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Markbass CMD102P distortion and clicks


Fraktal
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I recently bought a third hand MB CMD102P and Im having some sound issues. I'll describe them the best I can so hopefully some of you MB owners out there can advise me.

I set the gain pot to full, since my passive bass cant light up the clip led, it has fairly low signal output (MEC soapbar passive pickups), so I assume Im doing right. All EQ at 12 o'clock save for the VPF filter wich is turned off. Then, with master pot set barely above first dot, the amp will distort for a fraction of second with every loud note attack, as if the limiter was reacting a bit late. Sure, it has a fair volume, but still, for such an state of the art 500w amp I was expecting more headroom and/or a faster reacting limiter. The higher I set the master pot, the more "compression" gets added, and I also hear a few high frequency clicks while sustaining a note, kinda similar to electrostatic sparks noise. Lowering the gain pot and raising the master doesnt seem to change anything.

I thought these amps were supposed to have a very clean sound? Have you guys ever noticed these things with your MB combos?

Thanks a lot!

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Allo!

I've used mine for nearly 4 years with no probs, however, as noted, I'd also recommend trying another bass, with higher output. Does the LED actually illuminate at all with your bass (sounds as though that might be the issue - if its not lighting up, you don't know where you are at, hence you are overdriving the input stage?). I'd personally get the whole unit serviced. Might be worth contacting Markbass to find your nearest service centre - www.markbass.it

Nick

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[quote name='Fraktal' post='258650' date='Aug 9 2008, 01:45 AM']I recently bought a third hand MB CMD102P and Im having some sound issues. I'll describe them the best I can so hopefully some of you MB owners out there can advise me.

I set the gain pot to full, since my passive bass cant light up the clip led, it has fairly low signal output (MEC soapbar passive pickups), so I assume Im doing right. All EQ at 12 o'clock save for the VPF filter wich is turned off. Then, with master pot set barely above first dot, the amp will distort for a fraction of second with every loud note attack, as if the limiter was reacting a bit late. Sure, it has a fair volume, but still, for such an state of the art 500w amp I was expecting more headroom and/or a faster reacting limiter. The higher I set the master pot, the more "compression" gets added, and I also hear a few high frequency clicks while sustaining a note, kinda similar to electrostatic sparks noise. Lowering the gain pot and raising the master doesnt seem to change anything.

I thought these amps were supposed to have a very clean sound? Have you guys ever noticed these things with your MB combos?

Thanks a lot![/quote]

Have you checked that the light is working? sounds to me that you are overloading the input.
This isn't right and i would get in touch with who ever you got it from (assuming you have tried another bass)

Edited by dave_bass5
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I sold it to Daniel and the combo was working without any distortion, clicks or any thing else. I

It had actually been played by another Basschatter 2 days before it was sent and I'm sure they would happily confirm it was working perfectly.

It was wrapped up like a baby in £20 worth of bubblewrap and the heaviest duty box I could find.

I don't believe that a fault with the amp would have developed during the journey, so to be honest I'm stumped.

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[quote name='Old Horse Murphy' post='261507' date='Aug 13 2008, 01:05 PM']I sold it to Daniel and the combo was working without any distortion, clicks or any thing else. I

It had actually been played by another Basschatter 2 days before it was sent and I'm sure they would happily confirm it was working perfectly.

It was wrapped up like a baby in £20 worth of bubblewrap and the heaviest duty box I could find.

I don't believe that a fault with the amp would have developed during the journey, so to be honest I'm stumped.[/quote]

I agree. these things are built very well and my SA450 has over 150 gigs behind it with no problems at all.

I think its the bass or lead. I would try and get it to the point where the light will come on first. Even maybe plugging in an ipod or CD player, just to check its working.
Ive never had to run an amp with the input gain full up (im sure someone has but im talking about me). I find the input stage of my MB heads to be good.
I can get the light to come on on any of my Basses if i trun it up enough but never past 3 o'clock.

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Yeah, the light works, but to light it up I need to set the gain up to full, then strike all 5 strings at once very violently, then I can see the blue led lighting up for a fraction of second. Nothing new here, my previously owned Trace Elliot GP12X preamp behaved exactly the same, its just my bass, it has lower signal output than average, and also passive. So no, I dont think there is a chance I can overload that Markbass preamp stage with my bass.
Then, setting the master at anything above the first dot will make it distort the initial attack of almost every loud note, quickly engaging (just a tenth of second after or so) what I think might be the built in power stage limiter. Mind that I never use compression, just a bass, cable and amp, to allow dinamics to be as natural as possible. This is something I cant really understand, ok, the thingie is loud, but I have never heard such kind of slow reacting limiter on any other decently priced and regarded bass amp. As an example, warwick combos usually have a built in limiter, but you will never notice it activating after a loud note attack, even though they are cheaper and less powerful than the markbass. Then there are also those annoying high frequency clicks when sustaining a note, but as said here before, that noise might be caused by dirty contacts.

I'll meet a friend this sunday and will try his Alembic on my amp, to see if any of these problems dissapear. Im just afraid the built in limiter might be too slow for my taste.

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Have you tried taking the line out in to another amp (or even PC). Just so see if maybe the pre amp is distorting. That might help narrow down the problem.
I had a similar sounding problem with my MAG Combo and im convinced its the power stage as when i used the line out in to another amp all sounded fine but by itself i couldnt turn the master up without it distorting, even less than 1/4 of the way.

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Oh, I forgot to say I use the bass frequently to record tracks at a friend's PC and the sound is absolutely clean and very powerful, using only a BSS DI box and nothing else, not even plugins! The same can be said about my previous 'dinosaur like' rig, wich was a Trace Elliot rack preamp using the built in crossover at 250hz into 2 Altair bipolar rack power amps (350w+1100w) and a Warwick Terminator 1000w cabinet, again, no distortion at all on loud note attacks or clicks during a sustained note, even running the preamp on max gain and output and also both power amps at max knob setting.

Damn, that amp was too heavy for me... It was a logistical nightmare when carrying to a gig: Around 100lbs just the rack flight case alone, and about 150lbs the cabinet inside its tailored flightcase. Wont argue on its tone, though!

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Like is said above, try putting a different source into the combo & also try a different lead between bass & amp. If you can get hold of another amp & cab then try running a cab from the combo without the speakers on the combo plugged in & vice versa if possible. Process of elimination.

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[quote name='yorks5stringer' post='262817' date='Aug 14 2008, 11:20 PM']Was not aware the little markbass II head, (which is what this essentially is) had a limiter: if there is distortion something ain't right in the signal chain....[/quote]

I agree - if there's a limiter, then thats news to me too!

I'd try another bass - if there's still a problem I'd arrange to get the amp checked out by a qualified repair person.

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[quote name='doctor_of_the_bass' post='262884' date='Aug 15 2008, 02:40 AM']I agree - if there's a limiter, then thats news to me too!

I'd try another bass - if there's still a problem I'd arrange to get the amp checked out by a qualified repair person.[/quote]

There is a limiter but its non adjustable and its for the power section (its in the manual) so if there is distortion at low levels i doubt its to do with this. The limiter is to keep the output clean at higher levels i believe.

I still think taking a feed from the preamp out to something else will help to eliminate the power stage.

Edited by dave_bass5
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[quote name='dave_bass5' post='262918' date='Aug 15 2008, 08:59 AM']There is a limiter but its non adjustable and its for the power section (its in the manual) so if there is distortion at low levels i doubt its to do with this. The limiter is to keep the output clean at higher levels i believe.

I still think taking a feed from the preamp out to something else will help to eliminate the power stage.[/quote]

Yep- there is a non defeatable limiter before the power section

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