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Gallien-Krueger MB800

#502
PauBass said:
...I have just received a GK MB800 and there's a few things I have noticed and I'm not so sure about:

- As soon as I turn the amp on there is a faint but noticeable background noise, kinda like a grainy white noise, not a hum. It is there always no matter what the gain, eq or master knobs are set to, even with the mute on and no bass plugged in. I

- The fan comes on pretty much after switching the amp on and it's quite/very noisy, noisier than any other amp I've had in the past (Ampeg PF-800, TH500, DB750, SVT4....) Even on standby the fan keeps running even after having played only for 2 minutes at low volume.

- Also when I switch channels it makes a popping sound, it only happen if I am playing when I change the channel, but not if I'm not playing at the time.

- The second Channel, seems to be quite a lot quieter than Channel A. Is this how it is?
Click to expand...
The MB800 has a shorting input jack, so the amp should be silent when nothing is plugged into the input.

Normal behaviour for the fan, is to cycle on for a couple of minutes periodically when the amp is idling.

Channel switching should be silent.

The only part that sounds normal is the gain staging.

The two volume controls on the right are not channel A and channel B masters.
  • The first one is a post-EQ attenuator for the B channel. You can think of it as the B-channel output volume, with zero representing no output, and cranked being unity gain.
  • The second one is a post-everything Master volume for the entire amp.
The only time channel B will ever be as loud as channel A, is when the channel B output volume is dimed. This allows you to crank the gain for some grit on channel B, then bring your levels back into balance by reducing the B volume. In this situation, A = clean, B = dirty.

It can also be used for a clean solo boost (or more accurately, a volume cut). Channel A has no output attenuator, so it's always your "loud" channel, even with both gain knobs matched. Turning down the channel B attenuator drops it below channel A, setting up your second level preset for quiet passages.
 
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#503
Got a couple gigs with my new (to me) MB800. Really liking it so far. Sure, there's some fan noise, but I never noticed it on the gig. The amp is punchy, thick and surprisingly stout sounding for how tiny it is. Great for both electric and upright. I dig it :)
 
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#504
B-string said:
Sounds like you received a defective unit. Contact the store you bought from, the factory in the US can't help much in the UK. If you have trouble with the store [email protected] might be able to apply the right pressure here and there ;).
Click to expand...

Thanks, I have sent them an email.

steve_rolfeca said:
The MB800 has a shorting input jack, so the amp should be silent when nothing is plugged into the input.

Normal behaviour for the fan, is to cycle on for a couple of minutes periodically when the amp is idling.

Channel switching should be silent.

The only part that sounds normal is the gain staging.

The two volume controls on the right are not channel A and channel B masters.
  • The first one is a post-EQ attenuator for the B channel. You can think of it as the B-channel output volume, with zero representing no output, and cranked being unity gain.
  • The second one is a post-everything Master volume for the entire amp.
The only time channel B will ever be as loud as channel A, is when the channel B output volume is dimed. This allows you to crank the gain for some grit on channel B, then bring your levels back into balance by reducing the B volume. In this situation, A = clean, B = dirty.

It can also be used for a clean solo boost (or more accurately, a volume cut). Channel A has no output attenuator, so it's always your "loud" channel, even with both gain knobs matched. Turning down the channel B attenuator drops it below channel A, setting up your second level preset for quiet passages.
Click to expand...

Great, thank you!

Mine definitely has the that grainy white noisy, as I said, even with the amp muted and nothing plugged in.
The channel pops are there too and are quite audible :(
 
#505
My apologies for resurrecting this thread, but I'm glad I stumbled upon it and it seemed more appropriate to ask here instead of the GK RULES...
I took in an MB800 about three months ago, second owner. I had been eyeballing the little beasts for several months, so when I found this one for the incredible deal I got it at I couldn't resist.
So far, just home use. Bottom line, LOVE IT! So much power and punch for days.
Today, jammin' out a bit, not pushing it at all ( can't push to hard through my 2x d112xlt's) sounded phenomenal as usual.
After about 30 mins the fans kick on, no biggie its happened before and they went off after a few minutes. This time they just stayed on... I stopped playing, still fans going... They stayed on and were very loud until I turned the unit off... Over an hour later.
This can't be normal, is there anything that can be done ??
Thanks for any ideas/ suggestions
 
#507
B-string said:
The thermistor that "senses" output heatsink temp could have gone bad causing full speed constant operation. But email [email protected], really nice folks at G-K and although I think his main job is Artist Relations he was/is tech department head.
Jason Findley Artist Relations



jason@gallien.com

209-234-7300 ex 105
Click to expand...

Great! Thanks so much. I'm hoping there won't be an issue with getting this repaired, considering I'm not the original owner and don't have a warranty
 
#508
MTN.bass72 said:
Great! Thanks so much. I'm hoping there won't be an issue with getting this repaired, considering I'm not the original owner and don't have a warranty
Click to expand...
I've seen a few guys with these high watt version Class D GK's. Out of the 4 I've seen in person, 3 had some sort of issue.

I love my GK stuff, but I'm weary about the high wattage class D stuff
 
#515
So I picked up a new MB800 to serve as a backup to my Aguilar DB751. I had a ToneHammer 500 for a backup, and it just seemed like it was a bit anemic. I decided that I wanted to try out the MB800 for a show and used it last night for the first time with my Berg NV610. WOAH!!! That little thing slammed!! It handled the NV610 like it was nothing. And the tone was just superb! The thought of hauling around the MB800 from gig to gig instead of the Aguilar DB751 has just gotten a bit more intriguing..... :-)
 
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#518
Tim1 said:
I am considering picking up a second hand MB800 to use with a 12 ohm Barefaced Two 10. Does anyone know how many watts it puts out into 12 ohms, and has any one tried this combination?
Click to expand...

Are you really sure it is 12 ohms? Is that due to a crossover network? In any case, I'd contact GK tech support and ask them.
 

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