Jcm800 sc20h hiss

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
I recently bought a new jcm800 sc20h and noticed there is a really loud hiss when I use the high sensitivity input and crank the pre-amp up to 7 or 8. Is this a common issue or should I return it and get a new one? I would not expect this from a high end brand...
 

Moony

Well-Known Member
Joined
Jul 3, 2015
Messages
1,445
Reaction score
2,143
Does it also hiss when nothing is plugged into the amps input?
 

Moony

Well-Known Member
Joined
Jul 3, 2015
Messages
1,445
Reaction score
2,143
No it doesn't

A certain noise floor is normal when cranking an amp that has a good amount of gain.
Could be that your guitar cable and/or pickups make things worse, that's why I've asked.

If the noise floor decreases drastically if you roll down the volume knob on your guitar, I wouldn't worry much about the amp.
Maybe you have some electromagnetic interferences at your place too. That's when singlecoils usually start to hum.
 

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
We'll I use hb pickups, but indeed when I only plug my guitar in there's a lot of hiss. When I put my effects between my guitar and the amp there's still hissing but a bit less. Nevertheless, how van I get rid of it? I had the same issue in the rehearsal studio (so different power outlets than at home)
 

Moony

Well-Known Member
Joined
Jul 3, 2015
Messages
1,445
Reaction score
2,143
You can also try a selected (low microphonics/low noise) 12AX7 in the V1 (first) spot and see if that makes things better.

And of course using a noise gate.
 

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
Thanks for the suggestion, just feels a bit odd to already tinker with a brand new amp.. I would expect it to just do it's work :)
 

Moony

Well-Known Member
Joined
Jul 3, 2015
Messages
1,445
Reaction score
2,143
I would expect it to just do it's work :)

It probably does his work.

You could order a second one and compare if in doubt.
It's hard to judge from a distance only from your words if the hiss is normal or not.

So far I haven't seen complaints about the SC20 that it has above average hiss. :shrug:
 

TXOldRedRocker

Where's the exit?
Gold Supporting Member
Joined
May 15, 2020
Messages
1,482
Reaction score
4,796
Location
Texas
Thanks for the suggestion, just feels a bit odd to already tinker with a brand new amp.. I would expect it to just do it's work :)

It is working.

As you are very aware, amps can make very loud noises out of just some metal strings vibrating. That string vibration disturbs the magnetic field of the magnets in the pickup. That disturbance becomes a signal sent through the pickup coil and ends up in the amp. Where it can become so very loud. The strings are very specific and their vibration makes a sound we call music. But imagine anything in your room that can disturb that very sensitive magnetic field. Something like a fluorescent light, a TV, etc. Its interference would be more constant, like white noise (hiss) or a 60 cycle hum.

So if the hiss is fully, or mostly, only occurring when you have your guitar plugged in, something is disturbing the magnetic field of the pickup. Minus any grounding issues or something less likely.

The room where I play has multiple tube amps, but it also has two computers, a TV, ceiling fan, my internet/WiFi router, batteries charging, etc. All my tube amps hiss when I plug in any of my guitars, if I don't have a noise gate connected. So, I have noise gates connected to all my tube amps. So I hear no hiss.

(And, for clarity, all my tube amps are plugged into a Furman power conditioner, which is in turn plugged into an isolation transformer, which is then plugged into a voltage regulator, which is plugged into a wall socket. To prevent noise through the power leaking in.)

So, it's normal in most houses with today's modern electronic appliances of so many types.
 

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
It is working.

As you are very aware, amps can make very loud noises out of just some metal strings vibrating. That string vibration disturbs the magnetic field of the magnets in the pickup. That disturbance becomes a signal sent through the pickup coil and ends up in the amp. Where it can become so very loud. The strings are very specific and their vibration makes a sound we call music. But imagine anything in your room that can disturb that very sensitive magnetic field. Something like a fluorescent light, a TV, etc. Its interference would be more constant, like white noise (hiss) or a 60 cycle hum.

So if the hiss is fully, or mostly, only occurring when you have your guitar plugged in, something is disturbing the magnetic field of the pickup. Minus any grounding issues or something less likely.

The room where I play has multiple tube amps, but it also has two computers, a TV, ceiling fan, my internet/WiFi router, batteries charging, etc. All my tube amps hiss when I plug in any of my guitars, if I don't have a noise gate connected. So, I have noise gates connected to all my tube amps. So I hear no hiss.

(And, for clarity, all my tube amps are plugged into a Furman power conditioner, which is in turn plugged into an isolation transformer, which is then plugged into a voltage regulator, which is plugged into a wall socket. To prevent noise through the power leaking in.)

So, it's normal in most houses with today's modern electronic appliances of so many types.
Thanks for the elaborate answer! I noticed that when I use 4cm to hook up my guitar via my multi effect unit to the amp, there is way less hiss! However, when I engage the pre-amp section of the amp it first gives a loud but short boom/pop (tricky to define) sound. What can that be?
 
Last edited:

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
It probably does his work.

You could order a second one and compare if in doubt.
It's hard to judge from a distance only from your words if the hiss is normal or not.

So far I haven't seen complaints about the SC20 that it has above average hiss. :shrug:
I noticed that when I use 4cm to hook up my guitar via my multi effect unit to the amp, there is way less hiss! However, when I engage the pre-amp section of the amp it first gives a loud but short boom/pop (tricky to define) sound. What can that be?
 

Maxbrothman

Well-Known Member
Joined
Jun 5, 2022
Messages
434
Reaction score
619
Palm mute all your strings. Does that noise go away? If so that's normal.

#1 purchase for starting anything with expensive amps and guitar gear is a power conditioner. Like a good one. Do you have a Furman or similar? That will save your amp and everything else plugged into it from potentially being damaged by a surge but they also clean up the power and that solves all sorts of noise issues if it's the power.

#2 go direct to amp. No pedals. Gain on 7-8 will have some noise. Do the palm mute test again. Should go away.

If you still have noise then something probably isn't right if it is present in the playing.

What are your settings?

Also, listen closely to the hiss. Does it sound like a radio transmission?

The normal hiss BTW is very easy to get rid of. Use a noise gate/noise suppressor pedal like a Boss NS-2.
 

Len

Well-Known Member
Joined
Sep 13, 2009
Messages
1,189
Reaction score
1,120
Can you post audio or video? It’s difficult to tell if your issue is normal without actually hearing it.

Make sure there’s nothing in the loop. The SC30 has a known issue with having a noisy loop.
 

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
Can you post audio or video? It’s difficult to tell if your issue is normal without actually hearing it.

Make sure there’s nothing in the loop. The SC30 has a known issue with having a noisy loop.
 

daanromein

New Member
Joined
Jun 24, 2022
Messages
14
Reaction score
3
I can't seem to post a video :( But it's in the effects loop due to the 4 cable method
 

bad565ss

Well-Known Member
Joined
Apr 5, 2015
Messages
455
Reaction score
840
Location
Waterford, Michigan, USA
Hiss is pretty normal if you have the gain and tone settings set on higher settings.
You only hear it when you stop playing generally.
A good noise gate on your pedal board will silence it.
 


Top