Replacing the last power supply cap

[adamct]

I'm not sure I want to tackle this, but has anyone tried fully replacing the last cap in the power supply with a film cap? Was there a noticeable change in the sound? I currently have that cap bypassed with a ClarityCap ESA cap, but I'm wondering if it is worthwhile to fully replace it. I tend to think the answer is no, but..."Inquiring minds want to know!"

What is the value of that cap (I'm at work and don't have the manual at hand)? I think it is something like 220 or 250uf, is that right?

I believe Paul mentioned that if you want to replace it with a 100uf 250V cap, then you need to add a choke as well.
Does the same hold true if using a 200uf or 220uf cap? I've been looking at a Solen PB FastCap 220uf / 400 VDC, or a ClarityCap TC 220uf 700VDC. Anyone have any experience with either cap? I have to admit the giant ClarityCap TC caps with screw terminals instead of wire leads look pretty damn cool...

Best regards,
Adam

[2wo]

Well first off did you like it when you bypassed the last cap? if yes then why not.

As a general rule, you can replace a electrolytic cap with a somewhat smaller film cap, how much smaller, is hard to say.

But the thought of adding a choke is appealing. How about something like 100uf-CX-7-100uf, I am just throwing these values out. Best to model it on PSUII.

That is if you take advise from a teenage girl      

[adamct]

Well, sure, I love the sound with the last cap bypassed. But actually replacing the cap, instead of bypassing it, would be a much more involved (and expensive) operation, so I want to make sure it is worthwile before I undertake it.

I think Paul's point was that if you replace the electrolytic power supply cap with a smaller value film cap, then you need to add a choke. But in the example he used, he was referring to replacing the cap with a 100uf film cap. I'm trying to figure out whether the choke is still necessary if I were to go with a much bigger cap: 200 or 220uf, which I think is close to the value of the electrolytic, although I can't remember the exact value off-hand.

Thus far I've stayed away from adding a choke, just because I didn't want to deal with the added complexity.

And John, I'll take your advice even if you don't quite look like your avatar...

[earwaxxer]

Hey Adam - I say, if you can replace an electrolytic with a film cap of the same value - why not! - as long as the film cap can handle the voltage, and your wallet can handle the price!

[adamct]

Eric,

A wise man once said:

"...this modding thing can get a bit crazy, its good to keep a level head about it. ... Its more about enjoying what you have. I wouldnt mod anything unless I felt I had a "reason" to. In other words, there is something that I would like to improve upon, and I'm motivated to solve that problem. Without identifying a problem, its a bit like shooting in the dark IMO."

  

I'm doing my damndest (spelling?) to keep a level head. I don't really have any complaints about my modded Crack, no problems or anything I want to improve upon. So I'm definitely shooting in the dark and would rather not go to the expense and hassle unless there is a reasonable prospect of success (meaning an audible improvement in sound).

Best,
Adam

[earwaxxer]

Eric,

A wise man once said:

"...this modding thing can get a bit crazy, its good to keep a level head about it. ... Its more about enjoying what you have. I wouldnt mod anything unless I felt I had a "reason" to. In other words, there is something that I would like to improve upon, and I'm motivated to solve that problem. Without identifying a problem, its a bit like shooting in the dark IMO."

  

I could not have said it better myself!

[adamct]

LOL! Touch

[2wo]

I don't have a crack but 220uf is a likely value. there would be no issue replacing it with a 200uf film of equal or better voltage rating.

My thought was, what is the cost of the big 200uf cap, compared to 2, 100uf caps, the choke is less then $20.

CLC with film caps is the way I am going with my SR-45 rebuild, I am thinking 100uf motor runs, got them already . 

And you are right, that is kind of an old photo...John 

[adamct]

You mean I could use something like this?

[2wo]

I am not sure if I was clear. you can replace the last cap with whatever you have on hand within limits. Voltage limits.

 Other than that it depends on how much hum you get, you won't hurt anything. 50uf is probably too low but hey, might work. Turn the vol up slowly and check for hum.

 I am in the camp of the smallest best-est cap is the one for me.

Make no claim to being in the right camp...John   

[2wo]

You mean I could use something like this?

Not sure. I look for motor RUN caps. This sort of thing. check e-bay

http://angela.com/angelaascoilcapacitor50uf515vdc.aspx

[adamct]

Maybe I'll just get 12 of those and wire them into three sets of four...








Relax, I'm kidding. I wouldn't do that. Or would I?......

[2wo]

The ASC and other motor run oil caps are great in the power supply.
 They have fallen from favor lately because they do not command top dollar.

So sad...John

[Grainger49]

In ebay search for "oil capacitor" and you will find all kinds.  Larger values are getting harder to find.

[Paul Birkeland]

The actual first Crack that I ever built was back in 2004, and I used several motor run caps in the power supply. Ultimately I can recall that 100uf per section wasn't enough (I was using a CRC filter with a lot of resistance)   I actually ended up with more like 400uf per section in the end, and the experience of these experiments was very educational.

PB