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Old 14th July 2013, 06:18 AM   #31
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Quote:
Originally Posted by PMI View Post
Improved Capacitance Multiplier, first circuit boards:
Pete,

There is one unexpected benefit from your modified version of Mr. Evil's capacitance multiplier circuit - j-fet to ground instead of opposite rail. If one needs a single rail supply for amplifiers like Rod Elliott's DOZ, only positive side of the pcb should be populated with components and you have single rail capacitance multiplier.
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Old 14th July 2013, 05:15 PM   #32
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Originally Posted by ivanlukic View Post
...If one needs a single rail supply for amplifiers like Rod Elliott's DOZ, only positive side of the pcb should be populated with components and you have single rail capacitance multiplier.
Interesting, I had not thought of that, but you are correct, the two circuits are separate now (with the exception of the bridge).

In any case, I know you have been waiting, so here is the progress so far:

Circuit board inspected, and one minor error found in mounting holes for the pass transistor heatsink (not electrical).

One board assembled, dropout voltage set , and powered up with lamps as a load. Seems to be working so far, ripple is vanishingly small, nothing seems to overheat and everything looks stable so far.
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File Type: jpg PSU4_build5.jpg (225.1 KB, 760 views)
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Old 14th July 2013, 05:21 PM   #33
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Looks good. I'm glad you managed to keep the LEDs under the fuses; the importance of adding LEDs to everything cannot be overstated!

There's not a lot of room between the diodes and caps - is it difficult to get a screwdriver in there to attach the heatsinks?
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Old 14th July 2013, 07:00 PM   #34
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Looks good. I'm glad you managed to keep the LEDs under the fuses; the importance of adding LEDs to everything cannot be overstated!

There's not a lot of room between the diodes and caps - is it difficult to get a screwdriver in there to attach the heatsinks?
For me, no ...I like to put things into inaccessible spaces... sort of striving for the apple-inside-the-brandy-bottle look, and the LEDs inspired me....

Also, I had some other constraints on length of the board, b/c I am working on a "compact" chassis. The board is designed allow the diodes to mount from the bottom at 90-degree angle, so if desired the six (!) cheap and little heatsinks can be replaced with one large and cheap heatsink (or an even cheaper plate of aluminum).

When mounted on top, the diodes are assembled to the heatsinks first, then the heatsinks with the diodes are soldered to the board, with the board upside down and resing on the heatsinks. (I did not actually have the intended heatsink on hand today, so these are a substitute.) The 10.000uFd caps are soldered last, because they are the largest/tallest part.

So attaching the hatsinks is not a problem, de-attaching them after everything is soldered is another matter, or course.
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Old 15th July 2013, 07:00 PM   #35
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Pete,

Why are all rectifier diodes and pass transistors isolated from the heatsinks? At least, they look like they have isolation. Is it necessary?
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Old 15th July 2013, 07:40 PM   #36
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Originally Posted by ivanlukic View Post
Pete,

Why are all rectifier diodes and pass transistors isolated from the heatsinks? At least, they look like they have isolation. Is it necessary?
It is not necessary, as long as one remembers that the heatsinks become part of the cirquit and can be shorted with a test lead etc.

The pics are of my first board. I did not want to worry about one more short hazard while testing, so for me, it is a good idea...

I would have normally used screw terminals for testing, instead of Fastons, but I ran out, and did not want to have some of each on one board. Not ALL of the blade connectors (Fastons) need to be populated, in fact I doubt anyone would use all of them at the same time. That was something else useful only for flexibility in testing.
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Old 16th July 2013, 09:39 PM   #37
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Hi Pete,

any progress on your test?

Marc
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Old 16th July 2013, 10:34 PM   #38
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Hi Pete,

any progress on your test?

Marc
I tested with a small load approximately equal to the VSSA quiescent current, and compared to two other power supplies, w. 37V (35V nominal) rails. Jfet current is 5.7 mA, dropout voltage set to about 0.75-0.80V. I also ran the through-hole version of VSSA with the supply, and there was no hum or buzz, and no noise visible on the output with my scope, even w. very long power supply leads and an open chassis.

This is very approximate, using only my o-scope to measure:

#1, Bridge Rectifier and 2x4700uF/rail, 200mV ripple+ some diode sw. noise.
#2, Bridge Rectifier, 3x4700uF/rail, C-L-C-R-C, ~80mV ripple
#3, Improved Capacitance Multiplier, 10,000uF + 4700uF output cap, <10mV ripple

Basically what I am doing here, is comparing the output of a bridge rectifier with cap filter alone, to two methods of secondary filtering.

#1 is no additional filter. #2 is 0.33R+4700uF, #3 is the power supply I am testing. When I get a bit more more into it, I will post more accurate results and some pics.

Next step is to do a moderate load test at about 1A from both rails. I plan to do this using light bulbs as a load. This is not great for accurate measurement, because they take some time to stabilize as they get hot, but I do not have other suitable loads or a load bank.
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Old 16th July 2013, 10:48 PM   #39
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Thanks Pete for news.

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Old 18th July 2013, 07:18 AM   #40
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Pete, very good work!

My friends and I have built some different amps in the last years and we have always found some improvements making use of cap multiplier PSU instead of standard CRC or CLC PSU, especially for sonic nuances and in the width of music stage.

Till now we've manufactured them in Dalington configuration and with breadboards.

The circuits looks really promising and your boards professionally made.

Please go on with your tests and take me into account in case you decide for a small batch of boards or for a GroupBuy.

Thanks and regards
Nicola
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