What kind of diodes do you guys use for rectification in the power supply?
Tommy
What kind of diodes?
Moderators: pompeiisneaks, Colossal
Re: What kind of diodes?
I've used the standard Fender layout of 6, 1N4007's but on my latest build I used 4, 1N5408's. It's a general purpose 3A, 1000PIV diode. 2 should be enough but I decided to use 4 just to be safe. Since Fender used 6, 1A diodes, I decided to use the same current rating.
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Funkalicousgroove
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Re: What kind of diodes?
Fender used 6 because they weren't rated at 1000v like todays 1n4007, and thusly couldn't handle the peak inverse voltage. 4 1n4007's is totally sufficient.
Owner/Solder Jockey Bludotone Amp Works
Re: What kind of diodes?
Could someone please educate me about the "snubber" capacitors I sometimes see mounted across power supply diodes? What do they do with respect to tone, and what values are usually used? Also, has anyone tried any of the "fast recovery" or other high grade (audiophile-ish) diodes, and can you hear/feel a difference?
Thanks in advance.
D
Thanks in advance.
D
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Funkalicousgroove
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Re: What kind of diodes?
the snubbers are to prevent diode switching noise, and from what I understand, a Must-Have in the EU. I don't use them myself as I can't hear diode switching noise, nor do i care if it's there. As far as FREDS (fast recovery expatial diodes) Try them and see what you think, I know that they make a big difference in a plexi, not sure what they'd do for your ODS. Be sure to use BIG ones like 8A 1600V, I hear they fry pretty easy.
Owner/Solder Jockey Bludotone Amp Works
Re: What kind of diodes?
That's odd, I thought it was the current that's the issue. I always though that all the diodes need to handle the PIV but that the current rating would add as you use series diodes. I must add that it's been 30 years since electronics skuul though.Funkalicousgroove wrote:Fender used 6 because they weren't rated at 1000v like todays 1n4007, and thusly couldn't handle the peak inverse voltage. 4 1n4007's is totally sufficient.
Re: What kind of diodes?
Another option for "fast diodes" is the UF4007 - just like a 1N4007 but a "fast recovery diode". MUCH cheaper. Not so fragile.
Re: What kind of diodes?
current rating is a parallel thing, voltage rating is a series thing.
1N4001 diodes have a 1A at 50V PIV (peak inverse voltage, the maximum amount of reverse voltage that the diode can block before failure). Placing 4 in series gives you a PIV of 200V but you still only have a current rating of 1A. hth
1N4001 diodes have a 1A at 50V PIV (peak inverse voltage, the maximum amount of reverse voltage that the diode can block before failure). Placing 4 in series gives you a PIV of 200V but you still only have a current rating of 1A. hth
Re: What kind of diodes?
Could someone please educate me about the "snubber" capacitors
This question was asked at another forum, here was the reply:
When solid state diodes first appeared they were not nearly as tough as they are now. They were also not available in the higher PIV ratings or if they were they were a LOT more expensive!
The major problem was the surge currents at turn-on. IF the filters were sitting empty there'd be a split second of amps of current and then the flow would fall well within the ratings after the cap held some charge.
The PIV availability and cost was usually addressed by putting diodes in series. This revealed an unforeseen problem. No two diodes would have exactly the same internal resistance, or forward voltage drop. The difference might be "mice nuts" but during that first surge pulse of mucho amps it could mean that one diode saw more than it's share of the energy.
Also, the voltage drops across the diodes would not be equal. This is similar to the problem of stacking filter caps for a higher voltage rating and was solved exactly the same way by putting caps and sometimes resistors across each diode.
The idea is that the caps/resistors swamp out the differences between diodes and equalize the the energy each sees.
As diodes improved and got cheap this practice disappeared. Why bother when you could buy 1N4007's rated at 1KV PIV for pennies and just put an extra one or two in the string? No matter how unequal the drops across each diode were they could never exceed the individual diode's rating. An extra 1N4007 is cheaper protection than the cost and extra labour of a mess of snubber caps and resistors.
As for suppressing noise, that's a bit of a stretch. Yes, diodes can make noise as they switch on and off. If you're selling suppressor stuff or trying to make your amp more impressive to a buyer (audiophile!) you stop right there and say no more. If you're a techie you would add that filter caps are by definition big-ass bypass caps to any noise pulse. The inductance of the PT primary in the circuit also swamps out such pico-second noise pulses.
If we were talking about diodes rated at hundreds of amps in a supply for something like a DC motor in a factory the noise might become more than trivial and bother other equipment in the area. So in such cases suppression caps make sense.
This means that if again you're a salesman and not a tech you would add to your sales blurbs that "MY AMPS CONTAIN THE SAME DIODE NOISE SUPPRESSION CAPS USED IN BIG FACTORIES!" The implication being of course that if they're used in a big-time and expensive application then OF COURSE they make YOUR amp better!
This question was asked at another forum, here was the reply:
When solid state diodes first appeared they were not nearly as tough as they are now. They were also not available in the higher PIV ratings or if they were they were a LOT more expensive!
The major problem was the surge currents at turn-on. IF the filters were sitting empty there'd be a split second of amps of current and then the flow would fall well within the ratings after the cap held some charge.
The PIV availability and cost was usually addressed by putting diodes in series. This revealed an unforeseen problem. No two diodes would have exactly the same internal resistance, or forward voltage drop. The difference might be "mice nuts" but during that first surge pulse of mucho amps it could mean that one diode saw more than it's share of the energy.
Also, the voltage drops across the diodes would not be equal. This is similar to the problem of stacking filter caps for a higher voltage rating and was solved exactly the same way by putting caps and sometimes resistors across each diode.
The idea is that the caps/resistors swamp out the differences between diodes and equalize the the energy each sees.
As diodes improved and got cheap this practice disappeared. Why bother when you could buy 1N4007's rated at 1KV PIV for pennies and just put an extra one or two in the string? No matter how unequal the drops across each diode were they could never exceed the individual diode's rating. An extra 1N4007 is cheaper protection than the cost and extra labour of a mess of snubber caps and resistors.
As for suppressing noise, that's a bit of a stretch. Yes, diodes can make noise as they switch on and off. If you're selling suppressor stuff or trying to make your amp more impressive to a buyer (audiophile!) you stop right there and say no more. If you're a techie you would add that filter caps are by definition big-ass bypass caps to any noise pulse. The inductance of the PT primary in the circuit also swamps out such pico-second noise pulses.
If we were talking about diodes rated at hundreds of amps in a supply for something like a DC motor in a factory the noise might become more than trivial and bother other equipment in the area. So in such cases suppression caps make sense.
This means that if again you're a salesman and not a tech you would add to your sales blurbs that "MY AMPS CONTAIN THE SAME DIODE NOISE SUPPRESSION CAPS USED IN BIG FACTORIES!" The implication being of course that if they're used in a big-time and expensive application then OF COURSE they make YOUR amp better!