Modded Crack - add bypass cap, choke and Cree diodes

[adydula]

So help me understand this all...is the idea of replacing the diodes a good thing or a not so good thing? Based on some of the comments and concerns that Doc posted I am concerned and a bit confused. I would like to try this but not unless its really been "scoped" out....

Alex

 

[lthomash]

Alex, I do not believe that using Cree diodes improves the sound in Bottlehead gear, I have a bad habit of using the Cree's in most of my builds because they look "cool" not because they might improve the sound quality.

Lee Hankins

 

[Bacci]

I just tried them out because they are relatively cheap (like 10$), everyone who tried them was so wild about them and the diode bridge PCB is on promo but more importantly available at the moment at Partsconnexion.

To my ears the Cree SiC Schottky's sound like a nice upgrade both in noise and clarity, but why?
Most seem to think reverse recovery current (or better the lack thereof) is responsible for the goodness (but at "only" 50/60Hz AC... why?), maybe other properties like lower forward voltage drop, ... could be playing a role?
Bear in mind that everyone with one or more Crees already had a choke installed beforehand, which affects pretty much everything in front of the reservoir cap.

 

[Tom-s]

You want to look at the power supply. Right at that first cap would be a good place. Maybe on the heater secondary too. Look for spikes. The UF4007 is an ultrafast recovery diode and should have only a very tiny recovery spike. The Schottky should have none. Will the Schottky remove a spike from another diode? I dunno about that. People have used tube rectifiers after a SS diode because they are slooow and thus filter out the quick spike. They do the same for the musical transients.

Anyone tried this?

 

[Doc B]

Are you asking if anyone has looked for spikes on the heater secondary?

 

[Tom-s]

Yes.

*And i don't see what could be done about it if there was. Other than better wind the wires. Shielding the heater wires...

 

[Doc B]

The point is if you are seeing spikes anywhere you might want to change to a rectifier that puts out a smaller spike or no spike in the B+ supply. One could also try implementing an RRSF filter between the heater secondary and the tube sockets. This is tricky because you are pretty much limited to caps without any R or L, since they will add too much resistance to the circuit and the heater voltage won't be right.

This is why we went with the UF4007s. If the rectifier is quiet there is no spike that needs to be filtered.

 

[pingping]

I know I'm a bit behind here in terms of the age of the thread, but I've just fitted the Cree based rectifier in my Crack, and can immediately recommend it.

Cheap, quick, and no doubt that it is now pulling more detail than I was hearing before. I can't really argue with hearing new things.

 

[AllanMarcus]

pardon my ignorance, but is there BOM for the parts needs for the Cree/schottky rectifier mod?

Any instructions too? I sort of get it from the pics for the cree/board, but I'm not sure about the Schottky diode.

This seems like an easy, inexpensive mod that I would like to try.

thanks.

 

[ALL212]

This should be it.

http://www.partsconnexion.com/product26996.html

or Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style),"

If they're out let me know - I bought a few extra the last time.

 

[Leland Hankins]

If you want to go all out, I thread the hole in each diode via a tap, and then screw a nylon bolt through each diode, spaced 1/4 " apart.

 

[AllanMarcus]

This should be it.

http://www.partsconnexion.com/product26996.html

or Google "Discrete Bridge Rectifier PCB - TYPE 2 (TO-220 Radial Style),"

If they're out let me know - I bought a few extra the last time.

thanks. That's the board. What cree diodes are needed? And what Schottky diode is needed?

 

[ALL212]

Slow down - do some research...

Cree is the brand name, shottkey is the component type.

http://www.partsconnexion.com/product7559.html

Disclaimer - any information supplied is what I used under my own guidance.  Your ability to loosen the magic smoke is entirely up to your own skill level.

You need to read through the thread all the way carefully.  Especially noting that if you install these wrong or are not careful in what you're doing you can shock yourself or destroy the components.

 

[AllanMarcus]

Slow down - do some research...

Cree is the brand name, shottkey is the component type.

http://www.partsconnexion.com/product7559.html

Disclaimer - any information supplied is what I used under my own guidance.  Your ability to loosen the magic smoke is entirely up to your own skill level.

You need to read through the thread all the way carefully.  Especially noting that if you install these wrong or are not careful in what you're doing you can shock yourself or destroy the components.

Got it. I was schooled on Head-fo too. I'm a-learnin'. I've recently learned which way goes up on the tubes!

 

[AllanMarcus]

Ok. I got my board and diodes. I would just like to verify the next steps.

1) Remove the 4 rectifiers at 18,19,20, and 21.
2) Wire the board as show in the diagram below. I will probably just glue a nylon spacer to the bottom of the board and then to plate like shown earlier in this thread.

I assume the wires should be twisted to the board, also as shown in some of the earlier posted pictures.

Is this diagram correct?

https://cdn.head-fi.org/g/9937481_l.jpg

 

[Paul Birkeland]

Looks good.

 

[AllanMarcus]

Looks good.

Thanks! Mod installed and crack working. I have no idea if it sounds better as I have no temporal comparison skills, but I'm going to believe is sounds better. Exactly $10 better 

 

[Paul Birkeland]

I'm going to believe is sounds better. Exactly $10 better 

Maybe $9.95.

 

[m17xr2b]

Curious to hear the different in diodes myself but the board is forever not available. I see they have an assembled one but it's not using schottky ones. Is it what I need? As a last resort I'll get it just for the board and replace the diodes.
https://www.partsconnexion.com/ASSEM-77727.html

 

[ALL212]

I might have a spare or two.  Let me know if you still need one.