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Old 20th July 2013, 08:14 AM   #51
vgeorge is offline vgeorge  Greece
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Quote:
Originally Posted by PMI View Post
I have a few from my original order that are not already spoken for. If there is enough interest, I intend to order another batch.

Basic testing is done, the boards work, most of my remaining testing is to make sure that the selected resistor values are correct, where to set the dropout voltage, and measuring a few parameters so other people can compare results. I plan to finish testing this weekend.

Two sets of holes on the original boards have to be drilled out to fit. I plan to do this for any I send out.
We are waiting to finish your testing then!
No problem for me regarding the holes.
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Old 20th July 2013, 04:56 PM   #52
PMI is offline PMI  United States
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Default Test Results, Capacitance Multiplier as Ripple Filter

The following three pics show the voltage waveform at the input (top trace) and output (bottom trace) of the pass transistor on the power supply, at about 270 mA, 600 mA, and 1.25A steady current draw.

270 mA is representative of the standing (quiescent) current at the typical settings for LC's VSSA modules, two channels, and also the most common variants, like Shaan's PeeCeeBee version, and my through-hole VSSA boards. This is significant b/c the first goal of adapting MrEvil's circuit was to provide a clean linear power supply as an alternative to using the recommended SMPS (which of course has zero ripple by definition).

Test Conditions:

AC line input adjusted through a Variac for +/-35V DC nominal (34.5 actual), at the cap multiplier output.

Main filter caps, 10,000uF, 63V
Dropout voltage adjusted to ~1V using the trim pots on the power supply
Output caps, 4,700uF, 63V
Incandescet lamps were used as load, 120V/60W, 120V/125W, 120V/250W
Fluke 77 multimeter, Tektronix 2221A digital storage scope

Besides essentially zero ripple, I saw no signs of switching noise from the rectifier diodes at the output of the power supply, which was very encouraging for VSSA and its variants (very wide frequency range).
Attached Images
File Type: jpg PSU4_270ma_Idle.jpg (221.3 KB, 604 views)
File Type: jpg PSU4_600ma.jpg (220.9 KB, 577 views)
File Type: jpg PSU4_1250ma.jpg (213.0 KB, 566 views)
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Old 20th July 2013, 05:10 PM   #53
PMI is offline PMI  United States
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Default Test Results, Startup and Shutdown

One of my goals was a slow and controlled start, compared to rectifier/filter alone, and compared to other alternatives. The pics below show the rise time before the pass transistor and cap multiplier circuit, after the pass transistor (the output of the power supply), and the third pic shows the shutdown.

The startup shows a small notch at low voltage, but is otherwise smooth and gradual. There is no audible startup noise from the speakers. There is also no shutdown noise, unless the source is still playing.

These tests were using the amp as a load, so they represent results at ~300mA idle current.

Overall, I would say so far everything seems to work as described by MrEvil at the beginning of this thread.
Attached Images
File Type: jpg PSU4_Startup1.jpg (270.3 KB, 555 views)
File Type: jpg PSU4_Startup2.jpg (271.4 KB, 533 views)
File Type: jpg PSU4_Shutdown1.jpg (272.2 KB, 96 views)

Last edited by PMI; 20th July 2013 at 05:12 PM.
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Old 20th July 2013, 08:41 PM   #54
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Hi Pete,

Do to results i thinks goal is reached...

Marc
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Old 21st July 2013, 12:17 AM   #55
PMI is offline PMI  United States
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Quote:
Originally Posted by Idefixes View Post
Hi Pete,

Do to results i thinks goal is reached...

Marc
Hi Marc,

Yes, functionally, I am sure now it does what I had hoped.

I am very happy, less than 10mV at idle, including ripple and noise is much better than anything else I have tried...

I still have to look at the temperature rise at the heatsinks, and make sure I know at what point you have to increase heatsink size. I made sure there are options for heatsink size and vendor, and mounting from under the board, but I have no actual temp measurements yet.

For VSSA or PeeCeeBee version, or my through hole version with +/-35V rail voltage, the component values are correct. For maximum power as specified by LazyCat and by Shaan, at 45V rails, the main reservoir cap should be increased for best performance (15,000-22,000uF), and the pass transistor heatsink to the next size/height, or dual PSUs (which LC recommends anyway).

For amplifiers with a bias current which is significantly higher than VSSA, attaching the rectifier diodes and the pass transistors to a common heatsink will be the best solution. (A simple aluminum or copper plate will probably do fine).

P.
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Old 21st July 2013, 03:36 AM   #56
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Pete,

What would be the best choice of rectifier diodes for this kind of capacitance multiplier? I ordered MUR860, but I am a bit perplexed: ultra fast, fast recovery, soft recovery, Schottky....
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Old 21st July 2013, 12:22 PM   #57
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I'm not Pete, but will add my 2 cents ...

One of the 'softest/quietest' diodes that's readily available is the OnSemi MSR 860 or bigger brother MSR 1560, both TO220 packages.

Another one is the BYV29 - needs a decent heatsink for heavier currents (NOT the BYWs)

Actually, many people have used the MUR860 with excellent results and I found the addition of a basic RC snubber across the secondary windings to be also beneficial.
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Old 21st July 2013, 02:28 PM   #58
Jsixis is offline Jsixis  United States
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I'll take 2 of those boards, I am not in a hurry either so when/if you get enough to order count me in for 2
Thanks
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Old 21st July 2013, 02:51 PM   #59
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Count me for at least 2(may be more)for your next order. Thx
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Old 21st July 2013, 03:43 PM   #60
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Wow. You can count me in for 4 boards as you plan future orders.
Based on looking at Mr Evils original component choices, all parts seem readily available as documented except jfets. When you finish testing, can you share some of your BOM choices with us?
Mr Evil thanks for sharing your circuit, and PMI thanks for your follow up work and board.
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