question about 8 ohm speaker output at 50 watts

[toneguy86]

As most of you know the Lonestar manual and a little piece by the output jacks on the back of the LSC mention using the 4 ohm output when you run both channels at 50 watts. I have done this for awhile but after reading that section of the manual again, decided to try using 8 ohms again. I actually like the sound and feel better (probably because the amp is working just a bit harder).

Here's the question...nowhere does it actual say DON'T do this...in fact in the manual it is suggested, but makes comment about the sound maybe being preferable at 50 watts, especially for cleaner sounds...which is not me. There is a little note by the jacks suggesting this...but the manual actual doesn't say you can't. Does anyone know any real reason why this would be bad. I was going to try texting Mesa's customer service department...but thought I would start here.

Thanks in advance.

Mark

 

[MrMarkIII]

The manual I have says this:
"NOTE: At some point in your experimentation with the Channel Power Select switches, try setting one or both of the Channels to 50W and moving the Speaker Load to the 4 Ohm jack. This produces a brighter, snappier response that is great for certain applications, especially clean sounds.

There is no right way, but the difference in response is definitely worth investigating for both clean and overdriven sounds."

You're correct, nowhere does it say "don't do this", because "There is no right way".

Generally, speaker impedance mismatches cause faster power tube wear.
This is mentioned a couple times in the manual, just not specifically for this app.
Hope this helps

 

[toneguy86]

Ya. That is pretty much my reading of things as well, although I wasn't clear on why this would be a mismatch. Maybe someone could enlighten on that point.

I play enough that I do a tube swap once a year anyway so a little more wears it not the end of the world.

If anyone else has perspectives, I would appreciate it.

Mark

 

[elvis]

Running an 8 Ohm speaker on the 4Ohm transformer tap should run lower current in the tubes, and wear them slower, not faster. It will cause the load impedance to be twice as big as nominal.

 

[sam adams]

New LSC owner here.

So am I correct in assuming that on the 50w setting it's removing two tubes and doubling the impedance? For example the 4ohm jacks become 8 ohms and the 8 becomes 16?

 

[plan-x]

I don't think there is an ohm change in 50w mode. I'm no amp tech though.

 

[djw]

New LSC owner here.

So am I correct in assuming that on the 50w setting it's removing two tubes and doubling the impedance? For example the 4ohm jacks become 8 ohms and the 8 becomes 16?

Not a tech here either, but my understanding is that this is essentially correct. The semantics in the manual suggest to me that they wanted to avoid a lengthy technical description of why this does or doesn't work -- since it's safe, they just say go ahead and try it, it's ok. Mesas are tough enough that they can handle a one-step load mismatch with no problem -- not all amps are built to handle that though.

IIRC, they do mention that a mismatch in the other direction is bad (e.g., putting a 2 ohm load on the 8 ohm output) but that scenario is rare -- who has a 2 ohm speaker? I guess you could create a cab with a pair of 4 ohm speakers in parallel and get 2 ohms, but... you get the point.

Anyway, the way I understand it is it's *technically* correct (as far as it goes) to put the 8 ohm speaker on the 4 ohm output if you're running the amp at half-power (50w) for the reason stated above.

 

[MrMarkIII]

New LSC owner here.

So am I correct in assuming that on the 50w setting it's removing two tubes and doubling the impedance? For example the 4ohm jacks become 8 ohms and the 8 becomes 16?

If this were true, Mesa wouldn't suggest plugging the 8 ohm speaker into the 4 ohm jack. You wouldn't need to, would you?

 

[djw]

New LSC owner here.

So am I correct in assuming that on the 50w setting it's removing two tubes and doubling the impedance? For example the 4ohm jacks become 8 ohms and the 8 becomes 16?

If this were true, Mesa wouldn't suggest plugging the 8 ohm speaker into the 4 ohm jack. You wouldn't need to, would you?

My understanding is that at 1/2 power the output jacks are optimally suited for a load that's twice what they normally are.

The language is confusing here -- at least it is to me, since I'm a knucklehead when it comes to the technical aspects of this. "Doubling the impedance" is not really a fully correct statement in this sense -- but since I know what sam adams is getting at, it's essentially right in that you could replace the labels underneath the jacks with numbers that are twice their current value (from 8 to 16, and 4's to 8's). It just means the amp now wants a load with higher impedance to meet the output. The speaker hasn't changed, but a major factor in the equation (the energy coming out of the speaker jack) has. Leaving the speaker plugged in as-is won't hurt the amp, but it's a mismatch when the amp is running at half power (i.e., on two power tubes).

You can confirm Mesa's suggestion by looking at the back of the amp, where it says "BEST WITH 50 WATT" underneath the 4 ohm output jacks (on mine it says this anyway, mine's the 50/100 watt version).

 

[sam adams]

Thanks for the replies. At the first and only practice I've had with it, I tried running an 8 ohm Emperor 4x12 cab with the 8 ohm jack and while 100w setting sounded great, I didn't like the sound of 50w mode(still from the 8 ohm jack). Then when I tried the 4 ohm jack on 50w mode into the 8 ohm cab, I loved it. I went further and set it back up to 50w on the 8 ohm jack(now 16ohm) and ran into a 16 ohm Orange 2x12 and it also sounded fantastic. Ended up using that setup at my show the next day and it was perfect. I ended up confirming my suspicion when I sought out info online.

So yeah, on 50w mode your jacks technically turn into 8/8/16. Though Mesa is confident in their build quality and does not discourage you from a one step mismatch, and actually suggests experimenting with it, because a mismatch makes the amp sound a lot different.

My Orange RV100 act the same way on half power, but since it's 8/8/16 normally, it then turns to 16/16/32... :roll:

New LSC owner here.

So am I correct in assuming that on the 50w setting it's removing two tubes and doubling the impedance? For example the 4ohm jacks become 8 ohms and the 8 becomes 16?

If this were true, Mesa wouldn't suggest plugging the 8 ohm speaker into the 4 ohm jack. You wouldn't need to, would you?

That's actually exactly what they're suggesting and why they're suggesting it. You don't need to though. :wink: