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Old 5th September 2008, 07:37 PM   #1
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Default Breaking all the rules, a "custom" bridged story

I say "custom" because it's based on PSU boards from audiosector and LM4780 bridged boards from tech-diy. I'm using a single Plitron 300VA 18V+18V transformer (keeping the voltage low so I don't need a fan). According to the overture design guide, this voltage gives me approximately 115W per channel. At this point I've decided on a single rectifier board for both amps ("stereo" design). The PSU is going in a separate enclosure from the amp.

On the amp board, I changed some cap types from the example parts list. I changed the 1000uF cap to an FC and the 10uF to an EB. This gives all electrolytics in my system a lifetime of 3000+ hours @105C. All values were kept the same.

The PSU on the other hand, I've changed the design a bit. For smoothing caps, I've selected a 2,200uF FC cap for each rail. I also purchased a pair of 15,000uF TS-HA caps to add if I feel there isn't enough bass. Also note there are 1000uF, 10uF and 0.1uF caps on power on the amp board.

Now, I just read that it's better to put the "storage" caps (15,000uF) in the amp enclosure than the PSU enclosure. Would that be true in this case?

I understand, they're to give quick power when the bass hits, etc. and that the umbilical will reduce the speed with which that power could get to the amp. Also, would I use them in place of the 1000uF caps, or in addition?
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Old 5th September 2008, 08:46 PM   #2
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My personal preference is to keep the big capacitors far from the amplifier board, after all, bass does not requiere that speed, if it did, then it wouldn't be bass!

The reason, the big pulses that load them will radiate some EFI that you don't want to have near the amp board.
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Old 5th September 2008, 08:59 PM   #3
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Thanks for the input! I was hoping to put them in the PSU box, but unsure. First I'm going to test without them though, then jumper them in before I decide to use them or not. I suppose I could compare, jumpered in the PSU box or in the amp box.
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Old 6th September 2008, 02:47 AM   #4
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I keep my "big" caps 10,000uf on the psu.
if you want to try different caps value,use alligator clips.using alligator clips will make your job easy and fast to compare caps values.(be careful with big caps...They can store a big punch).

SAFETY FIRST!
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Old 6th September 2008, 03:05 AM   #5
lineup is offline lineup  Sweden
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Default Re: Breaking all the rules, a "custom" bridged story

Quote:
Originally posted by Redshift187

Now, I just read that it's better to put the "storage" caps (15,000uF) in the amp enclosure than the PSU enclosure. Would that be true in this case?

I understand, they're to give quick power when the bass hits, etc. and that the umbilical will reduce the speed with which that power could get to the amp. Also, would I use them in place of the 1000uF caps, or in addition?
I once posted about power supply caps, in one topic long ago.
I told people to put one BIG cap (4700/10000 uf) close to rectifier
and put some smaller 1000 uF close to power output transistors.

I got the following reply from The One and Only Nelson Pass:
it is better to put the other way:

Some 1000 uF right close to rectifier,
and at the Amplifier PCB board put some bigger (4700/10000 uF)
where the V+ and V- connections wires attach to the PCB.

So, as i have never forgot what The Master Nelson told me,
I advice:

1. Put some 1000 to 4700 uF right close to Rectifier diodes/bridge, in PSU unit.

2. Then draw you wires over to Amplifier Case/PCB

3. To the Amplifier Board, where you put in MAIN CAPS: 4700 to 15000 uF
somewhere at PCB V+ and V- intakes terminals.

(4. If you wish, especially if Chip is not very close to MAINS CAPS,
you can also put two 1000 uF right close to the CHIP V+ and V- supply PINS.)
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Old 7th September 2008, 12:18 AM   #6
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Well,some good designer like to put "big" caps right after brige rectifier. take a look here for a Bryston amp!.http://www.bryston.ca/BrystonSite05/BrystonDocs.html
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Old 24th September 2008, 04:59 PM   #7
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So at this point I'm almost done populating the PCBs. I bought 2 PSU boards, but only plan on using 1, so I made different PSU configurations that I can swap out to compare. On one, I used only a single 2,200 uF Panasonic FC on each rail.

On the other I used a snubberized setup consisting of the 15,000 uF Panasonic TS with a 0.1 uF Kemet Golden Max ceramic across the pins and a 0.1 uF Vishay MKP plus 1R metal film resistor after that.

I left the 1,000 uF FC caps off the amp boards for now, so I can test without them first, then add them if I want. There are 0.1 uF ceramic and 10 uF electrolytic on the amp board for PSU decoupling (is that the correct term?).
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Old 25th September 2008, 09:36 AM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Redshift187
So at this point I'm almost done populating the PCBs. I bought 2 PSU boards, but only plan on using 1, so I made different PSU configurations that I can swap out to compare. On one, I used only a single 2,200 uF Panasonic FC on each rail.

On the other I used a snubberized setup consisting of the 15,000 uF Panasonic TS with a 0.1 uF Kemet Golden Max ceramic across the pins and a 0.1 uF Vishay MKP plus 1R metal film resistor after that.

I left the 1,000 uF FC caps off the amp boards for now, so I can test without them first, then add them if I want. There are 0.1 uF ceramic and 10 uF electrolytic on the amp board for PSU decoupling (is that the correct term?).
tell us about the results when you have them up and playing.
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Old 30th September 2008, 10:32 PM   #9
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PSU is done and the small cap (2,200 uF) rectifier board has been tested and works. Transformer puts out 19.7V with no load. Rectifier board puts out +/-25.0V with no load. I built and used a lightbulb tester.
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Old 30th September 2008, 10:34 PM   #10
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Here is the power star ground. The green/yellow wire heading off on the right goes to the earth pin on the power entry module. The green wire on the left goes to the power exit module. The silver coloured wires go to the ground points on the rectifier board. You can see the terminal block for the transformer secondaries in the bottom left corner.
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