Question about Treble Shift on Mk IIB

[Dude2Dude]

Hi all,

I've read in the Mk IIB manual that, if pulled, the Treble Shift automatically engages in the lead mode. I'm assuming then that when you switch back to rhythm, the effect of the pulled Treble Shift should be null and void. On my amp, however, when I switch from lead (Treble shift pulled) to rhythm, the mid-heavy sound is still active in the circuit. (I have to manually push in the Treble Shift to disengage it in Rhythm mode.)

The "shifted" tone sounds great when pulled for leads, but sounds like crap when engaged and playing clean rhythm. Is there something wrong with the way my Treble Shift is wired? My amp is a very early HRGX IIB (serial number in the high 5300s, no SUS-4 mount).

Would like to know if this is normal or not, and if there is a way to wire things up so that it behaves in the way I'd like it to.

Thanks in advance!

 

[Dude2Dude]

Hmm, maybe that was too wordy. I'll try again:

On a Mk IIB, is the Treble Shift, when pulled, supposed to affect both the lead and rhythm channels? Or is it just supposed to affect the lead channel?

 

[mesaboogie6L6]

Lead channel. I have the same feature on my Mark III.

 

[Dude2Dude]

From reading the online manual, that's what I thought. Mine doesn't work that way. Wonder if it's because it's such an early model?

If anyone has a Mk IIA and they'd like to chime in with their experience, that would probably solve this.

 

[Rick Mark2A]

I don't know if this will help but I have a Mark IIA and the treble shift affects both channels.

 

[Dude2Dude]

Actually, that helps a lot. Maybe Mesa initiated the disabling feature in later Mk IIB models.

Any amp geniuses know if it would be an easy mod for Mike B to make mine right?

 

[tony777]

Both my C+'s does engage treble shift in both rhythm and lead mode, so I think it's normal.
It probably wasn't meant to do so, but it might be a leak or something in the circuit that was never taken care of completely.
It's only speculations from my point of view though.

 

[TattooU]

seems to only work for lead channel. IIb, ser.no. 107xx

 

[mark2boogie]

I don't know if this will help but I have a Mark IIA and the treble shift affects both channels.

Yes. It is exactly the same on my MKIIA and my now sold MKIIB. The "automatic engagement" that I saw was on a MKIIC and MKIII. But maybe some late IIB were fitted or factory modified with that feature :?: ...

A+!

 

[Dude2Dude]

I don't know if this will help but I have a Mark IIA and the treble shift affects both channels.

Yes. It is exactly the same on my MKIIA and my now sold MKIIB. The "automatic engagement" that I saw was on a MKIIC and MKIII. But maybe some late IIB were fitted or factory modified with that feature :?: ...

A+!

Hi Bruno,

From what I've read — and from the Mk IIB manual that you can download from Mesa's site — it seems that at some point in the run of the Mk IIB, Mesa added the "automatic engagement" feature. Would like to have that myself.

 

[gitapik]

I don't know if this will help but I have a Mark IIA and the treble shift affects both channels.

Yes. It is exactly the same on my MKIIA and my now sold MKIIB. The "automatic engagement" that I saw was on a MKIIC and MKIII. But maybe some late IIB were fitted or factory modified with that feature :?: ...

A+!

Hi Bruno,

From what I've read — and from the Mk IIB manual that you can download from Mesa's site — it seems that at some point in the run of the Mk IIB, Mesa added the "automatic engagement" feature. Would like to have that myself.

I've had my IIB since 1980. The Treble pull definitely effects both lead and rhythm modes. The "automatic engagement" feature was added at the very end of the IIB production period and then taken to the max with the IIC and C+. For my tastes, I'm glad mine doesn't have that feature, as there are times when I just don't want it on.

To the OP: the Treble pull is great for natural breakup when you have Volume 1 at 8 or higher. Those extra mids add more balls to the Lead channel, too. Great for blues and rock. But I'm with you: I'd have preferred a footswitch for it. I've found some ways around it:

1) The Presence control helps. In fact: the difference made by the Presence control is amazing.

2) The guitar's volume pot (though you do lose some of the sparkle).

3) The 5 band eq: instead of setting it for leads, dedicate it to rhythm tones and set it so it smoothes out the mids from the pull pot when you don't want them.

4) The obvious: turn it on or off, depending on the tune. I know that's not the best, but it's great for recording and tunes that don't require too many tonal changes. You can also just walk over the amp during performance and push or pull the pot according to the moment.

5) Don't use it. Personally, I like the clean channel on my IIB more than any I've ever heard. The lead channel's good and a pleasure to have when I'm playing straight through the amp, but I tend to use pedals for the dirt. Got some excellent ones that absolutely shine through the clean channel. There's nothing like an excellent clean amp, in my world...and that's what you've got in a IIB.

I've got a really nice list of suggested settings for the IIB from back then. I can post it here, if you'd like. They're really good with a great balance between lead and rhythm channels.