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Why Power Tubes Sound Different

hussamd

Power User
No such technology exists at this time.

This is all very interesting stuff, but I basically jumped off the forum board, right before we broached the universal question: Toilet paper - over or under? And that is as advanced as I'm willing to go, at this time.
Toilet paper under if you have a cat that likes to grab and run.
 

Durrani

New Member
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).
 

TJ Morgan

New Member
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
 

Billbill

Power User
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!!
 

Deaj

Experienced
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).
 

yyz67

Power User
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.
 

Anthony Griggs

New Member
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.
 

shemihazazel

Fractal Fanatic
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.
 
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