Speaking of contrarians. Mk VII owners; can you try something for me? Power tubes problem?

[JT]

So this is something that is an extension of my HX Stomp level issues thread. No need to read the thread but keep it in mind as a reference.

HX 3.6. Is there a snapshot volume issue?

So dumb question that I haven't seen anything about. Upgraded to 3.6. It switches amp channels via snapshots. One snapshot is considerably louder than the other despite the channels being volume matched in reality without the Stomp in the mix. Nothing amiss on any of the levels on any of the...

thegearforum.com

Try using the send of the VII to your FX unit (so Mk VII as your preamp) then the output that to the fx return of another power amp. No matter what; channel 3 seems to be MUCH quieter than 1 or 2. I have no idea what could cause this as it is super weird behavior. I was doing this to see how I liked EL34s with the Mark. Unsurprisingly; I do. Even with this limited testing capability to what they would do in the actual amp. Very promising results but that is besides the point here.

What is also odd is if I switch it and use the VII as the power amp and something else as a preamp; channel 3 is UNGODLY loud while 1 and 2 are MUCH quieter. Could this be a power tube issue?

 

[James Freeman]

The Master volumes are post FX Loop?
If you use external Preamp (modeler) into the FX Return, when you switch channels you basically switch Master volumes, yes?

 

[JT]

As a power amp; VII channel 3 is MUCH louder on same wattage settings. As a preamp; channel 3 is much quieter. It's super weird.

 

[James Freeman]

So the channel Master volumes do anything when you have something plugged into the FX Return?

As a power amp; VII channel 3 is MUCH louder on same wattage settings. As a preamp; channel 3 is much quieter. It's super weird.

It seems like the quieter Channel 3 preamp volume is compensated after the FX Loop.
I still need to know where the Master volumes are positioned for it to make sense.

 

[JT]

I need @Desertdweller or @PBGas to give it a go. Master works when used as a power amp. Probably presence too ( I know it does on the BL) but I'm tested out for the day.

 

[Desertdweller]

So this is something that is an extension of my HX Stomp level issues thread. No need to read the thread but keep it in mind as a reference.

HX 3.6. Is there a snapshot volume issue?

So dumb question that I haven't seen anything about. Upgraded to 3.6. It switches amp channels via snapshots. One snapshot is considerably louder than the other despite the channels being volume matched in reality without the Stomp in the mix. Nothing amiss on any of the levels on any of the...

thegearforum.com

Try using the send of the VII to your FX unit (so Mk VII as your preamp) then the output that to the fx return of another power amp. No matter what; channel 3 seems to be MUCH quieter than 1 or 2. I have no idea what could cause this as it is super weird behavior. I was doing this to see how I liked EL34s with the Mark. Unsurprisingly; I do. Even with this limited testing capability to what they would do in the actual amp. Very promising results but that is besides the point here.

What is also odd is if I switch it and use the VII as the power amp and something else as a preamp; channel 3 is UNGODLY loud while 1 and 2 are MUCH quieter. Could this be a power tube issue?

I don't have this problem. All 3 channels are decently balanced on mine. It could be a specific preamp tube. Check the manual for which tubes are specific to channel 3 and have a go at tube swapping to see if it changes things for you.

 

[Desertdweller]

So the channel Master volumes do anything when you have something plugged into the FX Return?


It seems like the quieter Channel 3 preamp volume is compensated after the FX Loop.
I still need to know where the Master volumes are positioned for it to make sense.

Not sure about the clean channel as I haven't really investigated fully, but channels 2 and 3 work on the VII work just like the JP2C. They are master volumes at the power amp stage. The preamp is sending a signal that's preset to a certain volume, which is great for fidelity in the FX loop effects.

 

[JT]

I don't have this problem. All 3 channels are decently balanced on mine. It could be a specific preamp tube. Check the manual for which tubes are specific to channel 3 and have a go at tube swapping to see if it changes things for you.

I'm going to have to dismantle this thing after all Packed in tight!

 

[paisleywookiee]

I'm going to have to dismantle this thing after all Packed in tight!

 

[Desertdweller]

I'm going to have to dismantle this thing after all Packed in tight!

It is really the most amp you can pack into such a tight space. From my experience, once you remove the power tubes and disconnect the reverb leads it's not too had to take out. Just make a point of remembering which reverb lead goes where! I have yet to take apart my VII, though I've taken apart a bunch of Marks in the past. PM me if you run into any snags or need anything.

 

[TSJMajesty]

This is just me, but if I just spent almost $4K on a new amp, I'd be very hesitant to "dismantle" it, unless by that, you mean start swapping tubes. I'm very mechanically-inclined, but I'd still want to be very careful re messing up something. I wouldn't want to give Gibson any reason to not honor the warranty.

How do the symptoms react to changing the wattage switches?

But yeah, I wouldn't be at all surprised if it's tube-related. Tubes are scarce, so who knows? Maybe someone paired 2 power tubes that fell out-of-spec for doing so, just so they could finish up that last box on a Friday.

I downloaded the manual (I like to keep several Mesa manuals on hand), and wow, this is one sophisticated amp!

 

[JT]

This is just me, but if I just spent almost $4K on a new amp, I'd be very hesitant to "dismantle" it, unless by that, you mean start swapping tubes. I'm very mechanically-inclined, but I'd still want to be very careful re messing up something. I wouldn't want to give Gibson any reason to not honor the warranty.

How do the symptoms react to changing the wattage switches?

But yeah, I wouldn't be at all surprised if it's tube-related. Tubes are scarce, so who knows? Maybe someone paired 2 power tubes that fell out-of-spec for doing so, just so they could finish up that last box on a Friday.

I downloaded the manual (I like to keep several Mesa manuals on hand), and wow, this is one sophisticated amp!

Agreed on top sentence. Though it wasn't quite that much. But still certainly cashy.

To do any tube swapping; you have to pull the chassis completely. Power or preamp. As I think over the symptoms; it seems like a preamp tube should have nothing to do with channel behaviors when you are using it strictly as a power amp?

 

[la szum]

Man, another reason to love the MKV even more. Didn't really need it, but they keep stacking up.

 

[TSJMajesty]

To do any tube swapping; you have to pull the chassis completely

Why? I looked at the pics of both the combo and the head, and they're just as accessible as any other Mesa amp I've owned/seen.

Edit: Is it the clearance of the tops (on the bottom) of the power tubes?

 

[JT]

Why? I looked at the pics of both the combo and the head, and they're just as accessible as any other Mesa amp I've owned/seen.

Edit: Is it the clearance of the tops (on the bottom) of the power tubes?

Yep. There is no room to safely maneuver.

 

[TSJMajesty]

Yep. There is no room to safely maneuver.

Wow! All so Mesa could use that same amp head shell, I suppose. That's crazy!

 

[JT]

Wow! All so Mesa could use that same amp head shell, I suppose. That's crazy!

Other than times like this; I like the small headshell. I might be able to get the power tubes out as the cage has just enough clearance. I don't trust the ability to dig around on the preamp tubes side though and then get the pins back in correctly with that limited visibility and space to move. Reading the tube layout isn't really any clearer than talking it out here either

 

[TSJMajesty]

As I think over the symptoms; it seems like a preamp tube should have nothing to do with channel behaviors when you are using it strictly as a power amp?

I might tend to agree, and this may not be relative, but Mesa power amps also use 12ax7 tubes (3 in both my 50/50 and 2:90), so maybe they are in use somehow...?

 

[JT]

I might tend to agree, and this may not be relative, but Mesa power amps also use 12ax7 tubes (3 in both my 50/50 and 2:90), so maybe they are in use somehow...?

Channel 3 is IIB, IIC and IV modes. When you look at the tube layout; it really isn't too clear which one could be the culprit as the gain stages are all over the place I'm going to start with V1 and work my way around. I should be able to pull the preamp tubes from the BL and use them for replacements.

 

[Deadpan]

In the past I've pull a couple power tubes to get in there.

Now, my JP2C sits with the front panel off.