Mesa 400+ problems or maybe not

geddyfan · #1 06-15-2011, 04:36 PM

Hey guys my 400 + seems to be losing power, note I said seems to be. Had it checked out today and it's putting out 240 watts clean before clipping. Is that reasonable for that amp. I don't ply it too often but it seems to me it was louder than it seems to be now. Any opinions appreciated. Brian

WhoDidTheElf · #2 06-15-2011, 04:46 PM

How old are the power tubes? They sound like they may be on their way out.

geddyfan · #3 06-15-2011, 04:51 PM

the amp is probably 10 yrs old but if they have 200 hrs on them i'd be suprised

BurningSkies · #4 06-15-2011, 05:05 PM

240 is pretty reasonable for that amp. In the best of times, it's a sub-300w amp...closer to 260-280. So depending upon the bias and any component float, you're in the ballpark.

geddyfan · #5 06-15-2011, 05:07 PM

shouldn't 12 6l6 tubes put out roughly 300 watts clean ?

BurningSkies · #6 06-15-2011, 05:11 PM

Quote:

Originally Posted by geddyfan

shouldn't 12 6l6 tubes put out roughly 300 watts clean ?

With perfect bias and optimization. but for the most part, you're not going to get that. That's why many of us refer to the 400+ as a 'sub 300w amp'.

WhoDidTheElf · #7 06-15-2011, 05:11 PM

Quote:

Originally Posted by geddyfan

the amp is probably 10 yrs old but if they have 200 hrs on them i'd be suprised

Isn't the rule of thumb around 100 hours should replace the power tubes?

Quote:

Originally Posted by BurningSkies

240 is pretty reasonable for that amp. In the best of times, it's a sub-300w amp...closer to 260-280. So depending upon the bias and any component float, you're in the ballpark.

Maybe some one pulled the blinders over me, but isn't the 400+ some where around 400 watts? Mesa's page has it at 500 watts at 2 ohms (should be the same regardless of ohms)
Mesa Boogie Bass 400+ Amplifier

BurningSkies · #8 06-15-2011, 05:12 PM

Quote:

Originally Posted by WhoDidTheElf

Isn't the rule of thumb around 100 hours should replace the power tubes?

Maybe some one pulled the blinders over me, but isn't the 400+ some where around 400 watts? Mesa's page has it at 500 watts at 2 ohms (should be the same regardless of ohms)
Mesa Boogie Bass 400+ Amplifier

Don't quote Mesa. They lie.

WhoDidTheElf · #9 06-15-2011, 05:16 PM

Quote:

Originally Posted by BurningSkies

Don't quote Mesa. They lie.

After doing a quick search I see what you're saying.

Still 10 years or 200 hours is quite a while for power tubes if I'm not mistaken.

Can you run 6550 in a 400+? That would surely get you much closer to that 500 number mesa is quoting.

anderbass · #10 06-15-2011, 05:20 PM

geddyfan,
Make sure your Effects return knob is set to '0' unless your using effects in the loop. Otherwise leaving it set up higher will lower your max volume.

You could also try patching a guitar cord between your Effects send and return jacks too, and see if its any louder. Try this easy test on the rear-panel loop, and also try it in the front panel-loop jacks. Let us know if this helped.

My 400+ had about the same max/clean output as yours, even after a new set of JJ power tunes and an adjustable bias mod. But if you crank it up higher into power tube overdrive it'll peak up to 400 or more watt output. So dont be afraid to turn those knobs up!

Quote:

Originally Posted by geddyfan

shouldn't 12 6l6 tubes put out roughly 300 watts clean ?

Yeah but the 400+ runs the powertubes at very consevitive voltages.

anderbass · #11 06-15-2011, 05:25 PM

Quote:

Originally Posted by BurningSkies

Don't quote Mesa. They lie.

Yeah because no one ever cranks a tube amp up higher than its clean-rating ... right?

They were quoting peak-power output, they just should of included that 'peak' word in the literature.

anderbass · #12 06-15-2011, 05:30 PM

Quote:

Originally Posted by anderbass

they just should of included that 'peak' word in the literature.

Whoops i was wrong, they did:

(quote) --> Mesa Boogie Bass 400+ Amplifier

No less than twelve fan-cooled 6L6 output tubes deliver 500 watts of transient power peaks with cool reliability.

BurningSkies · #13 06-15-2011, 05:33 PM

They're not the only company to quote peak...Behringer does too.

And there are no amp companies that I can think of that will list a 'distorted output' figure.

anderbass · #14 06-15-2011, 06:09 PM

Yeah nice, but anyways I wish all tube powered amp manufacturers listed both the clean and peak ratings. That would be much more meaningful info.

geddyfan · #15 06-15-2011, 06:13 PM

I'll try the patch cord when I get time. Maybe after supper

WhoDidTheElf · #16 06-15-2011, 06:41 PM

Yeah, make sure that's set at 0, it will almost cut your volume in half.

I just tested to see what would happen. Took the balls right out of the amp.

geddyfan · #17 06-15-2011, 06:47 PM

I tried the patch cord and t didn't help, don't get me wrong it still has plenty of power it just seems to me it used to have more. They tech said the tubes as far as being matched were ok. The range was from105 to 11 with only 1 tube at 111 and 1 at 109 everything else was 105 to 107

JimmyM · #18 06-15-2011, 08:49 PM

I'd stick with it, or maybe check your pre tubes. Tubes can last decades, and 200 hours is nothing unless you're running them full out all the time. 240w is pretty good in that amp and about all you can reasonably expect.

TommyKnocker · #19 03-09-2012, 10:28 PM

JimWasHere · #20 03-09-2012, 11:01 PM

I'm kinda curious as to why we're bumping a 9 month old thread... Is there a particular related problem that we might address? I mean, don't you already have one thread going on this Tommy?