valve amp and fuzz question

[omikin]

hi there,

i have a marshall vba400 which i run through a matamp 2x12 with eminence drivers rated at 800w.

my lead goes straight from my bass to the pedals, and from there into the passive input on the amp (i play a rick 4001). i use a bass tube screamer, a big muff, and a devi ever shoegazer. i try to keep the output level from the pedals on a par with the clean signal, which means on the tube screamer and the shoegazer the level knob is set to about a quarter.

i'm new to the world of valve amps, and i'm worried about damaging either the amp or the cab, so i'm basically asking if i should run the signal as i am, or should i run the bass straight into the amp and use the effects loop? will that make a difference?

am i in any danger of damaging anything, or should i not worry?

any help or advice would be really useful!

here's a link to what the shoegazer sounds like (through my little orange crush practice amp btw - apologies for the playing!)

YouTube - ‪Exit Music From A Film. DeviEver Shoegazer‬‏

thanks guys!

[Mr. Foxen]

Bass-pedals-amp is fine. But that head has enough power to eat your speakers, and the fuzz might cover the sound of the speakers tearing up (most fuzzes cut enough low that this won't be an issue). that is about the only possible worry.

[omikin]

I'm confused - the cab is rated at 800w so should be fine, shouldn't it?

[Mark Olson]

You may not melt the voice coils, but you could possibly tear the speaker cones. If you turn up loud and your speakers sound start sounding bad, just turn down. It may not even be a concern.

[Mr. Foxen]

The fuzz will make it sound bad, that is the issue, might not tell it is the speakers making the sound along with the fuzz.

The 800w rating is the melting rating, the slapping against the stops and tearing rating is lower, and frequency dependent, and Matamp don't know how to work it out. Other manufacturers do know, but won't tell you anyway.

[omikin]

I tend not to have the volume of the amp at more than about 4, and i only use the fuzz in a couple of songs rather than all the time, so do you think I should be okay?

on another note - if the matamp isn't enough to handle the amp on a more aggressive volume, would an svt410hlf do the job?

[Mr. Foxen]

Probably not, the Ampeg cabs probably have cheaper drivers than the Matamp. If you like the sound of the Matamp cab, just get another. The volume knob position doesn't tell you much either, max volume might be at 5

[omikin]

okay, you're really going to have to forgive my ignorance here.

are the matamp cabs showing a maximum rating at 800w rather than an rms rating? In which case would that mean the rms rating is somewhere in the region of 400w?

[coreyfyfe]

Originally Posted by omikin

are the matamp cabs showing a maximum rating at 800w rather than an rms rating? In which case would that mean the rms rating is somewhere in the region of 400w?

Forget the thermal rating entirely, it really doesn't mean a thing. Your concern should be with over excursion which no one is going to give you specs on anyhow. What people were trying to say is that you really have to listen to how hard you are pushing the speakers for that kind of thing, and the sound of stressed speakers will be covered up by the sound of the fuzz. As long as you aren't dumping a ton of low bass into the cab along with the fuzz you should be ok.

[Old Fart]

In my experience, fuzz can do more than mask dying speakers. It can cause the death. Good speakers can tolerate a whale of a lot of watts, as long as the signal is clean. Speakers get into trouble when the signal is square, as opposed to round. Distortion is a jagged signal, not round. Running that signal through your tube amp should soften the jagged edges. Solid state distortion is a bit jagged. Digital distortion is a clipped signal and a speaker-killer.

[coreyfyfe]

Originally Posted by Old Fart

Speakers get into trouble when the signal is square, as opposed to round. Distortion is a jagged signal, not round. Running that signal through your tube amp should soften the jagged edges. Solid state distortion is a bit jagged. Digital distortion is a clipped signal and a speaker-killer.

No offense but this is just plain myth. How would we ever listen to synthesizers or distorted guitars in an audio sample if this were true? Distorted signal from an amp can carry more power than the rated output of said amp and kill the speakers, but that has little to do with the type of wave being put out by the amp.

The reason I point this out is because many people think square waves will burn out their speakers--but even in the rare cases where the clipped wave does sort of resemble a square, if square waves really damaged speakers then how would we ever be able to listen to a recording of a synthesizer or a pipe organ? The "overheating piston" action that people claim occurs with a square wave simply does not happen in reality, at least not to any degree more than other big signal peaks; and again in reality clipping audio doesn't result in square waves anyway. The burnt-out coils that amp repair techs regularly deal with all resulted from too much power being sent into the speaker, completely regardless of whatever wave shapes were sent through it. You will hear lots of people--even senior audio professionals--recite the claim that clipping and square waves damage speakers as if it was "gospel truth", but it's really just a long-established myth that will not die. Here's how that myth got started, and maybe why it continues:

When you crank an amplifier to its maximum, and feed it a strong, spiky input signal, it can actually put out much more power than it is rated for--sometimes as much as double the amp's stated wattage. So for example when a bassist has a 200 W amplifier, and a speaker cab rated for 300 W, he might suppose that there's no way the amp could overpower the speakers; but if he dimes the amp's output, and plays aggressively, he certainly could blow those speakers, because he will be sending spikes much higher than 300 W into that cab, all night long. Yes, the amp will have been clipping like crazy, so he (and his amp repair tech) will usually assume it was the clipping that blew the cones--but it was the excess power that actually did the damage. On top of all that, tweeters (high-frequency drivers) are usually rated for a lot less power handling ability than larger speakers are; and the harmonics of clipped waves can mean a lot of extra energy up in the high frequency ranges that typically get sent into a tweeter; so it's fairly common for clipping at high volume to result in way too much power being sent into the tweeter, causing it to burn out. Just remember that the same wave shape, at a lower volume level, would not have done any harm.

source

There is also a lengthy discussion of this in the TB-Amps FAQ.

[omikin]

I may really reign in the use of the Shoegazer until I get that second cab then.

Just stick to the Tube Screamer...

[My name is Mudd]

Originally Posted by Mr. Foxen

Bass-pedals-amp is fine.

And that's what pedals in general are designed for; the effects loop is there for racked stuff, which have a different lvl output.