oneplustwo Aleph X build thread

[6L6]

On an amp at this power, discrete diodes might not be the best bet.

Get a pair of 200v 35A Vishay bridges and mount them with a little thermal grease under them.

 

[oneplustwo]

That's what I was thinking would be my next step. Is there any benefit to "double" rectifying? Trying to decide if I should remove the old ones or leave them there. I assume no negative effects at least?

 

[6L6]

A bridge for each winding gains you a few things -

More current capability on the bridges

Distributed heat compared to a single bridge

A reduction in transformer physical hum when current draws change

Can you link to the PSU board you are using? I would like to see a closer photo of it.

 

[oneplustwo]

Here's the link: Heavy Duty CRC Power Supply Kit for Class A Ampllifier | eBay

So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board? That makes sense to me if I'm going to go through the trouble of doing this in the first place. Just need to make sure i wire to the board properly.

I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?

I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.

 

[AudioSan]

6L6. it is a e-bay board. clone of the aleph PSU board from chipamp.com

 

[AudioSan]

just pull them out. then you short the pads for 2 of the 4 rectifiers.
like this:

Here's the link: Heavy Duty CRC Power Supply Kit for Class A Ampllifier | eBay

So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board? That makes sense to me if I'm going to go through the trouble of doing this in the first place. Just need to make sure i wire to the board properly.

I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?

I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.

 

[oneplustwo]

Got it. And the outputs of the rectifiers just go to the AC pads as such?

(+) of two of them to the left AC0 pad
(-) of those same to the right AC0 pad
(+) of the other two to the right AC1 pad
(-) of those same remaining to the left AC1 pad

 

[6L6]

So I think you're saying get four rectifiers, one for each winding, and parallel the outputs to the board?

No, you only need 2.

Parallel 2 of your windings two times, to get the transformer connected as intended.

Now you should have (2) 18v windings of 400VA each. Put a bridge on each.

I assume I can just leave the original rectifiers... They will basically act like shorts in this case, correct?

No. Remove them.

I'll go ahead and thermal paste them anyway to see if that cools them down appreciably as well. Not optimistic though.

It's worth a shot, but 15A diodes will not last long in that circuit even if cooled by submersion in a mountain stream...

 

[AudioSan]

yes. on AC0 it is (-)(+) and (-)(+) on AC1. you need to confirm that your board is the same. but i suspect it is

 

[oneplustwo]

@6L6 - Ah, gotcha. That makes sense. I was confused by "a bridge for each winding."

@AudioSan - your description is much simpler!

Thanks to both for your help! Much appreciated!

Now... to decide which rectifiers to get. Not sure I'm a believer in the super fancy ones, but then I haven't tried them before. I'm inclined to just the cheap 35A fairchild ones. Open to suggestions. Even the expensive ones aren't all that expensive I guess compared to the dollars I have in heat sinks alone!

 

[6L6]

When connecting the bridges to the cap board, the acid test is to make sure that the bridge negative connects to the capacitor negative.

 

[6L6]

Now... to decide which rectifiers to get... I'm inclined to just the cheap 35A fairchild ones. Open to suggestions.

Just get the Vishay bridges with slow diodes in them. Nelson prefers them for high-current supplies. I will link to the article where he talks about it.

 

[6L6]

Ok, here it is - read the heading under "rectifiers".

http://www.passdiy.com/pdf/powersupply.pdf

If you want to use a snubber capacitor (the caps he mentions in the last sentence) place a .22uf film cap across the AC side of the bridge. At least a 63v volt cap. Easy!

 

[oneplustwo]

Awesome... four rectifiers and four snubber capacitors are in my future.

Perhaps these. Hopefully I can find some .22uF film caps in my parts bin.

 

[6L6]

There is no real need for the 1000v rating. Use the 200v... Nelson does.

If your box is bare, something like this seems good - ECQ-V1J224JM Panasonic Electronic Components | Mouser

 

[oneplustwo]

They were only pennies more expensive so I thought why not. Is there a downside other than the extra few nickels I'll spend?

 

[6L6]

That has always been a question of mine as well... There has to be something, if there wasn't why wouldn't all diodes be 1000v??

I honestly don't know. I'm sure there is a discussion about it somewhere... I will ask my Guru when I get a chance also.

 

[toufu]

Hi Oneplustwo, I am thinking of building an 100watt Aleph X also. Can you post the BOM you are using? Thanks.

 

[oneplustwo]

@toufu - PM sent. Good to see a fellow San Franciscan on diyaudio!

@6L6 - Let me know if you find anything out. I'll probably just go ahead and order the 200V ones. Go with the devil you know and all.

Unless someone has 4 they have lying around they'd like to part with. Pet peeve paying more for shipping than the parts are worth! Too bad there's not amazon Prime for bridge rectifiers.

 

[oneplustwo]

6L6 - For the snubber caps, is .22uF critical? I have some that wima 1uF 100V caps and a few that are .1uF as well in the parts bin. I'll just order new ones if I need to... they're not that much anyway. Just feels good to use spare parts! =)

Also, could I use different ones for different rectifiers? Seems like a somewhat less than critical part where I can get away with that.