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The demonic nightmare of hum

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Graham Slee View Drop Down
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    Posted: 30 Jan 2021 at 8:24pm
I spent the first two weeks of my first separates system learning about 5-pin DIN cables because my cassette player wouldn't make a sound. While doing that, I was frustrated with hum from my turntable. Basically, I couldn't enjoy the great benefits of stereo sound - of owning a separates system. Mum's old record player was light-years better!

Sounds similar? I was 18. I am now 65.

Although I had bought what turned out to be a crappy Amstrad amplifier, it wasn't the amplifier's fault that I'd bought the wrong 5-pin DIN cable. It wasn't the amplifier's fault that I was getting loud hum. It was the turntable manufacturer's fault for earthing the turntable metalwork to the earth pin of the British three-pin plug.

Since then, I've been on a hum journey, which, like a recurring nightmare, raises its ugly head every few weeks. I once thought of writing down every occurrence of hum I'd ever stumbled across as a user-reference but realised it might eclipse War And Peace for the number of pages required.

After covering all the "normal" causes with numerous customers and tragically failing, I realised the old devil called satan had duplicated himself into an ever-increasing battalion of hum demons. No longer did the correct wiring technique cure the problem, but they'd brought back valves (tubes). Those people were often Chinese with no understanding of vinyl due to the cultural revolution (I am not being racist here - a Chinese man said it).

The cellphone also lent a hand to the demons, so did the DECT phone. We also had microprocessor washing machines causing toroidal transformers in amplifiers to audibly grumble.

But worst of all, we had a new breed of amplifier designers who didn't understand how to internally ground the circuitry to prevent hum loops, but that didn't matter because vinyl was dead, and CD didn't suffer from it. The reason for that is the cartridge signal is a few ones of a millivolt, where the CD signal is a full volt (or thereabouts). A few one's of a millivolt of hum isn't noticed compared with CD's output, but swamps that of a record playing cartridge.

They stopped teaching magnetism in schools, and boys learned cooking instead, so we don't understand that wires wound tightly in a bundle (like in a cartridge) when placed in a magnetic field, output a voltage. Suppose that the magnetic field is alternating, caused by the proximity to inductive things such as an amplifier's transformer or even the turntable motor. In that case, the noise is easily induced into the cartridge's windings.

We can fire off interference from light dimmers and electronic transformers for halogen lighting and inject hum that way too.

We can unwittingly buy an unstable amplifier, or preamp, or phono stage because a non-technical reviewer opined about it. The interference from frequencies beyond human hearing - radio waves - can easily cause such circuits to oscillate at frequencies, again, beyond human hearing, and "detect" raster frequencies of anything from 50 - 100 Hz - hum again!

Even the cartridge wires inside the arm, like all wires, are inductive, which means they will pick up such noise. So then, a clever mechanical engineer makes a tonearm from carbon fibre. Everybody says Yay! I don't. What shielding does that offer? None.

But if that wasn't enough, the millionaire boutique cable companies make unshielded cables, which are a superhighway for noise injection. Then I hear "but it says it's shielded" only to discover it is mechanically shielded, but not electrically shielded. Do these marketing guys know no bounds?

The demonic nightmare of hum.



That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Sylvain View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Sylvain Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2021 at 6:02pm
Thank You for this  ...you have uncovered what has been nigling for some time .......the subject is much argued from people who have a commercial product to offer a cure and at very premium price sometimes MUCH higher than  the components but  '' hum hum hum ....had entered my head for many years now but it is not part of the Music despite what Spotify tells me 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote patientot Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2021 at 11:45pm
The dealer I buy my record cleaning supplies from sends me catalogs multiple times a year. In the back pages they push unshielded RCA cables very heavily from a certain brand. They don't come cheap either. 

I live near a number of radio and TV stations so I am quite paranoid about putting anything into my system that would act as an antenna or a source of interference with another component. 
SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 Feb 2021 at 5:50pm
Hum and interference are really irritating, unlike background noise you know it is something in your setup which makes it more frustrating. Worse when you find it is a dud product or worse still a deliberate flaw most reviewers forget to mention.

However, I had not thought of it as a demonic nightmare or presence till now... I see Graham's point.

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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