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Old 10th June 2004, 11:42 PM   #1
Bryan is offline Bryan  United States
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Default PS cap placement/type

Quick question,

Lets assume I have LCLCLC filter in my PS. Due to size constraints, I can only use 2 oil caps and 1 electro (2X ASC 370 volt, and 1X Panasonic TSHA). Would it be best to wire it:

elect-PIO-PIO

or

pio-elect-pio

Thakns,

Bryan
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Old 11th June 2004, 12:58 AM   #2
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Hi,

Bryan,

What are the respective values of your caps?

Have you run a sim like PSUD II on this?
Put in the values of the Ls and Cs to see if you don't get any odd tank resonances with some combinations.

Put differently, in such a well filtered and well regulated high Q supply I'd ditch the electrolytic cap altogether, use the 2 ASC PIO caps for the filtering and than use either another PIO or MKP as the last cap for best sonic results.

Just my .

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Old 11th June 2004, 01:20 AM   #3
Bryan is offline Bryan  United States
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Frank,

The elect is 56uF.

One PIO is 50uF
The other PIO is 60 uF

I intended to have the 50uF and 60uF PIO's in the ps chassis, with a final 60uF PIO in the preamp chassis directly before the VR tubes and ccs fed anode.

The space limitation is in the PS chassis, so I was thinking about using the elect as the first cap, followed by the PIO, which would put the LCLCL on the ps chassis, and then run the HV to the preamp as above. This way the chokes would all be in the PS chassic, where I want them.

Would having an electrolytic so far upstream affect the sound to an audible effect considdering the amount of filtering and regulation ahead of it?

Bryan
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Old 11th June 2004, 01:51 AM   #4
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Hi,

Quote:
with a final 60uF PIO in the preamp chassis directly before the VR tubes and ccs fed anode.
With a 60F cap across the VR tubes they'll go bananas on you...It won't work and I doubt they'll care to strike if it doesn't kill them first shot.

You can put the cap on the B+ rail, followed by a dropping resistor, followed by the VR stack and CCS.
Each VR tube can be individually bypassed by a small MKP cap of no more than 0.100F in total to prevent any tendency towards oscillation.

Quote:
Would having an electrolytic so far upstream affect the sound to an audible effect considdering the amount of filtering and regulation ahead of it?
I don't think so, considering the multiple Ls in the filter.
When in doubt, bypass it with 0.100F MKP of sufficient voltage rating, that should shunt the RF garbage to ground.

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Old 11th June 2004, 02:01 AM   #5
Bryan is offline Bryan  United States
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Thanks Frank,

I was somewhat unclear...

The PS is LCLCL- umbilical to pre chassis- C-dropping resistor-VR-CCS. The stacked VR tubes are individually bypassed with 0.056 ASC MKP.

Come to think of it, would the PS benefit from putting the VR's before the last cap? LCLCL-umbilical-dropping resistor-C-CCS-

Thanks,

Bryan
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Old 11th June 2004, 02:17 AM   #6
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Hi,

Quote:
Come to think of it, would the PS benefit from putting the VR's before the last cap?
I've seen that done before but am still wondering why they did that.
If you look at the VR tubes as Zeners with reasonable regulating capability for a given current range, I fail to see what good they'd do if you add another RC element which will do away with most of their regulation anyway.

In the case of the CCS load, noise isn't a big concern as the CCS' impedance and PSRR is so high that it'll never be seen by the tube anyway.

That said, I think both schemes would work but the CCS would work best when presented with a regulated voltage...
Which is why we thought of putting the VRs there in the first place.

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Old 11th June 2004, 02:24 AM   #7
Bryan is offline Bryan  United States
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Good to know someone is keeping me on track.

I'll keep it as planned, with the exception of using the electrolytic as the first cap. I will bypass it as well.

Thanks Frank!

PS. Math is at the top of the pyramid

Bryan
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