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Watts vs Volume (db)

Started by joecool85, December 22, 2010, 08:56:56 AM

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Jack1962

The output impedance from the tube is between 3k ohms and 8k ohms depending on what tube you are using. however I agree with most of what you are saying , the real difference is drum roll please , the tube is indeed a constant current source due to the output transformer , the transistor amp has it's signal dump directly onto the speaker. Myself I have and use both types tube and solid state I prefer the solid state for keys because the amp I'm using is a Peavey Musician you can use it for anything , best frequency response I have ever seen from a stock production amp. for guitar and bass I usually use tube amps because of the output power , I generally don't use anything larger than a 50 watt guitar amp for Bass I use my vintage Ampeg SVT with a 8x10 cab and a 15 jensen that I really don't remember where it came from I"ll put it up against any 500-1000 watt bass rig anytime lol


MTmopars

Such a good thread. While I am fairly novice to guitar amps and their application, I used to compete in car audio and many of the same principles apply here and have been stated.

Every 3dB is doubling the volume. So to double the volume get a 3dB more efficient speaker, double the cone area, or double the power. In car audio completion you could also port the enclosure to give 3-9dB boost at the frequency the port is tuned for.

g1

Quote from: MTmopars on April 05, 2014, 10:08:39 AM
Every 3dB is doubling the volume. So to double the volume get a 3dB more efficient speaker, double the cone area, or double the power.
No.  It was established that it takes 10db to double the volume in the first post  :).
The 3db boost in volume from the methods you mentioned does not double the perceived volume.
  In car audio competitions you measure SPL.  Does a given system with a 200W amp sound twice as loud as the same system with a 100W amp?
Double the power does not equal double the volume, you need 10db increase to sound twice as loud.

MTmopars

I stand corrected on part of my post. 10 db is doubling perceived volume. 3db is the gain from doubling power or speakers. It has been about 10 yrs since I was active.

Anomaly

I'm straying a bit here but.... I think perceived volume has a lot to do with the amplifiers natural EQ curve, cause if an amplifier has a good mid range response, and is of good quality it is going to be LOUD. I've owned many different amplifers, tube and solid state, and the higher quality solid state amps like the Randall RG's and Ampeg SS and VH series heads through a good cab are just as loud as equally rated tube amps, and they cut no problem too (when dialed in right). No one can say an Ampeg SS-150 or Randall rg100es can not cut through a mix, they cut through like butter.

Lady_Azurewolf

I am very very new to this whole topic and got myself a Woodstock GX-55R Amplifier the other day cheap from a second hand shop. Yep the question of watts came up. I   don't know how many watts it has.
But I have been told itno good for a bass guitar.
Yeah I don't even have half the knowledge of people here however I have found reading everyone's post absolutely fascinating.
Cheers all.

joecool85

Quote from: Lady_Azurewolf on April 11, 2023, 05:50:40 PMI am very very new to this whole topic and got myself a Woodstock GX-55R Amplifier the other day cheap from a second hand shop. Yep the question of watts came up. I   don't know how many watts it has.
But I have been told itno good for a bass guitar.
Yeah I don't even have half the knowledge of people here however I have found reading everyone's post absolutely fascinating.
Cheers all.

Go ahead and start a new thread and share a few pictures - specifically any labels or markings on the amp.  We should be able to help!
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Diary Of An Axeman

I use two Crate Power Blocks to pump four 4x12 early 1980's Laney cabinets , loaded with Celession Greenbacks and Fane speakers with two Peavey 2x12 cabs loaded with Sheffield 1230 speakers .
Before I started using them,  other guitarists were telling me that the 150 watts from the Crate CPBs , were not going to be as loud as my Marshall's, Carvins or VHTs .... Boy, were they wrong !!!!

JonnyDeth

The problem with this perspective is ultimately useable volume and wattage when you do a more thorough test of 100 Hz, 1 Khz, and 10 Khz with a sine wave. 1-watt @1 meter is using a 1 Khz sine wave, so it's dB rating isn't always the most reliable in terms of overall performance and projection.

Relative to this is the hardware distorting within a certain pitch range, as well as the speaker. You have to be prepared for potential crossover distortion, and many amps greatly lose efficiency in the lower frequencies at any volume. I agree that the speaker is one of the most important components regarding performance all across the board, and changing speakers may give you better performance and with a few more dB of useable volume, and that's a lot.

You must also take into realization that RMS/Peak wattage isn't telling you a whole lot in again, relationship to 100 Hz, 1 Khz and 10 Khz. Once you incorporate a speaker as the load on the circuit, you aren't dealing with watts, but the VAR of a resonant circuit. This is the precise point at which current and voltage meet in phase, and you get the most power transfer.
I've seen the most efficient systems built by using 100 Hz instead of 1 Khz exclusively to rate a speaker as well as the amp, and the VAR in equivalent effective wattage might be 10 watts compared to a 1 Khz sine wave resonating at 100 VAR(watts), or it might still be 100 VAR(watts) when using a 100 Hz sine wave, and that's phenomenal.

This is the final attribute where you also start to realize efficiency is overrated. I would rather have 100 effective watts of Class-A @ 100 Hz than Class-A/B or worse yet, Class-D. A really well-designed Class-A amp focused on VAR for 100 Hz resonance just as much as 1 Khz will be an animal not much can compete with. It's why some of these really old tube amps that weigh 150lbs will be just 30 or 40 watts, but they can compete with a modern Class-A/B or D that's full blast and rated 200.

joecool85

Quote from: JonnyDeth on March 20, 2024, 08:56:50 AMThe problem with this perspective is ultimately useable volume and wattage when you do a more thorough test of 100 Hz, 1 Khz, and 10 Khz with a sine wave. 1-watt @1 meter is using a 1 Khz sine wave, so it's dB rating isn't always the most reliable in terms of overall performance and projection.

Relative to this is the hardware distorting within a certain pitch range, as well as the speaker. You have to be prepared for potential crossover distortion, and many amps greatly lose efficiency in the lower frequencies at any volume. I agree that the speaker is one of the most important components regarding performance all across the board, and changing speakers may give you better performance and with a few more dB of useable volume, and that's a lot.

You must also take into realization that RMS/Peak wattage isn't telling you a whole lot in again, relationship to 100 Hz, 1 Khz and 10 Khz. Once you incorporate a speaker as the load on the circuit, you aren't dealing with watts, but the VAR of a resonant circuit. This is the precise point at which current and voltage meet in phase, and you get the most power transfer.
I've seen the most efficient systems built by using 100 Hz instead of 1 Khz exclusively to rate a speaker as well as the amp, and the VAR in equivalent effective wattage might be 10 watts compared to a 1 Khz sine wave resonating at 100 VAR(watts), or it might still be 100 VAR(watts) when using a 100 Hz sine wave, and that's phenomenal.

This is the final attribute where you also start to realize efficiency is overrated. I would rather have 100 effective watts of Class-A @ 100 Hz than Class-A/B or worse yet, Class-D. A really well-designed Class-A amp focused on VAR for 100 Hz resonance just as much as 1 Khz will be an animal not much can compete with. It's why some of these really old tube amps that weigh 150lbs will be just 30 or 40 watts, but they can compete with a modern Class-A/B or D that's full blast and rated 200.

Thanks for bringing up these points - all of them very valid and interesting!  While I am an advocate for solid state gear, I am by no means an expert and I love reading the in depth stuff some of our users here bring.  Thanks for joining the forum!
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

g1

Amplifiers are rated RMS into a resistive load, so VAR is not a factor at the amp side of things.

JonnyDeth

#41
Well, looks like I wasted all that time going to college for electrical engineering, thanks for the clarification  ::)
Speakers aren't resistive loads, and there are many types of amplifiers. In regard to audio frequency amplifiers, VAR is absolutely critical.

Loudthud

What is VAR and what does it have to do with anything ?

g1

#43
Quote from: JonnyDeth on March 20, 2024, 02:56:58 PMWell, looks like I wasted all that time going to college for electrical engineering, thanks for the clarification  ::)
If you can't apply it, I guess you did.
Amplifiers are rated into resistive loads to take reactive power out of the equation. 
Note that I specified amplifiers in my earlier comment to exclude what you said about speakers.

When one walks into a new room, it's best not to have the flamethrower on and start out with the idea that everyone else has it wrong.

JonnyDeth

Quote from: g1 on March 20, 2024, 08:39:30 PM
Quote from: JonnyDeth on March 20, 2024, 02:56:58 PMWell, looks like I wasted all that time going to college for electrical engineering, thanks for the clarification  ::)
If you can't apply it, I guess you did.
Amplifiers are rated into resistive loads to take reactive power out of the equation. 
Note that I specified amplifiers in my earlier comment to exclude what you said about speakers.

When one walks into a new room, it's best not to have the flamethrower on and start out with the idea that everyone else has it wrong.

Get a grip, you're the one being rude. The thread is about wattage, dB and output of a combined devices and how they relate to one another.
What I said is absolutely critical, and I was simply offering some factual information that is helpful based on the entire purpose of the thread from the OP. I wasn't rude, and I wasn't condescending, I just made a point, and you had an immature reaction twice over now. You literally tried to crybully me and I'm not interested. I'm under the impression I already need to be prepared to block you after that immature harassment.

VAR is what truly matters unless you're operating at a single frequency. Not all companies test their amplifiers the same way, but those that do it correctly will test it into an RLC tank circuit, or at least, an LC circuit. If they have built something truly special, they will test it with an LC circuit for 100 Hz, 1000 Hz and 10,000 Hz and they will also test it with sweep going from 100 Hz to 10,000 Hz.

So, any given amplifiers selected at random won't necessarily perform as well at 100 Hz as they do at 1 Khz.

Typically, the further you stray from a 1000 Hz sine wave in frequency, the worse the amplifier will perform in it's production of VAR, and for general purposes, we can use the 3 fixed frequency points defined by factors/divisors of 10 in the >< connotation of 1000 Hz, and regard VAR as watts.
An amp screaming loud with 100 watts @1 Khz may only push 20 watts at 100 Hz, and thus the owner is grossly dissatisfied with it's performance. Now a lot of amp manufacturers will produce a design that is so effective, but there are some out there that will produce nearly the same wattage at 100 Hz as they do at 1 Khz and 10 Khz. These are often used in the subwoofer competition industry and when a brand really wants to make an impact, they will produce test data for those 3 frequency points, design a speaker specifically for a selected frequency point, and that amp and speaker in combination will be at resonance producing the spec'd wattage because the manufacturer took a lot of pride in it's design.

You can always do the math using your desired speaker and run the tests yourself after calculating the necessary capacitor value to see what you get at 100, 1000 and 10,000 Hz.