where to find some capacitors.

[Alexo]

You can get uf5408's if you want less switching noise.

About the 10K/10 cap - you can get a couple of 4,700uf/35V electro caps from your local radio shack and run them in parallel for 9K4.

[Voodoo_Man]

Does the 1N5408 have less switching noise that a 1N4007?

In all honesty..........I don't know. Don't think I ever heard switching noise and wouldn't know it if I did hear it. How can a diode with no moving parts make noise like a mechanical switch anyway? Is there some hidden info on the datasheet?

God Bless,

john

[doctord02]

switching noise on a diode comes from the AC current getting alternately passed or blocked as it gets rectified into DC. It generally shows up as a 60 cycle buzz in the amp. I just wire a .001 ceramic cap across my diodes and that generally takes care of the problem.

[Voodoo_Man]

switching noise on a diode comes from the AC current getting alternately passed or blocked as it gets rectified into DC. problem.

Of course this would be the cause if switching noise were present. That's what rectifiers do.

It generally shows up as a 60 cycle buzz in the amp. I just wire a .001 ceramic cap across my diodes and that generally takes care of the problem.
.

"Generally" implies there are other symptoms. What would they be? When this topic started to appear on the net, I tried the "caps across the diodes" to hear the difference, or to not to hear the difference, as the case was. I'm just not convinced it's a problem.

God Bless,
John

[xk49w]

I tried the "caps across the diodes" to hear the difference, or to not to hear the difference, as the case was. I'm just not convinced it's a problem.

It is a potential problem and is caused by the reverse recovery time of the rectifier diodes. Basically the diode doesn't switch immediately and there is a current spike at the switching point where the current is still flowing in the pre-switched direction. Because of its rise time this spike can contain high frequency components that can be audible as a buzz. The paralleled capacitor absorbs the current from the spike, reduces the rise time and lowers the generated high frequency components.

If you don't hear a buzz then don't worry about it. Many (most?) amps don't employ caps across the diodes. Some do. I was just looking at a Fender Champ II schematic which uses .002u/1kV caps.

I have seen values as high as 0.01uF used in ham radio high-voltage supplies where eight or more diodes are stacked in series to meet the needed reverse voltage requirement. They also uses parallel resistors (470k) to equalize the voltage drops and to ensure that no one diode will see a momentary voltage that exceeds its reverse rating.

Here's a document on diode reverse recovery: http://www.microsemi.com/micnotes/302.pdf

[Voodoo_Man]

"It is a potential problem"........May be in some electronic circuits it is. Guitar amps seem to be immune.

"If you don't hear a buzz then don't worry about it."...........Great advice indeed. Over and out. Thanks for the document. Back to soldering.

God Bless,
John

[joebob]

These are the Mouser numbers

10000uf/10v 647-TVX1A103MCD $2.73
.1/50V 1429-1104 $.44
.22/400V 1429-6224 $.97
.1/600V 1429-6104 $.73

Dave

[wsaraceni]

awesome. thanks for that. i was looking for axial, thats probably why i couldnt find them.


as for the rectifier for the heaters. i actually have a rectifier here. dont know much about it. it says on the side

AC MP3510 V630 +


will that work here? what is the proper way to mount it in the chassis. looks like the bottom is exposed metal and there is a hole in the middle of it

[Voodoo_Man]

awesome. thanks for that. i was looking for axial, thats probably why i couldnt find them.


as for the rectifier for the heaters. i actually have a rectifier here. dont know much about it. it says on the side

AC MP3510 V630 +


will that work here? what is the proper way to mount it in the chassis. looks like the bottom is exposed metal and there is a hole in the middle of it

That P/N shows up as a 1000 Volt x 35 Amp Bridge at Mouser. W---a----y overkill. Suppose it would work, but if I were you, I'd get something more appropriate.

God Bless,

John

[wsaraceni]

does seem like overkill. i have the 1n5408 diodes that just came in the mail so ill use those. i hope this build works out for me as I am doing the layout myself for the first time. the chassis i have doesnt allow for the most streamlined approach.

[wsaraceni]

as you can see im full of questions that i should probably already know. the coming off of the DC side of the heaters there is a CAP. one side is +, the other is - or Ground. does the heaters wire pin 9 to the - side and pins 4+5 to the + side?

[Voodoo_Man]

as you can see im full of questions that i should probably already know. the coming off of the DC side of the heaters there is a CAP. one side is +, the other is - or Ground. does the heaters wire pin 9 to the - side and pins 4+5 to the + side?

4 & 5 to the minus, 9 to the plus, works for me.

god Bless,
john