Hello
I attached the circuit I'm currently learning, I want to change the diodes (which are old reference for 1n4007) to make the power supply less noisy.
I read every post on the subject and the pdf from Hagermann on snubbers. But i still don't understand very well.
Some EE said that that you alway need to use UF diodes to avoid the noise generated by the diode during the switching (noise which can ride thru the heaters and get to the preamp where they are amplified).
Another said that you don't need Ultrafast diodes in 50/60hz power supply, and that the ultra fast diode actually generates more noise as the cutoff is faster (so it creates a ringing frequency) & Even UF soft diodes can create more ringing than slow diodes, due to the fast rise.
I also read that it is not related to diode reverse recovery but just to transformer leakage inductance resonating with diode capacitance, and all diodes have capacitances, particularly schottky ones (altough they tend to be more constant than in conventional diodes). (FROM EVA)
___
I read a lot of papers and they both give points to these theories, but can someone clarify ?
Thank you
I attached the circuit I'm currently learning, I want to change the diodes (which are old reference for 1n4007) to make the power supply less noisy.
I read every post on the subject and the pdf from Hagermann on snubbers. But i still don't understand very well.
Some EE said that that you alway need to use UF diodes to avoid the noise generated by the diode during the switching (noise which can ride thru the heaters and get to the preamp where they are amplified).
Another said that you don't need Ultrafast diodes in 50/60hz power supply, and that the ultra fast diode actually generates more noise as the cutoff is faster (so it creates a ringing frequency) & Even UF soft diodes can create more ringing than slow diodes, due to the fast rise.
I also read that it is not related to diode reverse recovery but just to transformer leakage inductance resonating with diode capacitance, and all diodes have capacitances, particularly schottky ones (altough they tend to be more constant than in conventional diodes). (FROM EVA)
___
I read a lot of papers and they both give points to these theories, but can someone clarify ?
Thank you
Attachments
I generally use UF4007 or similar for HV rectification duties.
If you are concerned about rectifier noise a 0.01uF 1kV disc ceramic cap placed across each diode is usually adequate.
You can also add a snubber across the secondary. A lot of discussion on snubbers here, do a quick search of the forum for threads.
If you are concerned about rectifier noise a 0.01uF 1kV disc ceramic cap placed across each diode is usually adequate.
You can also add a snubber across the secondary. A lot of discussion on snubbers here, do a quick search of the forum for threads.
Something else to note is that the center tap on this transformer is not strictly required, it is only used to force the voltage across the filter caps to be equal, the same came be accomplished with a pair of resistors in parallel with the caps.
Finally I think this might be better off in I&A since it is a musical instrument amplifier you are discussing. I will move it there.Edit: Moved, I think you will get many better answers here than in parts..
What makes you think that the PSU is noisy? This is a guitar amp, not high-end hi-fi.
1M pots directly exposed to grid current will be noisy, expecially when followed by a cascade of ECC83 gain stages.
1M pots directly exposed to grid current will be noisy, expecially when followed by a cascade of ECC83 gain stages.
Thank you guys
I though I would post in parts since I am more into the theory behind it, but I am new to the forum so thank you for your guidance kevinkr 😀
@DF96
Thank you for pointing this.
I know that the preamplifier section is ultimately going to be the main source of noise, but as an instrument amplifier changing the pot values will also alter the impedence of the 3 gain stages (and will change the feeling of the guitar player). But I plan to cover the preamp section later, I will try to make it less noisy and the 1M pots where in my sight (but I was more concerned about johnson noise, and planed to make them 500k). If you have tips you are welcome 🙂
It is just a study, and I am focused on the power section for now🙂
And the power supply is not that noisy (hum/buzz a little), and since it's a guitar amplifier the power section is alway pushed hard to make the power tube distort so it is more noticeable than in a hifi amplifier. But it's just to build "the best".
But as I said I am more into the theory behind diode switching noise, I posted this schematic since I am currently toying with this build. I try debunk the theory since I read a lot of clashing views.
I though I would post in parts since I am more into the theory behind it, but I am new to the forum so thank you for your guidance kevinkr 😀
Whoa thanks I didn't notice this, good tips.
@DF96
Thank you for pointing this.
I know that the preamplifier section is ultimately going to be the main source of noise, but as an instrument amplifier changing the pot values will also alter the impedence of the 3 gain stages (and will change the feeling of the guitar player). But I plan to cover the preamp section later, I will try to make it less noisy and the 1M pots where in my sight (but I was more concerned about johnson noise, and planed to make them 500k). If you have tips you are welcome 🙂
It is just a study, and I am focused on the power section for now🙂
And the power supply is not that noisy (hum/buzz a little), and since it's a guitar amplifier the power section is alway pushed hard to make the power tube distort so it is more noticeable than in a hifi amplifier. But it's just to build "the best".
But as I said I am more into the theory behind diode switching noise, I posted this schematic since I am currently toying with this build. I try debunk the theory since I read a lot of clashing views.
There is an article by Johm Camille that appeared in Sound Practices #7 posted here: Reducing rectifier noise in high voltage power supplies
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