Loud static white noise on new SV20H

[Bewlay]

I flicked the standby on my SV20H today only to hear very loud continuous white noise. This is with no guitar plugged in.
Turning the High Treble volume up makes the noise unbearably loud and the noise is gone with that volume down. The normal volume has a tiny bit of the same noise at max vol.
The amp is very new and, as Nigel would say, "still has the little tagger on it."

I'd say I've turned it on 10 or 12 times in total, it has never left the house, although, when I play it, I pretty much crank the 5W to full volume for brief periods, without an attenuator.
Because it's so new, I'm even afraid to take the back off and investigate. Why would this happen to an amp so new?

Things I've tried: different speaker cab, speaker cable, house socket, mains lead.
I've left it on for a while now at low volume and that noise ain't going anywhere.

I can't lay my hands on the manual right now even though I know it's somwhere in the house. Basically I'm looking for the warranty info.? Does anyone know the story there or, if I need repairs, should I contact Thomann where I bought it?

Any suggestions for what could be going on, greatly appreciated. Cheers.

 

[paul-e-mann]

I flicked the standby on my SV20H today only to hear very loud continuous white noise. This is with no guitar plugged in.
Turning the High Treble volume up makes the noise unbearably loud and the noise is gone with that volume down. The normal volume has a tiny bit of the same noise at max vol.
The amp is very new and, as Nigel would say, "still has the little tagger on it."

I'd say I've turned it on 10 or 12 times in total, it has never left the house, although, when I play it, I pretty much crank the 5W to full volume for brief periods, without an attenuator.
Because it's so new, I'm even afraid to take the back off and investigate. Why would this happen to an amp so new?

Things I've tried: different speaker cab, speaker cable, house socket, mains lead.
I've left it on for a while now at low volume and that noise ain't going anywhere.

I can't lay my hands on the manual right now even though I know it's somwhere in the house. Basically I'm looking for the warranty info.? Does anyone know the story there or, if I need repairs, should I contact Thomann where I bought it?

Any suggestions for what could be going on, greatly appreciated. Cheers.

Do you have any spare tubes? Replace them one at a time until you find the bad tube.

 

[Bewlay]

Do you have any spare tubes? Replace them one at a time until you find the bad tube.

Are you talking power tubes or pre-amp tubes? I think I have both although I'm not sure what condition the power tubes are in. They're not new anyway and I don't know anything about biasing for power tube replacement.
I assume, though, opening the back will void my warranty on the amp, if I have one.
I had a look at the receipt and I bought the amp at the end of June last year. Beacuse I've been using other amps for gigs and I've been away a bit, I'd say the amp has had less than 4 hours playing time in total.

 

[Pete Farrington]

Any valve can fail anytime, that’s why they need a warranty and valve amp users need spare valves.
I think these 20W amps have cathode biased output valves (?), so provided your spare ones are functioning, you should be able to swap them in.
You’ll need to check whether accessing the valves will affect the amp’s warranty. It would be crazy if it did.
The safest thing might be to swap the amp for a new replacement, but then you’ve got packing and shipping to deal with.

 

[Central Scrutinizer]

Marshall manuals are available online, just go to the Marshall website, click on your model. At the bottom of the individual model page , just click on the manual button.

Yes the Studio series amps are cathode biased.

You should have a 5 year warranty from Marshall, at least we do here in the States. Thomann has a warranty as well I believe.

Good luck.

 

[paul-e-mann]

Are you talking power tubes or pre-amp tubes? I think I have both although I'm not sure what condition the power tubes are in. They're not new anyway and I don't know anything about biasing for power tube replacement.
I assume, though, opening the back will void my warranty on the amp, if I have one.
I had a look at the receipt and I bought the amp at the end of June last year. Beacuse I've been using other amps for gigs and I've been away a bit, I'd say the amp has had less than 4 hours playing time in total.

Its a self biasing amp. Start with the preamp tubes one at a time, if the problem still persists move on to the power tubes. The amp has a 5yr warranty the tubes probably not, dont worry about the warranty.

 

[Bewlay]

Thanks for the responses. I didin't realise it was a self biasing amp. I mean I'm sure I did at some point but I must have forgotten!
Thomann has a 3 year warranty so I got in touch with them and sent them a video of the noise. I'll wait to hear back before I open it up.
I've been rehearsing & gigging with Vintage Moderns for years without any tube issues/ replacements so I was really surprised to hear this problem so early in the amps life.

 

[Gene Ballzz]

@Bewlay ,
Did the amp just suddenly start making this "very loud continuous white noise" or is it possible that it has always been there when the High Treble Volume is cranked? I own an SV20H and while I wouldn't call "the noise unbearably loud" there is certainly a surprisingly fair amount of white noise hiss with that channel fully cranked! From most reports I read, this seems somewhat normal, although many of those reports claim that different tubes can affect how loud that hiss tends to be. I do run that channel dimed, most of the time and simply tolerate the hiss in exchange for the glorious tones achieved!
Just My Experiencin'
Gene

 

[ido1957]

I returned a DSL20C combo 3 years ago because the hissing/wind noise was unacceptable. Makes me wonder if the same issue was incorporated in your amp. The tech at the store had 6 of the same unit on his bench and received notice from Marshall that is was "working as designed". I eventually bought a Katana with the refund I received. Sad because the unit had the sound I wanted (I was downsizing from a JCM900).

 

[Bewlay]

@Bewlay ,
Did the amp just suddenly start making this "very loud continuous white noise" or is it possible that it has always been there when the High Treble Volume is cranked? I own an SV20H and while I wouldn't call "the noise unbearably loud" there is certainly a surprisingly fair amount of white noise hiss with that channel fully cranked! From most reports I read, this seems somewhat normal, although many of those reports claim that different tubes can affect how loud that hiss tends to be. I do run that channel dimed, most of the time and simply tolerate the hiss in exchange for the glorious tones achieved!
Just My Experiencin'
Gene

Yep just stared happening. It rivals the volume of the guitar at any place on the dial. Previously, I'd been using it cranked and certainly there was a bit of noise there but exatly what I would expect from a cranked bright tube amp.
No, this new noise is unbearably loud and actually was getting louder/ worse as I messed with it yesterday. Something's not right.

 

[Bewlay]

Just giving an update on this....I replaced all tubes individually and it made no difference at all. I only had one spare pre-amp tube lying around so I replaced each one separately.
I replaced both power tubes together. So unless two or all three of the pre-amp tubes are gone at the same time resulting in the exact same sound, (which would be odd, right?) there is something serious up with the amp.
Thomann have agreed to take it back to take a look/ repair but it's a bit of a shame I have to go through all the packing up and being without the amp for a while.
I was convinced it was going to be a simple tube replacement fix.

Edit: I just remembered I had 3 preamp tubes somewhere else and I stuck 'em in. With all 5 tubes different, the noise is still there and as loud as ever. It's going back to Thomann

 

[Mike_LA]

I was convinced it was going to be a simple tube replacement fix.

Me too, thought for sure that was it.
Best of luck

 

[Cal Nevari]

I flicked the standby on my SV20H today only to hear very loud continuous white noise. This is with no guitar plugged in.
Turning the High Treble volume up makes the noise unbearably loud and the noise is gone with that volume down. The normal volume has a tiny bit of the same noise at max vol.
The amp is very new and, as Nigel would say, "still has the little tagger on it."

I'd say I've turned it on 10 or 12 times in total, it has never left the house, although, when I play it, I pretty much crank the 5W to full volume for brief periods, without an attenuator.
Because it's so new, I'm even afraid to take the back off and investigate. Why would this happen to an amp so new?

Things I've tried: different speaker cab, speaker cable, house socket, mains lead.
I've left it on for a while now at low volume and that noise ain't going anywhere.

I can't lay my hands on the manual right now even though I know it's somwhere in the house. Basically I'm looking for the warranty info.? Does anyone know the story there or, if I need repairs, should I contact Thomann where I bought it?

Any suggestions for what could be going on, greatly appreciated. Cheers.

I had the same problem with an SV20C and other MFers told me it was just par for the course with these amps. Very loud hum with that Treble Volume. I was able to tame it to some degree with an attenuator, which allowed me to play the amp at home with lower volumes. But even at the 5W output, the amp was way too loud for me. Also did not like the brittle quality of the sound. I ended up selling mine.

 

[Bewlay]

New update: The amp arrived back at my door this morning. I had no idea it was coming so I was very surprised to see it.
When I opened it, it started to make sense..but my heart sank. There was a note saying, 'no fault found, amp being returned'.

I nervously plugged it in and the noise is gone. Mad stuff.
I can't fault Thomann, they have been incredibly efficient. They previously sent me a email saying the amp had arrived but nothing since then, until it showed up this morning.
I tested this thing with different leads, plugs, speakers and eventually tubes over the course of about 10 days, every day, and it was unplayable.
The only thing I can suggest is that the knocking around of the shipping had set it straight?? Kind of like bashing the side of a TV to get the picture to come in! I'm only half joking.
I have videos of the noisy vs noiseless working/ non-working versions of this amp so I know I'm not going mad!

Happy for now but I sincerely hope it doesn't go rogue again.

 

[Sustainium]

Time to stop thinking about the noise and ROCK DAT BITCH.

 

[Bewlay]

Time to stop thinking about the noise and ROCK DAT BITCH.

Haha YES!!

 

[Bewlay]

I resurrecting this thread on the off-chance someone might have a new insight/ suggestion. The flippin noise is back on my SV20H.
And it's intermittent...but more there than not.
If I move the amp, the noise tends to go away temporarily. Well, recedes anyway. One time, I moved the guitar lead from input 2 to input 1 and the noise stopped instantly. Only to gradually return about 15 minutes later.
I've previously switched all of the tubes on this amp, which made no difference.

I'm loathe to go through Thomann again even though it's still under warranty. They've already looked at this problem and the packing up and sending is a real pain.
But I also don't really want to spend €100+ getting it seen to/ fixed when it's still under warranty and, for now anyway, it's not my gigging amp.
Thought I'd try here while I figure out what to do next! Thanks for reading.

 

[Bewlay]

One other thing I should mention, perhaps. I can't be 100% sure about the last but I'm pretty sure this noise has appeared after periods of disuse.
Not huge long periods but maybe a month or 6 weeks of the amp not being turned on. Reversing that by using it very regularly with the noise present didn't improve it the last time this happened.

 

[Pete Farrington]

Does the noise ever occur with a guitar plugged in and jumpered to both channels?
I’m wondering if the issue is just dodgy shorting switch contacts on the input sockets.

 

[Bewlay]

That's a good point but in truth it's occurred in every situation. Jumpered, plugged straight in, no guitar attached.
I'm thinking it could be an input issue. Last night I was messin around and I noticed if I picked up the head and dropped it (very lightly) down on its right side the noise dissipated.
This didn't seem to happen if I did the same on the left side. Mind you this is very un-scientific!
On the other hand, it would seem to point to a dodgy tube so I'll try switching tubes again.