mark IIb FX loop problem/question

[thecek]

Hi from Italy,
I've noticed a problem with the fx loop of my mark IIb.
I'd like to use a delay in the fx loop, but it works good only on clean tones.
With overdriven tones there is a loss of clarity and tone, which is more relevant with higher gain settings. The delay repetitions are confused and the overall tone becomes darker.
A similar thing happens with a graphic eq (the old blue version of the mxr 6 band eq, modified with a true bypass footswitch). In other amps I use the same pedal for increasing the volume during solos, but this method don't works with the markII.
The pedal seems not to work and when engaged there is a loss on the high frequencies.
So..
Is this a problem, in particular of my amp, or is it common for all mark IIb?
Maybe the delay and the graphic eq doesn't work because they are true bypass, while the loop needs buffered pedals?
I've read about the fx mod but I would like to keep the amp in its original specs.
And finally, how do you do for increase the volume during solos with this amp?

 

[thecek]

nobody?

 

[lesdavaz2]

Hi from Italy,
I've noticed a problem with the fx loop of my mark IIb.
I'd like to use a delay in the fx loop, but it works good only on clean tones.
With overdriven tones there is a loss of clarity and tone, which is more relevant with higher gain settings. The delay repetitions are confused and the overall tone becomes darker.
A similar thing happens with a graphic eq (the old blue version of the mxr 6 band eq, modified with a true bypass footswitch). In other amps I use the same pedal for increasing the volume during solos, but this method don't works with the markII.
The pedal seems not to work and when engaged there is a loss on the high frequencies.
So..
Is this a problem, in particular of my amp, or is it common for all mark IIb?
Maybe the delay and the graphic eq doesn't work because they are true bypass, while the loop needs buffered pedals?
I've read about the fx mod but I would like to keep the amp in its original specs.
And finally, how do you do for increase the volume during solos with this amp?

I have a MK III blue stripe. I only lightly used a Dunlop Crybaby and recently bought a Barber Tone Press. Both sounded AWFUL through the loop, and I just thought no pedal was going to sound good. Then, I just tried going though the front of the amp. Apparently, the effects loop in my amp is not a parallel loop, and that is the problem. This is supposed to be very pronounced with delay effects which I do not use. Try going through the front input. My pedals now sound great. As for the volume---turn up your guitar.

 

[thecek]

mmm mumble mumble...
I've read somewhere that markIIb's FX loop is probably the first FX loop appeared in the history of guitar amplifiers.
Just because it was one of the first experiment, it is not very good compared to others (and most recent) fx loops.
Mesa boogie has solved these problems with the markIIC series, in particular with the C+.
So, for many IIB users, the fx loop is considered useless.. I would like to know if this thing is shared from others.

 

[DaveP]

It's common due to the placement of the FX loop in the signal chain. This was corrected in the C+ and later model Marks.
There is an FX loop mod I believe that you could have done. Not sure of the exact procedure but possibly someone else will chime in with the details.

 

[dino2sf]

The FX Loop Mod will fix the problem. It will also make the reverb much more usable on the lead channel. It will make the lead channel sound MUCH, MUCH (IMO) better (no more farty, flubby distortion) even if you dont use the effects loop it greatly improves the lead channel. Mine sounds very close to my c+ now. It has slightly less gain than my C+ but the same tone. Mike B said its between a Mark II C and a Mark II C+ as far as gain after the mod (he called it a Mark II B+). I think having the mod done is a must if you want to use the lead channel and/or the effects loop on the Mark IIB. It cost about $300 for the mod last year.

 

[thecek]

The FX Loop Mod will fix the problem. It will also make the reverb much more usable on the lead channel. It will make the lead channel sound MUCH, MUCH (IMO) better (no more farty, flubby distortion) even if you dont use the effects loop it greatly improves the lead channel. Mine sounds very close to my c+ now. It has slightly less gain than my C+ but the same tone. Mike B said its between a Mark II C and a Mark II C+ as far as gain after the mod (he called it a Mark II B+). I think having the mod done is a must if you want to use the lead channel and/or the effects loop on the Mark IIB. It cost about $300 for the mod last year.

Yes, I've read about this mod, but for me is really difficult to send my mesa at Mike B from italy.
I should take it to an italian technician, but in my country there aren't..I mean, there are technicians but they aren't very good with mesa-style amps.. :roll:
On my marshall plexi I've done some simple mods, but this amp has a more simple schematics than a mark IIB, and I'm not so prepared..

 

[thecek]

Today I've tried the FX loop with a volume pedal, as described in this link http://www.ayanmusic.com/history.htm but it don't work.
I'm thinking that there are some problems in the fx loop of my mark 2b...

 

[gonzo]

the loop in my IIb has always worked just fine.

clean, switch to lead, sounds great.

don't know what to tell you.....

 

[thecek]

the loop in my IIb has always worked just fine.

clean, switch to lead, sounds great.

don't know what to tell you.....

Even the volume pedal trick?
Maybe the pot value in my pedal is wrong. It's a 250K, which effectively should be for passive circuits, maybe I should try a 25K.