What is causing this weird distortion coming from my amp?

Question

Here is the sound I'm talking about.

I get this sound, unless I strum ridiculously lightly, on different amp volume settings, with no gain, but is seems to become quieter if I turn pick volume knobs below 50%. The worst part is that with gain it sounds completely horrible.

I don't remember when this started exactly, but I think I remember something similar happening on and off last year. Now it appears to be permanent.

I've already tried asking about this on reddit and got suggestions to try with another guitar and another cable.

Another guitar was not available, but I tried hooking it up to an electric keyboard. Here you can hear me playing it, while adjusting the keyboard's volume knob.

I hear some distortion starting on medium volume, but am not sure, if that's just because of incompatibility to guitar amp.

I've also tried hooking up the amp to a computer, using the 6.3mm guitar cable and a 3.5mm cable, and playing some sounds on the computer while tweaking volume on both devices. I've noticed no distortion during those tests.

The amp is a B.B. Blaster.

Update

Based on the suggestions, I've tried playing in another room and with headphones. I could hear the distortion in both cases, headphones actually made it more audible. Additionally, I've checked the speakers and noticed a lot of dust behind the grills. I removed the dust, but the distortion didn't disappear. Didn't notice any other foreign objects.

Sometime next weekend I'm going to try and test the guitar and cable on another amp. Will post about the results.

Update2

So, I wasn't able to free some time last weekend, but I brought the guitar to a music shop yesterday. When the shop assistant plugged it in and started playing, there was none of the familiar distortion noticeable. I gave him the cable I was using to try with it. There was a noticeable signal loss, but still, no distortion.

I bought a new cable and tried playing with it after coming home. The distortion is still there. So, I guess the amp appears to be the most likely suspect now. I'll be bringing it to the store next week.

Update3

I brought both the guitar and the amp to the store. After plugging them together with a store cable I was able to reproduce the sound. What I understood from the assistants' explanation, the problem was with the amp's construction, it has got a peak volume, beyond which it can't go without the sound.

Answer 1

Basic troubleshooting demands isolation and substitution. You need to do some homework before anyone can render a meaningful answer. Here is your assignment:

1) substitute the guitar with another electric, do you get the same result?

2) if not, substitute the guitar cable, do you get the same result?

Now if you don't get the same result in the first test, this means the problem is likely the guitar. Now try this guitar on another amp, does the problem follow the guitar?

Likewise with #2, does the problem follow the cable?

The following is speculation:

If the problem is coming from this amp, I would take it to an amp tech and have him test all the electrolytic capacitors as these dry up over time (5 - 10 years) and then become less efficient. Electrolytic capacitors are generally used in a guitar amp power supply to filter the AC component of the DC voltage hence when not working correctly will add more hum and possible distortion to other components down the line.

Other amp related items: check your speaker, substitute a like size with same ohms and see if this is the issue, this could be a bad voice coil. Check to see that nothing fell into the speaker area, something that might rattle at higher volumes, or something that fell inside the amp (sympathetic vibrations from an alien object).

If you can isolate this to the guitar, perhaps the pick ups are adjusted too close to the strings.

Again, all speculation until you can isolate it.

UPDATE: One more test. Have you tried playing the same amp, same guitar, and same cable in a different room? Rare, but sometimes something in the room vibrates, or going to a different outlet may make a difference? Yes, it's rare but I want to cover all the bases.

Answer 2

My best guess says you have earthing problems. Try using a different power socket!

Answer 3

First, I'm assuming that your gain isn't cranked while your volume is up.

Second, connections can be bad. I'd first try turning knobs (normally volume or gain) and seeing how that affects the crustiness. If it goes away, you probably have a dirty contact in the know and you can try cleaning or replacing it, or (if you're lazy as I am) turning it a bunch to try to clean it.

Third, maybe a loose wire contact. I'd try to determine whether the distortion is affected by motion/vibration/gravity and that may help. If this is the case you'll then need to pinpoint it by opening the amp and poking around (carefully).

Lastly, and this is a bit desperate by now, there could be a bad component. The surest way to determine that is to have a schematic and a multimeter and probe inside checking.

Good luck, whatever it is.

Answer 4

factory solder baths are not the best solder joints and when you add the vibration of the high volume sound which also vibrates the printed circuit board inside the amp, the solder joints mechanically break down after a period of time. I suggest have a repair tech clean and re-solder all the joints.

Answer 5

When you state "with no gain" and this means the gain pot being at 0, you shouldn't be hearing anything really. If you do, this can mean that the ground line from the gain pot got loose and/or has a bad solder joint. In that case, the gain control will just put a variable resistance in the signal path which amounts to some change but not all that much. It would still be comparatively simple to overdrive the input stage.

Answer 6

First of all I wanted to say thanks for this discussion thread. I was having the same sound issue. My fix had to do with the pickup height. I'm using 10 gauge strings on a new Jackson SLX with installed hot rod JB/Jazz neck humbuckers and assumed 2.4mm was a fine height for the bridge. For some reason this guitar resonates in volume a bit more than what I'm used to. Ended up having to lower the bridge pickup to a little over 4.0mm and it sounds perfect now.

Answer 7

You must be having some preset or effect turned on (sometimes the problem can be very small but hard to figure out). I had a rock preset on my one which gave a distorted sound when I strummed my strings heavily with gain turned to 0 and volume set not more than 30%. I hope this resolves your problem.

Answer 8

I am joining an older discussion since it represents well an issue I had with a Made in UK Marshall AVT20. A small big and great sounding valve pre solid power amp. 1 channel with drive and volume + switch to select clean and dirty. You can easily find details and the schematics on line. the volume difference between clean/dirty is a known difference I could not tame even tikering with the design of the distortion path (changing resistors) or by substituting the aggressive 12ax7 with a 12at7 or even a mild 12au7 though it helps in reducing the melting in your face effect and gives to me much more usable sounds. The problem: with dirty switched on only, even with drive at zero, a not so faint distorted and clipped sound was following note by note same octave the input. totally annoying and spoiling the usefulness of an otherwise very pleasant and loud portable amp. because of the design it was evident that some input signal after the muscolar "dirty" treatment can bleed to the power amp. But the raspy, clipping distortion? I spent on no-hints checks a lot of time. Than I decided to change - in a desperate attempt- the double Op TL072 more on the fact that the false sound was remembering of a clipped one. Well' it worked. a faint clean sound is stll there a zero drive and max volume but it totally mix in and disapoear with the direct amp sounds without any annoyance. 0.70 eur cost.