Audible diode noise (?)

[WhopperPlate]

I am noticing a certain audible buzzing that can be heard seemingly directly from the power transformer/rectifier itself on several of my amplifiers that use 1n4007 diodes. This is not coming through the speaker, it is heard before the standby switch is flipped.

If I disconnect the rectifier from the circuit it goes away entirely

I do not hear this on my amplifiers using a square bridge type rectifier . Same brand and model transformers in each amplifier fwiw

Just trying to learn and understand…Has anyone shared this experience?

[xtian]

I've heard ABOUT it, but never experienced it in any of my builds (and I'm pretty sensitive to wayward noise in my builds). Some solve the problem with 100n caps across each diode, and another common solution is fast-switching diodes like UF4007.

[WhopperPlate]

The amps in question actually have 100n snubbed caps across the 1n4007.

In the past I have always used NOS diodes or modern 1000 v 25 amp bridge rectifier. It just so happens to be two of the amps that use 1n4007 that are audibly noisy . Again this is not through the speaker , but directly from the components themselves , at least that’s how it sounds

On a possibly related note, I have have been dealing with some significant intermittent 60 hz buzz that inconsistently fluctuates with the time of day and weather. The rectifier buzzing sounds just like the same 60 hz buzz, and I can actually hear it intensify during a storm with strong gusts of wind .

I figure it’s probably a combination of old power lines and a weak ground. I also live 1700ft from a 10000 watt radio tower , so when it gets bad it gets real noisy . I have brought the amps elsewhere and they are not noisy. I am about to have an electrician come out and I will discuss a dedicated ground rod installed to attach to my shop circuits…

I digress , it just seems worth mentioning in context. Maybe these parts are less tolerant of this grounding issue than others

[trobbins]

Perhaps best not to point the finger just yet. Do you have a link to a circuit schematic?

The schematic and your observations may indicate a few plausible concerns such as the parallel caps, and diode leakage, and humidity tracking - a bit too soon to really scope out the options.

Are you competent to make any measurements or do any electrical work?

Ciao, Tim

[WhopperPlate]

All measurements throughout multiple amplifiers check out

The 60hz buzz is a seperate issue that plagues all my equipment, whether I made it or not like I said the rectifier noise is audible without speakers

I have heard this before in other amplifiers I worked on, and they had 1n4007 as well now that I recall.

As far as it being related to the 60hz ground buzz I am dealing with in my home it seems very plausible , but like I said my amps without the rectifier noise are just as buzzy (intermittently) l. The rectifier noise doesn’t seem to impede the amplifiers performance in any drastic way afaik , but I am curious to learn the mechanisms of what I am hearing

[trobbins]

Does that mean you have used some of your amps (with the 1N4007's) in other houses/regions and there is no issue?

Can you confirm it is audible with the Standby off - and what the general circuit schematic being used is ?

Did you build all these 1N4007-based amps, or are they commercially made?

[TUBEDUDE]

A schematic will help.

[Stevem]

Please move!
It’s not just your audio gear that’s effected and infected by that transmitter near you, but your body also!!

[WhopperPlate]

Thanks everyone , I kinda veered away from the original question about the specific rectifier noise , but I have some updates that shine some further light overall .

Stevem, while I genuinely appreciate the concern , and have shared it myself, until I am blessed with that opportunity I am making lemonade.

Today my buddy and brought a few amps over to his house to investigate the differences. The 60hz buzz is absent at his home with all other amplifiers, even with single coils. The specific physical electrical noise/vibration emanating seemingly from the rectifier (audible with standby ON) remains.

To reiterate: though its unique to those amplifiers with 1n4007 diodes in the rectifier it does not manifest in the audio path and isn’t correlated with more noise , so it’s not presenting itself as problematic, it’s ultimately just intriguing to myself.

However , the 60hz hum/buzz is far more of a hinderance, which is location specific : my shop.

Returning there and testing further, at the same settings the 60hz hum/buzz is more audible WITH OR WITHOUT a guitar plugged in, of course no where near as bad with a guitar. Humbuckers buzz here far worse than single coils at my friends house.

possible conclusions at this point:

1) weak house ground
2) dirty neighborhood electricity
3) EMI from multiple construction sites , nearby neighbors electronics, Radio tower
4) all of the above

I mentioned the radio tower previously, but I tried installing the RF leak caps on the input and it didn’t effect anything, so I have assumed it’s electrical at this point, but I personally can’t dismiss anything.

I also turned off every breaker except the shop circuit. No change.

FWIW I am plugged into a ETA power conditioner and a ISOBAR power strip. They make no discernible difference.

Also fwiw these are simple Marshall type circuits and layouts . Nothing fancy .

[WhopperPlate]

SteveM

You know Dumble lived a little bit farther away from the same towers in the 70s, maybe that’s why he moved lol

Jk I don’t know

[CraigGa]

I have some experience searching for noise sources that interfered with broadband services.

The radio tower is unlikely to be the problem, the most likely source is a switch mode power supply or a dimmer. The best technique is to use a battery powered AM radio tuned off station at around 200khz, you should hear a loud buzz.

Switch off all the breakers one by one until it goes quiet, then put the noisy breaker back on and switch off everything on that breaker one by one until you find the offending article.

We often found that the faulty appliance didn't power up again afterwards which sometimes got us into trouble ("well it was working until you turned up!").

At a push you can use the car radio if you can get it near the shed.

Craig

[brewdude]

Are you sure it’s not the power transformer humming?

[gktamps]

You hear this when plugged into any receptacle?
You've used a stethoscope or tube to isolate the noise to the rectifier diodes?
Tried touching them with chopstick while hearing noise?
Old house? Is neutral tied to ground buss bar in service panel?
Are hot and neutral reversed?
Did you test for DC riding on the AC line?
Spiky AC?
Bad ground? We had a dodgy ground at the service panel - new ground rod, clamps and wire helped.

[sluckey]

When I was in tech school back in the '60s, our class went on a field trip to visit a 50KW AM radio station. The thing that impressed me the most was our visit to the tower. The entire tower is the antenna. And you could hear the radio broadcast music playing in the tall grass. Very vivid memory. I barely remember the transmitter electronics. Funny how this topic triggered that memory.

You don't have any grass stashed in that amp do ya?

[WhopperPlate]

Thank you all for the advice!

Sluckey, no grass in my amps …what would give you that idea ?

Scoped the AC, it looked smooth and even. No spikes

taking CraigGa’s advice and using the AM radio trick I found at least one pesky house circuit inducing noise… even without any electronics plugged into 120vac…no noisy electronics to speak of as far as I know.

In fact there is only one circuit in the whole house that doesn’t induce further noise , and it’s not my shop circuits lol .

Old House grounding has always been suspect. the plugs for the shop circuits check out safe on a plug in meter , but a few other house circuits are open ground.

Electrician coming tomorrow. I am hoping the solution is something as simple as a grounding stake or two. From reading other posts I am thinking a dedicated ground rod for the shop Circuits. I hope the old electrical doesn’t open up a can of worms .

Thanks again for the advice everyone