# 100 watt guitar amp does not sound good at low volume levels?

Discussion in 'General Electronics Discussion' started by dietermoreno, Dec 30, 2012.

1. ### dietermoreno

238
0
Dec 30, 2012
100 watt guitar amp does not sound good at low volumes?

Is my reasoning below correct?

The reason that your 100 watt amp can not have a distortion from natural distortion from gain at a quite enough volume for home use has nothing to do with the electric power rating of the amp.

Electric power rating of the amp is not the same thing as mechanical power rating of the amp.

Electrical power and mechanical power both use the watt as the standard unit, but the power rating listed on the amp is refering to electric power rating.

Mechanical power rating is not usually talked about, instead usually it is discussed in its relationship to the unit of sound intensity, the decibel.

Sound intensity=Mechanical Power/Surface Area

decibles=watts/meters squared

I = P / ((4)(pi)(r)squared), where I = intensity, P=power, and r=radius

This means that in ideal conditions, a speaker cone with a larger speaker cone surface area will produce a greater sound intensity at the same power applied than a smaller speaker cone.

This means that in ideal conditions, a speaker cone with a a greater power applied will produce a greater sound intensity at the same cone surface area than a lower power applied.

The half wave rectifier in the speaker converts the sinusoidal wave of the alternating current guitar amp signal into half of its waveform (either removing the positive amplitude or removing the negative amplitude of the sinusoidal wavefrom). The signal at half of its waveform is a series of electromagnetic pulses that induce a force of mechanical pulses at the speaker diaghraphm using a dynamic speaker coil apparatus using electromagnetic induction.

There is never ideal conditions, which make it so that two speaker cones of the same surface area can have the a lower intensity for the speaker cone with a greater power applied to it if a certain non-ideal real world condition exists.

The speaker coil does not have perfect efficiency of conversion of half wave electromagnetic waves into sound waves. Even worse, the efficiency is frequency dependent. The frequency dependent efficiency causes some frequencies to be louder than other frequencies, causing either undesired clipping or not enough natural distortion at a low volume.

More expensive speakers can have better frequency response.

Also this problem is made even worse by the fact that electromagnetic waves amplified by the guitar amp also have frequency dependent efficiency.

More expensive amps can have better frequency efficiency response. The lowest grade of amp is class A. The highest grade of amp is class D. An amp with the correct frequency efficiency response connected to a speaker with the correct frequency efficiency response should sound theoretically as good with the gain at 1 as the gain at 10. This never occurs with tube amps. Solid state amps solve this problem to a degree, but still not perfect. Still, a higher grade amp and a higher grade speaker coil will make a more equal frequency efficiency response to make the amp have the desired distortion at a lower gain to be the same desired distortion at a higher gain.

Also depends how you define "gain". Some amps have master volume control, some amps only have gain control. The "master volume control" and the "gain control" are both gain settings, but gain settings of different physical phemomenon. We have already defined that applied power will increase sound intensity given ideal frequency efficiency response. Power is related to current, directly proportional and voltage is related to current with impedence.

Ohm's Law for Alternating Current: P=(I squared)(Z) V=IZ P=IV, where P=electric power in watts,

I=electric current in amperes, and Z=impedence in ohms

Voltage is the actual amplitude of the electromagnetic waveform. However, voltage has nothing to do with the end intensity of the sound waveform, but it is related by Ohm's Law. Power is what controls the end intensity of the sound waveform. If impedence is increased to a current, then the power will increase. If impedence is decreased to a current, then the power will decrease. If power is increased, then either voltage or current could be increased. If power is decreased, then either voltage or current could be decreased. Therefore, if impedence is increased to a current then the either voltage or current could be increased. Therefore, if impedence is decreased to a current then either voltage or current could be decreased. Therefore, impedence stays the same if voltage is increased and current is decreased at the same time. Therefore, impedence stays the same if voltage is decreased and current is increased at the same time. Long distance power transmission lines use high voltage and low current at the same impedence as an equivalent high current and low voltage. The reason that long distance power transmission lines use high voltage and low current instead of low voltage and high current is because current can not easily be stepped up and down in the real world (even though it can be using Ohm's Law) and voltage can easily be stepped up and down in the real world.

Guitar amps also care about stepping voltages up and down because amplification vacuum tubes need about 400 volt AC compared to the speaker coil can only handle up to 40 volt DC before electric arcing because it is using DC so it is not a continuos signal so electric arcing would occur at 400 volts using DC. Since the voltage of the speaker coil is fixed at 40 volts DC, that means that the intensity of the speaker coil can not be determined by voltage. What determines the intensity of the speaker coil is power.

Power does not cause clipping of the wave forms, voltage causes clipping of the wave forms. Therefore, the voltage can be maintained to the same level but at a different power using a power escape for the extra power to escape to ground using resistors to route some of the current and voltage of the current away from returning to the voltage amplification to prevent feedback using a voltage divider resistor network, colloquoly known as either an attenuator if it is a stand alone circuitry device, or known as the master volume control knob if the guitar amp already has such voltage divider resistor network.

2. ### davennModerator

13,991
2,018
Sep 5, 2009
Ohhh gosh
there's just so many false understandings in all that
Am wondering where to start.......

doesnt really make sense

irrelevent --- an amplifier doesnt have a mechanical power rating .... it isnt an engine or some other mechanical device

there is NO half wave rectifier in a speaker
dunno where you got that from ???

nothing has perfect efficiency.... EVERYTHING has losses

sometimes but hi cost can sometimes just be a scam

nonsense

Ohms law doesnt work for AC. AC we use inductive reactance and capacitive reactance
do a google search for definitions

pretty much all incorrect

for a given voltage across a load, decreasing the impedance ( resistance) of the load,
more current will flow, therefore the load will be disapating more power

again incorrect, the speaker works with an AC voltage/current signal
pretty much all amplifiers tube or transistor use transformers in the output to drop the high AC voltage to something that the speakers can handle

not really what happens, but I will let some one else better explain this to you

cheers
Dave

Last edited: Dec 30, 2012