Still Confused About Big Amps

[Prostheta]

I'll vouch for the "air you can move" factor of course! If I recall correctly, halving a frequency requires a larger factor in terms of power to run a driver to move a correspondingly larger amount of air. I prefer 4x10" cabs, although I have considered an 18" extension cab in which case my amp power becomes so much more relevant.

Then again, I don't play dub or any other sub-bass types of music so I think twice as many 10" speakers and a valve head will see me better :-D

[goat]

['Prostheta'

I think twice as many 10" speakers and a valve head will see me better :-D]

+1 on the more 10`s

Move that air

I think if you add an 18,I would throw in Bi-amping a horn in there,but more 10`s and dropping the mids really does the trick on the valve head.

Here`s a quote from The Ampeg site about their 4x10 halfstack

"The SVT-410HLF actually moves 10% more air than two 18-inch speakers, and 25% more than three 15-inch speakers! And those leviathans simply can’t respond to transient peaks as quickly as four tens can."-Ampeg

[Prostheta]

I agree about the response to transient peaks, but low and slow bass frequencies aren't expected to move as fast drivers reproducing mids or highs anyway :-/ I guess they have to move *further* because of the logarithmic nature of sound, but this doesn't ring right somehow....

I smells hyperbole!

That's a fair comment by Ampeg if the cabinets are attempting to reproduce the same frequencies, but low frequency program material such as sub-bass (low B on a bass anyone?) in a dub style would sound a LOT better through 18s with the mids supported by 10s or even 8s.

On reflection, I would have no need for an 18 or a 15 in my setup because I rely more on frequencies 140-160Hz upwards to get my sound. Anything below that (other than the fundamentals) detract from the focus and tightness of the amp.

Anyway. Enough bass rambling I guess. Back to "big amps".

[Drak]

It's gotta be tough for you in France to find some of the older tube amps that would fit your bill, but I could offer two suggestions.

1. Gibson BR-6

2. Magnatone M-4

I would flat out guarantee you you could DIME both of these amps in your little club and get that power tube soak you're looking for without hurting -anybody's- eardrums.

I've owned probably well over 30 amps or more, and I know both of these will fit your bill.

Finding one of these in France is another battle alltogether.

Both of these amps dimed are much quieter than, say, a vintage Ampeg Jet, which is also pretty small, but these don't get even as loud as an old Jet.

You could also look for some of the older Magnatones, a Melodier or Student, I never had those so I can't comment on them, but I know they're also small and not too loud.

I do believe your best bet is to really get into the OLD amp world and start investigating things out, or just take my advice.

The Gibson would probably be easier to find, and easier to retube (2-6V6, 1 5Y3, 3 6SN7'S) You'd think a 2-6v6 amp could be pretty damn loud, and they can be, but it depends on the circuit surrounding them, and the Gibson simply doesn't get that loud at all, and all those tubes are easily available on eBay for cheap. The only ones you'd shell out any money for would be the 6v6's, the rest you can buy used for cheap.

The suitcase M-4 uses a pair of 6GW8's, an almost unheard of power tube for guitar amps, but you can still find them pretty cheap on eBay really.

Or you can get the amp Mattia and I prefer, hehehe...

[Prostheta]

Man, that's like an amp where knobs go on vacation.

Knobland on the subcontinent of Dimetania.

[Drak]

Believe it or not, each knob actually does something. :D

[Mattia]

Believe it or not, each knob actually does something. :D

Oh, it's worse than that...each knob does something useful, and each turn modifies how the others interact with each other. It's never quite as simple as 'I'll just turn the bass up a little'...but it souns friggin' awesome. Paul Rivera's a fantastic amp designer and builder, and personally answered the email I shot the company inquiring about the details on my amp (which is pre-M and -S designations, early model).

If I wanted a combo, I'd very, very likely get an R30 or Chubster40. Because the TBRs are built like tanks, and weigh almost as much.

Edited February 11, 2007 by Mattia

[Mickguard]

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[pmarlin]

Believe it or not, each knob actually does something.

Speaking of knobs, the guitar player in my sons band said his amp wasnt working so i told them to let me take a look at it, So after messing with it for 5 seconds i got it working. I went to my sons room and said " tell phillip to stop smoking pot" he replied "why" i said " because he had all the tone knobs on zero, it works fine if you turn them up"

[Mickguard]

Well a deal came up on ebay this morning, guy selling a new 2x12 cab with Jensens at a good price. So I bought it. My amp might be underpowered for it, we'll see. I might end up removing one of the speakers, in that case, it'll make it easier to carry around too.

[Mickguard]

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[jnewman]

I think the new cabinet with 2 12's will make a big difference in how loud your amp is. I like Jensen speakers - which ones are in the cabinet? On the subject of small amps, I finished the chassis and electronics of my 5E3 narrow panel tweed Deluxe build tonight, and I think I'm in heaven. I like little amps . I still haven't figured out exactly its wattage rating, I've read between 12 and 18 watts. Coincidentally, I should have a Jensen P12Q for the little Deluxe come in on Thursday.

The Vox tone is pretty cool too! AC15's are nifty.

Edited February 14, 2007 by jnewman

[Mickguard]

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[biliousfrog]

I've just had another look at the ZVex nano head video ( http://media.zvex.com/nano.mov ).....0.5 watts of coolness, I wants me one of those

[Mickguard]

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[westhemann]

So does this mean that one way to use more watts is to run them through more speakers?

duh i thought i covered that...to push more speakers you need more wattage...but in the end you are getting a better "spread" of your sound throughout the space you are in

[Mickguard]

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[jnewman]

Are you saying that the amp is actually louder with the 1x10" built in speaker than with the 2x12 cabinet? That's odd. The Jensens in the cab must be the super-inefficient ones. Are you sure the cab is the right impedance for your amp's output jack?

Into a given load, i.e. using an 8 ohm speaker or cab on the 8 ohm jack, your amp will be putting out the same amount of electrical watts period. The sonic volume, however, depends a LOT on the speakers you're using, how efficient they are, and how many there are.

[Mickguard]

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[biliousfrog]

it comes down to impedence & although I can never quite get my head around it, it works something like this...

300w at 8ohms into an 8ohm cab will give you 300w of output

300w at 8ohms into 2x 8ohm cabs will essentially give you 150w because the 2x 8ohm cabs will have twice the resistance & give you 4ohms. The same thing would happen if you used a single 4ohm cab.

That's why many power amps will list the output into different cabs eg. 300w@ 8ohms, 150w@ 4ohms, 75w@ 2ohms..... So, if the Laney is running at 15watts into an 8ohm speaker & you then attach another 8ohm cab you'll end up running at 7.5 watts. Unfortunately, tube amps don't like being put under too much stress so if you are trying to drive a cab with higher impedence than recommended you could blow the amp.

That's how I've come to understand it, I'm sure that there's more to it & someone will be able to give more info.

[Mickguard]

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[marksound]

I think you should give your ears time to get used to the higher fidelity of the new cabinet before you start trying to fix things. You may just be hearing the entire spectrum of sound rather than just the harsh highs you're used to.

[Mickguard]

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[jnewman]

it comes down to impedence & although I can never quite get my head around it, it works something like this...

300w at 8ohms into an 8ohm cab will give you 300w of output

300w at 8ohms into 2x 8ohm cabs will essentially give you 150w because the 2x 8ohm cabs will have twice the resistance & give you 4ohms. The same thing would happen if you used a single 4ohm cab.

That's why many power amps will list the output into different cabs eg. 300w@ 8ohms, 150w@ 4ohms, 75w@ 2ohms..... So, if the Laney is running at 15watts into an 8ohm speaker & you then attach another 8ohm cab you'll end up running at 7.5 watts. Unfortunately, tube amps don't like being put under too much stress so if you are trying to drive a cab with higher impedence than recommended you could blow the amp.

That's how I've come to understand it, I'm sure that there's more to it & someone will be able to give more info.

First off: Twice the resistance of 8 ohms is 16 ohms, not 4 ohms. 4 ohms is LESS resistance than 8 ohms. Two 8 ohm speakers/cabs in series have twice the resistance, 16 ohms. Two 8 ohm cabs in parallel have half the resistance, 4 ohms.

For stereo amps, you have it backwards. A stereo amp puts out a specific voltage swing on the output. This voltage swing, divided by the impedance, gives you current. So far we have V/R=I. Now, power is voltage times current. So we get Power= V^2/R. So if we decrease R, we actually increase power. For example, my Halfer stereo amp is rated per channel at 150W at 16ohms, 250W at 8ohms, and 400W at 4ohms (It's a beastie, that's conservative RMS output, not peak).

A solid state guitar amp should also work this way, but a tube guitar amp requires a specific impedance speaker to be connected to that impedance's output, with the end result that the power output is about the same regardless of speaker impedance as long as you're matching impedance correctly with output transformer output.

You should not encounter a situation in which your amp can't drive a cabinet, even if it's only 5 watts, or 1 watt. The speaker rating is purely how much power they can use without damage. Of course, high powered speakers tend to be made much more stoutly, so it takes more power to get speaker distortion, but speaker distortion is a pretty small part of most guitarists' preferred amp tone. Speaker sensitivity is measured by the volume of the speaker in dB 1 meter from the speaker with 1 watt input over the range of frequency response for that speaker. The least sensitive Jensen speakers are about 94dB. The most efficient Jensens are about 100dB. 6dB is a BIG difference. Most modern 10" speakers are rated around 94-98dB. If you have the most inefficient Jensen speakers in the cab and a pretty efficient 10" built in, it actually is entirely possible for the 10" to be louder.

Mickguard, let us know how you like the AC15!

Edited February 15, 2007 by jnewman

[Saber]

Like jnewman was trying to explain, the efficiency or "sensitivity" of the speaker is the spec that determines how loud it is, and it's quoted as the number of dB measured at 1W,1m.

A difference of 3dB is equivalent to double the power in Watts. So for example, a Vintage 30 that's rated at 100dB will sound as loud with 10W pumped into it as a G12T-75 that's rated at 97dB will sound with 20W pumped into it. So maybe the Jensens just have a lower sensitivity.

Of course, all this applies only if the speakers that you are comparing are of the same impedance.

Edit: Nevermind, jnewman posted as I was typing.

Edited February 15, 2007 by Saber