When people start talking about tube vs. solid state anything in the guitar world, most opinions state that the latter is inferior.
Although a tube amplifier creates beautiful music, making a buying decision based on the idea that solid state tech is typically inferior isn’t always the right path to take.
This issue has become such a focal point that even rectifiers have become targeted as being tube or solid state models. When we take a closer look at this technology, you’ll see that how the power gets transformed matters less than the quality of the signal path.
Tube vs. Solid State Rectifiers
Tube and solid state rectifiers transform an AC power source into a DC one that amplifiers use to product sound. Solid state models are small silicon diodes that have no internal compression, providing a less expensive way to create results. Tube rectifiers perform the function more slowly.
When looking at the tube vs. solid state rectifier debate, the discussion is really about how much authenticity a musician wants from their playing style.
Solid state rectifiers produce an accurate, crisp, and authentic sound because of how they convert electricity into a one-way flow. Tube rectifiers need more time to generate the same result.
Although both end up creating DC power from electricity at the outlet, the tube version doesn’t move fast enough to keep up with the demand when big chords get hit and the amp is pushed to its limit. That causes a voltage drop for a few milliseconds, creating what the industry calls “sag.”
Sag is what delivers the compression that offers the classic tube amplifier sound. It’s a bit spongy, delivering a bloom that creates iconic tones.
What Does a Rectifier Do?
Rectifiers perform the action of converting alternating current (AC) power into direct current (DC) resources. It is a diode, whether solid state or tube, that provides a gateway that causes electricity to start flowing in only one direction.
The power enters the amplifier from the wall plug using AC voltage. It then works its way down a path through the power transformer until it reaches the rectifier to become DC energy.
This change is necessary because the rest of the amp’s circuitry is built to use DC, not AC power.
In most guitar amps, the process involves bumping up the voltage to the amount that the other tubes require in the circuit.
When you plug an amp into an American outlet, you’ll receive power at 120VAC. Once the transformer gets a hold of that energy, it gets bumped to approximately 330VAC.
That’s when the rectifier transforms it from AC to DC power, creating another voltage increase to about 400VDC.
It’s important to remember that the rectifier isn’t part of the signal chain. That means the instrument’s signal won’t pass through it at any point during its routing.
If that’s the case, why is there a tube vs. solid state rectifier debate to consider since a guitar’s tone isn’t affected by the design?
■ What Is Biasing?
Biasing is the initial operating conditions settings for the current and voltage of active devices. Most amps, whether they use vacuum tubes, diodes, or even transistors, require a steady D supply at each terminal to function correctly.
The voltage or current is a bias.
The alternating current signal that leads to them gets super-positioned on the direct current bias.
When you look at the amp’s circuit that supplies the steady voltage or current, you’re looking at what is called the “bias” circuit.
Transistors and rectifiers must be bias to ensure the output signal doesn’t drive the energy away to a non-linear operation.
In the typical setup, the AC mains come from a transformer. This path goes to the rectifier, which then leads to a filter to reduce the risk of distortion occurring.
Once that occurs, the power supply hits the voltage regulator before becoming usable DC output.
This process is necessary because the AC waveform is not constant. When it reaches its peak positive value, it tends to degrade. The reverse occurs for the negative value.
Those measurements are what create the equation that lets you determine the efficiency of any rectifier:
E = P(DC)/P(AC).
Information About Solid State Rectifiers You Need to Know
Solid state technology isn’t anything new. The first diodes appeared in the 1950s, and the industry has been evolving that tech to meet various needs ever since.
The first solid state rectifiers were horribly expensive. Once the assembly process became refined, they quickly became the cheapest thing you could put into an amp, which meant they were used quite often.
The solid state rectifier has no internal compression. Since they response to different stimuli instantly, it’s extremely rare for musicians to experience a voltage drop when routing a guitar through amps with this technology.
That’s why you can always find solid state rectifiers in amps that have the highest wattage levels available. When you work with tube-based tech, it’s rare to find an amplifier listed over 40 watts.
Since you get a tight sound with less sag, the lower frequencies tend to have more headroom when using a solid state rectifier.
That means bass players and electric guitars in the lower register have more definition, making them an excellent solution for bending, picking, and anything in the metal genre.
If you push the amp hard, you can still get a bit of sag at the extreme. It won’t ever compare to what tubes deliver, which is why you’ll see most enthusiasts lean to the classic design instead of the silicon diode.
Why Use Tube Rectifiers Over Solid State Rectifiers?
The primary benefit that tube rectifier technology provides is the slower startup time. Not only does this feature potentially increase the life of the power supply, but it also reduces over-voltage problems in situations when you’re turning on the amp.
That means you don’t have as much risk of arcing when excessive plate voltage exists within the power pathway.
|Why Use a Tube Rectifier?||Outcome of Using a Tube Rectifier|
|Supply Ripple and Nose Floor||DC power is a voltage used to power the end equipment in the amplifier. Supply noise from this resource creates a ripple because of the voltage fluctuations it delivers. Tube products create smaller fluctuations, reducing the levels of unwanted noise that appear in some amps.|
|Tone Shaping||Tube rectifiers make guitar amps sound different when clipping than those that use solid state technologies. When there’s a larger demand, you’ll experience a greater loss. It can be up to 60V for some models. By decreasing the energy available to the power supply, distortion occurs through the compression.|
|Filter Capacitor Lifespan||Tube amps work at high voltage levels, raising the cost of power supply design significantly. High-voltage components are specialized manufacturing products, with filter capacitors often running more than what you’d pay for dinner with the family. Using the same style of rectifier ensures that you’re maximizing the lifespan of the unit without compromising the quality of your tone.|
|Equipment Protection||When the power tubes are cold with no idle current, the voltage is at its highest potential. That’s because the supply is essentially unloaded. It can take up to 30 seconds (and often more) before everything is ready to work at its operating points. The tube rectifier reduces the risk of managing excessive voltage within the system because it warms up at the same rate as the other pathways.|
|Standby Switch Compatibility||Some amps use a standby switch to let the power tubes reach their operating temps before allowing access to the high voltage. That design is compatible with tube rectifiers, ensuring that arc failures don’t occur. Some experts believe that this option can extend the life of the components, but there is no direct evidence to suggest that it does.|
Sag has zero place in a Hi-Fi amp, which means tube rectifiers work against the results that some musicians want to achieve.
Tube rectifiers do provide more series resistance than solid state designs. That means more loss is experienced when routing the guitar through its pathway.
If you select the correct filters for your system, this effect is typically mitigated without much difficulty.
You’ll get a stable supply – unless you want to have sag introduced into your playing style and tone.
Are Tube or Solid State Rectifiers Better?
Guitarists that need a fast and tight response from each note and chord find a better delivery with solid state rectifiers. When heavy sag and improved compression recognition are necessary, a tube rectifier is a better solution. Each one has a place in a musician’s arsenal.
When I was 17, I snuck out of school, took the truck to the big city, and made my way to the music store. I know – I was such a rebellious kid.
I was on a quest to find a new guitar. My weekend job didn’t let me get away at all, and my folks didn’t want me driving the truck at night. In my youthful mind, that meant I needed to take things into my own hands.
As I plugged in each guitar I wanted to try into various amps, I purposely played “Stairway to Heaven” to be annoying. I know – taboo today, but it wasn’t THAT bad when the song was relatively new. As I tried each one, there was one amp in particular that made each instrument shine.
It was the Vox AC30. Although I ended up coming home that day with a Mesa Boogie Mark II-B combo (that was on sale for a great price) and no guitar, I fell in love with that other amp. As soon as I could bring it home, I added it to my collection.
For me, the tube or solid state debate is a bit pointless. You need one of each to maximize the flexibility of your playing style.
I tend to use the tube amps for my practice and recording sessions, while the solid state tech does a better job on stage – especially when I need to mic the output.
If you only want to get one amp, I’d recommend the Vox AC30. It’ll deliver consistent results for you in virtually any situation.