Burned up my Walkabout?!

[Colonel Monk]

I use my scout at 2 ohms daily and never had an issue!
The only time i had a problem i was running it on its own at 4 ohm, i had stuffed my coat behind my amp not thinking about the vent and in the middle of our second set the amp just cut out...
Light was still on, tubes where still bright but no sound, after a few seconds it came back but cut again soon.
I just plugged straight into the desk and carried on, its only the next day that i realised it was working fine and assumed it must have been cutting because of heat! (the club was so warm i was literally pouring with sweat, and im sure my poor amp didnt appreciate having its air vent blocked!)
Since then i never had another issue and im always careful not to obstruct the air vents...

All that to say that im surprised your amp didnt go in protection mode like mine did!

Right! Every experience I've read where peeps have used 2 ohms it has been fine.

There's alot of "Oh I wouldn't do that" around here but if the engineers say 2 ohms min then that's what they mean! If your car's engine has a 6000rpm redline then that's what you can do! Even though you maybe shouldn't use it all the time it is the line which is permissible.

Whatever, that's not the issue.

I did try it out again on Sunday, and there is still a persistent problem - the volume of the amp is about 20% of what it was. I will be taking it to an authorized repair shop for repair but was curious if anyone had a similar issue, and what ended up being wrong. So far there's nobody responding, so I'm thinking this is fairly rare.

This one is a black silkscreen, pre-input switch and the cab is pre-player control network - I've had it two years I'm guessing it's 5+years old.

To the manual quoters - I'm nearly sure that the Mesa manuals have undergone some changes in the language regarding using 2 ohms. I don't recall reading that in my print manual when I first got the amp.

I do understand why they don't recommend it - this is because it's not 100% tolerant of all volume conditions at 2 ohms. Meaning, that others have reported thermal shutdown with master levels past noon, so the current wording in the manual says as another poster mentioned: "you can do it, but don't cry if it clicks out on you during your set"

I guess the thing I don't understand is why the thermal protection didn't keep the amp from being damaged. There is clearly something wrong with it now, probably caused by the extreme heat condition - but in a yes/no fashion seems the thermal protect should have clicked on sooner.....

 

[Colonel Monk]

Oh, and Bill - I see what you're saying about 4 ohms, but - I think Mesa designed this combo with a 4 ohm speaker to make it as potent and compact a combo as possible. If you add another speaker to use the 300W it's not really compact.

As an 8ohm combo it's only 165(?) watts? I have had a few other 200W combos over the years (solid state ampeg) and on their own in a loud-ish band sitchy they just don't have enough volume/punch/headroom.

The WA 12 is kinda plenty powerful, though the 12" speaker doesn't move enough air. The 15" version does, and keeps up nicely with a band and you still have only one speaker to move around.

I don't think they were off the mark. Once I have two amps, one for each speaker I'll be a happy man. And I'm guessing having the extra headroom with the 15 is gonna be stellar.

 

[barr63]

Hey Guys:

In a spectacular mixture of success and failure, my walkabout failed me at a gig saturday night.

On wednesday, I got my newly acquired Scout 15 to pair with my WA12 combo. 2 ohms. Proved it out at practice on Wednesday night, playing gain at 1 and master at noon for about 4 hours. It was loud, proud, and sounded GREAT. I was in tone heaven, with my walkabout tone finally having the bottom I had been missing.

Saturday, I'm playing at much lower volume - say gain at 1 and master at 9-9:30. Again, sounding just awesome.

We had noticed it was warm on stage - drummer was sweating and seems though the doors and windows were open, the heat was on, and there was a heating duct blowing 140 degree air into the back of my Walkabout! Damn!

So, after the 5th song in our set, it dies on me at the end of Cold Shot. Gone, then came back, but at 20% of the volume. It smelled a bit funny (uhoh) and when I tried turning the volume up, it just wasn't there.

Any idea what might have happened? I thought with thermal protect it would have clicked out before damage occurred? It's happened to me on my Mp600 but it was always normal when it came back on.

Didn't want to run 2 ohms, but as I had a pending trade for another walkabout head I figured at lower volume I could pull it off, especially when it worked the other night (but that room was probably 65 degrees). My plan is for each 4 ohm cab to have it's own amp.

Luckily, I had my MP600 in the car and was able to finish the gig in style with the single Scout 15.

All in all, it was a great gig, even with some drunk chick falling on our guitar players mic stand and bending knobs on his effects with her fall. Good Times..

I did the the same thing with mine couple of years ago. You CANNOT run the walkabout @ 2 ohms. Did you try calling Mesa? They did right by me even though it was "my fault". GREAt company!!

 

[lomo]

Oh, and Bill - I see what you're saying about 4 ohms, but - I think Mesa designed this combo with a 4 ohm speaker to make it as potent and compact a combo as possible. If you add another speaker to use the 300W it's not really compact.

:

The point is that making it 4 Ohm does NOT make it more potent anywhere but on paper.

 

[BassmanPaul]

A thermal protection circuit is all well and good but generally they take time to operate. Thermal inertia of the sensor causes this along with other factors. In the case of the blocked vent at 4Ω the amp is in comfortable territory and the protection had time to operate. Running at 2Ω everything happens that much faster and, in the case of the OP, the output stage went before the protection could kick in. Most likely all of your output MOSFETs will need to be replaced. When one goes the rest tend to follow. As with all MOSFET output stages the new set will have to be closely matched to each other for reliable operation.

 

[Colonel Monk]

The point is that making it 4 Ohm does NOT make it more potent anywhere but on paper.

What are you saying, that 165W at 8ohms is as loud as 300W at 4ohms? Explain Please.

If a 4ohm speaker does not provide you with an opportunity to gain volume by pulling more power and current from the amp then why do it at all? Why not have a 1000ohm speaker then?

 

[naturalkinds]

What are you saying, that 165W at 8ohms is as loud as 300W at 4ohms? Explain Please.

If a 4ohm speaker does not provide you with an opportunity to gain volume by pulling more power and current from the amp then why do it at all? Why not have a 1000ohm speaker then?

I think his point -- colloquially put -- is that a 12" woofer can only handle so much juice, after which feeding it more wattage will not result in a higher SPL.

What happens if you feed 2000W to a 12" woofer? It would probably blow. What about all 300W? You probably get the 'farting out' that most of us have experienced when we push small rigs.

 

[lomo]

Exactly. The 300 watt rating is the amount of power it would take to melt the voice coil. Looooong before that (around 175 watts) the 12 will stop getting louder and begin to compress and eventually distort. Like BF posted, the 300 watts is pure marketing hoopla. I have had the 4 and 8 side by side and the 4 is NOT louder.

 

[kevmoga]

Exactly. The 300 watt rating is the amount of power it would take to melt the voice coil. Looooong before that (around 175 watts) the 12 will stop getting louder and begin to compress and eventually distort. Like BF posted, the 300 watts is pure marketing hoopla. I have had the 4 and 8 side by side and the 4 is NOT louder.

Which really begs the question of why they bothered with a 4 ohm 12-inch Walkabout in the first place. Why didn't they just make them all 8 ohms? It would have certainly eliminated a lot of agoninzing for those of us who want to add a cab.

 

[ishouldbeking]

Which really begs the question of why they bothered with a 4 ohm 12-inch Walkabout in the first place. Why didn't they just make them all 8 ohms? It would have certainly eliminated a lot of agoninzing for those of us who want to add a cab.

They sell them in 4 ohm for exactly the reasons Bill Fitzmaurice said earlier... customers want what "sounds" more powerful on paper. They want maximum wattage, whether that means more volume or no. Since most people probably bought one of these combos with no plan to buy an extension cab, the idea of only using half the available wattage "sounds" like wasted power.

That said, I think I'm gonna leave my combo as a 4 ohm and use the 8 ohm extension. The main lesson I'm picking up is to be judicious with master volume and not to try and squeeze more out of these cabs than you can. For my purposes I'll probably be running this with the 8 ohm extension 90% of the time, both at rehearsal and gigs. The only time I'd use this as a single speaker combo would be for recording, radio shows, acoustic gigs, or things that don't require stage volume. And if I play a bigger show (been known to happen!) I've got a 4 ohm 610 i can plug the head into.

 

[lomo]

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That said, I think I'm gonna leave my combo as a 4 ohm and use the 8 ohm extension. The main lesson I'm picking up is to be judicious with master volume and not to try and squeeze more out of these cabs than you can. For my purposes I'll probably be running this with the 8 ohm extension 90% of the time, both at rehearsal and gigs. The only time I'd use this as a single speaker combo would be for recording, radio shows, acoustic gigs, or things that don't require stage volume. And if I play a bigger show (been known to happen!) I've got a 4 ohm 610 i can plug the head into.

It'll work fine and sound great. I used 4 and 8 12s together for a while and only eventually swapped the 4 for an 8 so I could use other heads (only good to 4 Ohms) with the same cabs.

 

[Colonel Monk]

I did the the same thing with mine couple of years ago. You CANNOT run the walkabout @ 2 ohms. Did you try calling Mesa? They did right by me even though it was "my fault". GREAt company!!

Again, people do it all the time without issue. Did you read what else has been said in this thread?

So I think a blanket "NO NO YOU CAN'T DO IT" is not correct or appropriate. No need to debate it further.

I suppose I should have asked the question more clearly as in HOW MUCH DID IT COST TO REPAIR, AND WHAT WAS WRONG.

 

[Colonel Monk]

I think his point -- colloquially put -- is that a 12" woofer can only handle so much juice, after which feeding it more wattage will not result in a higher SPL.

What happens if you feed 2000W to a 12" woofer? It would probably blow. What about all 300W? You probably get the 'farting out' that most of us have experienced when we push small rigs.

Seems a separate issue - I'm asking above if there is equality between the same head at 4 and 8 ohms. Not "usable" volume. I know what you guys are saying, but that's not what I'm talking about.

For some, distorted is preferable to clean, and vice versa. What you call UN-usable for some, it totally acceptable for another. One of the Walkabout's greatest strengths IMO is that is very musical when dirty.

I don't have any Scout 8's so I can't comment specifically on that, but I do have other 8 ohm cabs that I have used the Walkabout amp with - and yes, clearly with the 8 ohm cab you have to turn the master higher to achieve the same perceived volume you can get with 4ohm cab and a lower master setting.

In that way, technically I don't see how you can say they are the "same" unless you're using the "usable volume" argument literally.

Regarding the 300W being a marketing gimmick? Eh, not really.

The Walkabout is also a standalone head, and it's a head that puts out 300W @ 4ohms. That's really a fair amount of power to work with depending on the cabs you have in your stable. It's true you can't move alot of air with a single 12" speaker regardless of 4 or 8 ohms, but that head could power 2 - 8ohm 8x10s within it's sweet spot, and that is power. In that context the 300W ain't no marketing hype.

However, I'm beginning to see the wisdom of having the Scout cabs as 8 ohm.

My experience though in mixing 4 and 8 in the same rig, is that the 8 ohm Speaker has less volume. In other words, they aren't balanced.

I just got my second Walkabout head last night and do in the weeks to come I'll be doing some experimenting with slaving the second amp.

My goal is to have two Scout 12s and two Scout 15s. I want to do some experimenting with stereo and also dry/dirty separate rigs.

 

[Chef]

You guys can argue all you want about the Walkabout being 2 ohm ready, but, my original walkabout manual says it's 2 ohm safe.
The OP has stated his rear panel has 2 ohm minimum right there on the back panel.

furthermore, a mesa employee addressed this, directly, in the first walkabout megathread, here:
http://www.talkbass.com/forum/showpost.php?p=1577087&postcount=4

quote Ben Strange:
''Technically it's rated at 300 watts into 4 ohms, which should be plenty for most people. However, we've been torture testing a Walkabout at a 2 ohm load at the factory for a while, and have yet to get it to even get hot. I think it's safe to say that you could add another 4 ohm extension and run it at 600 watts for when crazy loud just isn't enough, and you need to push it into stupid loud.''


I've had all three versions of this amp
red face
black face
black'd out

and I've run them all at 2 ohms with no issue. Not just "hook up two cabs and take advantage of the extra juice," but dog whip them for all they're worth, all night.
I like the clean fat tone the walkabout does, but don't like it when it gets overdriven and compressed, so "all it's worth" for me is about noon on input and master.

ymmv, do as you personally see fit, etc.

 

[Colonel Monk]

You guys can argue all you want about the Walkabout being 2 ohm ready, but, my original walkabout manual says it's 2 ohm safe.
The OP has stated his rear panel has 2 ohm minimum right there on the back panel.

furthermore, a mesa employee addressed this, directly, in the first walkabout megathread, here:
http://www.talkbass.com/forum/showpost.php?p=1577087&postcount=4

quote Ben Strange:
''Technically it's rated at 300 watts into 4 ohms, which should be plenty for most people. However, we've been torture testing a Walkabout at a 2 ohm load at the factory for a while, and have yet to get it to even get hot. I think it's safe to say that you could add another 4 ohm extension and run it at 600 watts for when crazy loud just isn't enough, and you need to push it into stupid loud.''


I've had all three versions of this amp
red face
black face
black'd out

and I've run them all at 2 ohms with no issue. Not just "hook up two cabs and take advantage of the extra juice," but dog whip them for all they're worth, all night.
I like the clean fat tone the walkabout does, but don't like it when it gets overdriven and compressed, so "all it's worth" for me is about noon on input and master.

ymmv, do as you personally see fit, etc.

Chef, well-said, as always...

Mine also says "2 ohms minimum"

Having burnt up amps before at 8 ohms, just because you burnt one doesn't mean you were running it at too low a load. Sometimes it's just bad luck, or you're trying to get too much out of it. I burned up my Ampeg B2 at practice a few months ago - it's been losing top end volume for a few years now (needed a re-cap?) and I had it full on to keep up - thar she blows!

One thing I didn't mention earlier was that this head took a tumble about a year ago - it vibrated right off the top of a stack of 115 and 410 and hit the stage - still worked, but the chassis was a bit bent up around the toroid and a few broken standoffs. Might could be that set me up for this failure with the heating duct and 2 ohms? We will see.

Still love the Walkabout Head, and now that I have two I will always have a spare if I need it.

 

[ishouldbeking]

My experience though in mixing 4 and 8 in the same rig, is that the 8 ohm Speaker has less volume. In other words, they aren't balanced.

So are you saying that having one cab receiving less power will cause a noticeable change in tone? I know there will be slightly less volume on tap, and I'm not concerned about that. But are you suggesting there will be a tone or phase issue because of the power imbalance? I was under the impression "imbalanced" cab combinations had more to do with matching different types of cabs (i.e. 410 + 115) rather than matching cabs that have different levels of resistance.

 

[naturalkinds]

My experience though in mixing 4 and 8 in the same rig, is that the 8 ohm Speaker has less volume. In other words, they aren't balanced..

Of course the 8 ohm has less volume in a stack of 4 ohm/8ohm cabinets! It's getting less wattage than the 4 ohm it's daisy chained to on account of its higher impedance.

That doesn't overthrow Lomo's point.

Lomo's point is that 300W through a single 4 ohm cabinet will have the same useable output as 185W through a 8 ohm cabinet.

 

[Colonel Monk]

So are you saying that having one cab receiving less power will cause a noticeable change in tone? I know there will be slightly less volume on tap, and I'm not concerned about that. But are you suggesting there will be a tone or phase issue because of the power imbalance? I was under the impression "imbalanced" cab combinations had more to do with matching different types of cabs (i.e. 410 + 115) rather than matching cabs that have different levels of resistance.

No, the tone per se is the same, but the 8 ohm speaker doesn't get an equal share of the power from the amp. Simple physics:

P(power in watts) = I^2(current in amps squared) x R(resistance in ohms)

Essentially, the lower the resistance the more current that is able to flow. This is why a 4 ohm load on the amplifier can produce more power than an 8 ohm load, and a 2 ohm more than 4, etc.

So pairing a 4 ohm 12" with 8 ohm 15", the character of the 12" will be dominant.

 

[bass4worship]

8 ohms = safe load
4 ohms = safe load
2 ohm = No load / more current / not safe

 

[Chef]

clearly, you never read the walkabout manual.
also, clearly, you ignore the many, many amps that are 2 ohm safe.