Jazzmaster Ultralight Output Power

[jorgemg1984]

Hi!

I want to buy some new cabinet to my Jazzmaster Ultralight head and I am having some trouble with the measured output power. I want to buy cabinets that can handle the power the head puts out - blowing a speaker is something I would like to avoid.

The amp says it puts 250w at 2 ohms. I talked to Fender and they told me 200w at 2 ohms and that the power drops by half at 4 ohms and again at 8 ohms. Talked to Jensen and they told me the speaker on the JMUL cabinet is a regular 2 ohm Neo (which means 100w rated power and 200w musical power).

I know watts measurements are very different from company to company and amp makers like to inflate watts - Fender recognized 200w output power versus 250w advertised. And in my experience the "half-power rule" doesn't apply - Henriksen puts 160w - 4 ohms, 120w - 8ohms and 100w - 16 ohms. Acoustic Image also mentions reduction of power as ohms increase but not half-power - the Clarus 2R mentions 500w - 2 ohms, 400w - 4ohms and 250w - 8 ohms.

Is there any way of knowing exactly how much power the JMUL delivers at 4 ohms and 8 ohms? (At 2 ohms I am fine with the stock cabinet)

Thanks!

[cjm]

Originally Posted by jorgemg1984

Hi!

I want to buy some new cabinet to my Jazzmaster Ultralight head and I am having some trouble with the measured output power. I want to buy cabinets that can handle the power the head puts out - blowing a speaker is something I would like to avoid.

The amp says it puts 250w at 2 ohms. I talked to Fender and they told me 200w at 2 ohms and that the power drops by half at 4 ohms and again at 8 ohms. Talked to Jensen and they told me the speaker on the JMUL cabinet is a regular 2 ohm Neo (which means 100w rated power and 200w musical power).

I know watts measurements are very different from company to company and amp makers like to inflate watts - Fender recognized 200w output power versus 250w advertised. And in my experience the "half-power rule" doesn't apply - Henriksen puts 160w - 4 ohms, 120w - 8ohms and 100w - 16 ohms. Acoustic Image also mentions reduction of power as ohms increase but not half-power - the Clarus 2R mentions 500w - 2 ohms, 400w - 4ohms and 250w - 8 ohms.

Is there any way of knowing exactly how much power the JMUL delivers at 4 ohms and 8 ohms? (At 2 ohms I am fine with the stock cabinet)

Thanks!

My question is...Does it actually matter? Under what circumstances in a jazz setting would it be appropriate to actually deliver even 100 watts to a speaker cabinet?

[jorgemg1984]

I have played non miced gig with several horns, piano, bass, drums... I have had to put the JMUL fairly loud sometimes and the Henriksen almost maxed out once. In an ideal world you would be always through the PA but that doesn't happen always... Wouldn't an Henriksen at 75% of volume blow a 70w speaker?

[stevedenver]

i am assuming that the head doesnt have an impedence selector option-like a marshall for example-

theres a reason they used 2 ohms-and i imagine its headroom among other things-
i know too that the dender matching cab was very light-so perhaps the 2 ohm neo made this possible

i know that generally speaking if you mis match impedence youre asking for trouble sooner or later with the amp-the tranny

might i suggest simply contacting avatar or weber or mojo music supply-and ordering a cab with 2 ohms

[cjm]

Originally Posted by jorgemg1984

Wouldn't an Henriksen at 75% of volume blow a 70w speaker?

I wouldn't necessarily expect it to, unless the input signal from the guitar was being subjected to some sort of preamplification before it reached the amp.

An amp rated at 200 watts, and operated with the volume knob at "11", isn't always delivering 200 watts to the speaker...often not until the input signal is at the knee of compression or actually clipping depending on the amp design.

I mean, think about how many guys worked with big bands back when 15 watt amps (or less) were the norm.

Even when you can't run through a PA, if a speaker rated at 100 watts can't handle it...the problem isn't the speaker. The problem is you're too damned loud.

[jorgemg1984]

Originally Posted by stevedenver

i am assuming that the head doesnt have an impedence selector option-like a marshall for example-

theres a reason they used 2 ohms-and i imagine its headroom among other things-
i know too that the dender matching cab was very light-so perhaps the 2 ohm neo made this possible

i know that generally speaking if you mis match impedence youre asking for trouble sooner or later with the amp-the tranny

might i suggest simply contacting avatar or weber or mojo music supply-and ordering a cab with 2 ohms

It's a solid state amp - it can be used at anything equal or above 2 ohms. Even the manual says it and I have used it with an 8 ohms EV with no problems! (it probably works even better because the heat is lower). My problem is not using at 4 ohms or 8 ohms - is how much output power it will provide...

[jorgemg1984]

Originally Posted by cjm

I wouldn't necessarily expect it to, unless the input signal from the guitar was being subjected to some sort of preamplification before it reached the amp.

An amp rated at 200 watts, and operated with the volume knob at "11", isn't always delivering 200 watts to the speaker...often not until the input signal is at the knee of compression or actually clipping depending on the amp design.

I mean, think about how many guys worked with big bands back when 15 watt amps (or less) were the norm.

Even when you can't run through a PA, if a speaker rated at 100 watts can't handle it...the problem isn't the speaker. The problem is you're too damned loud.

Hmm good - have learned something new today! I was not too loud - non-guitar players are used to tell us to turn down the amp and no one told me to do it so I was fine!

[cjm]

Originally Posted by jorgemg1984

Hmm good - have learned something new today! I was not too loud - non-guitar players are used to tell us to turn down the amp and no one told me to do it so I was fine!

Okay...did it ruin the speaker?

[jorgemg1984]

No - but the speaker was a good match for the amp! EV 200w 8 0hms vs Henriksen 200w 8 ohms...

[cjm]

Originally Posted by jorgemg1984

No - but the speaker was a good match for the amp! EV 200w 8 0hms vs Henriksen 200w 8 ohms...

Here's the point I was hinting at:

Let's compare a Henricksen solid state amp rated at 160 watts to a typical Fender Twin tube amp at 85 watts.

At "only" 85 watts, the Twin was so loud that the United Nations defined it as a weapon of mass destruction.

The Henricksen is rated at about twice the wattage of a Twin. Why?

Because the secret to a good solid state jazz amp is to design an almost absurdly over powered amplifier and then never operate it at anything approaching its rated output power.

You weren't delivering anything remotely close to 200 watts to that speaker unless you and your band members are terrorists.

[BigDaddyLoveHandles]

Originally Posted by cjm

Here's the point I was hinting at:

Let's compare a Henricksen solid state amp rated at 160 watts to a typical Fender Twin tube amp at 85 watts.

At "only" 85 watts, the Twin was so loud that the United Nations defined it as a weapon of mass destruction.

The Henricksen is rated at about twice the wattage of a Twin. Why?

Because the secret to a good solid state jazz amp is to design an almost absurdly over powered amplifier and then never operate it at anything approaching its rated output power.

You weren't delivering anything remotely close to 200 watts to that speaker unless you and your band members are terrorists.

That's true. People often talk about "tube watts" versus "SS watts".

[pingu]

Hi all

This a complicated buisiness because there are many variables
and many ways of measuring power o/p

Peak
Music
RMS etc

and at what distortion percent is the o/p quoted(0.01 per cent THD etc)

We're all used to feeling the peak distortion of valve amps
in fact we dig it ,
(not talking distort fx here , talking about a clean fender tube sound)
a SS amp doesn't distort on peaks as prettily
so we try to stay out of the distortion zone with SS amps !
they just crack and fart when hit too hard

That is why you need a high watts (100 ish ?) SS amp to compete with a
delux or wattever

The lab guys use a continuous sinewave when doing these measurements
Whereas we play guitar or other music waves through em

Sorry to not directly answer the question .... its physics n that innit ?

[jorgemg1984]

Originally Posted by cjm

Here's the point I was hinting at:

Let's compare a Henricksen solid state amp rated at 160 watts to a typical Fender Twin tube amp at 85 watts.

At "only" 85 watts, the Twin was so loud that the United Nations defined it as a weapon of mass destruction.

The Henricksen is rated at about twice the wattage of a Twin. Why?

Because the secret to a good solid state jazz amp is to design an almost absurdly over powered amplifier and then never operate it at anything approaching its rated output power.

You weren't delivering anything remotely close to 200 watts to that speaker unless you and your band members are terrorists.

I did a mistake I meant "vs Henriksen 120w 8 ohms"... Oh so I don't have to worry about blowing a speaker according to you! So what exactly would be the output of an heriksen at 8 ohms for example? If not 120w then how much?

[jorgemg1984]

Originally Posted by pingu

Hi all

This a complicated buisiness because there are many variables
and many ways of measuring power o/p

Peak
Music
RMS etc

and at what distortion percent is the o/p quoted(0.01 per cent THD etc)

We're all used to feeling the peak distortion of valve amps
in fact we dig it ,
(not talking distort fx here , talking about a clean fender tube sound)
a SS amp doesn't distort on peaks as prettily
so we try to stay out of the distortion zone with SS amps !
they just crack and fart when hit too hard

That is why you need a high watts (100 ish ?) SS amp to compete with a
delux or wattever

The lab guys use a continuous sinewave when doing these measurements
Whereas we play guitar or other music waves through em

Sorry to not directly answer the question .... its physics n that innit ?

Even if you didn't answered my question I learned more about the subject - so thanks anyway!

[cjm]

Originally Posted by jorgemg1984

I did a mistake I meant "vs Henriksen 120w 8 ohms"... Oh so I don't have to worry about blowing a speaker according to you! So what exactly would be the output of an heriksen at 8 ohms for example? If not 120w then how much?

I would be confident the rating of 120 watts into an 8 ohm impedance would be accurate.

However, the actual output power is dependent on the signal input power as well. It is exceedingly unlikely that you possess an electric guitar capable of saturating the first stage of amplification in that amp. So the actual output would be less.

How much less? A lot less, but there is no way to know "exactly" how much less. But practical experience with other amps, particularly tube amps rated much lower than 120 watts is an important clue that the actual power output is less than 40 or 50 watts. You simply cannot run 120 watts into a loudspeaker and play with a piano, bass and drums in a jazz setting unless you're also running them through a massive PA and causing hearing damage to club patrons within 75 feet of the bandstand.

Perhaps the problem comes from thinking of an amplifier's volume pot as a power output control. It's really not -- it is a gain control. Power is power and gain is gain. They are not the same thing.

Let's imagine an amplifier stage rated at 10 dB gain maximum, and we present it with a 1 watt input signal. The output signal should be approximately 10 watts. If we increase the input signal strength to 5 watts, the output should be approximately 50 watts. And so on until we reach cut off.

We can continue this thought experiment by pretending to set the amp's volume control where you normally set it for club work. You're at home, and you like to keep things fairly quiet during practice sessions. You plug your guitar in and the guitar's volume control pot is turned nearly off. Hold a chord and very lightly rake the strings with your right thumb. The sound from the amp is very quiet and you can be assured that the output power as measured across the speaker leads is very low.

Now, crank the volume on your guitar wide open and using the heaviest pick you can find, hit that chord as hard as you can without shifting the bridge on the guitar. Congratulations. You just blew the windows of your living room out and your neighbors are fleeing down the street screaming in terror.

But you didn't touch the volume control on your amp even though the output power varied by several orders of magnitude.

So...a Henricksen rated at 120 watts into a 8 ohm impedance...even with the volume control on the amp at maximum, is exceedingly unlikely to be sending anything close to 120 watts to the speaker in any jazz setting, and the fact that you have to crank it up really just means the input signal from your guitar is less powerful than the input signal used by the designer to verify the amp's performance.

You wouldn't play through an 85 watt Fender Twin Reverb set at full volume would you? So you know you're running less power than that with either your Henricksen or the Jazzmaster Ultralight...no matter what they are rated at....

[jorgemg1984]

Wow, thanks man! I really need to start learning more about all these issues but I am more focused on music right now... but I will be leaning step by step!