FAQ

  1. Are all of the amps hand-wired?
  2. Are PCBs (printed circuit boards) used in the amps?
  3. Can I customize an amp's logo or name?
  4. Can I customize an amp's tolex?
  5. What type of speakers are available?
  6. Can I choose custom speakers for an amp or cabinet?
  7. Can I request any add-ons or special modifications to the amp that I want to purchase?
  8. Can you build me a complete custom amp from scratch?
  9. What's your current build time?
  10. What transformers are used in the amps?
  11. What tubes are used in the amps?
  12. Are there any "Class A" amp models?
  13. What does fixed-biased and cathode-biased mean?
  14. What is negative feedback?
  15. What is the difference between a tube rectifier and a solid-state rectifier?
  16. What type of components are used in the amps?
  17. What type of wood is used in the cabinets?
  18. Do you service other brand name amplifiers?
  19. Do you ship amplifiers outside of the US?
[ ^Top ]1. Are all of the amps hand-wired?

Yes, all of the amps are hand-wired using custom-built turret boards. This tends to be a common method of building hand-wired amps and one of the most reliable and easiest to work on.

[ ^Top ]2. Are PCBs (printed circuit boards) used in the amps?

None of the major sections or components of the amps' circuits are built using printed circuit boards. However, depending on the circuit, PCBs may be used for a few small support components, such as FX loops, switching boards and the low voltage power supplies that may drive these small support components. Without getting into the hand-wired vs PCB debate, we believe using PCBs for these small components is appropriate, while adhering to hand-wired construction for the rest of the amp build.

[ ^Top ]3. Can I customize an amp's logo or name?

No, you cannot customize an amp's logo or name. A lot of work went into the design of the different SonicTone amp models to establish the SonicTone brand. We want to make sure they are recognizable as SonicTone amps.

[ ^Top ]4. Can I customize an amp's tolex?

If the custom tolex request is a line of tolex carried in stock, we can consider the request. Contact us for more information about a possible custom tolex request before placing an order.

[ ^Top ]5. What type of speakers are available?

We offer premium 12" Celestion speakers. We provided a limited selection of popular Celestion speakers with both ceramic and alnico magnets.

[ ^Top ]6. Can I choose custom speakers for an amp or cabinet?

Yes and no. The stock combo amps are matched with certain speakers to ensure that they sound the best they can. In some cases, there may be an option to upgrade the combo speaker selection to a premium speaker selection for an additional cost. For speaker extension cabinets, there is a range of speaker options that can be selected for our 2x12 and 4x12 cabinets at the point of purchase. Of course, different speaker selections will vary the price.

[ ^Top ]7. Can I request any add-ons or special modifications to the amp that I want to purchase?

Not at this time. While it is possible, it is a logistical challenge to field requests for custom add-ons and mods which could easily spiral out of control and impact production timelines for all customers. So, the models are only available as they are shown on the website with the features listed.

[ ^Top ]8. Can you build me a complete custom amp from scratch?

Not at this time. While it is possible to build more "a la carte" custom amps for customers, it's much more of a logistical challenge that would impact production timelines for all customers. Only the models listed on the website are what is currently available.

[ ^Top ]9. What's your current build time?

Current build time on most builds is 5-6 weeks, but it subject to change based on the current production schedule and availability of parts.

[ ^Top ]10. What transformers are used in the amps?

Transformers are really the heart of any tube amplifier and they are critical to the sound and the reliability of an amp. We use only high-quality, U.S.-made, custom-wound transformers, designed to our specifications. These transformers match the construction methods and specifications of the classic, robust transformers that were commonly used in the amp circuits that are the basis for SonicTone amplifiers.

[ ^Top ]11. What tubes are used in the amps?

In today's global climate, the availability of tubes has had some challenges, but the tube amp industry has persevered. Taking that into account, we attempt to source the best tubes that are available at the best prices.

We provide a few options for the selection of an amp's tube set. We have a "basic stock" option that is included in the base price. These are typically affordable, well-performing tubes like J/J tubes, or a comparable set. The amps will perform well and sound very good with a basic stock set of tubes. We then offer a "preferred stock" option which is an upgrade from the basic stock tube set. This will typically include more robust brands like Electro-Harmonix or Sovtek. After that, we offer two different sets of "premium" tube upgrades with either Tung-Sol or Mullard brand tubes, if they are available for an amp's circuit.

If you select Tung-Sol, all of the preamp tubes and power tubes will be Tung-Sol. If a rectifier tube is included in the amp, a Tung-Sol rectifier tube will be included, if it is available.

If you select Mullard, all of the preamp tubes and power tubes will be Mullard. If a rectifier tube is included in the amp, a Mullard rectifier tube will be included, if it is available.

[ ^Top ]12. Are there any "Class A" amp models?

There is a significant amount of marketing hype and misinformation out there pertaining to "class A" tube amplifiers. Somewhere along the way, the term "class A" became a marketing buzzword to sell tube amplifiers that were purported to have highly sought-after classic tonal qualities. The truth about the tonal qualities of an amp is much more complex than just the class of operation of the amp.

This is a fairly technical discussion, so first, a few definitions:

Saturation: The maximum point in the swing of the waveform, which typically produces the highest amount of current and lowest amount of voltage. The valve (tube) is said to be "wide open" or "fully on" at this point.

Cutoff: The point in the swing of the waveform where the voltage is highest and current is 0. The waveform is no longer amplified and the valve (tube) is said to be "off" at this point, hence the name "cutoff."

Class A: A class A amplifier is one that is biased in a way that allows the plate current to flow for the full, entire 360 degrees of the input cycle. Therefore, the tube is always "on," current is always flowing and it never goes into cutoff. Due to the inefficient nature of this class of operation, class A tube amplifiers tend to be lower powered amps.

Class AB: A class AB amplifier is one that is biased in a way that allows the plate current to flow for more than half of the full 360 degrees of the input cycle, but much less than the full 360 degrees of the input cycle. The tube is allowed to go into cutoff and "rest" for a short period of time. This class of operation is more efficient and is a popular class of operation for medium-to-high powered tube amplifiers.

Push-Pull: A push-pull amplifier utilizes opposite sets of power tubes - usually a pair or quartet - to conduct the alternate cycles of the input waveform. If more than two tubes are used, it is called "parallel push-pull," as the additional tubes are configured in parallel on each side of the output section. The input waveform is typically "split" by the phase splitter before the power tubes and then each half is passed to the input grids of each set of power tubes. It requires a center-tapped output transformer, where the two amplified halves of the waveform are then combined back together as a single waveform before driving the speaker. Push-pull amps allow for the use of smaller transformers and have the added benefit of power supply hum cancellation. They also minimize harmonics and distortion. It is a complex topology, but one that is typically more efficient, generates more power output and minimizes crossover distortion. Push-pull amps can be biased for class A operation, but are typically biased for class AB operation.

Single-Ended: A single-ended amplifier is a simple topology where the entire input waveform remains intact and is completely amplified by one or more power tubes. Because of this, there is no need for a phase splitter in a single-ended amp. Multiple power tubes can be tied together in parallel, creating what is called "parallel single-ended." Also, the output transformer is not center-tapped and has a special "gapped" construction to prevent core saturation. Single-ended amps require larger transformers and do not reject the power supply hum like the push-pull configuration does. However, they do emphasize even-ordered harmonics and asymmetrical clipping which are considered more pleasing. This topology is less efficient and commonly utilized in lower powered amps. Single-ended amps are typically biased for class A operation.

Cathode-biased: The bias method of the power section of an amp where it is self-biased via a cathode resistor and capacitor. Typically with this method, the tubes runs "hotter" and the output is less efficient.

Fixed-biased: The bias method of the power section of an amp where it is biased via a negative DC voltage applied to the grid. Typically with this method, the tubes runs "cooler" and the output is more efficient.

Negative Feedback: A method of injecting a small amount of signal from the output transformer back into the phase splitter to flatten and extend the frequency response. It makes the amp's output stage cleaner, reducing unwanted distortion and improving stability. Some amps are designed without negative feedback which allows the output stage to produce more harmonics and have a more dynamic response.

There are a few schools of thought when defining an amp and its class of operation.

A strict purist might define the "true class A sound" as a class A, cathode-biased, single-ended amp with no negative feedback. There are advantages and disadvantages to this topology, but sonically, there is a pleasing harmonic overdrive, saturation and response to this amp configuration that many guitar players love. This amp topology is often what people are referring to when they yearn for the class A sound.

Those that are looser with the definitions would possibly call a cathode-biased, push-pull amp with no negative feedback a "class A" amp, like the circuit in the SonicTone RC30. That type of amp circuit and many of its iterations have famously been marketed as "class A" amps over the years. However, it could be argued that these amps are not class A, but simply cathode-biased, push-pull, class AB amplifiers that have no negative feedback. But, that particular topology does give an amp a very "class A-ish" sound.

The SonicTone amplifier line-up has a number of cathode-biased and fixed-biased amps, and they are labeled accordingly. All of them are push-pull and there are none that are single-ended. Therefore, in the "strict" sense, there are no "pure" class A, single-ended SonicTone amplifiers. But in the "looser" sense, one might succumb to fancy marketing and refer to our cathode-biased amps as "class A." We'll leave it up to you to decide.

In summary, here are some helpful facts:

  • A class A amp can be either single-ended or push-pull.
  • A class A amp can be fixed-biased or cathode-biased.
  • A class AB amp can be fixed-biased or cathode-biased.
  • An amp being cathode-biased is not a definitive indicator of class A operation.

[ ^Top ]13. What does fixed-biased and cathode-biased mean?

Biasing an amp requires setting the amount of DC current flowing through the power tubes while no signal is present. A popular analogy for biasing is like setting the idle on a car. This prepares the tube for proper operation when a signal is applied to the grid and insures the tube will operate within a acceptable and desired range. Setting the bias incorrectly can result in the tube running too "cold," producing an undesirable sound - or running too "hot" which could damage a tube and shorten its lifespan. When the bias current is extremely high, a condition known as "red-plating" can occur. This is when the internal plate of the tube visibly glows red hot. If left unchecked, red-plating can severely and permanently damage a tube.

There are two different primary methods to bias the power tubes of an amplifier: fixed-biased or cathode-biased. The fixed-biased method is also called grid-biased, and the cathode-biased method is also called self-biased. A common joke about the two methods is that the fixed-biased method is adjustable and the cathode-biased method is fixed and not (easily) adjustable, which lends to the confusion on this topic.

To bias a tube amp, the bias current has to be adjusted and set to an optimal operating value. With a fixed-biased amp, a negative DC voltage is applied to the grid of the tube. That amount is adjusted, usually with an available bias pot, to increase or decrease the bias current of the tube. With a cathode-biased amp, the cathode is connected to a resistor and capacitor to ground. The amount of resistance then controls the tube's bias current. This is what gives the tube a "self-bias," but is also why cathode-biased amps really can't be adjusted easily without disconnecting the cathode resistor and installing a new one of a different value.

In general, cathode-biased amps run hotter and are less efficient and tend to be lower powered amps (40W or less.) Fixed-biased amps run cooler and are more efficient, and therefore can generate more power.

The type of bias of an amp has an effect on its sound. Typically, cathode-biased amps have more dynamics, sustain and harmonics. They also naturally overdrive more easily. Fixed-biased amps have a firmer feel and have more headroom, which is good for big clean amps, or high gain, modern amps, where most of the distortion is coming from the preamp.

The SonicTone amp line-up offers both cathode-biased and fixed-biased amplifiers, and they are labeled accordingly in all marketing materials.

[ ^Top ]14. What is negative feedback?

Negative feedback is something that most amp circuits utilize to help flatten and extend the frequency response. It generally makes the amp's output stage cleaner, reducing unwanted distortion and improving stability. It usually achieves this by injecting a small amount of signal from the output transformer back into an earlier stage of the amp, like the phase inverter. The more negative feedback is injected, the more it will increase the damping factor and give the amp a tighter, stiffer feel. This can be advantageous to subdue and amp that may close to the edge of instability or experiencing unwanted oscillations. However, too much negative feedback used where it's not needed may make the amp feel too stiff and sterile, hindering some pleasing overdriven characteristics of an amp. Negative feedback is a simple tool used at the end of an amp's circuit to fine-tune and balance out the amp. Many amp circuits use it to varying degrees, while a few amp circuits don't use it at all.

A handful of SonicTone amplifiers come with a negative feedback selector switch, which allows you to select the amount of feedback injected. This switch is called the "punchy/smooth" switch. On the "punchy" setting, there is less negative feedback, so the amp will be more aggressive, dynamic and "punchy" sounding. On the "smooth" setting, there is more negative feedback, so the amp will be tighter and more "smooth" sounding.

[ ^Top ]15. What is the difference between a tube rectifier and a solid-state rectifier?

The rectifier is the first component in the amp's power supply that starts the process of converting - or "rectifying" - the incoming AC voltage into the required DC voltage that the amp needs. The rectifier and the power supply does not process or amplify the audio directly, but the design of the power supply and the chosen rectification will have an effect on the amp's feel and response while playing.

A rectifier is simply a diode. The earliest versions of diodes were vacuum tube rectifiers. As solid-state diodes became more readily available - and less expensive - they became viable options as substitutes for tube rectifiers. Both achieve the same objective, however, a tube rectifier has different internal properties than a solid-state diode. The tube rectifier has internal resistance which creates a voltage drop and "sag." This effects the immediacy of available voltage from the power supply and gives the amp a different feel. Furthermore, a tube rectifier has limits which hinder it from being an option for higher power amplifiers, which is why they are typically used in more vintage, lower powered amps.

Some SonicTone amplifiers come available with both types of rectification and a "tube/solid-state" rectifier switch. This allows the player to chose the type of rectification they want. When set to the tube rectifier, the amp will produce a slightly more vintage sound, where there is a little more compression and sag with the sound. Some players prefer this, saying that it gives the amp a more vocal and spongy sound and that the notes have a nice "touch" or "bloom" to them. However, if that's not your preference, switching to the solid-state rectifier will give the amp a slightly more aggressive sound with a more firm and immediate response.

[ ^Top ]16. What type of components are used in the amps?

We don't subscribe to any special "mojo" theories about particular components. We use the best of what's available to deliver a clean sounding, stable amplifier. Many of the myths surrounding these special or "vintage" style components tend to only add noise and reduce the stability of the amplifier.

[ ^Top ]17. What type of wood is used in the cabinets?

All of the woods are affordably sourced birch plywood. All cabinets are constructed using finger-joints for maximum strength and stability.

[ ^Top ]18. Do you service other brand name amplifiers?

At this time, we only service SonicTone brand amplifiers. We currently do not service any other brand of amplifiers.

[ ^Top ]19. Do you ship amplifiers outside of the US?

At this time, SonicTone amplifiers ship only inside the US. The amp circuits are all currently designed only for a standard US electrical outlet running at 120 volts/60 Hz.


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