"Rattling" sound in tube combo, at higher volumes

[Erlend_G]

So, I cranked my Blackstar just now,
and when the master volume went over 12'o clock, I was annoyed with a rather loud "rattling" sound,

best described as if you put grains of rice in a light bulb, and shook it.

I guess it's one of more of the tubes, being microphonic.

Is this considered "normal" and just something one has to live with, or do I need to replace the "faulty" tube(s) to get rid of it? :o

-Erl

[Erlend_G]

Another thing, that both concerns, and annoys me- is that this amplifier (Blackstar HT-20mkII) is NOT loud, for 20 watts.

I can crank it on a speaker stand, having the speaker face my ear- and not find it anywhere "loud" at all. Is there some way the amp can be faulty, and because of that, not produce alot of volume?

I know that 20 watts isn't alot, but my uncle's Fender Blues Jr. seems to my ears, to be twice as loud as my Blackstar. :/

-E

[Mincer]

I've used a lot of old Fender tube amps that make all sorts of rattling noises when cranked. That is part of their charm. But I wouldn't think it is right for any modern amp.

[JB_From_Hell]

Make sure all the screws/fasteners are tight.

[GuitarStv]

Make sure all the screws/fasteners are tight.

Yes, this. Stuff works loose over time, and low frequencies will rattle if there are any two hard things in close proximity that are able to move at all.

[beaubrummels]

So, I cranked my Blackstar just now,
and when the master volume went over 12'o clock, I was annoyed with a rather loud "rattling" sound,

best described as if you put grains of rice in a light bulb, and shook it.

I guess it's one of more of the tubes, being microphonic.

-Erl

Yes, microphonic V1 tube. Replace it with a 'low noise' one with smaller plates.

[NegativeEase]

Glad you found it -but to everyone's points -regularly tighten the chassis screws and speaker mounting screws or a top end buzz will follow at high volumes....

I do it several times a year, if it leaves the house for gigs -and maybe once a year otherwise.

[ehdwuld]

you could try wagging your finger at it in a disapproving manner

and chastising it by saying "Baaaadddd Tube, Baaadd"

that may make you feel better about it

[beaubrummels]

I feel like everyone has focused on the word 'rattle' and ignored this description: "best described as if you put grains of rice in a light bulb, and shook it."

Obviously I'm not there to hear it, but that is precisely the sound of a microphonic tube IME.

[Ewizard]

I second/third the microphonic tube assessment as well.

Combo amps are particularly subjected to LOTS of shaking, rattling, and banging around! This is hard on the amps internal parts and the tubes. When you are playing at performance level, the chassis is vibrating like crazy and the tubes vibrate too. The rattling ( rice shaker ) sound you are hearing is likely a tube having its guts shaken, and you can generally sus out a microphonic tube by tapping it with an implement of some sort while the amp is on. If you can hear the tink, or the subsequent disruption of the tube's internals when you tap it, the tube is microphonic.

As to the low volume, it is possibly a bad phase inverter tube, but any tube that is directly in circuit that has drifted in performance can also cause low output. V1 isn't always my first suspect if the volume is low because you would then also notice a lack of distortion from the preamp. I.E. you have to crank the gain up a lot to get any real distortion. Since each gain stage will buffer the last one at the very least, the most common low volume problem is from the PI tube not driving the power tubes hot enough. It may also just be that the power tubes are worn out, or the bias has drifted low ( A high probability with Factory amp setup and older tubes ).

The easy way is to do some tube swapping with a known good tube or to move the tubes to different positions to see if the problem persists. If you take the PI tube and swap it with V1 for instance, you should get your volume back, but you may have lower distortion from the gain knob, for example. Or if you have a good tube, simply replace it into each position until the problem goes away. As for the power tubes and their bias, you need to know a little more about amps to figure out if they are the issue. I can look at a tube while it's working and tell you if it is biased cold or hot, and if there is an adjustment knob, I can get the bias set by ear and be within safe limits every time, but I can't explain how to do it. In my 20+ years of working with tube amps, I just sort of learned how to hear and see where the tubes want to be biased at.

Sometimes, the FX loop, if it is in the circuit ( like in an Egnator Tweaker or Soldano SLO ), can cause low output if the contacts are bad. If the contacts are dirty enough can still pass signal, but can cause issues. This can usually be figured out by inserting a cable into the in and out of the FX loop to try and clean the contacts up a little. If this solves the issue, then of course a thorough cleaning of the contacts is in order.

I wish you the best of luck. I would start by doing some tube swapping. Keep track of what went where. Work out the problem by only doing one thing at a time, not all at once. You want to know where the problem was, not just fix it willy nilly.

[Erlend_G]

Thanks alot for the replies, guys!

I'll be ordering a full set (to be sure) of replacement tubes this month;

ask the dealer to get a set that works well with my amp.

...

I'm thinking about trying the "tapping the tube with a pencil" trick, to see what tube(s) are gone bad.

But still ordering a complete set. It can sit in my drawer until needed.

thanks alot

-Erl

[Adieu]

Tubes, speaker, loose jacks, whole dang enclosure... anything could be the source of your rattle in a cheaper combo

You could always shake it and see or even poke around to see if anything wiggles (unplug and discharge first)

[Erlend_G]

I'll take a good look at it, "everything", when I get my mood and energy levels up.

(been fighting some evil entities, and my own sins, lately...)

But it's important to keep amp & guitar in proper working order! .

I'll order a complete set of replacement tubes from a good website, I got my welfare today.

thanks again

-E

[esandes]

I had a combo bass amp that rattled and it turned out to be the bearings in the casters.

[Demanic]

I can recall searching for a rattle. Long story short, the drummer had left his sticks laying on top of his floor tom after the last time that we had played.

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