amp question

Posted on
Member Since: Nov 27, 2007

My mate just bought an "Orange" 15watt valve head and a 60watt box.

is it just me, or does it sound like the head may blow trying to power this box?

What's worse is, the guy from the music shop that sold it to him used a 4x12 box to test the head out on.
He says you can use a 4x12 with the head if you want!
Sounds like he is a bit of a snapperhead to me.

Does anyone think the same here?
Im just thinking the head aint going to last long with this 60 watt box,
and i guess im trying to get in quick so maybe he can take it back or whatever.

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Prince CZAR-ming
Since: Apr 08, 2004

Nov 14, 2008 10:24 am

Nope, the head will be fine. As long as the impedance is correct: amp has 8 ohm output, cabinet is 8 ohm. They need to match.

Basically, the valve head can run full power, into anything that can handle that wattage. You could run the head into 100 15" speakers if you wanted, as long as the total impedance is correct (see above paragraph).

It's kinda like a hose, that can push 15 gallons of water per minute. As long as the bin you're filling can accept 15 gallons per minute, you're fine. If the bin could accept 500 gallons per minute, the hose would still be fine. It's when you have a box that's less than the head output, that you would be concerned. Like pushing your 15watt head into a 10watt speaker / box.

Also, make sure the impedances match.

I am not a crook's head
Since: Mar 14, 2003

Nov 14, 2008 02:46 pm

A 15-watt that the Tiny Terror?

Orange amps rock. I wish I could afford one. They're kind of one-trick ponies, but their one trick is right up my alley.
Since: Nov 27, 2007

Nov 14, 2008 06:32 pm

tis the Tiny terror you speak of Tad.

Mmm, i was under the impression if the head is way under powerded, then it will be pushing too hard to power the box and be under too much load. and eventually kark it.

like when you gotta keep turning the volume up all the time and then one day, bang!

Ne'er ate 'er
Since: Apr 05, 2006

Nov 14, 2008 07:48 pm

Like ordinary light bulbs, tubes supplied with higher voltages over a period of time will fail sooner than tubes operated at cooler temperatures. Just basic physics there. It is best to have speakers that are efficient enough to get the sound level you want with the power you have.

The same is true for solid state amps, but there's something very important to remember about transistor output stages.

When an output transistor is driven past its maximum output into distortion, it generates deadly third-order harmonics that can zap speakers - especially tweeters - before you know it's happened. This is why, in a solid state situation, it's always best that your amp's output rating is beyond your speaker's input rating. The reasoning is that your speakers can handle short-term hyperextension better than they can handle high voltage distortion spikes.

I hope that made sense.
Since: Nov 27, 2007

Nov 14, 2008 10:05 pm

yeah Herb cheers for that, makes sense for sure.

the trick there is to know when the amp is actually at that point.
which comes back to correct matching.

we are talking a 15 watt head to a 60watt box.
might be ok maybe(im not so sure) but the music guy's suggestion that you can use a 4x12 is just ridiculous.

Its guys like that, that wreck ya gear.
I've had a few run ins with musicshop guys about really 2 rate info and opinions.
they peev me alot at times.
Not saying "all" musicshop dudes are like this, but there are too many over this neck of the woods.
they got no business being in the business if they dont know what they are talking about for this reason.

Czar of Midi
Since: Apr 04, 2002

Nov 14, 2008 10:28 pm

Nope, not ridiculous at all. Over the years I've done it more times then not. And ya, the Tiny Terror is a killer low wattage amp.

It can rip up a 4 x 12 without any problems at all.

Yes the tube life will be a bit shorter, but it is well worth it for the tone the thing will bring.

But as Tad stated, it is a bit of a one trick pony, although a very good sounding trick to say the least.

I ran a pair of their 50 watt head into 4 4 x 12's in the mid 70's and it was the loudest thing around.
Since: Nov 27, 2007

Nov 14, 2008 11:27 pm

well, i stand corrected.(blushes, looks at ground)

ok, well, i dint know that bout the tiny terror.
lucky i was only shooting my mouth of here and not to my mate before checking first. Man this site has saved my *** on so many levels now.

must only be the case with transistor amps?
its jus that a while back my mate blew an amp, or at least it smelled that way when he was playing thru a bass amp using a "big wattage" vocal pa speaker.
he just had to keep turining it up and up till the head started stinkin.
burnt something out.
maybe it was the wrong ohmage.

Prince CZAR-ming
Since: Apr 08, 2004

Nov 15, 2008 08:02 am

i was under the impression if the head is way under powerded

The head will make power on it's own, and send it out. It's up to the speaker bin to receive the wattage. If the reflected impedance is correct, and the speaker bin can accept the wattage, then all is good.

There's a few details here:

1. Tubes and heat: Tubes and tube amps are made to be dealing with a lot of heat. Tubes are small linear particle accelerators, and as such, can create temps in the thousands of degrees in normal running. The heaters alone are basically light bulbs, glowing a filament hot enough to glow.

2. SS amps and heat. SS amps hate heat. The finals are encased in silicone, which is not happy with heat. This is why you see large heatsinks attached to the finals.

3. Tube amp ohmage. Here's a big factor. When tubes (and SS amps) put out energy, they expect to see resistance pushing back. This is called reflected impedance. Think of you pushing a table across the floor. If the table had 0 weight (no resistance) you would shoot across the room, un-impeded by any obstacle. In amps, this un-impeded state will let the amps (or tubes) run at crazy high output, which can burn them out real fast. Also, burn out the output transformer.

Conversely, when you are pushing a very large table, weighing 2x or 3x what the first one weighs, you get tired very quickly, as it's very difficult and takes a lot of energy to push the table.

The table weight is impedance, measured in ohms. The amp is expecting to see 8 ohms, but you put 2 ohm speaker load, the amp will be running way over normal. The amp will be louder, but at the expense of the outputs tubes, and/or output transformer. Or, if the speaker load is 16 or 32 ohms, then the amp is working way harder to produce the wattage asked of it. This also can fry tubes and output transformers.

Herb brings up two points that are related, but have specific parameters when dealing with tube amps:

1. Voltage. Tubes run (mostly) on DC voltage, to make the amplification thing happen. Part of this is plate voltage. On the TT, it may be 400vdc (estimate). This is (somewhat) variable, to what you want for onset of distortion, clean headroom, what tubes, etc. This can be changed, but is best left to what the designer of the amp planned. The audio signal running through the signal path is AC. This is the sine wave that carries your sound. It is usually very small, and only about 1 volt. When you amplify the AC signal, and send it through the output transformer, you get large amount of AC, which is regularly referred to as wattage. This power rating can be determined by math, but I've not done enough math to present those formulas here.

2. Efficiency: Speakers have a efficiency rating, like 98db / 1w / 1m. This is stating that for 1 watt of energy, the speaker can generate 98 decibels of sound energy measured at 1 meter away. It's a pretty standard measurement, and most (if not all) speakers have this measurement. So if you have a 92db rated speaker, and put 1 watt of energy into it, you should receive 92db of sound out the other side. Unfortunately, it doesn't work that nicely, as there's heat generated, and other losses in the chain. But, it is a measurement that we can use to compare speakers against other speakers. A 104db speaker is going to be a lot louder than a 92db speaker, given the same amount of power going into it.

I agree about musicman types. I've found very few that were worth talking to. They spend most days dealing with people that blindly take what they have to say, so they don't have to be accurate. ( i may be exaggerating, but my experience tells me i'm right )

That's what's nice about the inet. You can get lots of opinions, for many people: some right, some wrong =).

Ne'er ate 'er
Since: Apr 05, 2006

Nov 15, 2008 08:46 am

Pat, so much is true about that.

Run those output tubes as hot as possible. That second-order harmonic is what makes the sound happen. Change tubes, and change often.

I understand you guys play guitars though. I'm just a silly old audiophile.

Czar of Midi
Since: Apr 04, 2002

Nov 15, 2008 08:44 pm

But Herb, remember you are a drummer on the inside.

Deon, ya it is very OK to push a 15 watt tube amp into a 4 x 12. Let the head warm up first though for sure as you will want nice toasty tubes running to get the best sound.

And the advice on keeping the tubes up is spot on by Herb there.
Since: Nov 27, 2007

Nov 16, 2008 06:20 am

so really, with my 120watt tube head and box, i could have possibly been better of with a 50 or 100watt head and push it a bit harder to get the tubes pumping without the current barage of volume i have to have it at now.

i use mine in a band situation atm and it doesnt get past 2 and half, not really smashing those tubes much.

maybe an attenuator is on the cards.
more money!

I am not a crook's head
Since: Mar 14, 2003

Nov 16, 2008 10:30 am

A 120 watt tube head?!? Holy hearing aids Batman!

Oh you'll fall in love with your amp all over again if you can get the master volume in that 7 - 10 range! With 120 tube-powered watts, turning the master up that far would probably shake your house to pieces.

The formula that I've heard is that you need 10x more power to make your amp twice as loud. So a 100 watt head wouldn't sound any noticeably different than a 120 watt head, and a 50-watt head would only be barely quieter than a 100-watt head.

The solution is 1 of 2 things:

1- get an attenuator like you said (and you won't regret it!)

2 - get a low wattage tube amp. Like in the 5 - 18 watt range. Then you can cook those power tubes without being heard from outer space. The only thing you're sacrificing is clean headroom (how loud you can turn up the amp's clean channel without it breaking up). 5 tube watts through a 4 x 12 is surprisingly loud. If it isn't loud enough, mic it!

Prince CZAR-ming
Since: Apr 08, 2004

Nov 16, 2008 01:44 pm

Yeah, a doubling of wattage only makes a 3db increase of perceived volume. But, you get breakup earlier with a lower wattage amp.

That's why a lot of blues players play through old Fender Deluxe Reverb amps. They're 22 watts (there abouts) and sound great turned up on 10. The players leave it on 10, and 'play' the amp with guitar volume, pick attack, pedals, etc. The amp is running full bore the whole time.

I've not played through an attenuator, but I know Tad loves his, and there's plenty of people I have read from that use one to play out.

I've read somewhere (i think on tedweber's site) of a kid with a JCM900 that never has his master above 3. Said he loved the amp. The poster then turned up the master, and dropped the volume, and the kid about fell over. He never knew the amp could sound that good.

For tube amps, there's two type of tube (overdrive) distortion: preamp, and output. The preamp tube distortion is easier to get: turn the master down, and turn the volume up. But, the preamp distortion is more brittle, and fizzy.

Conversely, if you keep the volume more moderate, and turn the master up alot, then the preamp tube isn't making any overdrive, the output tubes are making the overdrive. This type is usually more even order harmonics, like herb said: smooth, and full bodied. But you have the huge volume to contend with, unless you get a low wattage amp, and turn it up full.

Czar of Midi
Since: Apr 04, 2002

Nov 16, 2008 02:11 pm

That was the only reason I sold my Soldano was it was a 100 watt head. I didn't really need all that after touring stopped.
Since: Nov 27, 2007

Nov 16, 2008 09:36 pm

oh the ol Soldano. man that was a great amp head. apparently they made the Mesa to try mimick the same sound.

not the same though.

yeah Tad, the attenutor will be next on the list, maybe even today or tomorrow.

Pjk, i use my amp with the pre gain on about 5 and run a pedal in front with that on 5 out of 30 on the distortion.

im gonna turn the distortion down more i think and go for more a cleaner sound than current, and get the anntenutor going so i can thrash the tubes more for a thicker sound that way, instead of too much distortion. just cant be done without the attenuator though.

I've had the amp on 4 and yer just asking for a catasrophe going any louder than that. its just way too loud.

Czar of Midi
Since: Apr 04, 2002

Nov 16, 2008 11:31 pm

Ya, the mesa is a completely different sound. I played a dual for awhile as well as having a Boogie.

I am not a crook's head
Since: Mar 14, 2003

Nov 17, 2008 12:37 am

Even an attenuator will only tame such a powerful amp to a degree without seriously degrading the tone of your amp. You can shave off 4 or 12 dB off of the signal, but much more than that and it'll be pretty conspicuous sounding.

Just go into using an attenuator with realistic expactations about how quiet you can get your amp without it getting squished and lifeless.
Since: Nov 27, 2007

Nov 17, 2008 07:02 am

yeah i will try it out first for sure.

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