Please help me with IIC/IIC+ identification

Ivan Horvat · Feb 25, 2025

Hello everyone!

I am a new member of this forum and have just acquired a MESA Boogie Mark IIC, but I am unsure what version exactly - sorry if this has been posted before, I searched online but couldn't find the answer.

The amp is the 110V blonde combo version, serial 12084 and there is a 12/83 mark on the chassis where the tubes are. There are markings "MB" under the power cord, and "-" above the power cord (so far I've only heard about IIC and IIC+ but not IIC-). It has the Type MS-12 speaker, serial 005630, and the transformers read "MESA 60-162318 EIA606-325" (this one is hard to discern due to double stamping), "MESA 38-15115 EIA606-330", and "MESA 185225 EIA606-234. For the fourth transformer, I am unable to provide info as of now because it would require me to remove the chassis from the cabinet. Also, it has the "PULL DEEP" knob.

I also did the "loop test", and attached please also find a video I took. I don't understand clearly the results to be able to tell if it is a IIC or IIC+.

Thanks,
Ivan

rarebitusa · Feb 25, 2025

That a fairly late serial number in the IIC run. If you want to get more details look at the Mesa For Dummies Guide, packed with great info.

https://boogieforum.com/threads/mark-iic-guide-for-dummies.18184/post-530089

Congrats on the amp!!!

Oh with the loops test you should manipulate both the lead and gain controls with the note ringing

Fiveband · Feb 25, 2025

You might want to pull the chassis and post clear pics of the part numbers on the circuit boards, and the condition of the boards themselves.

Ivan Horvat · Feb 25, 2025

Thanks for the replies guys! I went through the Mesa For Dummies guide, though still some questions remain open for me.

Like you said, Fiveband, the only way to know is to pull the chassis I guess. In the meantime I had contacted MESA customer support and they also told me the same. (Props to MESA, they responded lightning fast! Kudos.)

Before I do that, I will redo the loop test tomorrow, but from what I've heard today in person, there is some influence on the volume and sound. But I will redo it and record tomorrow to be sure.

The amp sounds great to me either way.

rarebitusa · Feb 25, 2025

Ivan Horvat said:
The amp sounds great to me either way.

The MS-12 speaker is fairly rare as well, the cab looks to be in beautiful shape. The date written on the chassis Dec/83 would still have seen the production in the IIC timeframe.

The loop test is definite, the squeal heard on your test is a bit questionable as to what it is.

One other thing to note or try. The Fx loop of the IIC was placed before the Lead Drive chan and the IIC+ had it moved to after the lead chan. If you have a pedal with a direct monitor out you could see if that direct out changes with the lead drive engaged, since what one would hear out of the direct out is just from IIC chan 1.

Ivan Horvat · Feb 26, 2025

I tried the loop test (guitar straight to loop return) again and below are the results.

I seem to notice some change in volume/tone when I turn the LEAD DRIVE knob, but it is very very subtle - albeit there is a difference. Hopefully my phone mic picked it up and it can be heard in the video.
Moreover, I turned the other knobs as well, and the only one that made significant difference is MASTER 1, as showcased in the video, while turning both VOLUME 1 and LEAD MASTER made no change to the volume/tone at all.

I am not sure if that indicates that the amp is a regular IIC or not, but hopefully someone can chime in.

Thanks everyone once again!

PS. rarebitusa, currently I do not have access to such a pedal nor the majority of my setup since I am not at home home. But thank you for the suggestion, I appreciate it.

rarebitusa · Feb 26, 2025

Ivan Horvat said:
PS. rarebitusa, currently I do not have access to such a pedal nor the majority of my setup since I am not at home home. But thank you for the suggestion, I appreciate it.

ok no worries. I haven't done the loop test in a while and will try it later.

I'd suggest one more thing. Take a cable and put it in the Send jack that should decouple all of the circuity before it. Set Vol 1 = 5, Master 1 = 2-3, Treble = 5, bass, mid = 2. Pull Lead pushed in. Hit a note and adjust vol on Master 1 to a moderate level. Set Lead Drive, Lead master = 5. Hit a note and pull the Lead Pull out. Vary the Lead Master volume. Note changes.

The other thing you can try with the same above settings with Lead Pull pushed in, the cable removed from the Send and the guitar now in the input jack. Hit a chord and push/pull the Treble shift. If you hear a change in tone that is IIC.

Ivan Horvat · Feb 27, 2025

Thank you man, I will see what I can do (another thing is that I currently have only one guitar cable at my disposal - don't ask why haha).

It seems like I will have to pull the chassis after all, the only way to know what it is for sure.

Wyzard · Feb 27, 2025

99.9 percent sure it's a IIC. Great amps IMO.

rarebitusa · Feb 27, 2025

Ivan Horvat said:
Thank you man, I will see what I can do (another thing is that I currently have only one guitar cable at my disposal - don't ask why haha).

If you can try the push/pull Treble shift, should be easy enough... I'm kinda curious

Ivan Horvat · Friday at 6:57 AM

I have pulled the chassis out in the end. Seems like a regular IIC to me, although I'm no expert. Also there is an easter egg sticker on the chassis. Hopefully that guy graduated from college

rarebitusa · Friday at 11:09 AM

Very Cool, yea I'm thinking that is a IIC. When they do a "+" upgrade to an RP10 it gets a bit messy

for comparison attached here is a shot of a IIC+ RP10 modified by MikeB. The pdf is a graphic of the IIC layout, which is really handy to reference. Congrats and enjoy.

Ivan Horvat · 2025-03-08T04:17:14-0500

Rarebitusa, thank you for the info!
Now, the question is... should I upgrade it or not? I will be going to the US in July and could take the chassis with me and send it to Mike B. Currently the upgrade costs 1.1k.
Is the + really that better, would I be missing out not upgrading?
Also, this could be one of the last clean mkiic's, so that is my concern as well.

Sorry if this is offtopic.

Fiveband · 2025-03-08T11:47:09-0500

Yes you should upgrade before Mike B retires. And you should ask if he can install the Graphic EQ as well.

rarebitusa · 2025-03-08T12:38:25-0500

Ahhh is the + better??

depends on who you ask. Also depends alot on what you are looking for in an amp and if the intent is to keep it.

The + upgrade will change the Lead Chan big time, in fact usually MikeB will call an upgrade customer and verify they want to do the mod cause in his words... "it will not be the same amp". There's a major increase in gain and a shift in the freq content. Plus the + mod re-positions the fx loop after the lead chan and makes it usable. This 2nd point is really important for the non-GEQ models cause running a GEQ in the loop is often desired.

WRT to resale... the upgrade will certainly increase the value, but a non-GEQ 60W IIC+ doesn't demand the same kind of asking prices as ones with a GEQ or SimulClass. Now as @Fiveband mentioned MikeB is the one who you'd want to do the upgrade. He used to also do an integrated GEQ upgrade, not sure if he still is offering that.

But if you dig the amp currently, think it has the right gain level for your style and plan to keep it then maybe it's not worth it. However if you're on the fence then I'd definitely go for a MikeB + upgrade. Just one player's 2 cents

David Filippi · 2025-03-08T15:04:44-0500

Fiveband said:
Yes you should upgrade before Mike B retires. And you should ask if he can install the Graphic EQ as well.

You know I was reading in the Mark V manual and Doug West puts in a few paragraphs on IIC+ tone. He's a big advocate of the non-EQ IIC+ models because they use a different, smaller coupling capacitor at the end of the effects/EQ stage. So maybe hold off on that.

Ivan Horvat · 2025-03-09T06:50:18-0400

Thank you for the replies guys!

I would not be doing it for resale, I'd like to keep the amp. Maybe what I could do is find someone in Europe who is looking for a IIC and would be willing to trade his IIC+ for my IIC plus compensation on my part. But since we're talking about a very niche thing, who knows if and when someone like that would show up.

I still have some time to think about everything and decide.

Thanks!

Please help me with IIC/IIC+ identification

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