone tell me which wire would be positive? The one with the solid white stripe or lettering for SB3?
Thanks

crooner · « **Reply #50 on:** 17 Apr 2007, 12:13 am »

Usually the white striped is the positive wire. I would check with a multimeter (set for x1 ohms) for continuity just to make sure. Insert one probe inside the barrel (positive) and touch white striped wire with the other. If there's continuity, then it is the correct positive wire going to the SB.

Quote from: Nick77 on 16 Apr 2007, 11:52 pm

http://i59.photobucket.com/albums/g295/mrnick_2006/Picture272.jpg

I stole this off an elpac cord I had laying around, can anyone tell me which wire would be positive? The one with the solid white stripe or lettering for SB3?
Thanks

Russtafarian · « **Reply #51 on:** 17 Apr 2007, 06:26 am »

Here's my DIY SB3 PS:

9vac transformer highjacked from a 3 amp PS, hexfred diode bridge, 4 Panasonic FMs in parallel for 6,000uF capacitance, 11uF ERSE polypropylenes on the input and output of the LT1086 5vdc regulator, Jensen 6,800uf 4 pole cap after the ERSE on the regulator output. The regulator (hidden by the Jensen cap connections) is heat sinked to the aluminum utility box via a ceramic pad.

AC cable is a Venhaus Flavor 2 grounded to the case. DC cable is Canare star quad microphone cable. Of course I'm plugging it into a Felicia BPT. About $120 in parts, half of which is the cost of the Venhaus power cable and the Jensen 4 pole cap. Much quieter and more liquid sounding than the stock PS.

Next up (when I can find the time), SB3 analog output mods.

Russ

crooner · « **Reply #52 on:** 17 Apr 2007, 10:46 am »

Nice supply Russ!
I find the linear supply makes the most difference in the midrange and bass. Not subtle, definitely!

CornellAlum · « **Reply #53 on:** 17 Apr 2007, 01:23 pm »

Russ,

Is there a reason your Jensen 4-pole is "naked?"

Thanks, I will post some pics tonight of my PS.

D~

Russtafarian · « **Reply #54 on:** 17 Apr 2007, 03:53 pm »

Soldering iron burns had the Jensen's outer jacket looking a bit ratty. So I stripped it down for a more sexy appearance.

I would have used an identical Jensen instead of the Panasonic caps, but I blew it up a few months ago after inadvertently wiring it up with the wrong polarity. The four connection points on those caps always baffle me. That was an expensive mistake!

Russ

ctviggen · « **Reply #55 on:** 17 Apr 2007, 04:11 pm »

Very nice! It makes me wish I had time to do this kind of stuff.

Folsom · « **Reply #56 on:** 19 Apr 2007, 05:15 am »

What amperage are you guys running? I can see the 5v...

F-100 · « **Reply #57 on:** 19 Apr 2007, 05:37 am »

My Power-One is rate 5 VDC at 3 AMPS.

crooner · « **Reply #58 on:** 19 Apr 2007, 06:13 am »

My latest supply is based on a 12A Condor medical grade open frame unit. 65,000 uF of filter capacitance.

It has so much energy storage that the little LED stays lit for almost a minute after power down!

tanchiro58 · « **Reply #59 on:** 19 Apr 2007, 07:10 am »

Quote from: Russtafarian on 17 Apr 2007, 03:53 pm

Soldering iron burns had the Jensen's outer jacket looking a bit ratty. So I stripped it down for a more sexy appearance.

I would have used an identical Jensen instead of the Panasonic caps, but I blew it up a few months ago after inadvertently wiring it up with the wrong polarity. The four connection points on those caps always baffle me. That was an expensive mistake!

Russ

Hi Russ,

What values does the Jensen lytic cap have? How do you connect from main PS circuit to which poles of the cap? Which one you do not use? Thanks.

Tan