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Old 3rd April 2006, 08:11 PM   #1
jayme is offline jayme  United States
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Default PSU design tweaks

Here is the PSU design that I've started to investigate further. I've modeled it in Duncan's PSUD2, and it seems to have decent speed and control.

It is a CLCLC-2xRC (the last RC is really two separate resistor-cap networks for channel separation).

Now...I've seen some additional tweaks in some schematics, such as:

1) a small silver mica cap (~40nF) across the secondary outputs before the rectifier bridge.

2) a diode placed in parallel with the choke, such that it is a short-circuit when current flow is negative

Any recommendations / thoughts / comments on these additions? I can't model them in PSUD2, so I'm not sure what they do in terms of response...

Thanks,
Jayme
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Old 3rd April 2006, 09:08 PM   #2
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what are you using it for? i'm interested in choke filtration as well.
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Old 3rd April 2006, 10:00 PM   #3
jayme is offline jayme  United States
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I'm building an Aikido-style (www.tubecad.com) linestage preamp using 6SN7 / 6SN7.

I'm starting with a simple rectified and filtered PSU design, and the heaters will be driven with AC.

I'm also interested in opinions on whether the supply should be a super-fast slightly underdamped (providing a voltage swing slightly past the target, and then a ramp down to the target) or a nice fast damped supply. (for instance, substituting a 50uF cap for the 100uF cap in the diagram above).
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Old 4th April 2006, 10:32 AM   #4
lndm is offline lndm  Australia
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I'm pretty sure the cap could be one of two things. Either tuning against ringing (which I can't comment more about, I do it with resistors), or RF rejection.

Sorry not sure about the diode but since you've been there with PSUD, you must know how a badly chosen choke in a ps can ring, diodes are often used for protection.

Heres an interesting one, you can put a capacitor in parallel with one of your chokes and tune it to your hum frequency. Much quietness to be had here
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Old 4th April 2006, 02:18 PM   #5
jayme is offline jayme  United States
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Yeah, I've found a few links to tuned chokes. I figure I'll try the PS without the bypass cap, but if I hear any humming I will try to calculate the proper cap value and test it out.

Lately, I've been trying to optimize the performance of the PSU design by increasing the speed (ie ramp of the voltage), but maintaining good damping on the steady-state ripple.

Any thoughts on damping/underdamping and voltage overshoot?
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Old 4th April 2006, 02:36 PM   #6
lndm is offline lndm  Australia
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http://www.siteswithstyle.com/VoltSe...C_ringing.html

I have found this a very good read. There are other very good articles on the site, some similar to this.
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