Aleph P 1.7 pwr. supply choke clc - diyAudio
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Old 2nd November 2005, 04:03 AM   #1
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Lightbulb Aleph P 1.7 pwr. supply choke clc

Hi, I am in the process of getting together all details and mods in order to build an Aleph P 1.7.

Here is my latest IDEA: Replace R73 3.3ohms with an inductor to form a clc filter.

I am going to use two seperate chassis for the power supply and digital/data with just the analog and minimal shielded in the other(low voltage power switch, volume relays).
I will have plenty of room in the power supply only case to place the 4 inductors and I shouldn't have to worry about any interactions with magnetic fields on the audio boards.
I am not sure of what values I might want, but this is what I had in mind:
Goertz Copper Foil Inductor AIR CORE
DCR 0.661 ohm
35mm tall x 85mm diameter

Is this going to do anything to that diode noise that everyone is building snubbers for, maybe I should just go with a higher mh Iron core?
I believe that this mod will be an improvement based on what I have read so far, mostly on power amps, but would appreciate any comments or experiences. I know that this preamp is regulated by Q23 so would this possibly RUIN the sound as the reduced impedence at high frequencies??? Probably would be restored by the following caps. I am really not 100% sure.

What should the values be for the clc or does the BIGGER IS BETTER concept apply?
Should the DCR of the choke equal or come close to the R73 value of 3.3 ohms in order to keep the power supply voltages the same?
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Old 7th November 2005, 03:51 AM   #2
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Just downloaded PSU designer 2 from Duncans Amp Pages. I
am just trying to see the effects of a clc after the bridge rectifier versus a plain c filter. I am not sure how accurate this program is or how close my numbers for the load of 100 ohms, but it would appear that there is less ripple for the 2000mf. capacitor only and an increase in ripple for the 1000mf. 6mh. 1000mf.

How can this be???
2.9 v ripple for the CLC
2.7 v ripple with C only and .5v higher mean
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Old 7th November 2005, 04:52 AM   #3
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Oh I see now, I guess that the values of capacitance are to low to operate correctly.
With a readjusted load resistance of 525 ohms (equaling the 12.5 watt power spec from the aleph p manual for one half of the circuit) and:
2040 mfd. first C
2mh(0.2ohm) and 6mh(.415ohm) L
2720 mfd. second C

Note: using 680 mfd. 100v panasonic fc for this circuit and the capacitance has been increased by about 2 in all areas after the first turn on/off timer caps for the mute control

I now get a reduction in ripple without a significant one in voltage but only with the 6mh. inductor:

just the caps = 239.38mv ripple 78v mean
2mh = 344.92mv ripple 77.8v mean
6mh = 53.4mv ripple 77.97v mean

I guess the 2mh just doesn't match with the load, capacitance, and/or voltage. Does this all sound right?
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Old 7th November 2005, 05:05 AM   #4
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3.3 ohms instead of the 6mh do the same to the ripple however with a 77.52v mean.
The resistor does the same at all frequiencies while the inductor will decrease the high frequiencies even more!!! That is my interest with them
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Old 7th November 2005, 11:41 AM   #5
MRupp is offline MRupp  Germany
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Given the pretty low current draw you could use much higher values for the chokes, e.g. 22 - 27mH or even more. These don't need to be air-coils so you could use inductors for loudspeaker crossover networks as an option.
Martin Rupp
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Old 9th November 2005, 01:17 AM   #6
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So the core doesn't effect the anything if operated at very low power?

Wow! Check out these results with a 15 mh steel core from Zalytron and only $21.73:
77.95v mean
113 uv ripple

I think thats good enough for me, I'm sold however I am rethinking about disturbing the R73 resistor, maybe the even impedence their is just what it's designer intended! I don't want to mess anything up so I will just put the 15mh choke after the first set of bridge rectifier caps.
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