Amplifiers, The Musical Sort

[Infamy]

I guessing there are a few people on here that have played around with amplifiers.

I have a hummer, but only when switched to phono, everything else is as it should be.
It hums away when nothing is connected no earth cable no turn table.
The problem has come to the point where it has to be fixed as I had a big pulse come through the speakers while playing a record recently.
Beyond ground loop and bad connections are there any components that could be causing this problem?

Thanks

[ivconic]

ground loops and bad cabling...
electrolytic caps in the phono preamp path can degrade over time, leaking DC or introducing hum...
high-value resistors (47k–100kΩ) in the input stage or feedback loop can become noisy or drift, causing hum...
... a sagging B+ rail or bad filter capacitor can manifest there first...

[Infamy]

Thanks that helps.

[ivconic]

Back in the old days... approximately when Jesus and John met on the Jordan River (I remember it like it was yesterday)... I was intensively involved in audio technology... some particle of memory remained.

[ivconic]

Let's clarify a few things (it's also useful for the topic of metal detectors)...
High gain stage issues,
the phono input amplifies the tiny signal from a cartridge (a few millivolts) up to line level (~1–2 V).
Because of this very high gain (40–60 dB), any small interference, ground loop, or bad shielding will also be amplified dramatically.
The standard 47 kΩ / 100–200 pF input is very sensitive to external noise.
A floating phono input (nothing connected) acts like an “antenna” and easily picks up hum from mains fields, transformers, or nearby electronics.
Turntables usually have a separate ground wire to the amplifier.
If this isn’t connected properly, you often get a loud 50/60 Hz hum.
Even within the amplifier, a poor ground path in the phono stage can cause noise.
The phono input is the most sensitive stage of the amplifier.
If there is hum or loud noise only there (and not on line inputs), the cause is usually grounding/shielding, a floating input, or failing components in the phono preamp.
I didn't deal too much with turntables in my life, but I did with guitars and guitar amplifiers.
What you described is a very common problem with guitars and guitar amps.
So I guess my analogy is not wrong.

[ivconic]

Ah this brings back memories!
How we the "socialist poor" used to try to become the Rolling Stones at the end of the 70's!
In the absence of money (money was not the problem, but the lack of technical goods in stores), and due to the great desire to play "electric" guitar; we used old tube radios as amplifiers!
It all sounded like wild cats in a sack but had a "natural distortion and fuzz" that was "in" and a big thing at the time!
However, if you do not ground such a radio well; suddenly in a second you get an afro hairstyle, just like Hendrix and your guitar sounds too psychedelic!
The rich rotten "west" used LSD and we "poor" did not use good earthing! (In the end, the effect is the same...)
Everyone manages as they know how!
What you consider a problem today; we considered it a good sound effect at the time!