Hi chaps, new UK member here, MKIIB advice needed.

[ossyrocks]

Hi Chaps,

I'm new to the board, having just registered. I'm a complete amp nut, I've had lots of them over the years. I started out in my teens with a vintage Vox, moved through plexi Marshalls, then Boogies (MKI and Studio 22) and Fenders. I've dabbled with the Dumble style amps too, my friend nearby owns a real Dumble. Anyway, having come full circle (I'm now 46) I'm hoping to get back into Boogies and this weekend I bought a hardwood Boogie MKIIB #7069 with the hope of making this my main amp for my 335.

The amp has me a little puzzled, so I need some advice from those here who have more experience with them. If anyone can help me out I'd very much appreciate it. I'd also like you to look at the amp and determine if it's original or modified in any way, which could explain some things.

I'll list my concerns in order.

1. The reverb is quite weak, even on 10 on the clean channel it's not that present, but when going to the lead channel it then sounds swampy.
2. On the clean channel, it gets louder up to about 4 on the master, but then after that, any further master increases have no effect.
3. The lead channel lacks gain, with the first volume on 7 and the lead drive on 10, there really isn't enough gain for the kind of lead lines I play. Only when adding the boost function can I get close to enough gain.
4. The lead channel is very dark and muddy, I'm struggling to get any crispness out of it. If I eq the lead channel for enough gain and top end, my clean channel is really toppy.

The amp looks original inside, see pics below. The amp is currently running all NOS Phillips 12AX7's in the pre-amp and Sovtek 5881WXT's in the power (I will change these). I have questions too about the ins and out's on the underside of the chassis. There are THREE RCA phono connections underneath the chassis, the reverb tank plugs into two of them, one is un-used? I also have two 1/4" jack sockets under there, one labelled pre-amp and one labelled Boost & Graphic. I had thought that it was supposed to be Reverb & Boost?

Anyway, I hope you can help me guys, I'm digging the clean channel and the added boost with my 335, I just need to get to the bottom of the reverb and the lead channel really, as well as understand what's going on underneath.

Amp Front:

Amp Back:

Ins & Outs underneath - The RCA phono on the left is not currently being used:

Chassis underside:

Inside:

Cable from Reverb Tank, NOTE bare blue wire....

Reverb connected:

Cheers,
Rob

 

[SonicProvocateur]

Welcome to the board, Rob!

There are several threads on the board here about fixing the weak reverb on the IIB. It is common on that model.

What are your settings with the master at 4? With the master at 4 it should be shaking the walls! The 5881 is a 6L6 replacement tube, but is also something like 15% less output and doesn't have the same tone (not as strong or modern, IMO). I personally have a distaste for the 5881's and would go with some 6L6GC's. The master setting thing could be one of several things; settings, the power tubes, crapped out preamp tube or something else.

As for chasing your lead tone, I would suggest getting some new tubes that fit your playing style and plugging them in. The IIB amps are pretty middle of the road tone wise and gain wise, so you can either tame them or let them go wild with tube choices. Forum members are great for giving suggestions! If gonzo chimes in here, he has some amazing tones!

Can't say much about if it's modded or not...maybe someone else can. Anywho, welcome to the board!

Cheers!
Jay

 

[gonzo]

sonic is right, experimenting with valves will help..


but with an amp that old, even tho yours looks to be in pristine condition, the internals have probably drifted out of factory spec.

i had a complete re-cap, along with a few other tweaks, a couple of years ago, and boy that did the job!
yours might just need the full tune up.


there is a point, where going higher on the master volumes of either the overall master, or the lead master, only gets you more saturation.

but the thing you describe, with the lead channel being dark and muddy, that doesn't sound right at all.

IF...... you are using any BASS on your lead channel, try dialing that right out to zero.....

one of the drawbacks with the shared EQ sections, is that the bass control adds a lot of FLUB to the lead channel, but sounds wonderful on the clean side.

for me, i used my GEQ to compromise between my live settings for low end......
when i record, i twist the knobs every which way to get what i want, but for live, i just have to find a happy medium, and live with a bit of lightness of low end on the clean, and a bit of flabby on the lead.


i like the pull function on the lead drive (bright) as well, it adds edge and gain, but i either bring the treble down to keep it from getting hazy, or just the opposite, drive the treble hard, and bring the presence down to about 2, and tweak the 2200hz and 6600 hz on the GEQ til i dial it in.


i personally think there is more gain than I can use, with just the drive and vol 1 dimed on the boogie, but i prefer a cleaner 'BASE' tone, and drive it with a boost pedal for the extra gain. i think that gets you more clarity, but touch sensitivity as well.


as far as tubes go, it all depends on whether you prefer crystal clean tones on clean, or slightly edgy.

you can try AT7's in the P1 slot, instead of 12ax7's.....

but if you want drive, you'll want hotter preamp tubes, and then find the right complement of power tubes for low end clarity.

 

[ossyrocks]

Thanks for the input. It sounds like I'll need to find someone to give it a once over here in the UK. Or....... I might enquire about getting just the chassis back to Mike Bendinelli, I think that is probably the way to go and he can give it some tweaks at the same time.

Does anyone know what's going on with my reverb cables, are yours plugged into the same locations as mine? Do you have a spare RCA phono socket like I do? Also, the Boost & Graphic socket, does anyone else have that?

I'm away in the north east for a few days so i won't be able to post until Sunday.

Thanks again,
Rob.

 

[mark2boogie]

Hi ossyrocks,

We have some little things nearly close :

- I am 47
- I have a 335 as a main guitar
- I have a Boogie MKIIA :

If you want more info, have a look to my Boogie MKII 60/100 Rev Eq thread... If you are not too "technical", it is useless to go that far in details, but let's help a bit... Give some possible general guidelinesFaute De Mieux...

1. The reverb is quite weak, even on 10 on the clean channel it's not that present, but when going to the lead channel it then sounds swampy.

Try to swap the reverb connection and see if it's better (I doubt, but...), otherwise there is probably a bad contact (reverb section of the relay) or a cut / out of value resistor. You should have a deep reverb in clean mode only at 3, and something similar, may be a bit less in lead mode. So the reverb problem is on the clean mode, as a "swampy" reverb at 10, in lead mode, would be normal. In lead mode, the reverb should work correctly around 3-4, not 10. See if you have that.

2. On the clean channel, it gets louder up to about 4 on the master, but then after that, any further master increases have no effect.

It's a misconseption. The master1 is wired in variable resistor, and even LOG, it is unprogressive (at least to my taste). The best is to rewire it in a classical pot : the level increase will be much more spreaded.

The lead channel lacks gain, with the first volume on 7 and the lead drive on 10, there really isn't enough gain for the kind of lead lines I play. Only when adding the boost function can I get close to enough gain.

Pull the bright switch (on the lead master), you should find more gain. It connects a by-pass caps which increases gain. The MKIIA and B ar not "gain factories" like the later versions - MKIIC, MKIII, etc - this is why I like them ! Think about Carlos Santana, not Rectifier... If you do not have correct gain, the by pass caps on the preamp stages may be dry, or some or all the preamp tubes may be faulty.

4. The lead channel is very dark and muddy, I'm struggling to get any crispness out of it. If I eq the lead channel for enough gain and top end, my clean channel is really toppy.

It may be the result of the booster. Not all MKIIA-Bs have the exact same circuitry, but it would be surprising to have a big difference. Again, suspect the bypass caps and the preamp tubes. Check the Presence control.

Also see how behave the amp with another set fo power tubes. Lack of treble, muddiness may result of faulty tubes.

My MKIIA had numerous problems, but nonetheless sounded already good as is, "like a promise", and after I reworked and serviced it, it sounds "as expected the promise" with my 335. So it is worthwhile... Then have your amp checked seriously.

A+!

 

[TiPiMods]

Thanks for the input. It sounds like I'll need to find someone to give it a once over here in the UK. Or....... I might enquire about getting just the chassis back to Mike Bendinelli, I think that is probably the way to go and he can give it some tweaks at the same time.

Does anyone know what's going on with my reverb cables, are yours plugged into the same locations as mine? Do you have a spare RCA phono socket like I do? Also, the Boost & Graphic socket, does anyone else have that?


Rob.

The reverb should be plugged into the two RCA which are close to each other, like on your picture. On my Amp it it was plugged in wrong. After mark2boogie gave me the right hint it worked perfektly. It should be strong even on 2. The third RCA on the left switches the reverb in and out with some Fender type switch.
On my MkIIB I always pull "treble shift" and "pull bright" which adds quite a lot of gain, instead of pull boost, which makes it too dark IMO.
Boost and Graphic is right, you need a stereo cable and the stereo switch, which is available on the Mesa Boogie shop page. (It is labeled: EQ-Reverb, which is wrong) I made me one by myself with two LEDs so you can see what is switched in and out.

Does somebody know, if Mike Bendinelli is working yet at Mesa or if he is already retired?

 

[TiPiMods]

Did you find out something about the blue wire? Is it wired to the tip or the ground of the reverb cable?

 

[brion]

[/quote]

Does somebody know, if Mike Bendinelli is working yet at Mesa or if he is already retired?[/quote]

Mike is still there. I have my Mark II B on his bench awaiting his service.

 

[TiPiMods]

Mike is still there. I have my Mark II B on his bench awaiting his service.

Do you let him do some mods too, or only a service?

 

[brion]

We discussed the loop mod. Here is what I gathered in talking to Mike about the Loop mod. The bottom line on the mod is that it changes the tone and feel of the amp as well as making the effects loop usable if you switch channels. The loop is fine if you set up your effects levels for one channel, the issue with the loop occurs when you switch channels and send more signal to the effects in the loop and clip the input. The mod brings the amp closer to a IIC or III in gain, but it changes the dynamics of the amp enough that some people end up not liking it. The mod is $300 now. I opted to leave the loop alone. I have a Mark III, I'm going to leave the Mark IIB the way it was designed and use it for the tones it has. I am having the filter caps replaced as well as any other components that may have drifted. I am also having the octal sockets replaced as the retaining tabs on one of them have bent which allows the board to flex when removing a power tube. When Mike is done, I will have a reliable amp for at least a couple more decades. He should be done with it early next week so I should have her back in 2 weeks.

 

[TiPiMods]

That's what I read a lot in this forum: the loop mod changes the sound quite a fair bit. I thought about it a lot the last couple of weeks, but I think I leave the amp as it is, because I really love it's overdrive sound, which is very dynamic and powerful. I don't need that much gain anyway cause my playing style is more into the Robben Ford or Santana blues and rock territory. If I need just a bit more gain, I kick in my old Bluesbreaker pedal to push the sustain. And I dont use the loop a lot, most of the time only for a volume pedal.
What I would like to change is the different reverb levels on the two channels, as on the lead channel there is less reverb as on the clean. I think I can fix that with some resistor tweaking.

 

[brion]

I think the loop mod addresses the Reverb disparity between channels as well. I like reverb on clean, but not on gain most of the time so the lower reverb mix on the gain channel should be fine for me.