Required voltage rating for PS smoothing/filtering caps?

[Deke609]

The feet (or legs, to be more precise) are cut from a piece of true 2" x 2" maple. All I did was router a channel in each the width of the base  panel thickness. They should be good for at least 2000 lbs or more! 

[EricS]

I like the look of the wooden legs!  A short while ago, I was looking at something like these on ebay, but not entirely sure if I want to use them or not.  Not sure how much weight they'll support since it seems they are intended for jewelry boxes...  I'm figuring a completed chassis will weigh in somewhere near 40-50lbs.

https://www.ebay.com/itm/4x-Antique-Brass-Jewelry-Gift-Box-Wood-Decorative-Feet-Leg-Corner-Protector-LY/163425802030

https://www.ebay.com/itm/8X-Antique-Brass-Jewelry-Wood-Box-Decorative-Feet-Leg-Corner-Brackets-Protector/333228809550

[Deke609]

Eric - Have you checked out Lee Valley?  http://www.leevalley.com/us/Hardware/page.aspx?cat=3,40993&p=41282


They're local to me (Toronto), but have a U.S. online sales site (linked to above). I've found their hardware to be pretty good.


cheers, Derek

[EricS]

Those are nice looking feet!  They certainly look more sturdy than the ones I found on Ebay.  Thanks for the link, Derek.  Too bad we didn't "meet" sooner, I was just in Toronto about 5 weeks ago for a conference...

[Paul Birkeland]

Looks like one of your goals is to prevent ringing on B+ when power is applied? A resistor or current source load to model the rest of the amp probably (obviously?) isn't going to show what's happening on B+ since the rest of the amp has a "wake up" phase (tubes warming up, etc.) Is it possible to load your PSU model with a piecewise current source that has a ramp up period? I guess the difficulty with that is modeling the ramp up behavior. I suppose you could scope your amp's B+ to get some approximation.

This can be pretty hard to model accurately.  Some time ago I built a pair of all directly heated 300B amps, and they passed signal within a second or two of being on, but this amount of time depended significantly on the specific 300Bs I used.

[Deke609]

I'm going to try to address to the possibility of transformer ringing with snubbing. A clever guy over on DiyAudio put together a little pcb circuit for "no math" snubber calculations called "Quasimodo the bell ringer": https://www.diyaudio.com/forums/power-supplies/243100-simple-math-transformer-snubber-using-quasimodo-test-jig.html Essentially, it puts an adjustable snubber across the secondaries, rings the transformer, and you adjust a pot to determine the most effective damping while scoping the transformer. And then you measure the pot resistance to find your snubber value. I picked up the board and parts, but haven;t put it together yet, so I can't vouch for it. But it seems to be pretty well received. 


Just something fun to learn with.


cheers, Derek

[Raymond P.]

This can be pretty hard to model accurately.  Some time ago I built a pair of all directly heated 300B amps, and they passed signal within a second or two of being on, but this amount of time depended significantly on the specific 300Bs I used.

Yeah, I think PSUD is a good tool for analyzing quiescent states and not good for anything else, such as power up ringing in LCR circuits or transient response. For all that other stuff, you really need full blown circuit simulator (e.g. HSPICE), but even that won't simulate variations in tube "wake-up" times.

[EricS]

Derek - break out the soldering iron and build Mark's Quasimodo board!  It works great and helped me quiet down a 750VA transformer in my modular PSU build for various First Watt amps.  Results on the scope are quite striking as you adjust the pot.

[Deke609]

Cool! Thanks Eric. This should be fun.

[Deke609]

I can't believe it worked! The install of the new LCLC power supply filter config went without a hitch.  I thought for sure that this was going to be the time that something went pop and boom. But it worked! I went with the 4H (65DCR) - 10uF - 6H (150DCR) - 200uF config I previuosly posted about. Voltages checked out and it sounds great. At the very least, it definitely doesn't sound worse. And I'm pretty sure it sounds a bit better.    



cheers, Derek

[EricS]

Congrats on the successful mod, Derek!  Looks like tonight is a good night for projects 

[Deke609]

Thanks Eric. I saw that you've made progress with your project as well. Good stuff! Looking forward to reading about the final implementation.


cheers, Derek