rectifier switching noise

[hylaphone]

OK folks, I tried a bunch of your suggestions over the past week, and some other ones I found while internetting:
- Twisted primaries and secondaries tightly
- Piggybacked a small value poly cap across the reservoir cap
- Cap across the secondaries
- Cap + pot in series across the secondaries
- Caps + resistors across diodes
- 10 ohm "slurring" resistor between the bridge and 1st cap
- Checked for noise on my mains line
- Tacked in a new transformer entirely away from the chassis
- Probably a few other tricks I can't remember

I only succeeded in changing the character of the buzz. None of these things really reduced it.
Mind you, the humdinger pot works pretty good but is cumbersome to implement and is more or less effective at different volume/tone settings.

This afternoon, I made a rudimentary DC filament supply (FWB, CRC filter). The amp is DEAD quiet now.
I knew this already from trying out a lantern battery, but was surprised how easy it was to build a quiet rectified heater supply.
Despite my determination to root out the source of the buzz, this seems like the most elegant solution.
Besides, I don't like having little caps everywhere

I sure appreciate this thread, I did learn a lot!

[R.G.]

OK folks, I tried a bunch of your suggestions over the past week,[...]
I only succeeded in changing the character of the buzz. None of these things really reduced it.
[...]
This afternoon, I made a rudimentary DC filament supply (FWB, CRC filter). The amp is DEAD quiet now.
I knew this already from trying out a lantern battery, but was surprised how easy it was to build a quiet rectified heater supply.
Despite my determination to root out the source of the buzz, this seems like the most elegant solution.
Besides, I don't like having little caps everywhere

So what you found is that your tubes leak AC from the heaters?

Rule 1 for tube amps is to always suspect the tubes. There is a reason they're in sockets.

[Gingertube]

I went searching for something I posted to a SS HiFI Power Amp Forum some years ago.
Found it ...

Copied Here:

Skip to the last 3 paragraphs if you don't want to wade thru' any of the physics.

Whenever you have a P and N type semiconductor material the P type has an affinity for electrons (called holes - somewhere for electrons to go) and the N type wants to give electrons up for each of them to attain their most stable states. This has to do with the properties of the doping elements.

When you bung em together to form a PN Junction in a diode (Anode and Cathode respectively) or a transistor junction electrons flow from the N to the P creating a "depletion region" around the junction - that is its depleted of "holes" and electrons. The electron flow is terminated when the electric potential created by this flow of electrons (charge) is sufficient to resist any more flow. The depletion region will have a certain width

The junction (depletion region) will therefore has an electric field across it and hence has capacitance.

This junction capacitance has a Reverse Recovery charge (Qrr). That is, before a diode can turn off this stored charge has to be removed (by recombination of majority carriers). Current has to flow to remove this charge. Therefore as the AC voltage reverses on a rectifier diode there will be a pulse of current in the wrong direction before the diode actually switches off. This puts a noise spike on the power supply rail which has very high current rise time (di/dt). Filter capacitors are not very good at removing (shunting to ground) this noise spike because they have a small amount of inductance and inductors resist current change. Therefore you end up with a noise "SPLAT" on the power supply rail.

The differences in Silicon, Ultrafast Silicon, Schottky and Silicon Carbide Shottky of interest when using them as rectifiers is how fast they can turn off and how large this Current "SPLAT" is before turning off. This is obviously directly related to their Reverse Recovery Charge (Qrr). Small capacitors across each diode can help to absorb this splat and for some time they were in fact required by Electromagnetic Interference (EMI) standards for all commercial products (at least in Europe - I don't know if this is still true).

SKIP To HERE:
So here is the useful (representative ONLY) Qrr data:
Standard Silicon Diodes Qrr approx 500 nC (nano-Coulombs)
Ultrafast Silicon Diodes Qrr can be down to 100 nC
Schottky Diodes Qrr 50 to 70 nC
Silicon Carbide Schottky Diodes Qrr <20nC

Oh - To answer the original question - the other thing you need to know is that the noise spike associated with the current "SLAT" makes your amp sound seriously crap and that its edge speed is often fast enough to radiate into anything that looks like remotely like an arial (resistor leads, connecting wire etc). It can make the sound very "harsh" and is typically noticed mostly in the smoothness and detail of the high frequency "top end".

End of copied material.

That point about the pulse of current in the reverse direction before the diode turns off seems to be missing from the discussion in the thread above. That pulse is the source of the noise spikes.

The picture in post #19 is very typical. I had problems with my "Junkbox Trainwreck" on which I ran a voltage doubler supply with 1N5408. The 1N5408 had seriously bad switching noise observable on the Oscilloscope connected to the speaker wires (OT secondary). UF5408 fixed it.

Cheers,
Ian

[R.G.]

Yep. Rectifier slam off, ring the antennae, radiate a buzz.

[trem]

https://www.youtube.com/watch?v=SBqLOrlA7QI

I am too lazy to look back through my own post. Sorry if this has already been linked.....but I was wondering what the heck a "Tunnel Diode" is...?? .......and accidentally ran across this video about "Basics of Reverse Recovery Time in a Diode"

[R.G.]

Neat vid.

On "tunnel diodes": these are real, no-fooling teleportation devices. Tunnel diodes have a junction region set up with an **insulating region** dead in the middle of it. The insulating region is very thin. It is so narrow that quantum mechanical processes have a reasonable chance of happening on a noticeable level.

Electrons are not tiny little marbles of electric charge. Electrons are instead regions of space that the electron charge and mass are probably in. The probability is highest at the middle of the distribution of probability, and tapers off toward the outside. If you sum up the probabilities, you get to 1 (i.e. you're certain there's an electron in there somewhere!) but the region of probability still extends for quite some distance.

I know this sounds like me making things up again, but it's actually a good, terse description.

In the tunnel diode, with electrons pushed up against the insulating region, there is a probability that an electron with most of its probability-cloud is really on the OTHER side of the insulating barrier. And sometimes it really is. This happens with equal probability for electrons on both sides of the barrier, so no real current flows, on average. However, with the regions on each side of the insulating barrier designed as a diode, and with the diode voltages set up to conduct, an electron has a better chance of being pushed against the anode side of the barrier, and once it sometimes actually is across the barrier, the diode/voltage action sweeps it out the cathode.

A current flows **through the insulating region**; this was described by the early experimenters with these diodes as quantum-mechanical tunneling, the electrons going through a metaphysical tunnel through the insulating region, and they became "tunnel diodes".

[R.G.]

I don't see an "edit" button on the thread, and I do see some typing issues: here's a corrected version for the inevitable quantum engineer that will wander by:
============
Neat vid.

On "tunnel diodes": these are real, no-fooling teleportation devices. Tunnel diodes have a junction region set up with an **insulating region** dead in the middle of it. The insulating region is very thin. It is so narrow that quantum mechanical processes have a reasonable chance of happening on a noticeable level.

Electrons are not tiny little marbles of electric charge. Electrons are instead regions of space that the electron charge and mass are probably in. The probability is highest at the middle of the distribution of probability, and tapers off toward the outside. If you sum up the probabilities, you get to 1 (i.e. you're certain there's an electron in there somewhere!) but the region of probability [i.e. where it maybe is] still extends for quite some distance.

I know this sounds like me making things up again, but it's actually a good, terse description.

In the tunnel diode, with electrons pushed up against the insulating region, there is a possibility that an electron with most of its probability-cloud
on one side of the barrier is really on the OTHER side of the insulating barrier. And sometimes it really is - like "oops, I'm really over here now. With no particular bias, this happens with equal probability for electrons on both sides of the barrier, so no real current flows, on average. However, with the regions on each side of the insulating barrier designed as a diode, and with the diode voltages set up to conduct, an electron has a better chance of being pushed against the cathode side of the barrier, and once it sometimes actually is across the barrier, the diode/voltage action sweeps it out the anode.

The electron seems to be on one side of the barrier, then the other side with no transit time at all. Zero. That makes sense if it was probably here and possibly over there, and then something made it be probably over there and only possibly here. Quantum tunneling is still being tested, and I haven't seen anything that says that any time delay at all is involved. I find this astounding.

A current flows **through the insulating region**; this was described by the early experimenters with these diodes as quantum-mechanical tunneling, the electrons going through a metaphysical tunnel through the insulating region, and they became "tunnel diodes".

[trem]

RG....per usual, thanks for the great info.
Per usual...most of it is over my head.

1. I do think of Electrons as tiny little marbles. Waiting to go somewhere that does not have any Electrons, or maybe find some Protons to play with.
Electrons have "mass" so I assume they also have a shape.?

2. If you already mentioned it above, I am sorry, but.......what are some Uses/Applications for a Tunnel Diode.? I am not sure I have ever seen them mentioned in my basic electronics text books.
Thank You

[Gingertube]

Tunnel Diodes used in VERY high frequency circuits, MHz and even GHz.
Used for detectors and oscillators.
Here is one description:
Tunnel Diode and its Applications | Electrical4u
Cheers,
Ian.

[R.G.]

1. I do think of Electrons as tiny little marbles. Waiting to go somewhere that does not have any Electrons, or maybe find some Protons to play with.
Electrons have "mass" so I assume they also have a shape.?

You're not the only one to whom quantum mechanics is supra-cranial. One of the most famous is Albert Einstein. Actually, I think Einstein understood most of it, but he flatly disagreed with it. The business about things only probably happening, not certainly happening or not, was a big deal to him, as were the oddities about particles becoming "entangled" and then separated some great distance, whereupon you could measure something about one particle, and the other particle's similar feature becomes fixed, not probable. Einstein called this "spooky action at a distance" and refused to believe it. Einstein's comment on the probability items in quantum mechanics is famous: "God does not play dice with the universe."

Of course, Einstein was wrong, and God (or somebody!) DOES play dice with the universe, at least at the quantum mechanical level.

Electrons have mass. They interact with other particles on both a fields and a momentum basis. But - well, here's one. The popular idea about electrons is that they "orbit" the nucleus like little Sputnices, or International Space Stations orbiting earth. This is incorrect. Each electron exists as a probability shell (!) all around the nucleus. It's not just that they orbit so fast that they act like they're everywhere around the nucleus at once, they really ARE (probably...) every where at once. Electrons can share shells with certain rules, and the chemical nature of the atom depends on the shell of electrons exposed and how full it is.

The mechanical nature of the world depends on electron shells banging into one another and excluding one another. When you whack your hand into a table, no subatomic particle touches - only the fields of the electrons collide. The physical size of the particles are so dramatically much smaller than the size of the electron shells, that if you could magically turn off the shell-colliding fields, all matter would pass through other matter like nothing was there. The chances of subatomic particles actually hitting one another is highly, highly studied by particle physicists, and it's vastly smaller than the chances of electron-shell fields interacting.

If you want to really get open-eyed about electrons and what they are that you didn't know about, read about double-slit experiments. These were done with photons first, but confirmed to happen with electrons. This experiment can bend your mind several different ways.

An isolated electron, or one electron in the sea of free electrons in a conductor, exists (I think...) as a spherical ball of probability, the probability being densest in the middle, and faintest at the outside. The fundamental nature of the Uncertainty Principle (note the capital letters) is that you cannot simultaneously know the position and speed+direction of (for instance) an electron. Measuring one disturbs the other. You knock it off course or change its speed to find out where it is, and you move it to know how fast it's going.

They ain't marbles! I love to read this stuff. Seriously - who could make up things this weird, but have it all be consistent? Even more mind blowing, who could tell that it appears more and more that particles, fields and forces are an expression of a set of equations; there may not be anything at all except the math.

Sorry - I feel much better now.

[trem]

Gingertube.....Awesome.....!!!
Thank You

[trem]

Thanks RG......I am partially digesting it now.
Thanks Again

[Jazz P Bass]

Quote:"The chances of subatomic particles actually hitting one another is highly, highly studied by particle physicists, and it's vastly smaller than the chances of electron-shell fields interacting. "

The term used by physicists to describe the ease that a particle is likely to be hit"

The Barn.

[Leo_Gnardo]

The term used by physicists to describe the ease that a particle is likely to be hit"

The Barn.

Right, as in "can't hit the side of a barn." Who says physicists don't have a sense of humor? And there they go, at CERN and Brookhaven and Fermilab etc. whacking together all sorts of particles. Must be fun! Photos of that accelerator gear, whew, that's impressive.

[trobbins]

They certainly know how to make a ccs with <1ppm tolerance - they should spin off that regulation scheme for hi-fi valve amp users - I'm sure some afficiando with enough cash would jump at the chance