Sv20h feedback

[albybasso]

I had problems with my head, a Marshall SV20h, the head goes into feedback immediately. I use jump channels. I tried replacing the preamp tubes, but the problem persists. When I use an overdrive the feedback increases dramatically. What could it be?

 

[PelliX]

new MF'er!

What do you mean by feedback, it squeals when you turn the guitar volume up? Or does it scream and oscillate without anything plugged in?

Note that this is a non-MV amp and feedback may be expected within reason at close quarters...

 

[albybasso]

it happens when I turn up the volume of the guitar, both with the neck pick up and the bridge pick up. I tried to move, walk away, but it doesn't change. Excuse my ignorance, what does non mv amp mean?

 

[speyfly]

Since you've rolled tubes I would start swapping patch cables and instrument cables (do make sure you're using instrument cables and not speaker cables).

 

[PelliX]

it happens when I turn up the volume of the guitar, both with the neck pick up and the bridge pick up. I tried to move, walk away, but it doesn't change.

Where are the channel volumes and presence set roughly and how are you typically from the cab?

Excuse my ignorance, what does non mv amp mean?

Non-Master Volume. Many amplifiers have a master volume control which sets the overal output level, some however don't and are basically always at full tilt and you simply set the amount of signal you give it. That's the short version. Yours is the latter type, like its "bigger cousin" the 1959 Super Lead. While yours is a little more tame, note that a small room and an SV20 don't go well together without some additional measures.

 

[thesunship]

what kind of pickups?

 

[goldtop0]

The SV20 has a bright cap that causes the amp to hiss (and squeal if you're up close to it) on the High Treble channel, a 4.7na. If you change it to a 100pf cap it'll take that out of the picture.

 

[Jubilant]

Do yourself a favor if you don’t have one buy a jhs little black box pedal and put it in your fx loop.Use it as a master volume and your problems should go sway.Unless your guitar is the problem then try another guitar first.If you get the pedal it’s only 60 us dollars and works like a charm.

 

[Jethro Rocker]

Basics first. As mentioned above, what pickups, volume and other settings, and proximity to amp cabinet. If it is really high and you are close in a smaller space it stands to reason.
Put a pedal with a volume control in the loop as menrioned. You will not get the same power saturation this way though.

 

[Dogs of Doom]

yep, my 1st thought was, that there isn't enough information in the OP...

what guitar (brand/model)?
what pickups?
What speakers?

how loud & how close?
cables good?

There's always a chance that something could be wrong w/ the amp, but, there's so many other variables...

best bet is to start at bare minimum.

guitar >> amp >> speaker

if it's feeding back at that point, you've got a problem somewhere in either the guitar, or amp.

an amp like this will show you whether you have good pickups in your guitar, or not. Cheap pickups, especially single coil, will be noisy & will be prone to feedback.

but, since nobody knows what you have, there's no way to diagnose.

ask incomplete questions, get incomplete answers...

 

[albybasso]

Where are the channel volumes and presence set roughly and how are you typically from the cab?



Non-Master Volume. Many amplifiers have a master volume control which sets the overal output level, some however don't and are basically always at full tilt and you simply set the amount of signal you give it. That's the short version. Yours is the latter type, like its "bigger cousin" the 1959 Super Lead. While yours is a little more tame, note that a small room and an SV20 don't go well together without some additional measures.

Presence at 12 o'clock, high channel volume at 9 o'clock, low channel volume at 12 o'clock.. I am positioned about 3 meters from the cabinet on the side

 

[albybasso]

what kind of pickups?

Seymour Duncan APH-2S Slash Alnico II Pro​

 

[albybasso]

what guitar (brand/model)?

Sire L7

what pickups?

Seymour Duncan Slash Alnico pro 2

What speakers?

Marshall 1960 4x12

how loud & how close?

hi channel at 9. low chanel at 12, i'm 3 meters away from cab

cables good?

all cables are Roland

There's always a chance that something could be wrong w/ the amp, but, there's so many other variables...

best bet is to start at bare minimum.

guitar >> amp >> speaker....

i've the same problem in this configuration.

 

[PelliX]

Presence at 12 o'clock, high channel volume at 9 o'clock, low channel volume at 12 o'clock.. I am positioned about 3 meters from the cabinet on the side

Alright, so you're running the SV into a 4x12 cab, volume around half and you're ~3m away from the cab. How big is the room?

cables good? all cables are Roland

While I'll presume that they're alright, the brand says nothing about the condition of a cable. "Does your car work?" - "It's a Ford."

 

[albybasso]

Alright, so you're running the SV into a 4x12 cab, volume around half and you're ~3m away from the cab. How big is the room?



While I'll presume that they're alright, the brand says nothing about the condition of a cable. "Does your car work?" - "It's a Ford."

the cables are new, they are 2 weeks old, I tried to replace them to eliminate the cable problem. The room is approximately 5 meters x 5 meters.

 

[PelliX]

the cables are new, they are 2 weeks old,

Mate, I'm not trying to give you a hard time, but do understand that the age of a cable says nothing about its condition. That said, you ruled that factor out - so that's cool.

The room is approximately 5 meters x 5 meters.

This is pretty small to be cranking an SV, at those volume and gain levels I could well imagine things spiraling into feedback. Does the squeal stop if you mute the strings with your hand?

 

[albybasso]

Mate, I'm not trying to give you a hard time, but do understand that the age of a cable says nothing about its condition. That said, you ruled that factor out - so that's cool.



This is pretty small to be cranking an SV, at those volume and gain levels I could well imagine things spiraling into feedback. Does the squeal stop if you mute the strings with your hand?

Meanwhile thanks for your answers, yes, if I touch the strings with my hand the feedback stops. as soon as I lift my hand it starts again. At home I use a captor X, could it be enough to solve the feedback problem?

 

[PelliX]

Meanwhile thanks for your answers, yes, if I touch the strings with my hand the feedback stops. as soon as I lift my hand it starts again. At home I use a captor X, could it be enough to solve the feedback problem?

Yes, some form of attenuator would certainly be the way to go, if you ask me. It sounds [pun vaguely intended] as if you're simply at the edge of what the space permits. Give it a shot with the Captor X.

 

[albybasso]

I'll take the Captor X to the testing room on Monday and try to see if anything will change. I will keep you updated! Thanks so much! Your info was really helpful to me.

Yes, some form of attenuator would certainly be the way to go, if you ask me. It sounds [pun vaguely intended] as if you're simply at the edge of what the space permits. Give it a shot with the Captor X.

 

[6StringMoFo]

Meanwhile thanks for your answers, yes, if I touch the strings with my hand the feedback stops. as soon as I lift my hand it starts again. At home I use a captor X, could it be enough to solve the feedback problem?

This sounds normal.