Help! Mesa Boogie Mark Five:35 High Gain/Volume Squealing

Hi all!

I've been dealing with noise issues on my Mesa Mark Five:35 for the past few months and was wondering if anyone could help. Specifically, I purchased the amp brand new on December 28, 2020 and have noted that the amp is excessively noisy on Channel 2's Mark IV mode. In particular, I cannot operate the amp with the volume past 10-11 o'clock with the gain set above 1-2 o'clock without uncontrollable squealing even without anything plugged into the amp besides a guitar. This seems odd as the setting are within the parameters set out for volume and eq in the manual and are taken directly from the John Petrucci Mark V youtube demo. I've tried using an ISP Decimator II G String noise gate to try to take this away, but the noises are still very evident when you start playing and it seems to raise the background noise floor quite a bit when not engaged. Also, I've tried replacing all of my instrument cables, installing new power amp and preamp tubes and playing straight into the amp with no pedals.

I currently play a Gibson Les Paul Standard with a Duncan Sh5 in the bridge and Sh1 in the neck and a Fender HSS strat with a Duncan JB in the bridge. Does anyone else experience this with their Mark Five (is this normal)?

My settings are as follows: Channel 2 - Mark IV Mode -Gain and Treble=1 o'clock, mid=11 o'clock, bass=10 o'clock, presence=11:30 o'clock, volume=10:30 o'clock, 5 band eq in traditional V shape.

Mike

Have you tried a replacement preamp tube? Get a couple of spares and try them in each preamp socket starting with V1.

I replaced all of the pre-amp and power amp tubes with brand new Mesa tubes.

Try the saturation mod. 12AT7 in V4 and V6, that's in the 90 watt version. Not sure what that translates as in the 35 watt version.

It lets you dial in more gain. All credit to Apeman for discovering it.

Mike_Blaszk said:

I replaced all of the pre-amp and power amp tubes with brand new Mesa tubes.

Click to expand...

Is this with the guitar's volume turned all the way down to rule out microphonic pickups?

I would contact Mesa. My Mark Five:25 does not behave like that and the amps are pretty similar. I can set the master all the way up and the gain to about 3:00 or my gain all the way up and my master at about 1:00 before it starts to howl.

Don said:

Mike_Blaszk said:

I replaced all of the pre-amp and power amp tubes with brand new Mesa tubes.

Click to expand...

Is this with the guitar's volume turned all the way down to rule out microphonic pickups?

I would contact Mesa. My Mark Five:25 does not behave like that and the amps are pretty similar. I can set the master all the way up and the gain to about 3:00 or my gain all the way up and my master at about 1:00 before it starts to howl.

Click to expand...

The squealing disappears when the guitar volume is turned down.

Ok so I'm not crazy. You don't experience the same thing and I talked to a Mesa rep over the phone today and he said the settings I have shouldn't be producing the noises im getting. He suggested its likely either a bad preamp tube or something wrong with my guitar electronics (pickup grounding/winding, etc). I will try rolling preamp tubes as was suggested above in case I got a bad new tube and get one of my guitars checked out.

Hi,

I also use a Mark 5 35 and had similar squealing issues. I used a 412 traditional recto cab with it and also used similar settings as you do.

First of all, what cab do you use and how large is the room you are playing in? When doing it in a really small room with these amounts of gain you are gonna get feedback no matter what. Try moving around to the side or the back of your cab and see if it still squeals. If it stops you are just standing too close to the speaker.

Also please report if the squealing stops when you flip to speaker off and use headphones. In my case it did.

Next question, are your pickups covered? Covered humbuckers, even when they are wax potted tend to feedback earlier and even when all the strings are muted. Try hitting the pickups with a chopstick or pencil without hitting the strings and see if there is a loud noise or even squeal out of your amp. If so you need to re-waxpot your pickups and/or check the wiring of your guitar.

Depending on the room size, guitar and speaker it is quite normal at these settings to get squeals.

AaronR said:

Hi,

I also use a Mark 5 35 and had similar squealing issues. I used a 412 traditional recto cab with it and also used similar settings as you do.

First of all, what cab do you use and how large is the room you are playing in? When doing it in a really small room with these amounts of gain you are gonna get feedback no matter what. Try moving around to the side or the back of your cab and see if it still squeals. If it stops you are just standing too close to the speaker.

Also please report if the squealing stops when you flip to speaker off and use headphones. In my case it did.

Next question, are your pickups covered? Covered humbuckers, even when they are wax potted tend to feedback earlier and even when all the strings are muted. Try hitting the pickups with a chopstick or pencil without hitting the strings and see if there is a loud noise or even squeal out of your amp. If so you need to re-waxpot your pickups and/or check the wiring of your guitar.

Depending on the room size, guitar and speaker it is quite normal at these settings to get squeals.

Click to expand...

I use a Mesa 2x12 Recto Cab and I'm playing in my basement which is about 14x18 feet. As for changing position in the room, I can literally exit the room into my hallway and still get the squealing and the noise is present when I play through my headphones using my Universal Audio Ox Top Box (haven't really used the cab clone though). Some feedback is understandable, but its constant and uncontrollable anywhere from 10:30 and above on the volume dial.

With regards to pick-ups, both of my guitars have uncovered pick-ups and their electronics are getting looked at as we speak.

Okay, the fact that it is present in headphone operation also rules out the guitar electronics pretty much.
Some part of the circuit is running beyond stability and oscillating.

As I do not expect Mesa to design an amp that way, there could be a component like a capacitor or resistor that got too warm and now is in a range that destabilises the circuit.

Without schematics available it is hard to rule out which part of the circuit is at fault. Mesa should probably take it in to fix it. They know their circuit best.

AaronR said:

Okay, the fact that it is present in headphone operation also rules out the guitar electronics pretty much.
Some part of the circuit is running beyond stability and oscillating.

As I do not expect Mesa to design an amp that way, there could be a component like a capacitor or resistor that got too warm and now is in a range that destabilises the circuit.

Without schematics available it is hard to rule out which part of the circuit is at fault. Mesa should probably take it in to fix it. They know their circuit best.

Click to expand...

I'll post updates as things progress. Gotta wait for my guitars to finish getting looked at, then will provide the Mesa rep I spoke with with an update and see what they say. In an ideal world I'd just be able to walk into a music store and plug into another Mark Five with the same settings and equipment and do a direct comparison with my amp but Ontario is locked down at moment (no in-store shopping) for Covid and the dealer that I purchased from will not take my guitar(s) in and run a test with the same settings on one of their in-stock Mark Fives.

Note: the local Mesa repair guy I spoke with seemed to agree with you about your schematic/circuit fault point.

Just heard back. Both guitars are in perfect working order and there are no issues with pick-ups/electronics.

Based on the headphone test the guitar electronics were pretty much ruled out.

The next question would be if the instability is occuring in the preamp or poweramp. For that you can check if turning down the presence control gets rid of the issue. If it does that indicates a problem in the poweramp.
You should also monitor the FX send, like plugging it into you audio interface or multi-fx and listen through headphones. Does the squealing still appear in the headphones? That would indicate an instable gain stage in the preamp.
For both tests try to engage and disengage the reverb and eq and see if that makes a difference (it really should not) and report back. These tests can also help the Mesa service to narrow down the problem.

I will try some of the other things recommended above tomorrow or some time next week, but today I got the opportunity to run my equipment on my main floor which is a larger space than my basement. I experimented with the same Petrucci settings, the 'Mark IV Tight Rhythm' and 'Mark IV Lead' settings from the instruction manual and the Mark IV settings from the Mesa Boogie Mark Five:35 Rock Playthrough official YouTube video (all in 35 watt mode). All of the settings except the 'Mark IV Lead' setting from the instruction manual produced the same squealing in all directions within the 15 foot radius of my instrument cable (some areas worse than others). Also, I noted that the settings produced the same squealing in 25 watt mode and 10 watt mode, although the noise wasn't as powerful with my HSS Strat outside of 10 feet from the amp (still evidently there). Even still, the noise is there with or without eq engaged and regardless of which direction the cab is pointed in and is not present in the neck pickup position.

Try a different head to speaker cable. A few years ago I bought a 5 foot livewire brand 10 gauge cable and I got a new thicker, quieter tone.

It won't hurt your wallet buying a nice speaker cable and I bet you'll be impressed with the upgrade like I was and wonder how a $30.00 cable could make such a difference. There is a good chance it'll cure your squealing noise too.

Markedman said:

Try a different head to speaker cable. A few years ago I bought a 5 foot livewire brand 10 gauge cable and I got a new thicker, quieter tone.

It won't hurt your wallet buying a nice speaker cable and I bet you'll be impressed with the upgrade like I was and wonder how a $30.00 cable could make such a difference. There is a good chance it'll cure your squealing noise too.

Click to expand...

Unfortunately, this does nothing. I have 3 different speaker cables at home that I've tried without success.

AaronR said:

Based on the headphone test the guitar electronics were pretty much ruled out.

The next question would be if the instability is occuring in the preamp or poweramp. For that you can check if turning down the presence control gets rid of the issue. If it does that indicates a problem in the poweramp.
You should also monitor the FX send, like plugging it into you audio interface or multi-fx and listen through headphones. Does the squealing still appear in the headphones? That would indicate an instable gain stage in the preamp.
For both tests try to engage and disengage the reverb and eq and see if that makes a difference (it really should not) and report back. These tests can also help the Mesa service to narrow down the problem.

Click to expand...

If I turn the presence control all the way down it doesn't get rid of the issue. Also, if I play directly into my Universal Audio Ox Top Box via headphones without any pedals or anything it doesn't squeal. It actually seems like the only thing that brings that squeal back via headphones is when my ISP Decimator II G String is connected and I have the volume on my amp set to the same level that causes the issue through my cabinet.

Ultimately, it just seems that this is how the amplifier functions within the given treble, gain and volume parameters. Either the volume and/or gain and/or treble control(s) have to be reduced to a certain level in order to avoid whatever is causing this issue internally (this setting seemed to cause the amp to eat through tubes within a few months, so my guess is that the settings are pushing the amp beyond some internal limitation). However, its worth noting that a power supply and full instrument cable change did help slightly with the amount and onset time of the squealing. Anyway, great amp, but a little disappointed in the EQ limitation which, obviously, doesn't exist on the full size Mark V.