JVM-1 noise

[Coronado]

Picked up a JVM-1h about a week ago. Seemed to be working fine at first, and I started to notice that a hum is beginning to grow louder. Here is what I know (and have done) so far: Different power cords, different outlets of the house, plugged directly into input (different cords, no effects), different guitars (running it into a 4x12).

If its on the clean channel, the hum is so faint you can barely hear it (even on full volume). On the OD channel with the gain on one and volume nearly full, the hum is faint. The louder the gain, the louder the hum. The hum is quite loud when volume is on 3 and gain on full. This was the floor model and the only one they had left. Possibly preamp tube? Hum is present with our without guitar plugged in.

Greatly appreciate your thoughts, and thanks in advance for the help.

 

[Stringjunkie]

Make sure the tubes are seated well first. If so I would change them 1 at a time to see it thats it.

 

[Coronado]

Thanks! Will do - hoping its just a tube issue. I'll check how they are seated. If they are okay, I'll then try some different tubes.

Sure appreciate the help!

 

[Stringjunkie]

No worries. I had to reseat the tubes in all 3 of my 1w because they were doing exactly as you said.

 

[Sweetrock]

Thanks! Will do - hoping its just a tube issue. I'll check how they are seated. If they are okay, I'll then try some different tubes.

Sure appreciate the help!

Hi , how did you solve the problem ?

Same problem here , a humming PT or OT with more when resonant switch engaged .

Thanks .

 

[Coronado]

I've noticed that different tubes do have an impact on how much hum and background noise comes from this amp. I have read just about everything I can find on the internet around what can be done. As some tubes will help minimize the hiss, I generally think there is just a LOT of gain on board with this amp, and you have to somewhat back off the gain a bit. Here is something else I'm wondering. I run my JVM-1 through a 4x12, and I think what's happening is somewhat of an amplified hum (excuse the pun). I just picked up a 1x12 last night and am about to plug into it for the first time. I'm wondering if simply because there is only one speaker, that the hum will be somewhat less. I think I will still hear the hum, but I also believe that there will be less hum, as I wont hear it coming from all 4 speakers. I may be totally crazy on this, but I have found that those who run 1x12 and 2x12's seem to have less of an issue.

Disclaimer: I may be totally off my tree and totally wrong about this. I'll follow-up later today and let you know what I find. I just know that with my 4x12, no matter what I have done, that hum is there. Even very low volumes with gain at 3/4 - full, the hum is very loud. Hoping less speakers will mean less amplified hum? I have a NOS RCA 7025 that I am going to try in it (V1). Wondering if this tube will help take down some noise.

I have also found that turning the treble way down and upping the presence helps eliminate background noise as well.

Here is a schematic in case you are interested in doing some tube rolling.

 

[Coronado]

Forgot to add - you are absolutely right. When I engage the resonance, the hum goes WAY up (quadruples). Wishing it had a knob so you could control the amount, like on a DSL40C for example. Without the resonance engaged, to me, it sounds a bit thin.

 

[Sweetrock]

Hi Coronado ,

Thank you for the instant reply ,

My JVM-1 is a Combo and it has a 8 inch speaker ,

When I play the amp in store , I didin't notice anything but when I am at home and plug it into a 1X12 V30 cab , I heard that hum and I understand that it's a 60 or 50 Hz hum that comes from power transformer because the bigger speaker gets the lower frequency can be output .

That's also same as what you said , in 412 it is more than 112 and 112 is more than 108 .

8 inch speaker don't produce 60Hz. and that's why they use 8 inch speakers in JVM and DSL series.

I will try another JVM in the store next week to see if they are all the same .

Hakan

 

[ampmadscientist]

Forgot to add - you are absolutely right. When I engage the resonance, the hum goes WAY up (quadruples). Wishing it had a knob so you could control the amount, like on a DSL40C for example. Without the resonance engaged, to me, it sounds a bit thin.

Is the preamp sitting on top of the power amp? Move it away and test again.

Are ALL effects pedals UN-plugged?

LIFT the ground of the preamp...
Ground only the power amp. Make sure there is only ONE ground to the power, not multiple grounds.

Multiple grounds cause ground loop HUM.

 

[Sweetrock]

I must also mention that ,

It is not related with the guitar , it is there even if the guitar is not pluged in .

And also it is not related with the volume , it is there even if it is high or low in volume .

Resonance switch gets it high even if the volume high or low .

I wish Mr.Alvarez pop up here and tell us something about that .

But , I know , he is busy .

Hakan .

 

[Sweetrock]

Hi Mr.Ampmadscientist ,

This is not the preamp JMP1 ,

This is 50th anniversary 1 watt series of JVM-1.

Sorry .

 

[Sweetrock]

Thanks , anyway .

 

[Georgiatec]

Check your 4 main bolts are nice and tight too. I noticed if they become loose or you are playing the amp completely out of the head box, there is a hum. My guess is tubes though. When I first bought a JCM1 after a few days there was a hum.....took it back to the dealer and they gave me another. I've rolled 100's of tubes into that little sucker now and some hum, some don't.

 

[ampmadscientist]

Hi Mr.Ampmadscientist ,

This is not the preamp JMP1 ,

This is 50th anniversary 1 watt series of JVM-1.

Sorry .

No guitar plugged in?
Noise increases with volume setting? (no guitar, just the amp)

Noise sounds like Bzzzzzzzzzzzzzzz?

Probably filament noise.
However, it is possible to get all of this buzzing out.

 

[Sweetrock]

No guitar plugged in?
Noise increases with volume setting? (no guitar, just the amp)

Noise sounds like Bzzzzzzzzzzzzzzz?

Probably filament noise.
However, it is possible to get all of this buzzing out.

No noise increases with volume settings.

It's not buzz , it's hum.

It's not 120 HZ. hum , it's 60Hz.

 

[Sweetrock]

https://youtu.be/GrVtX0QGNls

I will check the preamp tubes .

 

[Sweetrock]

Hi to whom it may concern ,

First thing first ,

Nothing changes with the tube rolls .

Second ,

I went to the shop to check the other (last one) JVM-1C even if it is better .

No way , both are same and I see that this is a design failure .

As I said previously , it is not that distinctive in 8 inch speakers .

And I must also say that in 0.1 watt mode it's barely noticiable .

That's all for now .

Cheers !

Hakan .

 

[Coronado]

I've tried rolling tubes, and as GeorgiaTec mentioned, still have the hum. From what I have read online, there are a lot of people who talk about this hum. Starting to think that with that much gain, its probably gonna have some hum. I will say that when I put in new tubes, (JJs), the hum went down a bit from the stock tubes. My thinking was that perhaps the amp probably sat at Sam Ash for quite a while with people turning it on and instantly playing it?

I have a NOS RCA 7025 that for some reason seems to help quiet down my 74' 1987. AmpMadScientist mentioned in another thread that higher gain tubes will produce more noise/hum, and I tend to agree. The RCA significantly also helped to quiet down my DSL40C at higher volumes on the red channel.

I did find that running my JVM through the 1x12 helped. I find that just scaling back the gain helps reduce the hum. Anything beyond 5 (or noon) and you begin to hear the hum much more, and to be honest, 5 is pretty much all the gain I would need. At around 7 it begins to get a bit too thick and loses shape for me.

 

[Sweetrock]

Hi Coronado ,

This hum is nothing to do with the gain or volume ,

It is there even if the gain and volume is all the way down , and if volume and gain is up , the level of the hum is same but only some kind of gain hiss occurs .

If resonant switch engaged , hum goes up significantly .

If 0.1 watt switch engaged , hum goes down dramatically .

With small speakers , hum is hard to notice , when speakers are getting bigger and increasing in piece , it is louder .

It might be a power or output transformer humming that comes from speakers .

I think , I will learn to live with it because I love that little bastard .