The “Tubes to Look At” (but that don’t amplify)
In recent years a trend has spread for low-cost “tube amplifiers”. Many users, attracted by the visual charm of glowing tubes, hope to own a piece of “vintage” or “warm” electronics. Unfortunately, in many cases what they buy is not a real tube amplifier, but a sophisticated trick: tubes installed only for looks, while the actual “work” is done by TV-grade IC chips or simple transistors.
These devices, which I call fake tube amps, rely on visual illusion and marketing and are often sold at rock-bottom prices. Their aim is to attract beginners or anyone who wants “tube sound” without spending much. In reality, gain, power and linearity are all handled by solid-state circuitry disguised behind purely decorative tubes.
In this article I explain how to spot them, why they are harmful (even to the tubes themselves), and why it is far better to buy a small solid-state amp than to fall into these traps.
What a Cathode Follower Is and Why It’s the Favorite Trick in “Fake Tube Amps”
A cathode follower is a well-known vacuum-tube configuration: it provides no voltage gain but works as a buffer, simply “following” the grid voltage, offering high input impedance and low output impedance.
In practice:
- The signal applied to the grid is “repeated” at the cathode with the same amplitude (or slightly lower).
- The tube operates with 100 % intrinsic feedback, giving a linear response but no gain.
- It’s useful as a buffer to drive following stages that need current, but it cannot deliver voltage amplification or power.
If an amplifier uses all its tubes as cathode followers, they do not actually “amplify” the signal but merely repeat it—at extra cost and without adding useful voltage or power. In such cases the real work is clearly done by hidden chips or transistors.
When these tubes are fed with very low plate voltage or used in a “soft” way, they don’t act as true active stages but as almost passive elements full of internal feedback. Systematic use of the cathode-follower trick in fake tube amps is an elegant way to create the impression of a genuine tube circuit while drastically cutting weight, cost and complexity.
Cathode Poisoning and Why Tubes Die
At this point it’s important to explain a phenomenon common to many of these amplifiers: cathode poisoning. It is an irreversible degradation of the emissive surface of the tube’s cathode that greatly reduces its ability to emit electrons when the heater is on but there is no plate voltage, or only very low plate voltage.
How Cathode Poisoning Happens
- Tubes use a cathode coated with alkaline oxides (barium, strontium, calcium oxides) to lower the work function for electron emission.
- If the heater is on but there is insufficient plate current or voltage, the cathode cannot form the proper space charge. Impurities or ions bombard the surface, depositing insulating material or altering the oxide layer, thus lowering emissivity.
- The tube effectively “gets sick”: emission drops, distortion rises and the tube often becomes unusable. This condition is usually irreversible.
Leaving a tube with its heater powered but without proper current draw slowly poisons the cathode. In fake tube amps this is often by design: tubes are deliberately run at low voltage to cut costs, so their real functionality quickly fades.
Why a Solid-State Amp Is Better than a Fake Tube Amp
If you want to spend as little as possible, buying an amplifier that advertises “tubes” but is largely solid-state is a risky decision:
- The tubes are destined to degrade.
In these circuits, tubes operate in non-ideal conditions and wear out quickly. Spending money on expensive or NOS tubes is like throwing them in the trash. The best advice is to use the cheapest tubes available, such as JJ, Tesla or Sovtek, since the circuit will never exploit their potential. - Actual gain and sound quality depend on chips or transistors.
The active element is an integrated circuit or transistor, so the sound is shaped by that silicon, not by the tubes. At best the tubes add a bit of distortion and signal degradation. - Performance is often worse with the tubes in place.
It’s common for these amps to sound better with the tubes bypassed, with lower distortion and slightly more power. I’ve personally demonstrated this on one of these fake tube amps (see next section). - Early failure risk.
Operating tubes in such marginal conditions accelerates wear, sometimes ruining them within a few months. - Real tube sound has a cost.
A genuine tube amplifier requires heavy output transformers, high-voltage supplies and careful engineering. It’s unrealistic to expect all this for a few dozen euros or dollars.
If you’re not ready to invest in a true tube amp, you’re better off with a small solid-state amplifier: it will deliver better and more reliable performance.
How to Recognize a Fake Tube Amp
Spotting a fake tube amp is not hard if you know what to look for. Key signs include:
- No output transformers.
A true tube power amp driving loudspeakers always has heavy, expensive output transformers. If you don’t see them, the amp is almost certainly fake. Sometimes the “transformers” are just empty plastic or sheet-metal boxes with a few wires inside. - Very low weight.
The lack of transformers and high-voltage power supplies makes the amp unusually light compared to a real tube design. - The “Christmas tree” look.
Flashing digital displays, multicolored LEDs and bouncing VU meters that keep blinking even with no music are typical of toy-level gear. A serious hi-fi amplifier doesn’t need these light shows. - Bluetooth and gadget features on a so-called tube front panel.
A fake tube amp with Christmas-tree lights almost always comes with built-in Bluetooth reception.
Light weight, missing real transformers and decorative lights are all strong warning signs.
A Real-World Example of a Fake Tube Amp
Here’s a real case I examined years ago that perfectly illustrates these issues. It was incredibly light, with transformer covers that looked convincing at first glance but were actually empty plastic shells. Inside were four tubes serving only as stage props: two 6N1 double triodes (equivalent to 6N2/6N1P) and two EL84-type tubes.
All of them were wired in cascade as cathode followers and powered with only 24 V plate voltage—far too low to achieve meaningful amplification. The rest of the circuit consisted of an op-amp before and another after the tube section, because at such low currents the tubes could not drive anything.
Although less than a year old, the tubes were already “rotten,” with severely reduced emission. I then ran an experiment: I bypassed the entire tube section by bridging the grid and cathode pins so the signal would no longer pass through the tubes.
The result was striking: the amplifier kept working perfectly without the tubes, delivering slightly more power and lower distortion than when the tubes were in circuit. In the video below you can clearly see the inevitable “Christmas tree” display still blinking away.
Measurements confirmed it. With the tubes installed, distortion at 1 W RMS was about 0.079 %; with the tubes bypassed it dropped to about 0.05 %. Power output rose from about 10 W into 8 ohms with the tubes to about 15 W without them. The bandwidth remained the same, from 35 Hz to 48 kHz, showing that the tube section added no real gain. In the photo below you can see what was truly amplifying the signal…
In short, those tubes were not only useless but actually degraded performance. The conclusion was clear: spending money on expensive or NOS tubes for such an amplifier is pure waste, because the circuit will never use them properly. If replacement is needed, stick to the cheapest tubes you can find, and if the unit is truly a fake tube amp the wisest choice is to stop investing in it and move on to something serious.
Fake Tube Amps in the “High-End” World: When Appearance Sets the Price
Don’t think these scams exist only at the budget end. I’ve personally seen “high-end” amplifiers sold for eye-watering sums that, beneath their gleaming exteriors, hid designs essentially identical to low-cost fake tube amps. The difference was purely cosmetic: brushed-aluminum fronts, machined knobs, vivid colors, flawless finishes and fancy packaging. Inside, however, the circuit was sometimes identical to products sold on Aliexpress for one-tenth the price, simply rebranded.
In such cases the exorbitant price reflects marketing and cosmetics, not better engineering. Spending more does not guarantee quality: even in the so-called high-end arena you may find amplifiers that, stripped of their glossy shells, are worth no more than a toy. Always look beyond the shine—the real value lies in the circuit, not in the paint or the logo.