That's insulting and unnecessary. Maybe the moderation problem around here is all the attitude about moderation issues?
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Volume difference between tube and solid state amps.
- Thread starter fireincairo
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That's insulting and unnecessary. Maybe the moderation problem around here is all the attitude about moderation issues?
When the power delivered by an amplifier is measured, a resistive "dummy load" is connected to the output. A sine wave generator is connected to the input. A voltage reading (note 1) at the output is taken (at some amount of distortion ( note 2 )) and the result is converted to watts by the formula P=E^2/R. When you listen to an amplifier, a speaker must be connected. The trouble is the dummy load is not a very good approximation of the load presented by a speaker ( note 3). The dummy load is a worst case never seen in real life load.
The simple fact of the matter is that a tube amp can deliver more volts to a speaker than it can a dummy load of the same nominal impedance ( note 4). This is generally about 2dB more ( note 5). A solid state amp only increases by a fraction of a dB in most cases. The proof of this is left as an excercise for the student, warm up your oscilloscope or boot up your SPICE program.
Note 1: AC RMS volts are used because they make the formula work.
Note 2: To be fair when comparing two amps the same amount of distortion should be used.
Note 3: A speaker's impedance is equal to the dummy load resistance only at certain frequencies. At other frequencies the speaker's impedance is higher. Since bass guitars generate harmonics and not pure sine waves, some of the frequencies to be reproduced fall outside the speaker's low impedance frequencies.
Note 4: More volts applied to a speaker make it louder.
Note 5: It is assumed that increased voltage is an increase in power.
A tube amp's advantage is best heard when two different speaker cabinets are connected in parallel like a 15 and two 10's. The (hopefully) staggered resonance broadens the high impedance zone to all frequencies in the bottom octave.
The simple fact of the matter is that a tube amp can deliver more volts to a speaker than it can a dummy load of the same nominal impedance ( note 4). This is generally about 2dB more ( note 5). A solid state amp only increases by a fraction of a dB in most cases. The proof of this is left as an excercise for the student, warm up your oscilloscope or boot up your SPICE program.
Note 1: AC RMS volts are used because they make the formula work.
Note 2: To be fair when comparing two amps the same amount of distortion should be used.
Note 3: A speaker's impedance is equal to the dummy load resistance only at certain frequencies. At other frequencies the speaker's impedance is higher. Since bass guitars generate harmonics and not pure sine waves, some of the frequencies to be reproduced fall outside the speaker's low impedance frequencies.
Note 4: More volts applied to a speaker make it louder.
Note 5: It is assumed that increased voltage is an increase in power.
A tube amp's advantage is best heard when two different speaker cabinets are connected in parallel like a 15 and two 10's. The (hopefully) staggered resonance broadens the high impedance zone to all frequencies in the bottom octave.
The trouble with this is that when the tube amp sounds louder, it's because it's actually putting out more power than the SS amp. If you were to measure the actual power output of the two amps, and match them, then run them through the same cabinet and measure the volume, they would be exactly the same. The only reason people perceive a difference is because a tube amp rated for a certain wattage can actually be capable of putting out as much power to the speakers as a SS amp of a higher rating. Of course, at that point the tube amp will actually be well into its distortion range, even if it still doesn't really sound like distortion, while the SS amp will not have reached the point of distortion. When a SS amp reaches distortion, you know it immediately, like somebody just threw the "suck" switch.
BTW, this is actually quite easy to measure. Just put a clamp ammeter around the speaker leads, or connect a voltmeter across them. Since we know the nominal impedance, we only need one other number to calculate the power output. Then put an SPL meter in front of the loudspeaker.
No, not fact: uniformed opinion. You hold the presumption that in order for volume to increase, power must increase. This is false. Volume is MUCH more than simple disappation of power. It is quite common for different "kinds," but otherwise equally measured, of watts, output AC of varying current and harmonics to have easily measurable differences in acoustic output
I don't know about you, but I don't feel like my mind is being expanded here at all. At the end of the day, a watt still equals a watt, and volume, meaured in dB's, is alot more complicated than this debate. And, for some, it will never be answered or understood. Enjoy the amp you have, crank the volume as much as you can, and let it rest.
Please explain how you think that equal amounts of power into the same load can produce different volumes. Voltage is measured in RMS. Even if the harmonic content is dissimilar, if RMS voltage = RMS voltage between the two, the delivered power is equal.
Equality in delivered power does not mean there is equality in volume; that requires identical signals. Differences between the signals is correctly assumed and stated. Identical voltage and different current is one answer already provided. Identical voltage and different harmonic content is another.
Yes, but we have a known nominal impedance, and we are measuring for one of the two unknown quantities, either current or RMS AC voltage. Any two of those three factors will give us enough information to calculate output power. So, if we set the amplifiers to equal output, by setting them to equal output current or equal output RMS AC voltage, they are by definition producing the same amount of the property that we *didn't* measure, be it either voltage or current.
The only thing that can possibly be different is the harmonic content of the signal, which would produce a different wave form. This is specifically the reason why the voltage measurement is done as "root mean square".
If you focus on just this one variable, you still have your answer standing right in front of you. Different waveforms are interpreted by human ears to be different volumes even when the RMS voltage measurements are identical.
OK, I have a rig I play around with at school that is a pretty good comparison. 1st I have a Hartke 115XL 8 ohm speaker. I have a Alembic F1-X that I run into a EV dynacord SS power amp bridged that puts out 200 watts into 8 ohms. I also have an all tube Traynor YBA-2 that is also 200 watts into 8 ohms. I've been able to compare them side by side on many occasions. They are both loud as heck. The EV is a true 200 watts into 8ohms and most 200 watt SS heads are rated at 4 ohms and not 8 ohms. Anyway, the SS amp sounds the same at just about any volume up to clipping. Once it runs out of head room its' useful power is done. The tube amp does the same up to clipping but, once it starts clipping it starts adding some midrange grit that is louder but still usable. There is a range of power beyond its' rated power that is somewhat distorted but usable and in many cases desirable. If you were to analyze the sound you'd probably find that there is some added harmonics that make it sound louder but, there isn't anymore real power being produced. This whole SS/tube power thing doesn't really matter all that much. It's more the tube tone vs SS tone that makes us choose what we're after.
Well how much of that comes from being tube vs. ss, and how much of that comes from other factors?
OK.
So I think I realize now why folks tried to tell you this was a tough topic to discuss.
It's not because there's a lack of scientific research into the issue (Loudthud disproved that, or perhaps baffled me into thinking he did
) , but because what has been proven before at TB -- and again just now -- is that folks won't discuss this in a scientific way, despite your clear and limited question.SO, I'll ask you: why do you want to know? Is there some way you hope to apply this knowledge, like the selection of an amply-powered amplifier? Because TBers can help you there, if that's why you're posing the question. If you're really just asking out of curiosity, I think that in order to reach some sort of satisfaction you're going to have to just compare some amps and form your own opinion, in my opinion.
Lowbrow
I've played with a number of guitarist with half stacks of about the same wattage, both tube and solid state.
The tube amps didn't sound louder, just somewhat brighter and gainer and frankly the sound was less consistant than the solid state amps. As tubes heat up the sound changes somewhat.
For rock and metal I much prefer playing on stage with solid state amps. The tone is just more predictable and consistant from show to show.
I think guitarists that use tube amps tend to crank them because to get the sound they want they need to be cranked a little. With a solid state amp, the sound is more or less the same from low to higher volume.
The tube amps didn't sound louder, just somewhat brighter and gainer and frankly the sound was less consistant than the solid state amps. As tubes heat up the sound changes somewhat.
For rock and metal I much prefer playing on stage with solid state amps. The tone is just more predictable and consistant from show to show.
I think guitarists that use tube amps tend to crank them because to get the sound they want they need to be cranked a little. With a solid state amp, the sound is more or less the same from low to higher volume.
Some comes from the overload characteristics of the tubes. Some comes from the characteristics of the output transformer.
OK.
So I think I realize now why folks tried to tell you this was a tough topic to discuss.
It's not because there's a lack of scientific research into the issue (Loudthud disproved that, or perhaps baffled me into thinking he did
SO, I'll ask you: why do you want to know? Is there some way you hope to apply this knowledge, like the selection of an amply-powered amplifier? Because TBers can help you there, if that's why you're posing the question. If you're really just asking out of curiosity, I think that in order to reach some sort of satisfaction you're going to have to just compare some amps and form your own opinion, in my opinion.
Lowbrow
The real reason I wanted to know is because I'm searching out a tube amp head and I don't want to get one that is underpowered for typical rock band performance without a mic.
At first, I was hoping that 50-60 watt amps would suffice because I've owned a ton of 50 watt amps for guitar over the years and they're as loud as you'll ever need for any band situation.
There really has been a lot of good information shared in this thread, and I'm glad things have been clarified for me. It looks like I will likely be needint a 100-120 watt tube head for my bass rig. I was first envisioning a single 1x15 cab, but may opt for two cabs to push a bit more air if need be.
Also, it's just part of my personality: I don't want to just know what to buy, I want to know why I want to buy that. And now I do.
Thanks, everybody!
It's always better to have too much than not enough, you don't have to run it all out. I wouldn't show up at a typical rock gig with less than 200 watts tubes and a 2x15 cab.
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