Why Power Tubes Sound Different

The sound of a tube amplifier is partly a function of the circuit topologies typically used with tubes versus the topologies typically used with transistors, as much as the gain devices themselves. Beyond circuit design, there are other differences such as the differing electronic characteristics of triode, tetrode, and pentode vacuum tubes, along with their solid-state counterparts such as bipolar transistor, FET, MOSFET, IGBT, etc. These can be further divided into differences among various models of the said device type (e.g. EL34 vs. 6L6 tetrodes). In many cases circuit topologies need to account these differences to either homogenize their widely varying characteristics or to establish a certain operating point required by the device.

The low frequency roll-off can be explained by many tube amplifiers having high output impedance compared to transistor designs, due to the combination of both higher device impedance itself and typically reduced feedback margins (more feedback results in a lower output impedance).
 
I am new here but on a different note, is there a better way to run the Matrix amp say run the amp hot and my fx II xl + output down or vise versa? Looking at more of a tube sound, Sorry I couldn't start a new thread on this for dome reason

TJ
 
I pulled out the four EL34 tubes in my Marshall shoved four hotdogs in the socket and I've never received so many compliments on my live tone than ever before! Everyone should try this!!
 
I pulled out the four EL34 tubes in my Marshall shoved four hotdogs in the socket and I've never received so many compliments on my live tone than ever before! Everyone should try this!!

Hot dogs really do sound great in Marshall amps. The sizzle they add makes all the difference. Ball Park Frank's for the win!

I don't care for hot dogs in Fender amps generally speaking, but sweet Italian sausage works well in Fender's, most Mesa amps, and Dumble / Dumble clone amps.

Hillshire Farms Lit'l Smokies are an upgrade for traditional preamp tubes IMO (well except for the phase inverter, where I prefer a breakfast sausage link).

YMMV (your meat may vary).
 
I read Cliff's explanation years ago but it's now really sinking in: it's the "circuit context" combined with the tube's particular linearity/nonlinearity in that context that affects tone and feel.

Toilet paper under if you have a cat that likes to grab and run.

You gotta post a video of this.

I don't care for hot dogs in Fender amps generally speaking, but sweet Italian sausage works well in Fender's, most Mesa amps, and Dumble / Dumble clone amps.

+1

Ever try boutique pesto chicken bratwurst or turkey dill sausages from Whole Foods? Expensive and kind of one trick ponies but a nice change of pace.

For true retro NOS meat tubes you got to go German: Blut (blood) Sausage for screaming licks, Cervelat (brain sausage) for mind melting shreds, or Weisswurst (veal) for smooth, creamy tones.
 
Some History:
The EL34 is a pentode. The 6L6 is a tetrode with beam forming plates (beam tetrode). The 6L6 design was originally done to get a power tube that was not a pentode as that configuration was patented by Phillips. A pure tetrode characteristic curve has a kink in it that can make an amplifier unstable. KT series tubes are also beam tetrodes, where 'KT' => kinkless Tetrode.
 
Makes sense to me. Your standard 6L6 beam power pentode tube was designed to not only function in the audio range, but also is used as a transmitter tube at frequencies up to 30 MHz.

If the tube's power bandwidth is 30 MHz or even just ONE MHz, then it'd have to have a very flat audio response, or so I'd believe.

Tonal differences in output tubes are due to plate capacitance and plate loading. They interact with the inductance of the output stage transformer, causing a predictable variance from flat frequency response.
 
Given that this is the case, why are there even tube type parameters in the Pre/Power amp tabs of the Amp block? Seems like it just feeds into people's placebo effect and perpetuates the myth.
 
In the audiophile world and even in the musician's world, for that matter, there has also been some debate regarding the "sound" of one interconnect cable vs. another.

The reality is simply this: EVERY component, be it a power tube, a guitar cord, an RCA cable, or any other component in the audio chain has measurable characteristics: Resistance, capacitance, and inductance. The values may be very low, or very high, but they are never true zero nor truly infinite.

As such, these devices are an RLC filter. They WILL affect the system frequency response. By replacing one tube, or one cable, or one capacitor, with another type, even one with the same primary value (as in, a .022 uF capacitor replaced with a different type .022 uF capacitor, with a different type of construction, causing it to have slightly different R and L values), this will affect the frequency response of the system to some degree. If the change is large enough it will be audible. If it's small enough it will barely be measurable.

So, no, tubes (and cables) don't have a sound of their own but they do affect the system frequency response. This is why "different power tubes sound different." It's not the tube, but it is the interaction of the tube's specific parameters within the total circuit, affecting frequency response.

So...let's not split hairs. For a specific tube amp, swapping out tubes can alter the tone depending on the characteristics of the tubes being swapped.

But....two cables, having identical electrical characteristics, identical RLC values, and being of two radically different construction types and price points, will have an identical "sound" and so would two tubes that have identical electrical characteristics, but are physically different in design and construction. It is possible for different tubes, or different cables, to result in the same sonic result. If their parameters are the same.
 
It's not the tube, but it is the interaction of the tube's specific parameters within the total circuit, affecting frequency response.
I don’t know, this reasoning hardly makes sense to me. It IS the tube swap that’s changing the sound.
This is like saying the bright cap doesn’t have a sound. But changing the value affects the frequency response and changes the sound out of the amp.
I mean yes, everything in the amp is an electrical signal and doesn’t have a sound till you hit the speaker.
 
Once again, as I mentioned previously, it's the interaction of the tube's parameters with the circuit parameters that affect the frequency response.

I cite again, the venerable 6L6 beam power pentode, a tube that can operate in the audio frequency range and is also useful at any frequency up to 30 MHz. In fact a single metal can 6L6 can handle up to 100 watts RF power output at close to 30 MHz if it's kept chilled in cold water.

The tube itself has no intrinsic "sound" of its own. It's the COMBINATION of the tube and the circuit it's in that creates a frequency response profile, and thus a signature sound.

The circuit may be designed so that the tube has a very flat, very linear response over a very broad range of frequencies, or the circuit may be designed for a strongly shaped response using the tube's parameters as part of the tone shaping. (This is usually the case in guitar amps.)

From a purely functional perspective, you can swap tube types and get a different tone. But you can't expect a specific tube to give the same sounding results if you put it in an amp that has a different circuit and loads the tube differently.
 
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