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Old 2nd January 2012, 04:21 PM   #1501
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Thanks guys.

I guess I will skip the AZ1's for right now. Ebay they are running around $89 ea. I have the 80's so I guess I will stick with them for now.

Mogliaa

I am going to purchase 2) boards with the IXYS fets on them. Going to use two VR tubes to lower the B+ before the CCS plate load. I guess I could burn up the extra B+ with dropping resistors but I guess I like the looks of VR's.
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Old 2nd January 2012, 04:51 PM   #1502
mogliaa is offline mogliaa  United Kingdom
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Is not critical to regulate precisely the CCS input voltage, what is important is to eliminate ripple as much as you can whilst providing a lower supply output resistance. The shunt regulator is great for this. I have an CLCLC stage followed by a Salas regulator and is dead quiet.

What are you planning to use as your HT filtering stage?
Cheers,
Ale
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Old 2nd January 2012, 05:03 PM   #1503
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Hi,

One of my prior posts have attached files of the power supply and line stage chassis.
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Old 2nd January 2012, 05:04 PM   #1504
vgeorge is online now vgeorge  Greece
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One more vote for Salas regulator. Used VR tubes in the past and were more noisy and not so good sounding.
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Old 2nd January 2012, 05:12 PM   #1505
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Ok, i have a C L C with a VR stage followed by a CCS.

rectifier cap/40 mfd choke 30H 40mA cap 1500/450 resistor to ground followed by a VR stage cap and CCS
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Old 2nd January 2012, 05:24 PM   #1506
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by Original Burnedfingers View Post
Hi,

One of my prior posts have attached files of the power supply and line stage chassis.
an LC stage will be quite poor filtering for this preamp. it will provide around 9dB attenuation at 100Hz. See attached quick simulation in LTspice

What is the maximum capacitor recommended for the 80 rectifier?
I would suggest C1 being an 8-10uF oil motor cap and then moving the 40uF after the choke at least.

cheers,
Ale
Attached Images
File Type: png lc filter.PNG (74.6 KB, 507 views)
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Old 2nd January 2012, 05:35 PM   #1507
Salas is offline Salas  Greece
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32u C1 max if I recall correctly.
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Old 2nd January 2012, 06:03 PM   #1508
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Looked it up and 32 is max.



So, scrap the VR tubes?

I think the resistance of the choke I have is 595 ohms so I don't know that works in the simulation.

Did you notice that I have a 1500 mfd cap in the power supply?

Last edited by Original Burnedfingers; 2nd January 2012 at 06:05 PM.
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Old 2nd January 2012, 10:53 PM   #1509
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Will this work?
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File Type: jpg #26 line stage #2 001.jpg (146.5 KB, 481 views)
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Old 3rd January 2012, 04:07 AM   #1510
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FWIW, I have been able to measure 120Hz ripple getting through a single depletion FET CCS as you have drawn as the series element in your gas shunt regulator. Somewhere around -110 dB on the output of the preamp (really low, admittedly).

Replacing with a cascode CCS eliminated it completely. Note that when using the mu output of your active load, power supply rejection is lost, so any eensey weensey ripple will be present on your output. Up to you if that little bit matters.
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