This oscillation behaviour is reported in the old manuals also. Surely on the original Quad preamp manual and AFAIR on the 2C+ manual also (the one made with the typewriter). And I can confirm that, whatever tubes you mount, the Quad (mine one and another of a bud) self-oscillates at those settings. I think that, at least, the MK2C+, MK3 and Quad do that because of their versatility: the allow you to have a crunch on Rhythm mode and when cascade on the Lead it's obviously simply too much gain. That kind of gain that mush the tone, also. And the quality of attack is lost, also. I think I spent some months learning the basics on how to dial tones on those marks, aside metal settings that are only apparently simpler. And I had to cleanup my guitar tecnique also, because the amp revealed how I sucked. No surprise that Kirk Hammet was begging Hetfield to dismiss Marks and use other amps. For years. I must add, the Triaxis (I have one of the oldest, under #200) and the Marks from 5 to above, the JP, and all the "here and there" pseudo-replicas on other series, are not as flexible so they don't oscillate.
Hey, thanks for watching and commenting. This is my 5th Mesa Mark amp (IIB, a couple of III and a IV) and this is the first to oscillate with those settings, thus my surprise. Since, I've heard from other owners a mix of yes and no, that it happens or doesn't happen with their amps. If you look at 1 of my videos, I demonstrated my III+ red stripe with even more gain in the settings and making no oscillation sounds. I also agree that changing tubes would not rectify this issue. I have seen a video showing the inside of the reissue and it is the proximity of the cables/internal components that is the root cause.
Hey Paul. At least the JAN/GE 5751 did help but since that is early in the cascade, but it may not be the ideal position. I only suggested it as a feasible option. If the oscillation only occurs with the lead mode. You can try the 5751 in V4. The lead drive circuit for this amp uses V3B as the overdrive tube and V4A as the boosting stage. Since it creates an asymmetrical form of distortion some of the upper harmonics from the clipping caused by V4A may be just enough to trigger oscillation to occur. Looking at the schematics of the IIC+ original, when the lead mode is not used, there is a 3.3Meg resistor with a 10pF cap in parallel to it used as a bridge circuit to connect V1B to V2A. This circuit remains when using the lead drive mode and will be in parallel to the V3B->V4A circuit. That bridge forms a positive feedback loop, only if the output from V4A is greater in magnitude to the signal level provided by V1B. The 10pf cap in parallel to the 3.3Meg resistor on the bridge circuit will be less of a restriction for higher frequencies. The oscillation frequency may be in a range above our hearing, however, what is heard is probably a sub-harmonic of the fundamental frequency of oscillation. As it continues to oscillate, the sound will increase in volume as it is self- supporting by the bridge circuit that is acting as a positive feedback loop. There is a form of negative feedback on the V3B triode (120pF coupling the control grid to the cathode) but that may not be enough to prevent oscillation. Change in gain factor on V4 may improve the issue with the parasitic oscillation. Not sure how the 5751will effect the overall gain character of the desired sounds for the lead mode. If the 5751 drops the gain too much, try the EH7025 in V4. There is yet another tube that is similar to the Mesa branded JJECC83s and actually looks identical to it. I bought a few of them to try out in my Mesa amps. JJ E83CC is a frame grid, low noise floor version. If you buy any of those, double check the box and what is printed on the tube. My first set, I was shipped the wrong tube and got E88CC tube by mistake. There is also the long plate ECC803s with a bit less gain than the 12AX7/ECC83s, There is also the ECC83MG which is mid-gain. There are other tube brands out there. It does not have to be JJ. This oscillation issue is not something I have encountered with any of my Mesa amps yet. I guess that may change once I get the reissue IIC+.
Eric, thank you again for the GE JAN/5751 tube!! And for all the information! I also ordered Tungsol and Genalex 12ax7 tubes that claim low microphonics and yet still have high gain. Those will be arriving in the next few days. In the meantime, I will try both the 7025 and 5751 at the V4 position and share the results. Thanks again!
I've worked on quite a few Boogies from the early 80s up to present and this is a typical thing believe it or not. You look inside an early one and you see signal wires with other wires wrapped around them..its because of the same type of thing...which is to say lots of cascading gain stages requiring trickery to get it stable. While its totally reasonable to expect a 3k+ amp to be flawless, this is a little different...like buying a 2000hp race car then being disappointed because its loud, won't idle or drive straight. I say all that to make this point: If that's all these are doing at extreme settings, then I'd say the folks at Gibson/Boogie did pretty darn good. I've had to work on originals that were far worse off.
Thanks for watching and commenting. A few have said the same thing. This being my 5th Mark series amp (IIB/III+/IV) was the first to oscillate. So this was all new to me.
@@paulazzi1855 If you can get them try some Tungsram ECC83, I have had a few MK CII+ ocver the years and they all exhibited the same kind of oscillation problem but the tungsram were very good at calming it right down. The amp you have sounds really nice.
@troyshowalter8163 what do you mean by that? I brought the amp back and Mesa heard it, the shop heard it. We opened another IIC+ from a box and it was the same. Look up on TH-cam for other reissue that oscillate with high gain settings and you'll see a few.
Are you running the lead drive above 8 ? Also Since its mentioned in the manual, its probably inherent in the design. I have a couple Mesa high gain amp heads. I’m waiting to buy the II c + high gain and have never had extreme settings like that. I do run them aggressive like you. 😊The treble, mid and bass on the Mark amps are very interactive. If you raise the bass and mid, does it do anything to reduce the issue? Can you increase the treble with the EQ or does that give you the same result? You could also have a preamp tube that is on the edge of being microphonic.just trying to help.. diming the controls on the high gain amps will result in this including microphonic tubes.
Why not reach out to Mesa to have this amp either swapped or repaired? It seems your amp is the only one on TH-cam that is experiencing this, this seems like a QA/QC issue they'd handle.
Thanks for the comment. I promise you I am not the only one that the reissue oscillates at high gain settings. I have spoken with many others and with the exception of only 1, everyone else oscillates. At the guitar store, we opened another IIC+ and it also did the same. Here are 2 links from others. th-cam.com/video/-6PK-pIVU6U/w-d-xo.html th-cam.com/video/belJc2B6Frg/w-d-xo.html So, mine is clearly not the only one doing this. Oh, and I have reached out to Mesa and I have all the emails. They know about this and say it is to be expected.
The next fix is to listen to Dann Valentino and replace the cables with shielded ones inside the amplifier, do the proper cable managment. It's a shame Dann is that far away from you.
@@paulazzi1855 For me he is already a highly qualified technician. I don't know if it is right to call a certain person a replacement or the next someone. Everyone wants to be themselves more. And I think out of respect there is no one who could be Mike B. except Mike B. We're we are one of a kind.
This oscillation behaviour is reported in the old manuals also. Surely on the original Quad preamp manual and AFAIR on the 2C+ manual also (the one made with the typewriter). And I can confirm that, whatever tubes you mount, the Quad (mine one and another of a bud) self-oscillates at those settings.
I think that, at least, the MK2C+, MK3 and Quad do that because of their versatility: the allow you to have a crunch on Rhythm mode and when cascade on the Lead it's obviously simply too much gain. That kind of gain that mush the tone, also. And the quality of attack is lost, also.
I think I spent some months learning the basics on how to dial tones on those marks, aside metal settings that are only apparently simpler.
And I had to cleanup my guitar tecnique also, because the amp revealed how I sucked. No surprise that Kirk Hammet was begging Hetfield to dismiss Marks and use other amps.
For years.
I must add, the Triaxis (I have one of the oldest, under #200) and the Marks from 5 to above, the JP, and all the "here and there" pseudo-replicas on other series, are not as flexible so they don't oscillate.
Hey, thanks for watching and commenting. This is my 5th Mesa Mark amp (IIB, a couple of III and a IV) and this is the first to oscillate with those settings, thus my surprise.
Since, I've heard from other owners a mix of yes and no, that it happens or doesn't happen with their amps.
If you look at 1 of my videos, I demonstrated my III+ red stripe with even more gain in the settings and making no oscillation sounds.
I also agree that changing tubes would not rectify this issue. I have seen a video showing the inside of the reissue and it is the proximity of the cables/internal components that is the root cause.
Hey Paul. At least the JAN/GE 5751 did help but since that is early in the cascade, but it may not be the ideal position. I only suggested it as a feasible option. If the oscillation only occurs with the lead mode. You can try the 5751 in V4. The lead drive circuit for this amp uses V3B as the overdrive tube and V4A as the boosting stage. Since it creates an asymmetrical form of distortion some of the upper harmonics from the clipping caused by V4A may be just enough to trigger oscillation to occur. Looking at the schematics of the IIC+ original, when the lead mode is not used, there is a 3.3Meg resistor with a 10pF cap in parallel to it used as a bridge circuit to connect V1B to V2A. This circuit remains when using the lead drive mode and will be in parallel to the V3B->V4A circuit. That bridge forms a positive feedback loop, only if the output from V4A is greater in magnitude to the signal level provided by V1B. The 10pf cap in parallel to the 3.3Meg resistor on the bridge circuit will be less of a restriction for higher frequencies. The oscillation frequency may be in a range above our hearing, however, what is heard is probably a sub-harmonic of the fundamental frequency of oscillation. As it continues to oscillate, the sound will increase in volume as it is self- supporting by the bridge circuit that is acting as a positive feedback loop. There is a form of negative feedback on the V3B triode (120pF coupling the control grid to the cathode) but that may not be enough to prevent oscillation. Change in gain factor on V4 may improve the issue with the parasitic oscillation. Not sure how the 5751will effect the overall gain character of the desired sounds for the lead mode. If the 5751 drops the gain too much, try the EH7025 in V4. There is yet another tube that is similar to the Mesa branded JJECC83s and actually looks identical to it. I bought a few of them to try out in my Mesa amps. JJ E83CC is a frame grid, low noise floor version. If you buy any of those, double check the box and what is printed on the tube. My first set, I was shipped the wrong tube and got E88CC tube by mistake. There is also the long plate ECC803s with a bit less gain than the 12AX7/ECC83s, There is also the ECC83MG which is mid-gain. There are other tube brands out there. It does not have to be JJ. This oscillation issue is not something I have encountered with any of my Mesa amps yet. I guess that may change once I get the reissue IIC+.
Eric, thank you again for the GE JAN/5751 tube!! And for all the information! I also ordered Tungsol and Genalex 12ax7 tubes that claim low microphonics and yet still have high gain. Those will be arriving in the next few days.
In the meantime, I will try both the 7025 and 5751 at the V4 position and share the results.
Thanks again!
I've worked on quite a few Boogies from the early 80s up to present and this is a typical thing believe it or not. You look inside an early one and you see signal wires with other wires wrapped around them..its because of the same type of thing...which is to say lots of cascading gain stages requiring trickery to get it stable. While its totally reasonable to expect a 3k+ amp to be flawless, this is a little different...like buying a 2000hp race car then being disappointed because its loud, won't idle or drive straight. I say all that to make this point: If that's all these are doing at extreme settings, then I'd say the folks at Gibson/Boogie did pretty darn good. I've had to work on originals that were far worse off.
Thanks for watching and commenting. A few have said the same thing. This being my 5th Mark series amp (IIB/III+/IV) was the first to oscillate. So this was all new to me.
Have you done this test with a guitar plugged in, Does it still do it when the guitar is plugged in.
Hey buddy. absolutely! Oscillation, with certain amp settings, occur regardless of which guitar is plugged in or not.
@@paulazzi1855 If you can get them try some Tungsram ECC83, I have had a few MK CII+ ocver the years and they all exhibited the same kind of oscillation problem but the tungsram were very good at calming it right down. The amp you have sounds really nice.
ALREADY HAVING TO WORK ON THE GIBSON JUNK...
I guess that's just the price you gotta pay to get the chug.😁
And it sure does Chug!! 😃
Paul, where did you buy the mark IIc+ from ?
I preordered it and picked it up on the first available day, 12/3 from a guitar shop in McKinney. It's an authorized Mesa reseller.
@ ok, have you checked the lead drive ?
@troyshowalter8163 what do you mean by that? I brought the amp back and Mesa heard it, the shop heard it. We opened another IIC+ from a box and it was the same.
Look up on TH-cam for other reissue that oscillate with high gain settings and you'll see a few.
Are you running the lead drive above 8 ? Also Since its mentioned in the manual, its probably inherent in the design. I have a couple Mesa high gain amp heads. I’m waiting to buy the II c + high gain and have never had extreme settings like that. I do run them aggressive like you. 😊The treble, mid and bass on the Mark amps are very interactive. If you raise the bass and mid, does it do anything to reduce the issue? Can you increase the treble with the EQ or does that give you the same result? You could also have a preamp tube that is on the edge of being microphonic.just trying to help.. diming the controls on the high gain amps will result in this including microphonic tubes.
@@troyshowalter8163 yes. Vol1 Treble and lead drive are at 8. Bass at 0.5, middle at 0. Presence at 4.5, lead master varies between 4-8.
Why not reach out to Mesa to have this amp either swapped or repaired? It seems your amp is the only one on TH-cam that is experiencing this, this seems like a QA/QC issue they'd handle.
Thanks for the comment. I promise you I am not the only one that the reissue oscillates at high gain settings. I have spoken with many others and with the exception of only 1, everyone else oscillates. At the guitar store, we opened another IIC+ and it also did the same.
Here are 2 links from others.
th-cam.com/video/-6PK-pIVU6U/w-d-xo.html
th-cam.com/video/belJc2B6Frg/w-d-xo.html
So, mine is clearly not the only one doing this. Oh, and I have reached out to Mesa and I have all the emails. They know about this and say it is to be expected.
The next fix is to listen to Dann Valentino and replace the cables with shielded ones inside the amplifier, do the proper cable managment. It's a shame Dann is that far away from you.
@fedrek01 yes, 100%!! I believe he could be the next Mike B once Mike retires.
@@paulazzi1855 For me he is already a highly qualified technician. I don't know if it is right to call a certain person a replacement or the next someone. Everyone wants to be themselves more. And I think out of respect there is no one who could be Mike B. except Mike B. We're we are one of a kind.
@fedrek01 well said buddy!
@@paulazzi1855 Thank you!