[samplesj]

I created a new thread because the cheap replacement power supply thread is more focused to drop-in replacements, but if this needs to be merged with that its fine with me.

I've got a few SB2/3s around the house, but only 1 replacement supply (elpac).  I'd really like to upgrade the den sb3, but I wondered if it might not be better to upgrade the good system and just move the elpac in there.

Now, I'm a total newbie when it comes to power supply design.  I couldn't even start to design one myself.  Since Mike posted about his Felicia/SB power supply combo in this thread I asked him if I could "borrow" his design.

To be honest I don't have a clue how to figure out what rating I need for the diodes.  It looks like there are a few special cases that make it more difficult that just 8vdc transformer so 8vdc or 16vdc diodes.  Could someone double check that I've gotten the right values?

I'm going to go ahead and post the part numbers in case it helps someone else get a simple power supply going.

Digikey part numbers and pricing follows
1   LT1086CT-5-ND   3.75   (1.5amps) regulator
OR
1   LT1085CT-5-ND   6.50   (3amps) regulator

Mike used the 1086, but is it ok to use the 1085?  The SB2/3 is officially rated at 1amp, but the stock switchers are 2amp.  My elpac is only 1.5amp, but for just a few dollars difference it would be nice to have a safety margin if it doesn't hurt anything.  The transformer is rated at over 3amps so it should be able to feed the regulator.

1   MT3117-ND   13.52   (PL30-16-130B) transformer
4   P10208-ND    1.26   (EEU-FC0J472) 4,700u Panasonic FC caps
1   P10215-ND    1.99   (EEU-FC0J103) 10,000u Panasonic FC caps
4   HFA08TB60-ND  1.58   (HFA08TB60) 8amp 600V hexfred
1       294-1027-ND     4.90    heatsink (way way big, but why not)

I don't have a clue if this is the right values for the diodes.  From what I can make sense of it seems to be plenty big, but I just don't understand all those special cases (like flyback transformers).

Mike used a couple of Dayton (from PE) caps as bypasses and an Auricap.  In order to keep this simple I'll either use the Jantzens from PE or Sonicaps from Danny.  Below are the part numbers and pricing for PE

2   027-932      4.01 10u Jantzen cap
1   027-900      0.70 0.10u Jantzen cap


Other parts:
blank circuit board [Radio Shack or online]
mounting hardware (screws, washers, nuts, standoffs, etc.)
internal wiring
IEC or cut power cord (captive)
fuse holders
fuses (is 1amp fast too big?)
box

So it looks like for around $50 (giving a little more leeway since I forgot the heatsink) you can build a decent power supply.  Did I miss anything?  Are there ways we can make this better?

[Wayne1]

You will also need a heatsink for the regulator, a circuit board to mount everything on, stand-offs, screws, nuts and internal wiring. Perfboard can be found at digi-key.

Another alternative would be to get this kit from Welborne Labs

http://www.welbornelabs.com/psreg.htm



I do know that a Denver area audiophile is using this and is fairly happy with it.

[TomS]

Can you say how much current the whole thing really draws and/or needs for margin?

[samplesj]

You will also need a heatsink for the regulator, a circuit board to mount everything on, stand-offs, screws, nuts and internal wiring. Perfboard can be found at digi-key.

Ooops, good catch.  I kind of overlooked the stuff I've got in the parts box .

I'll go back and edit it to add that to the misc parts.

Another alternative would be to get this kit from Welborne Labs

I saw the welborne labs kit, but it doesn't have a transformer and it maxes at 1.5amps.  Although it is a proven design which is a really nice benefit .

Thanks

[mgalusha]

Can you say how much current the whole thing really draws and/or needs for margin?

Tom, your question prompted me to do some real measurements. The results can be found here: http://www.audiocircle.com/index.php?topic=24771.msg219713#219713

Mike

[samplesj]

I didn't give up on this, but I had to clear off a few other projects first.  I had a couple of PM inquires so I thought I'd bring this up for one last sanity check before getting started.

Ok, it looks like the 1.5amp regulator chip is just fine based on Mike testing.  Which is just as well since the 3amp chip is out of stock at Digikey.

While I'm posting let me ask another pair of layout/circuit design question.

The 4,700u and 10u bypass smoothing caps are all hooked up parallel on the hot line to ground right?  Is there a preferred ordering?

Similarly with the 10,000u and 10u/.1u bypasses caps to clean up the IC output are parallel on the hot to ground right?  Is there a preferred ordering here?

[randytsuch]

I threw together a PS using a 7805 in a TO220 package.  Puts out 1.5 amps max, I believe.

I mounted it on a pretty big heat sink, and it only gets warm.  Have been running it for a few weeks now, with no problems.

I also have, and use wireless, so it is the max power version.

Randy

[samplesj]

Ok, work has been crazy but I was finally able to get this thing built.  I tested out the circuit Saturday and got it into an MDF box Sunday.  A metal box would be nice, but I've got plenty of scrap MDF in the basement  and free is better than big $ for a nice case.

I've got Sonicaps in several speakers here and they seem to be good caps so I decided to splurge and used three (2 10u, 1 .1u) in this project.

Right now its just sitting on top of my Felicia.  I finally got my Lack tables on Friday so next weekend I should have a new rack so this isn't so close to everything else, but I had to put it somewhere now.

Now before I start talking about the sound let me point out a few things.  I've been running the stock power supply for a while because when I rewired the den system I swiped the elpac since I though the other supply would be done soon.  Work has also been really rushed lately with a couple of very tight deadlines.  Everything that could go wrong has gone wrong lately so I was really due for a good listening session.  I'm pointing all that out because maybe that is why it hit the spot so well.  Either way, it sounded incredible last night.  I've got it going again today and it still sounds great even though I can't just stop and critically listen while working.

To be honest I'm too burned out from other projects lately to mess with the den wiring again and try to do a head-to-head with the elpac, but right now I think its much better.  Overall it seems to be so much blacker/cleaner/quieter.  It also seems to start and stop on a dime.  I think because of its so quiet, the highs have a wonderful sparkle and are very clear without being bright.

So I guess all I am left with is a totally unscientific analysis, but in my opinion this was clearly worth the $ and was a very good improvement.  I'm really happy with it for sure.

Just as a warning Digikey apparently changes their part numbers occasionally because the caps I listed with their part numbers aren't the same now so I guess you can't use my part numbers after all.

[MarkM]

I just fired up my PS based on the Linear Technology 1085-5 voltage regulator.   I had some 4700uf 25v Nichicon Muse caps in the parts bin.  I bypassed them with a couple of Theta caps.  Made a FRED bridge and used the Tamura 8vac 3a trans.

Any one considering building one should make sure to use a large heatsink for the regulator.  That puppy gets quite warm.  I used a $4.95 metal case from Radio Shack.  

I can honestly say, I was not prepared to hear such a difference between the stock supply and the new supply.  Hard to believe a 5vdc supply can impact the sound to the degree that it does.

What I noticed most was the top end was cleaned up and the bass was a tad more in control.    I use the digital out on the SB3 to a diy highly modded Lite Dac 60.   The SB now competes with my transport and have a feeling the transport will be a dust collector.

I took the plunge and have ordered a couple of 4 pole Jensen caps.  No onto modding the digital out.

I would like to thank Mike for sharing his building tips.  This supply rocks.