I found a guy who winds transformers to order. I have not yet ordered the main pair because I want to get one half of the PS up and running with an ancient ILP dual 35V toroid that I have. Then, when I have measured the losses I will know exactly what AC voltage I need. Probably closer to 40V. This way I can tolerate higher rectification losses if I settle on the dual bridge config. Also need to be sure I get sufficient magin below 63V cap rating... aiming for 57V DC, no load, at 250V supply.
Very helpful. Initially I will hardwire with 0.8mm wire. This leaves more floor area for 4x rectifiers. I need max 2A RMS on each supply rail. Each screw-terminal cap (Vishay 101) can handle 8.1A ripple at 85deg (2 per rail).
Thanks. Do you think my last dual rectifier circuit is good to go? Hardwired, with dual '0V' lines joined at the output prior to 0V earth connection.
When you get to making measurements, then you may benefit from getting a PSUD2 simulation going to cross-check the diode and capacitor rms and peak currents, and whether you are able to measure the same output ripple voltage as the sim.
Yep previously I would have been tempted to order a centre tap tranny with three secondary wires. Now... having been educated, I can fully appreciate the value of two independent windings.
I have not yet purchased my transformers. Am working with a 35 year old ILP 625VA with 2x 35V secs. I checked continuity but did not power up yet 🙂
Star grounding is where you connect all grounds (read returns) to a single point. It really is impossible to do without having long leads or traces which is in many cases not good.
Here is a dual mono layout that I made some time ago. Hopefully it will work for you.
Attachments
Thanks a bunch Mark. Are you using a bridge there to block any ground current? I had the same idea - just to use another bridge rather than fiddling about with single diodes. I should buy shares in Fairchild at this rate.
Like AndrewT recommends, use a 25/35 bridge rectifier. The resistor reduces the ground loop current and the diodes pass the very high current in the case of a transformer meltdown.
Hi guys,
I found an illustration of what I wanted to do in an earlier diyaudio post:
http://www.diyaudio.com/forums/solid-state/194826-another-crescendo-me-problem-2.html#post2677991
This is the Elektor Crescendo PS for one channel with dual diodes.
Can anybody comment on the physical implementation? Contrary to previous discussions on this thread, this drawing (wood carving?) shows the power rails being connected (to rectifier and load) from the same location, a point on the bus bar midway between the two filter caps. Would this be 'dirty'?
Have I misunderstood? Thanks again in advance - Pops.
I found an illustration of what I wanted to do in an earlier diyaudio post:
http://www.diyaudio.com/forums/solid-state/194826-another-crescendo-me-problem-2.html#post2677991
This is the Elektor Crescendo PS for one channel with dual diodes.
Can anybody comment on the physical implementation? Contrary to previous discussions on this thread, this drawing (wood carving?) shows the power rails being connected (to rectifier and load) from the same location, a point on the bus bar midway between the two filter caps. Would this be 'dirty'?
Have I misunderstood? Thanks again in advance - Pops.
I cannot recommend that centre of charging plate for a reference voltage.
The PSU is a dual secondary to dual bridge rectifiers that are coupled via the charging plate.
I don't think that is a good way to create a dual polarity supply.
The PSU is a dual secondary to dual bridge rectifiers that are coupled via the charging plate.
I don't think that is a good way to create a dual polarity supply.
Yep agreed. I also don't see why you need less than 5 mOhms resistance between filter caps. I think its generally agreed that some small resistance gives HF filter benefit.
I'll just use solid core copper wire.
I'll just use solid core copper wire.
Thanks Andrew! Great stuff. I'll throw a few more 35A bridges into the Mouser cart.
Pops
My last big batch (50 or 100) of 25A bridge rectifiers is almost finished.
Recently I bought 10 off from a Far East Retailer to test and see whether the product they sell is any good. Tests not started yet.
I find I use 4 to 6 bridge rectifiers in each stereo amplifier. Two for the DNs and two or four for the AC to DC rectification.
Recently I bought 10 off from a Far East Retailer to test and see whether the product they sell is any good. Tests not started yet.
I find I use 4 to 6 bridge rectifiers in each stereo amplifier. Two for the DNs and two or four for the AC to DC rectification.
Thank you Gents for the amount of knowledge shared in this thread, didn't expect that! Now I know a bit more about PSU, but will still keep on asking ;-)
Cheers
Cheers
Hi Mark!
I see that there appears to be no ground connection to each power supply. You just show a chassis connection to each Amp. Is this the GND reference at the PS 0V output? Or how else is the centre rail connected to ground?
Many thanks for the clear diagram. POPS.
each amplifier is isolated from the other amplifier. They don't have a common Main Audio Ground.
Both amplifiers could have some exposed conductive parts. For that eventuallity, they each need the Safety connection to Chassis.
Both amplifiers could have some exposed conductive parts. For that eventuallity, they each need the Safety connection to Chassis.
Yes, I do this to reduce the size of the ground loop. Some even advice grounding the inputs. The problem here is that the thin traces between input and the power connection of the amp may not withstand the high current in the case of a transformer failure.
I connect plus and minus grounds at the amp. See the four leads between PSU and Amp. You don't need to copy this part. Your amp PCB is probably not designed to get best out of such a layout.
I connect plus and minus grounds at the amp. See the four leads between PSU and Amp. You don't need to copy this part. Your amp PCB is probably not designed to get best out of such a layout.
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Should I have a 10A quick blow fuse on the PS output? Does that take care of the problem? I planned to put slow-blow fuses on the secondary outputs from the transformer (in addition to low current slo-blo on the primary side).
What location / type is best?
Cannot say I understand grounding fully so I will build the PS in isolation and come back with questions then before I integrate the first Amp.
remove C3, all of them.
change C2 from a solo capacitor, to a snubber with C+R.
keep C1.
If you want effective EMI filtering of the mains supply interference, then place that at the mains side of the transformer.
C2 is a Wima mp3 x2 10nF 250V. What R should I add?
Will place that filter on the mains side. Will there be any real benefit from placing the filter on both side of the Transformer?
Also if I place that on e mains side should I rather use a 400v cap or 250 will be sufficient. I have an average of 230 in my mains.
Thanks
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