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Large caps in PSU without choke?

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G

G

Member
Joined 2002
Hi All,

I'm getting ready to rebuild my SE EL84 amp onto a nicer chassis and I have a question. I have a pair of dual section Elna Cerafine 220uF/450volt caps that I would like to use. Since I'm not using a choke in the PSU I should be able to use them shouldn't I? I have been using 32uF/500 volt dual section caps. Thanks.
 
EC8010

EC8010

Ex-Moderator
Joined 2003
A GZ34 is only rated for maximum reservoir capacitance of 60uF. If you put 220uF directly on its output, the ripple current will quickly kill it. However, there's nothing to stop you using a 68uF as a reservoir (modern capacitors are far closer tolerance, so the slight, but controlled increase will be OK). You could then follow that with RC smoothing using your 220uF capacitors.
 
fdegrove

fdegrove

diyAudio Senior Member
Joined 2002
Hi,

No, but I can hear the death screams of your power transformer's winding (unless it's hideously overrated) from here.
Click to expand...

Won't that depend on the state of the load when powering up?

:att'n: :att'n: Tip for DIYers with a good recollection of their own work:

If you decide to use such monster caps put a switch in the tail end of your bleeder resistor that's across them. Leave it open unless you intend to work on the bowls of the monster.

Put some safety warning near it, just in case you do forget.
:att'n: :att'n:

Errr....Mikael?....What kind of amplifier is that? :hot:

Cheers,;)
 
M

Mikael Abdellah

Member
Joined 2003
fdegrove said:
Errr....Mikael?....What kind of amplifier is that? :hot:

Cheers,;)
Click to expand...


It's my single ended KT88-amp. I know 2200uF is WAY overkill, but I have allways liked insanely big caps in the powersupply. This is my first amp ever, and I couldn't afford to buy all the chokes I wanted, so I ended up using big power-caps instead. Maybe I will use a couple of chokes in the future instead.
:D
 
SHiFTY

SHiFTY

Member
Joined 2002
I have a pair of dual section Elna Cerafine 220uF/450volt caps that I would like to use. Since I'm not using a choke in the PSU I should be able to use them shouldn't I? I have been using 32uF/500 volt dual section caps. Thanks.
Click to expand...

On the contrary, a choke allows you to use a large amount of capacitance after it. It limits the rate of change of current, so you could probably use 220uF after a choke without any problems.

However, any more than 50-60uF directly on your GZ34 will be problematic. I would stick with a 47uF cap for the first cap. Its only the cap which feeds the OPT which really impacts the sound, so your Cerafines should be good here. You can send the spare one to me :)

As someone else said, you could use SS diodes, but then yoiu would need a B+ switch to avoid the overvolting...
 
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