Why do tubes sound different

Very high impedance in the lower hz like ohms , and very low impedance in the upper octave and a half like an ohm or two. A good push pull triode with a moderately high output impedance maybe SIY says bad design would elevate the low end enough to notice, and soften the treble enough to notice. I could measure that. It wasn't just bias, it really sounded different.

Into my ESLs it is also possible the tube amp at least on peaks had some audible distortion that wasn't obvious enough to sound like distortion. Now I thought more than that sounded different. Some of the sense of space, a 3D quality SS amps didn't have.

I did my own tests at one point like what the Swedish AES did. Load an amp output with resistors, drop the level enough that input to output was unity gain, and feed that into another amp powering the speakers. I was using a VTL and a Spectral. To my surprise, the VTL fed into the Spectral exhibited all the space and 3D qualities which meant whatever the triode tubes were doing was captured accurately by he Spectral.

It was triodes being of superior fidelity, it was triodes having a pleasing coloration. This is not what I was expecting at all. Reversing positions the Spectral had all the coloration of a meter of interconnect.

You could tell if it was just interconnect to the amp or going thru the Spectral. In time I tried this with a few other amps. Now this wasn't blind listening on my part.

I did do this for one of my audiophile buddies. I switched with him out of the room several times. He could within seconds correctly tell me if the VTL was in circuit or not. He was not able to reliably tell as to whether the Spectral was in circuit, and took longer to answer.

Still single blind, and a couple minutes to switch. Plus I know the FR was different. In any case, people who want tube sound or believe in it, could use low powered tube amps like preamps feeding them into clean SS amps to have their cake and eat it too. I've even had in mind making a preamp with the right character.

Using 12AT7s in push pull circuits able to deliver a watt or so, transformer coupled and loaded by resistors on the output to be like a mini push-pull triode amp. You could even switch in a few elements to simulate loudspeaker loading. Probably should have done it years ago without saying what I was doing. Come up with some marketing story to sell. There is a solid amount of high-quality valve modelling in professional audio tools, from modelling amplifiers hardware DSP for guitarists, to modelling plugins etc for guitar amps and effects LA2A compressors etc.

The best ones essentially run something like SPICE in realtime and they have been refined over the last decade to be indistinguishable from the real thing yes, I've been involved in blind testing. I can imagine this making it into hifi before too long so people can choose it easily if they wish. Wombat Master Contributor. The people who like their clean perfect replica amps of today will be relegated to the back pages of history and niche markets just like the vintage tube amps crowd today.

You must log in or register to reply here. Similar threads. Little Dot D preamplifier measurements. Replies 7 Views 1K. May 12, mononoaware. Help me buy a tube pre-amp.. Replies 11 Views Here we have the opportunity for a larger variation because two tubes with the same Mu may not have the same gm as Rp differs.

Now add in the variation in operating point bias and it is easy to see why different maker's tubes sound different-even to the point of not functioning in some overly sensitive circuits. An extreme case of this is the 12AX7 in the Moscode Minuette.

George Kay and I found that while the Tugsram 12AX7 worked well in the front end of his unit, the smooth plate Telefunken did not.

The latter tube caused the gain to fall dB and the distortion to increase times. Any user discovering this in his home would certainly hear startling differences between the Tungsram and Telefunken 12AX7.

But the main thing he would be hearing is the difference between a functioning preamp and a malfunctioning one, though it still played. The problem stems from the fact that there is not enough loop gain for the feedback to provide consistent equalization at low frequencies. This means that the shape of the low end, and low-to-high tonal balance will vary with the Mu of the tubes.

Moving on to noise, there are four areas to look into. AC hum is rarely a problem as most designers use DC regulated filament supplies. But for those with some ripple, the filament construction becomes a factor. The 6DJ8 and 12AX7 are made with folded or coiled filaments depending on the maker-it is not part of the specification. A coiled filament will cancel hum whereas a folded one will not. Noise, however, is the big battle. To deliver their potential, tubes need high voltage.

Solid-state devices generally do not need high voltage so their power supplies are far simpler and much cheaper to make. Both solid-State and Tube amps have power transformers to run their power supplies. Tube amps generally raise the incoming voltage, rectify it, clean it and send it to the circuit at various voltages, from 6 volts to volts. Solid-state amps reduce the incoming voltage, rectify it, clean it and send it to fixed power rails that service all the devices attached.

The highest voltages in a Solid-state amp typically come from the output devices that drive the speakers. Solid-state amps do not require an output transformer. High voltage vacuum tubes have a high output impedance and require a transformer to decouple the high voltage DC from the much lower power AC music signal sent to the speakers.

Speakers will not run on DC, they will melt. The output Transformer also changes the high impedance signal of many thousands of ohms to a low impedance signal in the 2 to 16 ohm range to match with the speakers you connect. The transformers are the most expensive components in any amplifier. By eliminating a transformer, solid-state gets a huge cost advantage.

That leaves us with the Elephant in the room. Tube amps need vacuum tubes and that affects the entire design and construction process. Tubes are electro-mechanical devices that run on high voltage and produce a lot of wasted energy in the form of heat.

In order to operate, a vacuum tube moves a controlled flow of electrons from its cathode to its anode or plate. A red-hot filament heats the cathode and a cloud of electrons forms. High voltages of varying levels feeds different elements within the tube to direct the flow of the cloud, while a small AC control voltage regulates the flow volume.

Hence, the British term, valve. This process generates heat in vacuum tubes that could be degrees Celsius. Water boils at degrees C.

As such, the enclosure for a tube amp has special requirements for safety, to protect the user and innocent passersby. As scientific research improved, the use of a combination of dissimilar elements combined on silicon wafers to create voltage amplification occurred.

Home audio and musical equipment manufacturers jumped on this new technology. Most builders of vacuum tube equipment, viewed solid-state devices as a threat to their business or an opportunity to improve their bottom line if they modified their designs.

Since solid-state construction can be smaller, lighter and less expensive the elimination of the vacuum tube seemed to make sense. This opened the door to mass production and printed circuit boards. Most amplifiers today use some type of printed circuit board to mount their required components; both for solid-state and for Tube designs. Early printed circuit boards just eliminated the mounting points for components and the wires that joined them.

Components were soldered to the boards by hand. Modern solid-state amp construction is usually done on multi-layered printed circuit boards. The components are installed by robots and then soldered in an automated process known as wave soldering.

The primary goal is to make them fast and cheap by eliminating work done by people. You can get much higher quality solid-state amplifiers but the price rises quickly if you demand higher quality. Some guitar amp builders are still using non-conductive component cards with eyelets or turrets to mount their components.

This is well suited to vacuum tubes but not so much for solid-state. When it comes to cost, solid-state amplification really shines. This reduces the price of individual components to pennies. Since most designs do not use an output transformer there is a huge saving on that one item. After purchase, solid-state amps have virtually no ongoing maintenance costs.

They run cool, unaffected by vibration and will operate for days without a care. Failure in solid-state amps usually occurs very early in their life span, due to manufacturing defects. Vacuum tubes on the other hand, require a lot of manual labour and are produced in relatively small batches, making their cost to produce hundreds of times higher than equivalent solid-state devices.

The average tube amp has ongoing maintenance costs. Tubes are fragile and subjected to intense cycles of heating and cooling. Vibration and heat will degrade tubes and they are susceptible to developing stray noise and microphonics. Over time, the cathode coating material will be depleted and tubes become weak.

Tube replacement is inevitable and in the case of power tubes, technical skills are required to ensure the amp is correctly set up for proper, safe, operation. Most people do not have the skills to work safely on high voltage equipment like a tube amp, and must hire somebody to do this work for them.

Both solid-state and vacuum tube amplifiers are available as both cheap consumer products and very expensive professional grade equipment. After purchase, tube equipment will cost more to own. So far, I have compared the manufacture and relative costs of vacuum tube vs. It would seem that solid-state has everything going for it.

Cheaper, lighter, cooler and less expensive to operate. If this is true, why is vacuum tube technology still around after all these years? Here is the rub. Within that group of audio enthusiasts and musicians that really care about their sound, there are those that think vacuum tubes simply sound better and those that think solid-state is just as good or better.

Solid-state enthusiasts can provide highly technical data that supports their argument, as can those that favour tube based designs. There are really two sub groups when it comes to amplifiers.

Those designed to create music and those designed to reproduce music. Both use completely different audio sources as inputs and very different speakers to handle the output. Musicians want amps that can provide a wide range sound, from sparkling clean to highly distorted and harmonic laden. Home audio enthusiasts want amps that will reproduce the original source material as closely as possible. They do not want to create distortion they want to reproduce the distortion made by others.

Distortion is one of the key selling points for tube amp lovers. Solid-state amps do not seem to distort as musically as vacuum tube designs. The primary reason is that when you drive tubes hard the distortion comes on gradually and presents itself as gradual compression that blooms into distortion.

The high voltage supplied to vacuum tubes ensures that the output of the device seldom exceeds the voltage that runs it. Solid-state amps use lower voltage supply rails to operate and the output can exceed the supply voltage. When that happens, they do not start to compress and gradually clip. They simply cut off the output signal at that level.

Sine waves become square waves immediately and the sound is not pleasant. Solid-state distortion in its pure form sounds something like bees in a tin foil bag. Not the best for musical instruments and completely unacceptable for home audio enthusiasts. The nature of clipping and distortion also affects the harmonic content of the output signal. But the main reason both musicians and audiophiles alike love the sound of tubes is their even-order harmonic distortion. The primary difference is even-order versus odd-order harmonic distortion.

Perhaps a lesser known type of distortion, harmonic distortion of tubes is what fills out the sound and adds warmth. Without getting too technical, all amplifiers will have sympathetic distortion related to the original signal.

Tubes have mostly even-order harmonics referred to as second, fourth, and sixth. Solid-state devices have more odd-order harmonics third, fifth and so on. It is the even-order harmonics that will provide positive embellishments to the original signal, making it sound fuller. A technical article written by Russell O. Hamm published in in the Journal of the Audio Engineering Society described this as a choral or singing sound.

The odd-order harmonics produced by solidstate amplifiers produce a edgy or cut-off sound. It is not natural distortion or add to the original signal positively, and good ears with tire of it quickly. Dynamic range is another point of contention between the camps.

Solid-state does not seem to handle peaks or transients in the music signal as well as tubes. Essentially, I am talking about sound that goes bang or thump. This is likely due to that fact that tubes naturally have soft clipping and compression to handle transients and smooth those peaks and valleys. The amplification of bass guitar is an exception to this general rule. Low frequencies require more power to amplify than high frequencies.

A tube amp designed specifically for low frequencies requires a lot of output tubes and massive transformers to generate the power that most bassists require for live performance. This makes them very hot, very big and very heavy. The Ampeg SVT is widely regarded as king of the bass tube amps but it only delivers watts while modern solid-state sound systems can deliver thousands of watts in a much smaller, cooler package by using advanced operating modes such as class D.

If you are a skeptic, you should look at the direction taken by manufacturers of solid-state guitar amps. The advertisements usually feature genuine tube tone as a major selling point. In order to deliver on this selling point additional solid-state devices were developed that more closely mimic the clipping characteristic of tubes.

Helper circuits create things like asymmetrical clipping and distortion on demand, using simple diodes. The technology has really gotten good over time. The advent of amplifier modelling is perhaps the biggest chance for solid-state amps to sound like tube amps and has been a real bonus for recording applications. Just add a computer to your amp and season to taste. However, there is a cost associated when manufacturers create proprietary devices and circuits to emulate the sound of tubes.

When the product ceases production, any proprietary parts also cease production. Most popular tube amps are variations of circuits that have been around for more than 60 years and use a standard range of components. In their glory days, manufacturers of tube gear did use oddball tubes to fit their designs and today you will occasionally find amps that use tubes no longer in production. Most currently produced tube equipment uses standard, popular, vacuum tubes in their construction.

There is not enough sales volume to warrant the creation of new tubes due to their high production cost. If you have a tube amp today, you are likely going to be able to get replacement tubes in the future. What happens when your modelling amp loses its CPU? Are they still making it?

Finally, we should compare the ease with which a user can change the sound of their amplifier.