Need critical help with my Kemper! It fails me during rehearsal!

[RustyNotes]

Ok, some of you might know me from my "Need help with kemper live setup"-thread, but no I'm in trouble.

So I bought myself a Magnum 44 preamp, it's killer! The combination of a Kemper, the Magnum and the Marshall 4x12 is amazing.. until today.

Last week we practiced without a drummer. We used back tracks for drums and what not. Everything was working fine and dandy. But today, when we had a live drummer with us, everything got fucked up.

The kemper looses audio from time to time. It's like it's glitching out. Like i was having a "rotary" effect on it if you know what I mean? Could it be because of the vibrations from the loud music? We played loader today then what we did with the back tracks of course. First, I had my Kemper on the cab. But when the problem first started to appear, I tried moving it to the floor. Same results. I tried a different chord to the guitar, nothing changed. I know there is nothing wrong with my guitar or with my cab, cuz i tried with a 5150 top, and everything was fine. What could have caused the problem? The magnum 44 was set to around 11 o'clock.

Kemper - Main out (cab bypassed) -> magnum 44 -> Marshall 4x12
The sound glitches out from time to time, like I have a rotary effect on.

I tried my Kemper in the studio once I got home, it works as it should.
What do you guys think I can do to be able to stop this? It worked so good last week.

(Sorry for my bad english btw. I'm from sweden.)

 

[TheWinterSnow]

You say the cabinet works with a tube amp, the Kemper works in your studio...the only thing left is the Magnum 44. Its a solid state amp and since they can overheat unlike tube amps (well tube amps can overheat but that's a whole different conversation) and usually over overcurrent/overheating protection. The input of the Kemper may be too hot and is causing an overload as the device gets warmed up, you should try turning the volume all the way up on the magnum 44 and adjusting your loudness with the Kemper. Typically the volume knob on a power amp controls only the volume of the amp, not the gate, which is permanently set, if there is an input buffer between the volume knob and in input and it is getting overloaded, it could shut off, and conversely if you turn to kemper volume down and let the magnum amplify the full signal, it would be harder to overload the input. Keep in mind the power amp may only be a -10dBv input, and you may be overloading it with a +4dBu signal of the Kemper, of -2dBu if you are using an unbalanced cable. That has me come to think, perhaps the kemper is getting pissed off because you are shorting the neutral signal to ground when using a TS cable into a TRS jack if they didn't engineer it correctly. I don't know much about the I/O of the kemper or how you have it wired up.

I would say that I am 99% sure that is is the Magnum 44's over-temperature protection kicking in.

 

[RustyNotes]

You say the cabinet works with a tube amp, the Kemper works in your studio...the only thing left is the Magnum 44. Its a solid state amp and since they can overheat unlike tube amps (well tube amps can overheat but that's a whole different conversation) and usually over overcurrent/overheating protection. The input of the Kemper may be too hot and is causing an overload as the device gets warmed up, you should try turning the volume all the way up on the magnum 44 and adjusting your loudness with the Kemper. Typically the volume knob on a power amp controls only the volume of the amp, not the gate, which is permanently set, if there is an input buffer between the volume knob and in input and it is getting overloaded, it could shut off, and conversely if you turn to kemper volume down and let the magnum amplify the full signal, it would be harder to overload the input. Keep in mind the power amp may only be a -10dBv input, and you may be overloading it with a +4dBu signal of the Kemper, of -2dBu if you are using an unbalanced cable. That has me come to think, perhaps the kemper is getting pissed off because you are shorting the neutral signal to ground when using a TS cable into a TRS jack if they didn't engineer it correctly. I don't know much about the I/O of the kemper or how you have it wired up.

I would say that I am 99% sure that is is the Magnum 44's over-temperature protection kicking in.

Wait a second, I'm confused haha.. you say that you think it's the 44's over-temperature protection kicking in. Do you mean that the signal coming in to the Magnum (from the Kemper) is to hot?

Did i get it right? Turn the volume on the Kemper down, crank up the poweramp?

 

[TheWinterSnow]

If its over-temperature, there is nothing you can do other than play quieter. If it is an input overload, turning the volume on the kemper down and the volume up on the poweramp will do the trick.

Depending on how well the power amp was designed it should be able to handle the power of the input signal until the power amp distorts, but I wouldn't hold my breath, you may not overload (distort) the input but the signal may be strong enough to still overheat the power amp portion of the amp, which is bad design but what can you do.

You see the power amp actually has a preamp stage and the power amp, if the input signal from the kemper is too high, it can distort the input (preamp) of the pedal which would sound bad, or the preamp can have an automatic gain reduction or overvoltage shutdown which cuts sounds for about a second or two, the preamp goes into the volume control and into the power amp. There is a chance that the preamp can even though it has a clean signal can drive the poweramp into overheating, even if the preamp and the power amp are not distorting. If the power amp overheats, it can simply reduce headroom and thus distort or is can have partial shutdown or even full shut down, full shutdown meaning it cuts out for a few seconds.

I think that it is possibly a bad design and you are just overheating the thing though and it just has an intermittent shutdown so you don't loose all the signal even if it sounds like crap. 44 Watts isn't enough so I wouldn't be surprised if you are overheating it. My and and my guitarists line 6 Spider II HD150 (150 Watt) heads overheated and would get quiet and nasty distorted when they overheated. It would be the two of us and a drummer, no bassist or vocalists yet those 150 Watt heads would overheat just trying to keep up with a drummer. Mine, even though I abused it less fried out on me and works if you don't mind the volume dramatically rising, the tone shifting in sound and a very nasty high pitch squealing sound every now and then, even at bedroom volumes. So yea 150 Watts wasn't enough. For Solid State power amps you need at least 300 Watts to keep them from getting to hot, those 44's aren't made for loud band practice.

Question: Why didn't you just get the Kemper with the 600W Solid State amp built in?

 

[RustyNotes]

If its over-temperature, there is nothing you can do other than play quieter. If it is an input overload, turning the volume on the kemper down and the volume up on the poweramp will do the trick.

Depending on how well the power amp was designed it should be able to handle the power of the input signal until the power amp distorts, but I wouldn't hold my breath, you may not overload (distort) the input but the signal may be strong enough to still overheat the power amp portion of the amp, which is bad design but what can you do.

You see the power amp actually has a preamp stage and the power amp, if the input signal from the kemper is too high, it can distort the input (preamp) of the pedal which would sound bad, or the preamp can have an automatic gain reduction or overvoltage shutdown which cuts sounds for about a second or two, the preamp goes into the volume control and into the power amp. There is a chance that the preamp can even though it has a clean signal can drive the poweramp into overheating, even if the preamp and the power amp are not distorting. If the power amp overheats, it can simply reduce headroom and thus distort or is can have partial shutdown or even full shut down, full shutdown meaning it cuts out for a few seconds.

I think that it is possibly a bad design and you are just overheating the thing though and it just has an intermittent shutdown so you don't loose all the signal even if it sounds like crap. 44 Watts isn't enough so I wouldn't be surprised if you are overheating it. My and and my guitarists line 6 Spider II HD150 (150 Watt) heads overheated and would get quiet and nasty distorted when they overheated. It would be the two of us and a drummer, no bassist or vocalists yet those 150 Watt heads would overheat just trying to keep up with a drummer. Mine, even though I abused it less fried out on me and works if you don't mind the volume dramatically rising, the tone shifting in sound and a very nasty high pitch squealing sound every now and then, even at bedroom volumes. So yea 150 Watts wasn't enough. For Solid State power amps you need at least 300 Watts to keep them from getting to hot, those 44's aren't made for loud band practice.

Question: Why didn't you just get the Kemper with the 600W Solid State amp built in?

I'll try that on Thursday. They say that the Magnum 44 is loud enough for stage monitoring during open festivals, so yeah. I'll try your way on Thursday and see if that helps

I didn't buy the other Kemper cuz I didn't know I would be playing live. I bought it for studio use only. I joined a band later on

 

[TheWinterSnow]

I don't deny that it is loud, 44 Watts can be deafening, the problem is with heat management and efficiency, pushing a 44 Watt power amp to 44 Watts will create a lot of heat and will have high THD (Total Harmonic Distortion) reducing efficiency and creating more heat. At maximum power it is easy for the device to have thermal runaway (heat causes more current, more current causes more heat and the viscous circle continues until the amp destroys itself) if the amp is not mosfet based and the amp overheats. If you have a 300 Watt amp and you push it to 44 Watts it won't even be remotely hot. Keep in mind 300 Watts is only double the perceived volume as a 30 Watt amp, the higher Wattage amps do the same volume with better efficiency and therefore less heat.

You may also have a faulty power amp, its known to happen.

 

[kaomao]

I have the 44 magnum as well, and yes that's it! it is its fault!
It had done that to me but...... I just pushed it over the top, I mean I used it for some months attached to the 4ohm input on my cab, I wanted to be over the top ... lol now it is almost dead, the magnum I mean, kemper is fine of course!
I'm glad I bought this: http://www.kpa-solutions.com/camplifier/
It's just amazing

 

[RustyNotes]

I have the 44 magnum as well, and yes that's it! it is its fault!
It had done that to me but...... I just pushed it over the top, I mean I used it for some months attached to the 4ohm input on my cab, I wanted to be over the top ... lol now it is almost dead, the magnum I mean, kemper is fine of course!
I'm glad I bought this: http://www.kpa-solutions.com/camplifier/
It's just amazing

But that shit doesn't work for the rack model :-(

 

[RustyNotes]

Tried to crank the 44 all the way up, and keep the Kemper at a lower volume. Still have the same problem. Could it be the vibrations? I have it standing on the cab. I only have the problem when the full band is playing, not by myself.

 

[Nebulous]

If it was me, I would investigate the possibility of vibrations more. It will vibrate on the cab, it will vibrate on the floor.
I would suggest trying to put the Magnum on something to absorb some vibrations to test it out (pillow, soft foam, etc). If it stops the issue then it may need to live in a rack or padded flight case.

 

[RustyNotes]

If it was me, I would investigate the possibility of vibrations more. It will vibrate on the cab, it will vibrate on the floor.
I would suggest trying to put the Magnum on something to absorb some vibrations to test it out (pillow, soft foam, etc). If it stops the issue then it may need to live in a rack or padded flight case.

You really think that could be it? I mean, it's built like a tank.

 

[kaomao]

But that shit doesn't work for the rack model :-(

they can build a version for your rack, it's just the back metal plate of the camplifier that has to be different, inside the camplifier there isn't much, so it's not so much work to do

 

[kaomao]

dude get over it your magnum is fucked up, is dead. I'm so sorry for ya but that's the truth
When is doing what you're describing, it's just some electronics fucked up, bad caps or something (I'm not an electrician).
Mine is not working as it did before, but it's just my fault: I wanted to be like Stallone in "over the top" lol.

 

[RustyNotes]

they can build a version for your rack, it's just the back metal plate of the camplifier that has to be different, inside the camplifier there isn't much, so it's not so much work to do

Oh really? Didn't know that. Hard to install?

 

[kaomao]

Oh really? Didn't know that. Hard to install?

No it's just tighting 4 screws, very very very easy