Hum from a toroidal transformer

[Steven Holt]

I had the electrical system inspected a year ago, that's how I know it's not a grounding problem either.

That's good, but that's not what I'm talking about. I'm talking about a ground loop in the unit itself (and I would take a hard look at that chassis). Tell me, do you feel a slight 'sting' when you touch the unit when it's on?

 

[mhardy6647]

Do "we" know if this IFI "DC Blocker" is in fact a capable piece of equipment? I mean, I don't know...

EDIT: PS The simplest solution (still) appears to be a switchmode P/S "upgrade"!

 

[pjug]

Do "we" know if this IFI "DC Blocker" is in fact a capable piece of equipment? I mean, I don't know...

EDIT: PS The simplest solution (still) appears to be a switchmode P/S "upgrade"!

I assume you mean simple to change the amp + power supply component, not just the power supply!

 

[mhardy6647]

I assume you mean simple to change the amp + power supply component, not just the power supply!

I actually, honestly don't know -- something was said early on as to why a linear P/S...

 

[pjug]

I actually, honestly don't know -- something was said early on as to why a linear P/S...

I understand the amp is returnable so the easy thing is to get something else! Worth taking the hit returning to China and maybe there is a lesson somewhere in there. Don't mean to sound condescending -- I have learned my own lesson about buying gear from companies where returns are problematic.

 

[JSmith]

I actually, honestly don't know

Look, all I know is this talk of toroidal transformers is making me hungry...

If I take a leak near a high-voltage livestock fence, I’m not sure how much voltage it has, but I always make sure to keep a safe distance no matter what.

electric fences

Have you both seen the Mythbusters episode where this concept was tested on electric fences and even a HV rail line? Outcome was pretty much nothing in the end, as the stream of fluid wasn't constant enough, which could be seen when viewed with high speed cameras.

Mythbusters

n0tWorthy writes "The Mythbusters tested the myth that you could be electrocuted by peeing on the 3rd rail. The myth was 'busted' as the stream would be broken up due to distance and there wouldn't be a continuous path for the electrical current to follow. This seems to be refuted by a Monsanto...

science.slashdot.org

JSmith

 

[mhardy6647]

I love donuts.
But I digress.

 

[Angel II]

I never had a hum problem in my home until I bought an Atoll amp. Hum audible at the listening position ... My Hifi system has a dedicated mains supply so switched off everything else in the fuse box, amplifier kept on humming ... Installed a DC blocker, problem gone (https://audiosciencereview.com/foru...-to-help-stop-transformer-hum.948/post-874360). Replaced the Atoll with a Cambridge Audio amp (again with a lineair power supply) a year later, no hum problem without DC blocker (unless you put your ear against the speaker).

If the hum is audible from the listening position it is definitely a problem. My Atoll in80 signature I hear a slight hum when I put my ear close to the amplifier at 200 mm (absolutely negligible). I would say that it is physiological to hear a slight hum, but not further than 1 meter away.

 

[Maciekw]

PROBLEM SOLVED

Investigation so far has pointed to a faulty transformer as the reason for the hum.
To avoid playing with customs, instead of sending the amplifier back to Hong Kong for repair, I decided to replace the transformer myself.

Cymax sent me, at its expense, a new tested transformer. And after receiving it, I proceeded to replace it. It took me about an hour and a half, as I was forced to slightly modify the transformer shielding box. The new one was a tad bigger and did not fit on one side in the box.
As a precaution, I put pieces of damping mat on the shielding box.

And after screwing the case together, I turned on the amplifier with the new transformer.

It's SUPER! Zero hum from the transformer. ABSLOLUTE SILENCE!

And the amplifier itself is worth buying.

I hope that from my case CYMAX will start testing not only the electronics, but also, in the case of analog power supplies, whether the transformer does not hum.

On the other hand, I cannot recommend UPS as an international carrier. They are very greedy for your money. For the pickup of the transformer, I paid UPS its equivalent.

 

[Stereoed]

PROBLEM SOLVED

Investigation so far has pointed to a faulty transformer as the reason for the hum.
To avoid playing with customs, instead of sending the amplifier back to Hong Kong for repair, I decided to replace the transformer myself.

Cymax sent me, at its expense, a new tested transformer. And after receiving it, I proceeded to replace it. It took me about an hour and a half, as I was forced to slightly modify the transformer shielding box. The new one was a tad bigger and did not fit on one side in the box.
As a precaution, I put pieces of damping mat on the shielding box.

And after screwing the case together, I turned on the amplifier with the new transformer.

It's SUPER! Zero hum from the transformer. ABSLOLUTE SILENCE!

And the amplifier itself is worth buying.

I hope that from my case CYMAX will start testing not only the electronics, but also, in the case of analog power supplies, whether the transformer does not hum.

On the other hand, I cannot recommend UPS as an international carrier. They are very greedy for your money. For the pickup of the transformer, I paid UPS its equivalent.

I'm glad your hum problem is solved. What I noticed, though, is that the photos of the amplifier's interior don't show any measures to secure the cables. And the speaker terminals are soldered. Is that correct? I think these soldered terminals should have been insulated. I also hope they could have been crimped better, because a soldered joint unnecessarily increases the resistance. When did you buy the amplifier? Are you from Europe? Then, of course, a CE certificate would also be necessary. I don't see any CE marking.

Regards
Ed

 

[Maciekw]

I'm glad your hum problem is solved. What I noticed, though, is that the photos of the amplifier's interior don't show any measures to secure the cables. And the speaker terminals are soldered. Is that correct? I think these soldered terminals should have been insulated. I also hope they could have been crimped better, because a soldered joint unnecessarily increases the resistance. When did you buy the amplifier? Are you from Europe? Then, of course, a CE certificate would also be necessary. I don't see any CE marking.

Regards
Ed

I am from Europe. I purchased the amplifier directly from the manufacturer's website. The speaker cable connections to the terminals are soldered. I did not pay attention to the CE marking confirming (manufacturer's declaration) compliance with the required product standards. I don't really care about that in such simple devices as amplifiers. In terms of electric shock safety, everything is OK. Overall, I am very satisfied with the amplifier, especially since it offers exceptional value for money. And I have a lot to compare it to, given my long experience (over 40 years) in using audio equipment.
Best regards, Maciej

 

[transformer-coupled]

The "acceptable level" is up to you. And it seems that it's clearly unacceptable, to you.
Before you go all extra, external device fix hunting I would ask how far you have trouble shot this issue?
Can you lift the unit of the table and have the hum change or reduce in level? Have you tried placing the unit on some kind of foam
or even just a towel just to experiment?
Should cost very little and take mere seconds.

I would also state that it's entirely possible that the mounting bolt is loose. Mistakes happen, especially in high volume production lines where thousands of items are being made around the clock by low wage workers.
Don't rule out simple solutions until you have verified them.

Line DC or not, toroids can hum. When you purchase toroids raw from suppliers, at least reputable ones, they come with a rubber donut for mounting.
That donut is there for a reason.
It could also be that the mounting bolt is TOO TIGHT and is eliminating any noise damping compliance of the donut...
Or maybe there is no donut...

If you have determined not to send it back and are willing to open the chassis AND are comfortable doing so you could investigate the mounting bolt and perhaps
adding more cushioning under the toroid.
Obviously, only do this with the unit unplugged and only if you know what to look for.
If you are not comfortable opening the unit you will indeed be relegated to upstream devices.

Hi
Just received my Cymax purifi all linear power supply yesterday, more details here https://www.audiosciencereview.com/...-dual-mono-power-amplifier.58351/post-2487853 and had no noise at all, i use balanced but i know you mean about vibration noise coming from chasis and have to say it almost never hum but obviously with a 700w around power transformer sometimes , i have since 24h but i had only a slightly hum just a seconds somentimes it seems my zone alternating current is contaminated of dc sometimes but luckly is only 2% of time and very few. Have to say im a maniac of noise free devices, my wall clocks are all digital to avoid mechanical noise, i refurbishing a lot amplifiers because hum at box or hiss at speaker closely but it is not this 1et400a purifi all linear power supply , perhaps our models are diferents.
I advise you you use a dc blocker like there is some hifi brand sell.
Perhaps its my transformer based passive resistor-less preamp that isolates the power amp from any dc coming from dac etc
Good luck
Anyway i wouldn't trade our linear power supplied purifi amplifier by any vtv or nord or audiophonics smps-based class d amp which subjetively and not cientifically proof but in my opinion smps-class-d sounds sterile as a cold hospital.

 

[transformer-coupled]

PROBLEM SOLVED

Investigation so far has pointed to a faulty transformer as the reason for the hum.
To avoid playing with customs, instead of sending the amplifier back to Hong Kong for repair, I decided to replace the transformer myself.

Cymax sent me, at its expense, a new tested transformer. And after receiving it, I proceeded to replace it. It took me about an hour and a half, as I was forced to slightly modify the transformer shielding box. The new one was a tad bigger and did not fit on one side in the box.
As a precaution, I put pieces of damping mat on the shielding box.

And after screwing the case together, I turned on the amplifier with the new transformer.

It's SUPER! Zero hum from the transformer. ABSLOLUTE SILENCE!

And the amplifier itself is worth buying.

I hope that from my case CYMAX will start testing not only the electronics, but also, in the case of analog power supplies, whether the transformer does not hum.

On the other hand, I cannot recommend UPS as an international carrier. They are very greedy for your money. For the pickup of the transformer, I paid UPS its equivalent.

didnt read this wonderful!!!!

 

[transformer-coupled]

PROBLEMA RESUELTO

Las investigaciones realizadas hasta el momento han apuntado a un transformador defectuoso como la causa del zumbido.
Para evitar jugar con la aduana, en lugar de enviar el amplificador a Hong Kong para su reparación, decidí reemplazar el transformador yo mismo.

Cymax me envió, a su cargo, un transformador nuevo y probado. Tras recibirlo, procedí a reemplazarlo. Tardé aproximadamente una hora y media, ya que tuve que modificar ligeramente la caja de protección del transformador. El nuevo era un poco más grande y no cabía en un lado de la caja.
Como medida de precaución, coloco trozos de material amortiguador sobre la caja de protección.

Y después de atornillar la carcasa, encendí el amplificador con el nuevo transformador.

¡Es genial! El transformador no emite ningún zumbido. ¡Silencio absoluto!

Y el amplificador en sí vale la pena comprarlo.

Espero que desde mi caso CYMAX comience a probar no solo la electrónica, sino también, en el caso de fuentes de alimentación analógicas, si el transformador no zumba.

Por otro lado, no recomiendo a UPS como transportista internacional. Son muy codiciosos con el dinero. Para la recogida del transformador, pagué a UPS el equivalente.

Yeah this amp is worthy , i was from years mising my hypex ucd amp with linear power supply which i sold because was almost perfect dynamic clean, linear... but lacks detail and resolution. Ncore smps based was as purifi smps based sterile as a cold hospital room in winter so didnt work either for years i used tpa3255 pffb which is nice but lacks the dynamics and current headroom of ucd all discrete linear powerr supply.... till i discovered this , all the benefiocts of ucd linear psu based with resolution of topping b100

 

[Dave Bullet]

My Cambridge 840w hums at home. I took it to the local university for a listening session and there was zero hum. I blame my AC at home being contaminated with DC. I tried an ifi DC blocker and it did nothing. So I just accept it