660-ish limiter PSU build

Dmichel123

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I'm putting together a PSU for my limiter build. It is basically a 660, but I hope to build the PSU using all SS components rather than tube. I've got a PSU kit from eBay that I think I can make work for this. Here's a schematic of the kit PCB, with parts substitutions to suit this build.

Any concerns/tips?
 

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Kingston

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It'll work ok, but you would also get by fine with half the capacitance and the very first inductor/choke stage is quite unnecessary.

And you can improve it a bit, details https://groupdiy.com/index.php?topic=71122.0
 

Dmichel123

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I have checked out that thread. I suppose I could cut a trace or two on this eBay kit PCB to match what you've worked out.  Have you built a version of a 660?
 

Kingston

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Dmichel123 said:
I have checked out that thread. I suppose I could cut a trace or two on this eBay kit PCB to match what you've worked out.  Have you built a version of a 660?

Yeah I'm very familiar with 660 variants.

No need to cut traces just yet. It'll work fine as you have drawn it already. Build it first, measure it , and see if it needs improvements.
 

Dmichel123

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What I meant to say was, "Have you built a version of this regulator circuit  for a 660?". No need for a choke before the sidechain output section?
 

Kingston

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Dmichel123 said:
What I meant to say was, "Have you built a version of this regulator circuit  for a 660?". No need for a choke before the sidechain output section?

I meant there is no need for L1 in the schematic. Replacing it with maybe 1k (several watt) resistor reduces ripple more.

Yes I have built and I am currently using  variant of this circuit in several vari mu devices - one of them close to a 660 - in voltage ranges of 100-320VDC. Low parts count, simple but effective, they are great.

No vari mu design I know is fussy with PSU's. They'll run on pretty much anything and having a PSU like that ebay PCB takes you directly to the fancy section when plain passive RC cascade is often enough.
 

Dmichel123

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Kingston said:
I meant there is no need for L1 in the schematic. Replacing it with maybe 1k (several watt) resistor reduces ripple more.

Yes I have built and I am currently using  variant of this circuit in several vari mu devices - one of them close to a 660 - in voltage ranges of 100-320VDC. Low parts count, simple but effective, they are great.

No vari mu design I know is fussy with PSU's. They'll run on pretty much anything and having a PSU like that ebay PCB takes you directly to the fancy section when plain passive RC cascade is often enough.

Reg/Non-reg Varimu comps act differently, right?  And I'll want to use a regulated supply to make my limiter function like a 660?  I guess I can understand filtering not being super important on the sidechain amp, with it being push-pull AND the output isn't audio I'll hear... just control voltage.
 

emrr

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In theory if you're using the 440VDC tap the choke gives higher voltage from the lower resistance and better filtering at that voltage.    If you're not using that DC tap and need the voltage, there's not much use for it.  It depends on the resistance of the choke of course.  You can run the formulas for CLC versus CRC and see how you feel about it.  You could also view the choke as helping make up some voltage drop from a tube rectifier that you aren't fighting with SS.  As has been said sorta, I think PP amps are less fussy about PSU ripple.  You see lots of them as plug in console modules with no power isolation at all, other than viewing the output transformer pri windings as a pair of inductors.  I've got a couple early vari-mu with no regulation at all and low-spec current available from the PT, so B+ swings up and down with compression.  They work fine too....
 

Dmichel123

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Just realized the kit PCB schematic is this and not the one I posted....  :-[
 

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