Preamp Valve gone in ‘hissing’ amp?



Asked by: Megan Evans

Why is my amp hissing?





More often than not, when your amp is making a humming sound, it’s caused by dirty power, a bad ground connection, or fluorescent lighting. Below are a few things to consider when dealing with this pesky hum.

How do I know if my preamp tube is bad?

A bad preamp tube will become very noisy and produce hiss, crackle, and pop sounds, or create volume drops or loss. In some rare conditions, the tube can also lose its vacuum and fail completely.

What is a preamp valve?

Rectifier valves are used in power supplies to help with the process of turning an alternating current into a direct current. Preamp valves and power amp valves both increase amplitude – in other words they turn low-level audio signals into higher-level audio signals.

Why is my amp making a high pitched noise?

The higher pitched and more irritating ‘buzz’ is typically found emanating from the loudspeakers and is usually caused by a ground loop. The most common cause of hum is the ground loop – fortunately it is also the easiest to solve.

How do you remove hiss from an amp?





To mitigate speaker noise due to amplifier gain, try setting the gain stages correctly and match the speaker(s) to an appropriate amplifier. Oftentimes the amplifier is built into the speakers and is the only gain stage between the audio device and the speaker. In this case, turning the volume down is a good idea.

How do I get rid of hissing in audio?

Click the effect controls tab and twirl the effect open by clicking the arrow to its left. There you'll see a bypass checkbox.

How often should preamp tubes be replaced?

2 – 3 years

Preamp Tubes are generally at their best 2 – 3 years. Power Tubes are generally at their best 1 – 1.5 years. Rectifier Tubes are generally at their best 3 – 5+ years.

Can bad preamp tubes cause volume loss?

Use the wooden part to tap each of the preamp tubes and main power tubes. A good tube will be a dead ‘thud’ sound, so if you hear one that has a high ringing rattling sound, that’s the bad tube. Bad tubes will make volume drop and tone sounds will be dulled. When a tube goes bad, this is exactly what happens.



How do you test a valve tube?

Put the tube into your guitar amplifier, tester, or other tube-using machine. Turn on the machine to activate the tubes, and look for an orange, red, or purple glow. If the heated filament inside the tube glows orange like a setting sun, it’s usually a sign that the tube is healthy. The filament may be hard to see.

Why is my amp making a whistling noise?

sounds like microphonics(aka strange noises) in the preamp tubes. microphonics can be from unshielded preamp tubes(a little unlikely) or from a preamp tube going bad(more likely). newer preamp tubes don’t go through the QA like they did back in the day, so duds aren’t uncommon.

Why is my bass amp making a high pitched noise?

Spinnerweb It sounds most like shoddy electrical wiring. Or rather, you’re just getting interference from other appliances.



How do you fix an electrical ground loop?

Now I've seen people recommend removing the ground pin or using a ground lift plug on one.

What does ground loop sound like?

Ground loops can appear when there are two or more devices connected to a common ground and can sound like a low frequency hum, similar to touching the end of an instrument cable connected an amplifier. This typically happens when you are using a stereo guitar rig with two grounded amplifiers.

How do you check for ground loops?

To test for ground loop:

  1. Set your volt meter to the most sensitive AC setting.
  2. Disconnect the camera you want to test.
  3. Place one contact on any exposed metal of the chassis. …
  4. Place the other contact on the outside of the connector on the coax from the camera.
  5. Any value above 0 indicates a ground loop.

Why do ground loops cause noise?

When a ground loop occurs, the cable’s ground conductor (often the shield) ends up carrying both the audio ground and hum/noise caused by power flowing through the ground connection.



How do I stop sound in ground loops?

The ground loop can be eliminated in one of two ways:

  1. Remove one of the ground paths, thus converting the system to a single point ground.
  2. Isolate one of the ground paths with an isolation transformer, common mode choke, optical coupler, balanced circuitry, or frequency selective grounding.


What is a ground loop problem?

In an electrical system, a ground loop or earth loop occurs when two points of a circuit are intended to have the same ground reference potential but instead have a different potential between them.