Do you prefer vacuum tubes or transistors?

                                       Do you prefer vacuum tubes or transistors?

I'm a proponent of single-ended tubes myself, and the tube-vs.-transistor debates I often hear happening in the pages of consumer and music magazines use descriptive but imprecise language like "warm," "liquid," " Smooth" and "Dynamic".

But what do the engineers who actually design the devices think of tubes and transistors in terms of objective science and measurement?

The two professional societies that can say the most on this matter are IEEE (Institute of Electrical and Electronics Engineers) and AES (Association for Audio Engineering). Both professional societies publish peer-reviewed journals with articles written by engineers and scientists working in the professional and consumer audio industries, as well as cutting-edge academic research. If you're looking for a balanced perspective on this debate, direct yourself to one or both of these societies.

Below we provide you with some readily available IEEE and AES publications that will help you better understand the difference between solid state and vacuum tube electronics, their performance, and ultimately, their sound.

Cool sound of IEEE-tube,

IEEE published "The Cool Sound of Tubes" in its August 1998 issue of IEEE Spectrum. There's also a helpful sidebar between tube and transistor distortion in the same article. Finally, there is a useful table summarizing the pros and cons of tubes and transistors from a sound and design standpoint. Since this table is only available as a graphic image, we have transcribed the text from the summary table below, highlighting some key points that directly affect sound quality:

Vacuum Tubes – Advantages

Highly linear, no negative feedback, especially for some small signal types

Clipping is smooth and widely considered more musical than transistor

Withstands overloads and voltage spikes

Highly temperature-independent characteristics greatly simplify biasing

Wider dynamic range than typical transistor circuits due to higher operating voltage

Device capacitance varies little with signal voltage

Capacitive coupling can be accomplished using low value, high quality film capacitors

Circuit design is often simpler than semiconductor design

Typically run in Class A or Class AB to minimize crossover distortion

Output transformers in power amps protect speakers from tube failure

Maintenance tends to be easier as users can replace tubes

Vacuum Tubes – Disadvantages

Bulky and therefore less suitable for portable products

Requires high operating voltage

High power consumption, requires heater supply

generate a lot of waste heat

Less power efficient than transistors in small signal circuits

Low cost glass tubes are physically fragile

Easier to generate microphones than semiconductors, especially at the low level

The cathode electron emission material is used up, resulting in a shortened service life (usually 1-5 years for power tubes)

High-impedance devices, such as loudspeakers, often require matching transformers for low-impedance loads

Typically more expensive than equivalent transistors

Transistors – Advantages

Usually lower cost than tubes, especially in small signal circuits

smaller than equivalent pipe

can be combined in one chip to make an integrated circuit

Lower power consumption than equivalent tubes, especially in small signal circuits

Less waste heat than equivalent tubes

Can run on low voltage power supplies for greater safety, lower component cost, and reduced clearances

Low impedance loads do not require matching transformers

Usually stronger than tubes (depending on chassis construction)

Transistors – Disadvantages

Tend to higher distortion than equivalent tube

Complex circuitry and lots of negative feedback required for low distortion

Sharp clipping in a way that is widely considered unmusical due to the considerable negative feedback typically used

Device capacitance tends to vary with applied voltage

Large unit variations between key parameters such as gain and threshold voltage

Charge storage effects add signal delay, which complicates the design of high frequency and feedback amplifiers

Device parameters vary widely with temperature, complicating biasing and increasing the potential for thermal runaway

Cooling is less efficient than ducted cooling as lower operating temperatures are required to ensure reliability

Power MOSFETs have high input capacitance, making them ideal for voltage

Class B totem pole circuits are common and cause crossover distortion

Less tolerant of overloads and voltage spikes than lamps

Almost all transistor power amps have direct coupled outputs, which can damage speakers even with active protection

Capacitive coupling typically requires high value electrolytic capacitors, which perform poorly in audio extremes

Greater potential for radio frequency interference due to rectification of low voltage diode junctions or slew rate effects

Difficult to maintain; users cannot easily replace equipment

Older transistors and ICs are often unavailable after 20 years, making replacement difficult or impossible

I often see merchants selling transistors in a certain treasure saying: This power amplifier smells like a tube amplifier. What about a tasteless transistor power amplifier instead of buying a tube power amplifier directly? Their descriptions make people feel absolutely inaccurate.