GK mb115 problems... Salvageable?

benchbass · #1 02-26-2013, 08:54 AM

Hello all, I've had my eyes on the GK mb115 as a nice compact combo amp. My mother found a used one and surprised me with it for my birthday. Now there are a few scuffs and stuff but that doesn't really matter to me. What my concern is that if you turn the volume up at all on it, the sound becomes mega distorted. Like anything past half and it starts doing it and vibrating really bad. I'm sort of new on the scene and I'm not sure what the problem could be and I'm scared/ don't know if I'm able to open it up and have a look. Have any of you encountered a similar problem? Is it fixable? If I can I'd like to keep it because it was a gift, but if it's just gonna give me headaches I might need a new one. Thanks!

Edward G. · #2 02-26-2013, 09:02 AM

First, find out if some kind of warranty applies to the purchase. Do NOT open it up if you don't know what you're doing. Take it to an authorized repair shop, which is likely to be a local music store, and demo the problem. Often it's something simple.

Bass_Pounder · #3 02-26-2013, 09:10 AM

Quote:

Originally Posted by benchbass

What my concern is that if you turn the volume up at all on it, the sound becomes mega distorted. Like anything past half and it starts doing it and vibrating really bad.

Volume knob position means absolutely nothing.

"Half way up" does not mean half power.

Depending on how you EQ and use your basses tone controls, MANY amps hit full output and start distorting way before they are turned up "all the way"

RickenBoogie · #4 02-26-2013, 09:12 AM

First thing to understand is- it's a 1x15 combo amp. The position of the dials means nothing. Everything from your bass, right through all the eq controls will effect how far the spkr will let you go. If your bass has hot output, and you have the low bass eq cranked up, you will get less uesable volume. Sounds to me like either the spkr was shot when you got it, or has become shot by excessive use of low eq and/or volume. I suspect it's the spkr that needs repairing, but you'll need a pro amp tech to take a look at it.

Stev187 · #5 02-26-2013, 09:16 AM

Quote:

Originally Posted by benchbass

What my concern is that if you turn the volume up at all on it, the sound becomes mega distorted. Like anything past half and it starts doing it and vibrating really bad.

Before you take it in, read the manual and use the EQ and input/gain settings suggested. With all the MB combos, it's possible to dial in a setting that makes the amp "fart out," which could be what you are experiencing.

The settings are in the QUICK START section.

http://www.gallien-krueger.com/produ...60-0520-B0.pdf

--Steve

benchbass · #6 02-26-2013, 09:17 AM

Ok thanks for the help bass_pounder. If I have all 4 tone knobs set to mid, and the pregain and master volume to half and I still have the issue. I don't think it is hitting full output, because at half power I can't hear myself in my drummers basement when I play with him an my other friend on the guitar, and this amp is suppose to be a 200 W amp :P

Stev187 · #7 02-26-2013, 09:23 AM

Quote:

Originally Posted by benchbass

If I have all 4 tone knobs set to mid, and the pregain and master volume to half and I still have the issue.

From the manual:

Set the master volume to 3 o'clock. (MB210, MB115 and MB212 only) While playing, turn the input gain up to the desired volume level.

*Some passive instruments can have output levels similar to active electronics. If the sound is distorted when using the passive input, the active input should be used.
* It is recommended that the limiter be engaged during high volume applications.

Try setting the master to 3 o'clock and use the input gain as your volume control--see if that helps.

--Steve

benchbass · #8 02-26-2013, 09:30 AM

Steve, "fart out" is a good way to put it that's exactly what it sounds like! Ricken Boogie, what does "hot output" mean exacctly? I have an ibanez sr700 and I don't max out any of the tonal controls or anything. I have a feeling the speaker may be blown, but the funny thing is the sound still is pristine at lower volumes, like for practicing by myself at home it's ok. Is that possible with a blown speaker? Also any idea of a price range to take it in if, lets say the speaker is blown?

Stev187 · #9 02-26-2013, 09:53 AM

Quote:

Originally Posted by benchbass

Steve, "fart out" is a good way to put it that's exactly what it sounds like!

Not my term, but it sounds like that's what's happening. Use the settings above and see if you can get it louder without distortion. 200w should cut it in a band setting, but if your guitarist and drummer are really loud, you might be at the edge of this unit's capabilities.

Regarding "hot output," here's what the manual says:

*Some passive instruments can have output levels similar to active electronics. If the sound is distorted when using the passive input, the active input should be used.

Again, your speaker may not be blown. A number of us have had to spend a while "dialing in" the right settings with these combos to avoid this issue.

--Steve

Bass_Pounder · #10 02-26-2013, 10:00 AM

Quote:

Originally Posted by benchbass

Steve, "fart out" is a good way to put it that's exactly what it sounds like! Ricken Boogie, what does "hot output" mean exacctly? I have an ibanez sr700 and I don't max out any of the tonal controls or anything. I have a feeling the speaker may be blown, but the funny thing is the sound still is pristine at lower volumes, like for practicing by myself at home it's ok. Is that possible with a blown speaker? Also any idea of a price range to take it in if, lets say the speaker is blown?

The speaker may not be blown, but may have physical damage.

If the speaker has been pushed too hard, it can develop cone creasing (I can't find any pics online to illustrate).

This happens from over excursion of the cone, and looks like "extra" lines usually around the outer portion of the speaker near the surround.

If your speaker has this problem, it will sound fine at low volume, but becomes very distorted the more you turn up. There is no repair - the speaker will have to be reconed or replaced.

Bass_Pounder · #11 02-26-2013, 10:03 AM

Cone creasing:

http://olsenrepair.com/images/Test-8.JPG

http://www.talkaudio.co.uk/ipb/index...-speaker-cone/

Joe Louvar · #12 02-26-2013, 10:04 AM

Good info/advice above - FWIW (assuming the speaker/driver isn’t shot) the GK MB115 combo amps are a little bass heavy, try turning off the contour and rolling off a little bass.

Stev187 · #13 02-27-2013, 08:21 PM

Any news, OP? Did the unit get under control with different settings? Or do you think it's broken?

--Steve

B-string · #14 02-27-2013, 08:30 PM

If the speaker is damaged the replacement is here http://secure.netsolhost.com/272252....tegory_Code=S8.

Sorry should be the NEO http://secure.netsolhost.com/272252....tegory_Code=S8

benchbass · #15 03-12-2013, 11:18 AM

Sorry guys I've been super swamped with midterms and such these past weeks, I think I'll have time tonight to sit down with it and diagnose what's up with it

BassmanPaul · #16 03-12-2013, 11:52 AM

Quote:

Originally Posted by benchbass

Sorry guys I've been super swamped with midterms and such these past weeks

<Sigh> There's always an excuse!!

AstroSonic · #17 03-12-2013, 12:36 PM

First, definitely download the manual from the GK website. It is actually well written and provides a good starting point on using the amps EQ controls.

The EQ controls on this amp can be used to obtain a wide range of tones. Like the EQ on many amps, this amps EQ will require some playing with in order to develop a feel for what the various controls do and how they interact. You are playing an electric instrument. The amp is a part of the instrument that must be learned. It will not happen overnight. However, following the quick-start directions in the manual will get you some usable tones pretty quickly.

Perhaps the trickiest aspect of this amps EQ is the use and interaction of the gain, boost and volume controls. The amp will reach full output at relatively low settings of the 'master' volume control when the Gain or Boost controls are turned up. You will need to experiment with these to hear how they work.

Basses have different output levels. Those with relatively high output (called 'hot') will cause the amp to reach full output at lower gain, boost and master volume settings.

On this amp (and some other GK amps) the 'boost' control provides additional gain. The boost control is useful in adding 'growl' or overdrive distortion.

To obtain maximum volume in a mix, you need to bring up the mids, cut the bass and engage the compressor. As you push the amp into overload you will likely want to cut the treble a some, and maybe even turn the tweeter off.

IME, this amp should be able to keep up with 2 guitars and an drummer in small to medium spaces, provided that you afe playing at levels that do NOT induce ear ringing. If ringing is occurring ear plugs are needed to protect your hearing. These drop the spl received by your ears by several db. The amount of attenuation produced by most ear plugs varies with frequency, so they alter the tone. Many seasoned players would rather just turn things down by several db and not use the ear plugs.

Good luck!