My amp needs to be louder, said the novice

[Blick Fang]

Hello

I did some searching and surprisingly did not find a previous thread to this question so here goes. Now that one of my amps (solid state) is operational again, thanks to you guys, I want to get it louder. I am under the impression its as simple as:

How much louder? 50W? No problem

Swap out this component(s) or PCB with XYZ company's "louder" replacement parts and you are in like flint. It's not that easy is it?

Let's leave speaker efficiency out of the equation

I just don't under stand how this is rated 150W at 4 ohms and my tube is rated 120 and the tube amp is incredibly loud!

[Enzo]

You are mistaking power for loudness. Just like confusing horsepower with speed in a car. But a 120 horsepower Porsche 911 is a hell of a lot faster than a 400 horsepower tow truck.

If you take a 50 watt amp and double the power to 100 watts, if all else is the same, you will hear only 3 decibels louder output. For reference, the two input jacks on a zillion Fender amps are 6db different, so double power is less difference than those jacks.

And why should we leave speakers out of it? A speaker with 3db greater efficiency will make it the same louder as doubling the power. A speaker with 6db greater efficiency will have the same effect as QUADRUPLING your power.

Forgetting for the moment the differences between solid state and tube amps, the difference in loudness between a 120w amp and a 150w amp would be mostly inaudible, like 1 decibel or less. Adding 50 watts somehow to a 150w amp will add maybe a decibel if you are lucky. Power is not loudness.

Most people confuse sensitivity with loudness and power. They say "This amp is louder on 4 than my more powerful amp is on 7." But a 100 watt amp - or whatever its rating - only produces that much power when it is maxed out. The number on the preamp knob is irrelevant. AMp is loud on 4? FIne, now how much louder is it on 10? Maybe not much. Max all the controls, then compare them.

I know this always starts a war, but... a watt is a watt, and 50 watts will make a speaker a certain loudness, regardless of what kind of amp made it. SO tube watts and solid state watts are the same thing. HOWEVER, when you compare amp RATINGS, that changes. A 50 watt rated tube amp can make louder sound than a 50 watt rated solid state amp. How many decibels? I neither know nor care. We just must be careful whether we are comparing 50 tube watts or a 50 watt tube amp.

You want a louder amp? Sorry, but speakers is where it is at. Take a little 8" Champ, and connect the amp to a 4x12 cab. Amazing how much larger the sound is. Replace a ineffcient speaker with a more efficient one, and it makes a tremendous difference.

There are no louder parts. The power of an amplifier starts with its power supply. If the power supply can provide 50 watts, then that is all the thing can ever produce, regardless of the circuit changes you make. The amplifier circuits are nothing more than valves to control the glow of power from the power supply to the speaker. You want to install more or larger output transistors? That will only increase power output if you also enlarge the power supply. And that means higher voltage and current, meaning a new power transformer at the very least. Essentially, if you want your 150w amp to become a 200w amp, you will have to remove the existing circuitry and build a 200w amp in the old chassis.

[big_teee]

I always learn a lot reading Enzo's explanations.
Enzo Needs to write a Amp book for us Dummies!
Good job.
T

[Blick Fang]

Hi Guys

Enzo that sounds logical. But..

I have tried the same cab (2X12 8 Ohm) with each head. The volume level I hear, feel, what have you when my tube amp is on 1.25 is only attainable on the SS amp when it is on 7.5! The SS feels like it is running out of runway at that setting while the tube amp feels like it could knock down a brick wall if turned up further. Thats what baffles me! :-)

[eschertron]

Hi Guys

Enzo that sounds logical. But..

I have tried the same cab (2X12 8 Ohm) with each head. The volume level I hear, feel, what have you when my tube amp is on 1.25 is only attainable on the SS amp when it is on 7.5! The SS feels like it is running out of runway at that setting while the tube amp feels like it could knock down a brick wall if turned up further. Thats what baffles me! :-)

Two things that come to mind:

1. Have you tried slamming the input of the SS amp (with a boost/OD pedal) to see if the sensitivity is low, and needs the extra oomph?

2. The designers of the SS amp have probably included circuitry to minimize the chance that you'll actually clip the output transistors. You may indeed be 'running out of runway' when the gain reaches a certain point. Tube amps, on the other hand, are generally designed to exploit the power stage clipping. I have read (and am merely repeating) that a tube power stage rated at 120W can actually produce much more audio power once the signal approaches a square wave. I am sure that I will be corrected if this is not accurate

[g1]

Another thing is that the solid state amp is rated at 150W into a 4 ohm load, so it will be less power into 8 ohms (maybe 100 to 120W range).
And like Enzo explained, you can not compare the numbers painted on the dials. Maybe the tube amp doesn't really get much louder if you keep turning it up, even though it "feels" like it could.
Maybe you could tell us what the 2 models of amplifier are.

[Jazz P Bass]

Measure what you are hearing.

Put a volt meter, set to read volts ac, on the speaker leads.

Play each amp & write down that number.

Square that number & divide it by the speaker cabinet overall resistance & that figure will be the watts that the amp is delivering to the speaker.

[R.G.]

I have tried the same cab (2X12 8 Ohm) with each head. The volume level I hear, feel, what have you when my tube amp is on 1.25 is only attainable on the SS amp when it is on 7.5! The SS feels like it is running out of runway at that setting while the tube amp feels like it could knock down a brick wall if turned up further. Thats what baffles me!

You're making some easy-to-make mistakes.

1. The volume knob position has little to do with how loud the amp is at any given setting. For one thing, the taper of the pot itself can make the % of the amp's max power going to the speakers different at a given setting, even if things all get the same by the "full up" position. In my day job, we call this mistake "listening with your eyes".

2. Tubes are different from transistors. [well, duh...] The behavior of a tube when driven to and over the place it starts clipping acts something like a perfect compressor, fooling the human ear into thinking things are getting louder, when they're just getting more distorted. Look up Russell O. Hamm's paper on this topic. Tube amps often sound louder even if they're not.

3. You've taken one of the two things that can get you "louder" off the table. Speaker efficiency is the biggie. The other one is to get a bigger (i.e. more powerful) amplifier.

[Tom Phillips]

Another thing is that the solid state amp is rated at 150W into a 4 ohm load, so it will be less power into 8 ohms (maybe 100 to 120W range)...

In fact, since SS amps are MUCH more sensitive to the load than are tube amps, the SS amp may only be putting out ~75W into 8 Ohms. Add to that the fact that speaker impedance is really only 8 Ohms at a specific frequency there are other loading effects in play that could contribute to the SS amp sounding weak when driving an 8 Ohm rated speaker cabinet.

[Jazz P Bass]

It has also been noted that the SS amp as recently been repaired.

Maybe it is still not working correctly.

That is why I asked for a Vac reading on the speaker terminals.

[The Dude]

It would be helpful to know the models of the amps in the original post. We are comparing Mystery SS Amp 150W @ 4 Ohms with Mystery 120W Tube Amp. We don't know the impedance vs. power rating of the tube amp. We don't know if we're talking RMS or peak power for each amp. We don't know if the rating is at 1K or 20-20k. There are many variables and many ways different companies rate power. You have to be careful not to compare apples to oranges.

Just one "for instance". Is an amp rated at 100W RMS @ 1k equal to an amp rated at 100W RMS@ full bandwidth (pink noise)?

Edit: The point is that when comparing the output of amps, you need to dive into the specs a bit. One man's watt is not always the same as another's. Some companies like to "inflate" their output power ratings by using the spec that gives them the biggest number expecting that most people won't explore that number any further. A common practice these days is to publish the rating at 2 ohms in the ads. You have to look at the data sheets to see what the rating is at a "normal" impedance.

[Blick Fang]

Hey Guys

Thanks for providing input. As stated, I am a novice and I got a free lesson in speaker efficiency. Very cool, indeed.

The solid state amp is an Ibanez Toneblaster TBX150H rated at 150W @ 4 Ohms. It has a sound I kinda like for heavy stuff and the clean channel is not too bad. The Tube amp is a bugera 333XL Rated at 120W @ 16, 8 or 4 Ohm.

If I were to get a different SS amp that were louder, I might not get the tone the TBX150H provides (hence the need for more volume). Do you think maybe if I really wanted the TBX150H louder, I could run it through an external power amp? The TBX150H has no line out

Thank you again for helping with my quest

[soundguruman]

"If you take a 50 watt amp and double the power to 100 watts, if all else is the same, you will hear only 3 decibels louder output."

That is not correct.
It takes quite a bit more increase in power to double the actual loudness.
Typically, about 6-10X increase in power to double the loudness 3 db. Depends on the speaker a lot, really.

But, if you are using a more efficient speaker, you are on the right track to increase loudness, without increasing power.
(I was the first person in this forum to point out this fact...remember?)
Most guitar speakers are very inefficient. Most speaker cabinets are designed very poorly.
FYI- speakers that are very efficient are also very expensive. AND they must be used in a well designed cabinet to realize this increased efficiency.

A good example of efficiency is EVM speaker, or JBL speaker.
But still, without the correct design cabinet, you will not realize this increase.

An example of a poor design cabinet is ANY open back cabinet.
(twin reverb etc...)
Open back cabinet kills any efficiency increase. AND also kills bass response.

[soundguruman]

I always learn a lot reading Enzo's explanations.
Enzo Needs to write a Amp book for us Dummies!
Good job.
T

Except that his explanation is wrong.

[big_teee]

Except that his explanation is wrong.

No Offense, but Enzo has Probably forgot more than most of us will ever know about the repair, and electronic Biz!
T