Mesa 400+ Speaker Output Question

kjs · #1 12-05-2010, 06:24 PM

So, i've been playing this amp for a while and i've never been completely certain as to what is going on with the outputs, specifically their impedance. The transformers are pretty massive, so i haven't been overly concerned about it, but...still...

Now, on my amp, the little lightning bolt symbol appears inbetween the outputs above the words "4 ohm" and "8 ohm," making it more confusing to look at. But to clarify:

The top 2 jacks are both 2 ohms (respectively), the bottom left pair are both 4 ohms (respectively) and the bottom right pair are both 8 ohms, respectively.

Right?

BurningSkies · #2 12-05-2010, 06:28 PM

If your speaker load is a total of 8ohms, use the 8 ohm outputs. If your load is a total of 4 ohms use the 4 and if you have a total load of 2 ohms use the top two that are marked 2ohms.

kjs · #3 12-05-2010, 06:33 PM

Appreciate the reply, but i could use more clarity as i've been told multiple things over the course of using this amp.

A "yes" would do the trick here.

matt11 · #4 12-05-2010, 06:40 PM

The answer, in that case, is no. If you are running two 4ohm cabs, plug one into one of the 2ohm outputs and the other into the other 2ohm output. If you are running two 8ohm cabs, plug one into one of the two 4ohm outputs and the other into the second 4ohm output. If you are running two 16 ohm cabs, plug one into one 8ohm output and the other into the other 8ohm output. Hope that helps. Enjoy your amp, I really miss my 400+.

If you are not convinced, go to this link http://www.mesaboogie.com/manuals/Bass 400 Plus.pdf and read the summary under the heading Speaker Jacks. I know there's a lot of misinformation floating around, so it makes sense to be cautious.

paganjack · #5 12-05-2010, 06:43 PM

matt11 got it right. The impedance listed (2, 4 8) is the TOTAL impedance you are using. So one 8 ohm cab, use the 8 ohm jack. Two 8 ohm cabs (=4 ohms total) use the 4 ohm jacks.

kjs · #6 12-05-2010, 06:46 PM

Right, i understand all that and i'm pretty positive at this point which one are which, but i just wanted to confirm that there weren't some strange bi-amp assumed labels. (like the bottom two were 4 ohms total etc...which if it was the case, your answers would lead to further confusion)

I remember the first time i plugged into it though and thinking *** to myself. Mine looks like this, the lightning bolt always brings the word "bi-amp" into my brain, for whatever reason. It messed with the engineer at our last session.

BurningSkies · #7 12-05-2010, 06:47 PM

How many ways can we all say the same thing?

kjs · #8 12-05-2010, 07:44 PM

Great question.

Anyway, my question is not which jack to use, but rather what are each of the jacks, which has been mostly answered in a roundabout way.

"Use the 8 ohm jack" doesn't help me when i am not sure which jacks will give me 8 ohms.

Just want to confirm that the layout is as follows:

2 2
4 4 8 8

And that the bottom rows' labels aren't based on being summed or meant to be split etc etc, which has been covered.

kjs · #9 12-05-2010, 07:54 PM

To be even more clear, cab is 4ohms, i just plug into either one of the jacks on the bottom left...right?

Again, i am aware that i need to plug into a 4 ohm jack, but my uncertainty is in which jacks will be 4 ohms.

NecroticImbecil · #10 12-05-2010, 08:01 PM

Yes, lightning bolt is the universal symbol for biamp.

If only there was a manual you could read that would clear this up.

BurningSkies · #11 12-05-2010, 08:06 PM

Quote:

Originally Posted by NecroticImbecil

Yes, lightning bolt is the universal symbol for biamp.

If only there was a manual you could read that would clear this up.

What. Like this?

http://www.mesaboogie.com/manuals/Bass%20400%20Plus.pdf

kjs · #12 12-05-2010, 08:10 PM

Quote:

Originally Posted by NecroticImbecil

Yes, lightning bolt is the universal symbol for biamp.

If only there was a manual you could read that would clear this up.

There is, it does not explain the ambiguous labeling. Thanks for the hot tip though.

My question is one of labeling. The top inputs are not labeled and could be thought to be 4ohms as they are in a cluster with some outputs with 4 ohms written under them. I also wanted to make sure that when it says "4 ohms, *lightning bolt*" that each individual jack is 4 ohms, not 4 ohms together...which would be silly, but the amp is practically made for bi-amping and who knows what silly ideas Mesa had. Pretty sure i have my answer, anyway.

BurningSkies · #13 12-05-2010, 08:13 PM

Quote:

Originally Posted by kjs

There is, it does not explain the ambiguous labeling. Thanks for the hot tip though.

My question is one of labeling. The top inputs are not labeled and could be thought to be 4ohms as they are in a cluster with some outputs with 4 ohms written under them. I also wanted to make sure that when it says "4 ohms, *lightning bolt*" that each individual jack is 4 ohms, not 4 ohms together...which would be silly, but the amp is practically made for bi-amping and who knows what silly ideas Mesa had. Pretty sure i have my answer, anyway.

They are labeled. On the top edge above the two 2 ohm outputs.

And the 2x4 ohm taps you're talking about make for a total of a 4 ohm load, therefore if you have 2 8ohm cabs, those are the taps you want.

kjs · #14 12-05-2010, 08:14 PM

Understood. Appreciate the help.

I can see the label for the 2 ohm jacks on the head in the picture, mine does not have that label, for the record.

Thanks again.

kosmicwizard · #15 12-05-2010, 10:44 PM

yes!

Quote:

Originally Posted by kjs

So, i've been playing this amp for a while and i've never been completely certain as to what is going on with the outputs, specifically their impedance. The transformers are pretty massive, so i haven't been overly concerned about it, but...still...

Now, on my amp, the little lightning bolt symbol appears inbetween the outputs above the words "4 ohm" and "8 ohm," making it more confusing to look at. But to clarify:

The top 2 jacks are both 2 ohms (respectively), the bottom left pair are both 4 ohms (respectively) and the bottom right pair are both 8 ohms, respectively.

Right?

kjs · #16 12-06-2010, 10:15 AM

Quote:

Originally Posted by kosmicwizard

yes!

Thanks

bannerman · #17 12-06-2010, 10:23 AM

Sounds like you've got it.

Using the two 8 ohm jacks is no different from running your two cabs in parallel (ie, if your cab has two jacks you can daisy chain them which with normal wiring halves the load). So to re-iterate, if your load is 8 ohms, plug into the 8 ohm jack(s). If it's 4 ohms, plug into the 4 ohm jack(s), etc.

Just like everyone else said but with my own brand of confusion and clarity added. It's actually a very simple (in a good way) layout, but I had to read the manual to understand what the labels meant as well.

anderbass · #18 12-06-2010, 01:46 PM

Mmm... yours seems to be missing something

Quote:

Originally Posted by kjs

kjs · #19 12-06-2010, 01:57 PM

Not mine, but it sure doesn't have all of those toggle switches.

Let's hear it!

BurningSkies · #20 12-06-2010, 02:20 PM

Quote:

Originally Posted by kjs

Not mine, but it sure doesn't have all of those toggle switches.

Let's hear it!

Turns on and off the pairs of tubes...so you can run low-wattage.