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Old 12th May 2012, 11:39 PM   #1
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Default Power Supply Capacitors

Hi Everyone,
My name is Bob, and it had been a while since I built any audio equipment (almost 25 years), but I decided it was time to start again. About 3 months ago, I starting modifying and rebuilding a Hafler DH-101 preamp (with a lot of help from John at Musical Concepts) and am very happy with the results. I want to get started on building a new amplifier to go with it, and was looking at the HPA-nxV500 boards from Holton Audio in Australia to build around. I was starting on the power supply, and decided to use 2 older, but very heavy and well made transformers I still had to build a dual mono supply, but all in one chasis. They would put out the proper voltage and more than enough current. I started looking for caps and had a hard time finding 100 volt 10,000 uF caps. I was thinking of using 12 of these (6 for each channel). I found 3 possibilities, and was hoping I could get some opinions from the experts (or recommendations of others with suppliers). The most expensive & with best specs were Epcos B41456 Series @ 30A ripple & 9 mOhm esr and 12,000 hrs. @85. Next was Panasonic T-UP Series @ 7.97A ripple & 33 mOhm esr & 3000 hrs. @ 85. Last was United Chemcon @ 8.4A ripple & 18 mOhm esr & 2000 hrs. @ 85. The Epcos and United Chemcon are screw terminals, which is what I used in the past and am familiar with. I still have lots of old clamps for mounting them. The Panasonic are 4-pin snap-in, which I don't remember from the past. How would I mount these. Could I just use some blank perfboard (still have lots of this) and glue them down, and then just hardwire with solder underneath, or are there boards available just for holding the caps? Thanks in advance for any help or suggestions any one can offer.
Best Wishes to all,
Bob
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Old 13th May 2012, 12:28 AM   #2
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Bob:
Wellcome back to this splendid hobby!
Why don't you give us a single-line diagram and a mechanical layout of your design. Than we will rip into you!
Have fun! E
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Old 13th May 2012, 12:44 AM   #3
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Hi Bob! Long time ago I build some amps from Aussie amplifiers too, they are very good. Not too long ago I found even better ones...The T300 and the M400 from http://www.google.com/url?sa=t&rct=j...Mby38uFYpPqdkQ
I build the T300 and also the M400. I can only say good things about them. now I have the M400 playing in my living room as main amp. all what is said on their web is true. at on or off you will never here a pop noise, super quiet. This M400 was so good that it replaced my Bryston B60!!!
PS:For power supply caps, I use Mundorf audio grade 125c. I will never use 85c for power supply!
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Old 13th May 2012, 01:26 AM   #4
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You will no doubt get different advice from different people regarding bulk smoothing caps. Snap in ones are designed to be held in place by the PCB they are mounted to, that is providing the holes are drilled to the correct size. This, I would imagine, is exploited mainly in automated construction facilities where fitting the cap to the un-soldered PCB will hold the cap firmly in place. Obviously, if the holes are drilled too big they wont be held so well in place, but once soldered everything will be fine.

With regards to cap specs, the ripple rating is basically there to ensure that the caps aren't over stressed. If a cap doesn't have the ripple rating required for the given application then it will heat up and either grossly reduce its life expectancy or it will explode.

In a standard class AB amplifier this shouldn't be too much of a concern as the average current draw off the PSU should be very low and hence the ripple on the lines will also be low. As far as I am aware a higher ripple rating on a cap wont reduce the ripple present on the line when it is loaded, it merely represents the amount of ripple that the cap can cope with. Caps in parallel obviously share the the load.

With regards to ESR I wouldn't call this a particularly necessary component either in a standard amplifier PSU. Low ESR is generally wanted with high speed digital devices and only really makes a difference when the cap is mounted right next to the power pin, this is because if the cap is mounted further away the trace resistance starts to dominate. As smoothing caps are generally located a reasonable distance away from the amplifier circuitry, paying for low ESR caps would seem wasted in this application. Again paralleling the caps lowers the overall ESR.

The two parameters which matter by far the most is the effective capacitance and then how the cap is constructed internally. The internal construction will affect the capacitors life expectancy. High temperature long lifetime caps are very nice to have but they are also very expensive. If your case etc is nominally going to be pretty cool, say 40 degrees etc, then rating up to 125 degrees might be considered overkill. I'd certainly use 85 degree parts though.

Some will try and sell you audio specific caps and rave about them, in my opinion the large smoothing caps in the main PSU are not the place for these. If you do want to use a speciality cap then I would advise using these for the smaller local decoupling caps present on the amplifiers main PCBs.
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Old 13th May 2012, 05:42 AM   #5
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Bob--

I like to turn snap-in caps upside down so I can see the connections in perfboard work. You can use a Dremel-type tool or small drill to enlarge perfboard holes and crimp the posts down if you would rather use them conventionally. Snap-ins are really designed for PCB work.
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Old 13th May 2012, 06:11 AM   #6
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Try farnell or mouser for the caps. They are fast and reliable. Farnell has free delivery for orders over $20, mouser free for over $50. I looked at the sites and there are plenty of 10,000 uf available.
I prefer vishay caps over all else, more pricey though but quality is good.
Try bypassing with a few smaller caps if your budget extends that far eg 10,000uf bypassed with a 1000uf or 100uf then a small 1uf film cap.
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Old 13th May 2012, 09:04 PM   #7
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When I was reading datasheets, I found united chemicon had a worse ripple spec quoted at end of life than panasonic for the similar cap. Read your fine print carefully- I call that specmanship. Also the chemicon's and epcos I have bought have been made in a country where QA people have lied on the QA paperwork for baby food. I've been mostly buying long life nichicon, panasonic rubicon, made in oriental countries more fun to live in than the chemicons and epcos, IMHO.
10000 uf is a bit extreme for home use. I have a 650 W/ch PA amp I am rebuilding that had 2 10000 uf caps per channel. I replaced them with 6 each 3300 uf caps. 10000 uf snap in 2 terminal caps were $22, 3300 snap in caps were $3.50. I made a subassembly for the 6 caps per channel out of 2 pieces of lexan, bolted together with 6-32 screws (2 " long) and bolt running through to the PCB the original caps were mounted. I have the snap-in terminals running through drilled holes in the lexan to buss wire, 18 ga. I then glued the edges of the caps to the lexan with silicon seal. I put fender washers on my 6-32 screws so this subassembly doesn't strain the PCB unduly if the amp is slammed around. The amp has a big fan.
The 1.3k amp originally had 4 terminal snap in caps, 2 soldered to the traces, and 2 soldered to dummy pads to hold them down against the rough handling PA amps get. I couldn't even find 4 terminal snap in caps, except at the amp builder.
Farnell US (newark) and mouser US do charge freight. If you receive packages at a house, specify USPS shipment, saves you the $ home delivery fee for UPS or FedEx.
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Last edited by indianajo; 13th May 2012 at 09:12 PM.
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Old 14th May 2012, 03:20 AM   #8
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Hi Everone.
Thanks for all the replies. I got tied up with Mother's Day and wasn't able to get back to the computer during the day. Everyone's finally gone, and we're all cleaned up, so I finally had a chance to see all the posts. By the way, Happy Mother's Day to all the DIY Audio Moms out there. I put together a little diagram of my thoughts for my layout within the case (still have to build the case), but I couldn't quite figure out how to attach a jpg to the message, so I'll figure that out tomorrow, and post it once I do. I just checked out the website of those other amp boards mentioned, but other than a few specs, there's not much info on the site, so I'll probably give them a call to find out more. I have 1 customer and a fellow photographer that have used the Holton boards to build amps, and they both rave about them, but I haven't heard either system. I think I'll call my photographer friend, and ask if I can come listen to and see his amp. I got involved in a little side project yesterday. A friend built a capacitor bank of 160,000 UF with 65 Volt caps for his amp following an article he read in a magazine (I had no idea he was doing this). I guess they didn't mention anything about a soft start in the article, and he called me wanting to know why his house circuit breaker tripped when he hooked it up to his amp every time he turned it on. Since I knew I'd be needing a soft start circuit also, I built 2 of them on the perfboard I have. Basically, it's just a timer IC with a capacitor and trimmer pot to adjust the time, and a big aluminum cased resistor heatsinked to the chasis. When the amp turns on, the power goes through the resister until a relay, controlled by the timer kicks it out. I wasn't sure how long to leave power through the resistor, so I adjusted it for around 6 seconds. I tested it with a meter to be sure the relay switchover was taking place, and it was. So I mounted one in his amp and connected it to the AC wire going to the hot side of the transformer primary, mounted the resistor on his case, and it worked. No tripped circuits. W turned it on & off a dozen times, and it seems to work OK. I'm sure there are more sophisticated cuircuits using thermistors, but I just used what I had laying around, and since it seems to work, I'll use the one I made for myself in my amp. I'll probably build the case before I get the caps, as that will give me some more time to research and decide which ones. I looked at the Vishay, and they are expensive. At this point, the Panasonic T-UP seem OK unless I can find some screw tops that I like. They'd be easier to work with, since I already have lots af clamp mounts for them. I saw some Evox Rifa at Newark and wonder if anyone has any experience with them? I have a lot of .1 uF polypropylene film caps , and was thinking of using them as bypasses for each cap in the supply (one for each cap). I've had them a while (8-9 years), but they've never been used and should still be fine.I probably have about 70 or 80 of them. I was also thinking of using a bleeder resister on each cap for safety after turning off the amp. Would that have any negative effect on the sound? Please let me know what you think. Again, thanks for all the posts. Very Much Appreciated.

Best Wishes,
Bob

Last edited by u1022186; 14th May 2012 at 03:25 AM.
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Old 14th May 2012, 06:53 AM   #9
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Default caps

If you are trying to keep impedance low, max on ripple current and low on esr then resistors are no good.

I have no idea about your set up as i have not seen it but a high quality power supply needs to be on a seperate circuit board or even better build an external enclosure which lowers heat and interferance. This is really the most important point.

The best caps at the moment are the panasonic fm's and fc's also popular are nichicon pw's. I would have no hesitation in recommending panasonic or nichicon as they are a good and reliable company. I have also used vishay caps with excellent results, pricey but the extra bucks pay off with increased sound quality. So it depends on what you want and your budget. Stay away from chemcon epos and evox rifa.

I find that replacing power supply caps give the highest increase in performance when compared to any other area. This is because larger caps cost more so the power supply is always compromised due to manufacturers's budgeting constraints.
Also manufacturers tend to user smaller than optimal caps again to save money. Perhaps you could take a few readings and see what size caps are optimal for your setup.

I used to have a zero dac which was filled with rubucon za caps which are good, but the power supply has sxg's which no one has heard of before. Small signal path caps cost pennies large psu caps cost pounds.

Do not worry about ers figures, this is not the be all and end all. A good cap will have an ers of approx 0.1 ohm, a higher quality cap 0.01 ohm, if you subtract the two you will come up wth a figure the human ear cannot distingush between.
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Old 14th May 2012, 05:41 PM   #10
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Good Afternoon Everyone,
I was trying to add my image to a post, but I can not find the link to create an album to upload the image to. It says in facts to go to the user control panel and click on the link that says albums & photos, but I do not see that link. Can anybody give me a hint where to look.

Thanks & Best Wishes,
Bob
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