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In Reply to: RE: II. Power Supply posted by Paul Joppa on December 07, 2014 at 09:23:05
I found an ASC 50uf 515vdc PIO cap and Angela instruments.
Is 50uf close enough for C1?
Does ASC mean it's a Start cap?
I also found a Sangamo PIO cap that is rated 47uf and 600v, but it is listed as a start cap.
Any advice?
Jamie
Big speakers and little amps blew my mind!
Follow Ups:
ASC is the manufacturer and they do appear to be motor "run" caps at Angelas, at least if they are the same as these: http://www.ascapacitor.com/traditional_film.php50uF should be fine for C1.
I would pass on the Sangamo unless you can be certain you have a model that is suitable.
Edits: 12/07/14
Sangamo 772501
50uf, 720vac
Big speakers and little amps blew my mind!
I should clarify by being suitable, it is known as a "motor run" capacitor as opposed to a "start" Capacitor.
I have a bunch of 45 / 7 400 vac round motor run caps from this store. My understanding is that the DC rating is at least 1.4 times the 400 VAC rating. The store doesn't have them now but there are other caps with similar ratings.
I have had great success using Goop to attach these to steel / aluminium or polycarbonate. The bond is strong enough to hold them but not quite so strong that you can't remove them.
Maybe I will build design this since I have never done a 2A3 amp before.
ray
Hey Ray,
I knew there was a conversion. I learned a lot of this years ago, and then backed off DIY.
Thanks for the link.
Here is a film in oil cap, Obbligato, from DIY hi fi supply. 47uf and 630v. That may give me wiggle room for a 5u4g?
Jamie
Big speakers and little amps blew my mind!
The more the merrier.
Do you think those are fairly recent stock?
I will bookmark this site, although I didn't notice any run caps with a high enough voltage rating.
The link to a PDF on the Digikey site states:
RELIABILITY AND LIFETIME
AC capacitors are rated for a full service life of 60,000 h with an
estimated 94% survival rate when operated at full rated voltage,
60 Hz and rated ambient temperature.
SHELF LIFE
AC capacitors are expected to perform for their full service life
objective after being exposed to a maximum shelf life of 10+
years when stored in a controlled environment.
ray
Thanks Garg0yle,
I had just googled ASC. I'll do better next time.
Do you think 515v would allow going up to a 5U4G?
Another poster mentioned C2 as important. Is that the 100uf 250v cap?
Do you think the 100uf 350v Ultrapath cap is worth a nice cap?
I like the layout of Paul's schematic. It's the first one I ever seen done like that.
Jamie
Big speakers and little amps blew my mind!
In the revised circuit (I'll post it after a few more comments, with a new version number) I've suggested using four 100uF/350v caps, with C1 being two of them in series. Electrolytics really are happier with no more than 80% of their rated voltage on them.
Something similar is the case for film caps. I recommend digging up the manufacturer's literature and reading it; CDE is a really good starting point.
Thanks Paul.
Big speakers and little amps blew my mind!
I think, someone correct me on this if I am mistaken, that those two 100uF capacitors are actually seen as one 50uF capacitor with double the voltage rating of the lowest rated capacitor, in this case the lower rated cap is 250v, effectively making it a 500V rated cap to be a little higher then the 450V B+
Someone else will have to comment on whether these should be oil capacitors or not.
I myself am running out of room!
GargOyle,
No need for correction
http://farside.ph.utexas.edu/teaching/302l/lectures/node46.html
As I've mentioned before, the big oil caps are very good for the money. If prototyping, use em...unless you just don't have the space..
I personally have learned to totally dislike the sound of electrolytics in the PS (like a wet blanket draped over the speakers) ...with that said, much of this opinion has resulted from dealing with old commercial stuff that used cheap caps to start. I'm sure that there are some nice sounding electrolytics out there for the C1 position but they are almost certainly pricey compared to the big oil caps...
Stuben
OK Stuben, that sounds like a reasonable enough experience for me to maybe pursue the film cap route.
(Just to clarify, those little chassis mount Mr. Steady linked earlier were Electrolytic.)
My chassis is 12"x9"x2" so it will be a little tight.
Cheers.
"I myself am running out of room!"
Don't laugh, and I'll probably get flamed.
I've been collecting cigar boxes for a while as possible enclosures. I think I will do two for each monoblock. A power supply box, and the main box, connected by an umbilical cord. I think I will hard wire the umbilical.
Just playing,
Jamie
Big speakers and little amps blew my mind!
Parts Connection does have a nice selection.
I think cigar boxes would look very nice, although I'm not crazy about the all wooden box thing, it is something I have contemplated many times.
Ideally they would have a metal lining with the wood box around it, which is a little tougher in your case as you already have the finished boxes.
It's doable, just more a little more work, but hey that's part of the fun.
You might be able to get some of those Hammond chassis to fit from Parts Connection, as long as it works for the layout, IMO it wouldn't matter if the wooden box was a little bigger.
Yes, I thought about lining the boxes. I think diyhfsply has copper shielding. BH doesn't line their wood boxes, but I think they shield the signal wire instead.
After reading Paul's explanations, I decided to build it stock with the 5v4s, no modifications.
I think the Hammond OPTs might work well for me, because I would only use this amp in a very limited bandwidth, like 300hz to 1,800hz.
I want to give this a crack, but I'll go slow.
Jamie
Big speakers and little amps blew my mind!
"BH doesn't line their wood boxes, but I think they shield the signal wire instead."
Those amps do have a metal top plate to hold the parts together, maybe you could fit something like that to the underside of your cigar boxes, then use the shielding tape if necessary.
That way you won't have a problem if the cigar box splits it's lid etc.
Anyhow I'm just making suggestions, I'm sure you know what you are doing.
"Anyhow I'm just making suggestions, I'm sure you know what you are doing."
Not so much.
One step up from a bread board is what I'm looking for. I figure using two boxes (PS-main amp) will split the weight load. Maybe even mount the OPT inside the box.
Big speakers and little amps blew my mind!
47uf 600v Sonicaps were at parts connexion for $15.
Big speakers and little amps blew my mind!
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