# Is there a reason for caps in a can?



## whywhyzed (Jan 28, 2008)

Are can caps better? I can't find anything on line as to why they use canned cap instead of just p-p wiring them in under a chassis.


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## greco (Jul 15, 2007)

My guess is that the canned caps allow for more space to be available inside the chassis and possibly canned caps are more economical overall.


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## Lincoln (Jun 2, 2008)

I would agree with greco Dave that canned caps take up a lot less space on the chassis. Possibly safer as well. If you have room, I can't see any reason why you couldn't rewire with individual caps. Wait for one of the tech guys to show up and give us the real reasons. 
It can be real tough to find canned caps in the right values and they aren't cheap either even if you do find the right combo.


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## greco (Jul 15, 2007)

Lincoln said:


> .......Possibly safer as well.
> 
> .........If you have room, I can't see any reason why you couldn't rewire with individual caps.
> 
> .........It can be real tough to find canned caps in the right values and they aren't cheap either even if you do find the right combo.


Just curious as to what would make them safer (please understand that I'm not disagreeing with you..I'm just interested in learning) I'm guessing that you are indicating this because they are enclosed in a metal container and (also) have no long leads? 

I can remember a few threads where people building amps couldn't find the right values in canned caps and went to (axial) "regular" caps. 

Sorry....I wasn't clear in my post about the canned caps being more economical...I meant from a manufacturing perspective.


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## Lincoln (Jun 2, 2008)

greco said:


> Just curious as to what would make them safer (please understand that I'm not disagreeing with you..I'm just interested in learning) I'm guessing that you are indicating this because they are enclosed in a metal container and (also) have no long leads?


Yes, that's what I was thinking. Less wiring, fewer connections, and with the axial capacitors laid out on a board you would have more opportunity to touch the wrong spot at the wrong time and get a high voltage shock. Cans are much neater, and the wiring to them is compact and focused in one small area rather than laid out over 4 square inches.

I'm sure cans were the cheapest way to go during the "tube" era. Everybody used them, even Pepco.


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## nonreverb (Sep 19, 2006)

Once upon a time when several companies were makin' extruded aluminum can multi-caps, they were an inexpensive alternative where space, extra parts and labour were concerned. Fast forward to today and CE Distribution who bought out Mallory's tooling and machines. They are one if not the last original manufacturer of extruded caps uasing the standard base configuration. They now have that market cornered and ironically, have made them a very expensive alternative to regular axials.


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## cboutilier (Jan 12, 2016)

Lincoln said:


> Yes, that's what I was thinking. Less wiring, fewer connections, and with the axial capacitors laid out on a board you would have more opportunity to touch the wrong spot at the wrong time and get a high voltage shock. Cans are much neater, and the wiring to them is compact and focused in one small area rather than laid out or 4 square inches.
> 
> I'm sure cans were the cheapest way to go during the "tube" era. Everybody used them, even Pepco.


I think they last longer too. I have a 73 Pepco with original cans that still works flawlessly. I'm waiting on the mail man to deliver new caps for it.


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## knight_yyz (Mar 14, 2015)

IIRC, the caps in the can are actually multiple caps inside sharing a common negative which is the metal part of the can


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## Jamdog (Mar 9, 2016)

In vintage radios, can used to include multiple caps. They generally were bigger than other caps in the chassis. 
When recapping such radio, it's OK to use regular caps. Just make sure to have the right properties. 

Enjoy.


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## cboutilier (Jan 12, 2016)

Jamdog said:


> In vintage radios, can used to include multiple caps. They generally were bigger than other caps in the chassis.
> When recapping such radio, it's OK to use regular caps. Just make sure to have the right properties.
> 
> Enjoy.


Both of my amps are getting regular caps to replace the cans. It was either 4 dollars a piece for regular caps, or 40 bucks each for the 4 40/40 cans I needed.


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## nonreverb (Sep 19, 2006)

The only place I see a need for the CE multi cans is Leslie amps. It the only amp I've ever seen with Cinch can cap sockets. You can actually plug in your replacement can cap like you would do with a tube.....brilliant. Otherwise, probably best to replace the multi can with regular caps in most if not all other cases. IMHO


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## Lincoln (Jun 2, 2008)

nonreverb said:


> probably best to replace the multi can with regular caps in most if not all other cases. IMHO


And there is the official ruling we were all waiting to see. 

BTW,
What's your opinion on increasing the value of the first capacitor in the chain? For example, if the schematic calls for 20/20/20, I've seen a lot of techs replace that with 40/20/20 or 30/20/20. Good idea?


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## cboutilier (Jan 12, 2016)

Lincoln said:


> And there is the official ruling we were all waiting to see.
> 
> BTW,
> What's your opinion on increasing the value of the first capacitor in the chain? For example, if the schematic calls for 20/20/20, I've seen a lot of techs replace that with 40/20/20 or 30/20/20. Good idea?


From my research it's not a big issue at all. Lowering the first cap value can be problematic though, as some rectifier tubes require a minimum value of that cap. I think it's around 20 for a 5Y3GT.


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## nonreverb (Sep 19, 2006)

cboutilier said:


> From my research it's not a big issue at all. Lowering the first cap value can be problematic though, as some rectifier tubes require a minimum value of that cap. I think it's around 20 for a 5Y3GT.


Actually, it's quite the opposite. There is a max capacitance rating for tube rectifiers. Tube rectifiers don't like to see a prolonged short condition which a large capacitance can create due to the longer time it takes to charge them. You risk killing a tube rectifier in short order with a large capacitance following it.


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## Lincoln (Jun 2, 2008)

nonreverb said:


> Actually, it's quite the opposite. There is a max capacitance rating for tube rectifiers. Tube rectifiers don't like to see a prolonged short condition which a large capacitance can create due to the longer time it takes to charge them. You risk killing a tube rectifier in short order with a large capacitance following it.


So then you would only want to up the first capacitor on amps running or being converted to solid state rectification? What's the advantage of the larger first cap? Smoother ripples? Softer hit?


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## cboutilier (Jan 12, 2016)

nonreverb said:


> Actually, it's quite the opposite. There is a max capacitance rating for tube rectifiers. Tube rectifiers don't like to see a prolonged short condition which a large capacitance can create due to the longer time it takes to charge them. You risk killing a tube rectifier in short order with a large capacitance following it.


I remember reading they had a minimum as well.


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## nonreverb (Sep 19, 2006)

If the minimum is too small, the capacitance reservoir won't be able to smooth out the ripple resulting in a significant amount of hum. Also, the amp will compress more easily as current draw while operating will empty the cap more quickly causing a significant voltage drop. Especially with lower frequencies.
The other issue is the added stress to the power transformer. If the transformer is operating close to max spec (which some do) the longer duration of current draw to fill a larger cap can stress it as well.


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## Lincoln (Jun 2, 2008)

Well I certainly learned a lot of good things today. Thank you all 

I had an oh sh1t moment, because when I built my AA764 Princeton Reverb I used a 40/20/20/20 and a tube rectifier. But then I remembered that I also used a Deluxe Reverb power transformer, so it should have the extra grunt it needs to make things work.

But I also used a 40/20/20 when I built my vibrochamp using a stock PT. Not good. I gotta go back in there and fix that. B#(*


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## jb welder (Sep 14, 2010)

The max. capacitance ratings are for capacitive input filters. That means the cap is connected directly to the rectifier tube, no choke between. Where you have a choke between, these numbers do not apply.
For three fairly common rectifier tubes, the maximum capacitances are:
5Y3 20uF
5U4 40uF
5AR4 60uF


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## nonreverb (Sep 19, 2006)

Something I should mention is, with your Vibro Champ, B+ voltage is relatively low therefore based on that and the rectifier plate impedance and inherent transformer impedance, you can increase the capacitance...probably 40uF would be about as far as you could go.


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## WCGill (Mar 27, 2009)

My lovely Gibson Falcon has 40uf after the 5Y3 and has had from day 1, hasn't seemed to hurt the rectifier. The maximum ratings are for full output as I understand it and with sufficient resistance in the power supply, they may be exceeded but for the average person building a kit, stay close to the above-mentioned guidelines.


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## nonreverb (Sep 19, 2006)

I waded in to a huge discussion related to this over on the Organ Forum. The preamp in the Hammond B3/C3/A100 known as the A0-28 uses a 6X4 rectifier with....are you sitting down?....a 40uF primary cap and a plate voltage of approx. 400V. The design stayed that way for the 20 years they built them. There are instances where the tube goes south but I'm sure the frequency is no greater than the rectifier going in any given amp. Many have argued that drop resistors should be installed or that the capacitance be reduced......considering many of those preamps still have the original tubes in them after 40 + years suggests Laurens Hammond and his engineers took that into account.


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## Lincoln (Jun 2, 2008)

I love it when rules goes out the window. Hammond obviously had some very smart people working for him. 

Not knowing any better, I used a 6X4 years ago in the first 5F1 clone I pieced together. They didn't last all that long for me. I kept spares.


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## nonreverb (Sep 19, 2006)

Holy smokes! (no pun intended) that wouldn't last long at all!
I remember getting an AC30 in for repair with a 5Y3 for the rectifier. Obviously, that was the fault. What did amaze me though, is that apparently it had been in there for close to a year!! The amp couldn't have sounded very good.


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## J-75 (Jul 29, 2010)

I have problems getting 40/40 cans. the only ones I know of are CE's at about 40 bucks a pop. I use two 50/50's in place for solid state rectification apps. although I'd like to use a 50/50 and a 30/30 to balance out the 80 mf. total.
First, I'm P.O.'d that somewhere in history, the 'standard' values were changed - it clearly has no relationship to metrication as I see it. So, I invite replies that pertain particularly to audible differences in this 'over filtering' I'm doing. My parts guy says it won't matter.


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## epis (Feb 25, 2012)

I wouldn't bother, 50 years ago electrolytic caps were manufactured with +100/-20 % tolerance, especially because you mentioned solid state rectification.
Smaller caps at the end of the B+ string (preamp) were used only because of the cost, just to satisfy minimum requirement of filtering (decoupling).


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