Fender Jazzmaster Ultralight Ohm Question

BreederCreature

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I just got a Fender Jazzmater Ultralight head and amp. My goal is to run the 250 watt head through a new 250 watt 2x12 I'm getting in a few weeks. I tried the head with the 1x12 I got with it and it was real loud, but didn't sound very "big". I tried it with my Marshall 4x12, but had to run the cable through the head's headphone jack since the head's output has a speakon jack. The power was cut down a looooot because the head is 2 ohm and the cab is 8 ohm (I believe).

My question is, if I got a speakon to 1/4'' cable and ran that through the speakon output jack on my 250 watt head to the regular 1/4'' input jack on a 250 watt 2x12, would I still get all the power of the head or would it still be cut down?
 

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My guess is that you might damage the Ultralight head, because it's looking for a speaker load. By running it into another head, you might blow the output transistors. Another thing you might want to consider is running the output into another amp, you'll be overloading the input on the other amp.

Just from what I've read on the Internet, the Ultralight is a very clean amp.
 

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BreederCreature said:
My goal is to run the 250 watt head through a new 250 watt 2x12 I'm getting in a few weeks.

I'm a liitle confused and I hope it is only me. Ignoring cabinetry you have two amps and two speaker cabinets. In theory so long as you are aware ot speaker impedence you could use one amp to drive both speaker cabinets. That would require a speaker out jack on the amp and a External Amp in on the other speaker. You could also daisy chain the amps so that the Pre-Amp out from one amp was driving the other. The success depends upon matching levels but it lets you have the sound of the first amp and the power of the other.

However, in no way do you want to connect a speaker output from the first amp to a instrument or pre-amp input on the second amp. That is a real good way to fry one or both amps.

Hopefully CJ will chime in with some precise questions or a clearer description of what will work and the dangers.
 

BreederCreature

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I see what you're saying. Neither of my speakers have out's though, the new one I'm getting does, but I don't have it yet.

I'm just wondering if the ohm load would blow up the speakers? Or if I hooked up a 250 watt head to a 120 watt 4x12 for a "bigger" sound, would that fry it?

I'm also not really satisfied with the sound I'm getting from the jazzmaster head. I think I would smitten by the 250 watts and didn't think about the fact that it's a "jazz"master while I'm in a rock band haha. I'm hoping it may sound more rocking in a bigger speaker though.
 

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OK, so I was on crack when I read your first post.

The few references I could find on your amp were on a jazz forum, and you know those jazz guys, distortion isn't in their vocabulary. OTOH, it seems to me like it would take pedals very well. Can you beg, borrow or steal a POD to mess around with? Since it sounds like the Ultralight isn't going to add much spice to your tonesoup, I would try amp modeling boxes or a multi-effects box in front of it.

A buddy of mine daisy chains a POD and some old ART multi-processor and gets some decent sounds out of that.
 

capnjuan

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Hi BreederCreature ......how ya fixed for technical data? Do you know what the output impedance of the headphone circuit is? How about the primary output? I'm not sure I can help much but I can tell you that not matching amp output impedance and speaker impedance will put your gear at risk.

The transistors were designed to operate into a specific 'load' or impedance; the resistance offered either by the voice coil of one speaker or multiple speakers wired so that the total impedance matches your gear. Some information on wiring speakers to achieve varying impedances http://colomar.com/Shavano/spkr_wiring.html

If you blow the output transistors, they will ruin your speakers too. No, I don't think it's a good idea to connect 250 watts of signal to a speaker array or cabinet rated for 120 watts. Sucess in 'daisy-chaining' outputs to inputs depends mostly on impedance-matching between the input signal and the circuit. At the risk of sounding like a wet blanket, if you don't like what the amp does, maybe you need a different amp????

Edit: a better reply below. cj

Good luck with your amp! cj
 

BreederCreature

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I have no idea about the headphone jack, but I'm pretty sure I shouldn't try to use that as the main out anyway haha. I bought a speakon to 1/4" converter today, but my cab is at my drummer's house and I'd rather look into it first than just go and blow everything up if that's the case.

The jazzmaster head is 2 ohms, I think that's the impedance of its output. I have no idea about the Marshall cab, but I think the head is 115 or 120 watts.

My master plan is to get the most power out of the new 250 watt 2x12 I'm getting while taking up the least amount of space in the back of my car (for giging/touring). So I figured the Jazzmaster would be pefect, being 250 watts and suuuper small. I think the ohm load would be ok with my new amp, so I think I'll just use my Marshall cab for the time being.

I have a POD, but I never really got a sound I liked out of it. I could try it again cause it's been a while, but that's at my drummer's house too haha. I think I'll mess with it when I record this weekend.
 

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IIRC, Marshall cabs are 16 ohm? Might be better for the fender to rewire it to 4 ohms, but I don't think you'll hurt it, maybe just cut the power a little bit. You still should have enough volume to stun pigeons in a 3 block radius. :lol:
 

capnjuan

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Hi BreederCreature: sorry for the sloppy reply above - a brief 'lecture' follows. Your 250w amp will do 250watts of 'work' if and only if there is no more than 2 ohms of impedance across its outputs. For example, if you had a new 1/2 ton V-8 pickup with nothing in the bed, it might do 120 mph. If you put 500 pounds in the bed, it might only do 100mph. If you put 1,000 pounds, it might not do better than 80mph.

The 'work' done by your amp is 'inversely proportional' to the 'load' or impedance presented by either an individual speaker's voice coil or by a group of speakers wired to provide the equivalent impedance. So, while your amp may do 250w of work at 2 ohms, it will only do 125w at 4 ohms, 60 watts at 8 ohms, and 30w at 16 ohms.

Your 4X12 cabinet should have a plate on it indicating it's impedance. If not or if there's any question, you can measure the impedance or resistance between the hot and common leads or jack elements. if your 4X12 is an 8 ohm cabinet, your amp will do 125w of 'work'. See this link for re-arranging speaker wiring and connections: http://colomar.com/Shavano/spkr_wiring.html

Good luck with your music and your amp! cj
 

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capnjuan said:
'inversely proportional'

Who would have ever expected that phrase on a guitar forum?

Like your pickup truck analogy too. I know about speaker loads but it has been a long time since I had to explain them.

Back when I used to pay attention to my equipment's power specs (as opposed to now when weight and the ability to fit in the car are more important) most of amps I ran into were rated for a 8 or 4 ohm load, usually depending on the cabinet the manufacturer paired it up with. Is it now more common to cite a 2 ohm load or are more and more cabinets 2 ohm? I also recall the games people played with peak vs. RMS power and when solid state amps started being rated at some distortion level as in "300 watts RMS into 4 ohms at 5% THD". I remember being amused because "stereo amplifiers" were rated at .1% or .01% THD.
 

BreederCreature

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Ohhhhhh, I think I understand now. So in order to get the full amount of watts and output, my 2 ohm head would need to connect to a 2 ohm amp, but it can work with other ohm loads, it would just take more "work", cutting down on the output it can power to an amp?

My new 2x12 is 16 ohms, so that would mean although it can handle 250w, my 2 ohm, 250w head, can only give it 30w since it's working harder because of the impedance difference?

Would I be able to re-wire the amp myself? Or does it not work like that hha
 

capnjuan

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fronobulax said:
...most of amps I ran into were rated for a 8 or 4 ohm load ... Is it now more common to cite a 2 ohm load or are more and more cabinets 2 ohm? .... I also recall the games people played with peak vs. RMS power and when solid state amps started being rated at some distortion level as in "300 watts RMS into 4 ohms at 5% THD". I remember being amused because "stereo amplifiers" were rated at .1% or .01% THD.
Hi Frono; agree, back in the day, it was mostly 4 or 8 ohms. Don't know if the 2 ohm is 'standard' these days but it's a way for mfrs to say: 'this is what the amp can do - you figure out how you want to use it'. Sort of gets them out of trying to anticipate what users like BreederCreature might do once the amp leaves the store ... and warranty ... and you're right, lots of hype associated with the magic 'watts'; the higher the better and THD was for the weenie stereophiles to worry about; after all, at stadium volume levels, how much can THD matter?
 

capnjuan

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BreederCreature said:
Ohhhhhh, I think I understand now. So in order to get the full amount of watts and output, my 2 ohm head would need to connect to a 2 ohm amp... Hi BC; not exactly. To get your amp do 250w of work, you need a 2 ohm cabinet (or 'load'), not another amp.

but it (the head) can work with other ohm loads, Yes it would just take more "work", cutting down on the output it can power to an amp? Almost; the amp would 'do' more work resulting in fewer watts of ouput.

My new 2x12 is 16 ohms, so that would mean although it can handle 250w, my 2 ohm, 250w head, can only give it 30w since it's working harder because of the impedance difference? Yes; just about. Your amp must 'work' to overcome the 16 ohm load; that is, work harder than it would if it were only pushing a 2 ohm load.

Would I be able to re-wire the amp myself? Or does it not work like that hha. No no; touch the amp and your warranty - if there is one - is gone; you can re-wire the 2X12" cabinet. For example, if your 2X12" has a pair of 8 ohm speakers, they can be wired in parallel to 'provide' a load of 4 ohms to the output of your amp resulting in +/- 125watts
I'm just guessing but a 2X 16 ohm cab sounds like two 8 ohm speakers in series. If you're not comfortable with messing with this though, I strongly suggest picking up one of your buddies and a case of beer; let him screw with it.

Forgot to mention that all this cab / impedance swapping only applies to transistor amps. Unless a tube amp has separate transformer taps or there's a schematic indicating that there are provisions for other than an 8 ohm load (however it's achieved), operating the amp into other than it's rated load will ruin the amp. :evil:

cj
 

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capnjuan said:
and you're right, lots of hype associated with the magic 'watts'; the higher the better and THD was for the weenie stereophiles to worry about; after all, at stadium volume levels, how much can THD matter?

Major topic drift.

When I was in college my room/suitemate for 3 years was also a bass player. One fine spring day when we were studying with the windows open some moron had their windows open and were blasting some unlistenable cr*p (probably disco 8) ) for everyone to hear. We lashed up the Ampeg head that was putting out 200+ watts into his 1x15 cabinet, my Peavey that was 200+ Watts into the 2x15 and my stereo that was 60 watts per channel into the Advents and drove it all from a turntable. We put on the 1812 Overture and played all 18 minutes of it. From the time we were finished to the end of the semester no one else put ther speakers in the windows so that they could sun bathe to their music of choice.

Interesting that this probably wouldn't even happen today. The high end stereo fad has been dead for a long time and everyone would just wear their iPod or equivalent while catching rays on the quad.
 

capnjuan

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fronobulax said:
.....Interesting that this probably wouldn't even happen today. The high end stereo fad has been dead for a long time and everyone would just wear their iPod or equivalent while catching rays on the quad.
HI 'Frono: My oldest brother is a life-long audio/stereophile; early on he acquired miles of R-to-R tape, classic and pop LPs from the 40s and 50s and acquired / traded gear to optimize his enjoyment; I credit (blame?) him for my interest in audio. He's had mid-fi and genuine hi-fi gear; conrad johnson, Audible Illusions, magnepan, Theil, Cary, Quad, on and on. 'Back in the day', the objective was to reproduce and enjoy how the music sounded either live or like it did when it was recorded.

My niece, who is pretty 'hip' musically, has no interest whatsoever in the hardware side; 'fixed assets' if you will binding the owner to the leather chair and a copy of yesterday's New York Times - at least as she sees it. For her; it's 'what', or 'in what manner', she's listening to music and not 'how' it sounds. She might listen to an LP and say: 'Gee, that sounds great' but she'd have no interest in the equipment necessary to re-create the more better good listening experience.

Too bad; I can remember listening to Dire Straits' Telegraph Road on my bro's 10 wpc / high-efficiency gear, like your Heath equipment, presence, sound-stage, projection, like the music was floating in the room. Today, it's 'screw that'; they can always watch the vid ... the image trumping the sound.

Hi-fi gear doesn't have the widespread popularity it once had but one man's disinterest is another's obsession; Wavac Amps on AudioGoN $20K new, steal 'em for $8,000 (not including insurance and shipping :wink: )

Wavac.jpg
 

BreederCreature

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So as long as the head doesn't have tubes, I can interchange it with different ohm loads?

I have a Marshall head that I'm pretty sure has tubes, so I shouldn't play that threw anything that doesn't have the same ohm load? I'm pretty sure the Jazzmaster doesn't have tubes.
 

capnjuan

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BreederCreature said:
So as long as the head doesn't have tubes, I can interchange it with different ohm loads? Yes.

I have a Marshall head that I'm pretty sure has tubes, so I shouldn't play that threw anything that doesn't have the same ohm load? I'm pretty sure the Jazzmaster doesn't have tubes. Yes again re/ the Marshall; what model is the Marshall? Sometimes they'll put into on the back, sometimes not. If there's a question, you can look up the schematic and find out. Don't know the Jazzmaster but unless it's a reissue of a 60s design, the chances are it doesn't but you might consider opening it up to take a look.
cj
 

fronobulax

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capnjuan said:
BreederCreature said:
So as long as the head doesn't have tubes, I can interchange it with different ohm loads? Yes.
cj

If the amp is solid state then it can safely handle a range of speaker impedences at the cost of reduced output, correct?

If the amp is a tube amp, unless it is specifically designed to handle a range of speaker impedences. then it can only be safely used at the design load, correct?

A different, but related question would be is the ability to drive different speaker loads a function of amplifier design or amplifier technology (i.e. transistors vs. tubes)?

Thanks.
 

capnjuan

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fronobulax said:
If the amp is solid state then it can safely handle a range of speaker impedences at the cost of reduced output, correct? Yes, that's right.

If the amp is a tube amp, unless it is specifically designed to handle a range of speaker impedences. then it can only be safely used at the design load, correct? Yes; because of the windings around the core of the output transformer. Good stereo equipment offers separate 'taps' for different loads; guitar amps typically do not although the Silvertone 1482 is a good example of an exception.

A different, but related question would be is the ability to drive different speaker loads a function of amplifier design or amplifier technology (i.e. transistors vs. tubes)? Below
Yes; it's a tubes v. transistor matter but mostly because of what's known as impedance matching; the job that the transformer does; a job not needed in a transistor amp. Roughly speaking, transistors are high current, low voltage, and low impedance whereas tubes are low current, high voltage, and high impedance. The internal resistance in the body of a output tube can be 5000-6000 ohms; for the speaker to be musically responsive, its impedance, or resistance between its poles, has to be low; like the 4 / 8 / 16 ohms commonly seen in instrument amps.

While there are output-transformerless amps ('OTL'), they have never been a commercial success. The output transformer allows one side - the tube side - to operate at high impedance and the other side - the output side - to operate at low impedance. Good grade stereo transformers like those in the popular Dynaco ST 70 have taps allowing varying speaker loads. Because they have as many as 4 sets of taps (windings), they also cost more. Instrument amp transformers typically do not offer additional windings although the popular Silvertone 1482 has both 4 and 8 ohm taps.

This constraint on loading a transformer can be gotten around by wiring multiple speakers to reduce the load. If, say, I had a 2X12" cabinet, if I wired two 16 ohm speakers in parallel, the 8 ohm transformer would never know the difference. The only other useful thing here is the 'half/double' rule. Without wrecking anything, you can hang a 4 ohm load on an 8 ohm transformer or a 16 ohm load because each is half or double the rating but connecting a 16 ohm load to the 4 ohm taps of a 1482 is no good.

Finally, very few mfrs have put the money in the output transformers of smaller amps. In high power amps, the are probably the most expensive component. If you can find it, take a look at the tranformer on DKL's Martin/Dearmond amp a/k/a ToneQuest who apparently is duping these for market; modest power amps w/ large transformers is a model for great tone. Anyway, the impedance / loading in tube amps is driven by the dependence of the tube on a transformer to match it's impedance to the load. cj
 
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