Conversions, Modifications, & Customization

Bassman Faceplate and Schematic

Within an artist's sound, there are four major components:

  1. the musician
  2. the guitar
  3. the amplifier
  4. the speaker/cabinet

A significant change to any one of these components can elicit an equally significant change to the tone and response of this system. Many of us have struggled to get the sound we want by only focusing on one of these components. Whether you are trying to imitate another or break from the pack, getting that special tone can be a challenge. Although I am an amplifier specialist, I look at the whole system when considering the tone you are after.

Whatever your needs are - be it a full Conversion, simple Modification, or an entire Customization, we are here to fill those needs.


A Conversion is the process of changing an amplifier (or FX pedal) from one version to another. For example, it is possible to convert a pedal's circuitry (such as the Tube Screamer) from a newer model to that of an older model, simply by changing a few components.

For whatever reason, there are many amps that never really "made it" and are not very collectible. In my opinion, these are great amps to work with. For instance, I recently converted the electronics of a Silver Face Bassman into that of a model 5F6 (early Black Face). Since the Silver Face amps are not particularly collectable, I thought it would be interesting to transform it into something with a much richer, vintage sound. And, if for some reason I want to change it back later, it can be done since none of the changes are permanent.

As another interesting example, I have converted an old Wards Airline Amplifier (model GBC-9052A) that I picked up many years ago when I was in high school. It used a quad of 6L6's and came with a 6x10 speaker cabinet. At first, I just changed the tubes and replaced a smoked resistor. Then several years later I restored the amp back to stock. It sounded okay but it was not quite what I was looking for. Because this chassis has some nice features, various conversions are possible. These features include:

So, I decided to convert the Airline's circuitry into that of a 45W Plexi-style. It has turned out to be a wonderful amp and quite a conversational piece -- think: unassuming Wards chassis with that "eruptive" Marshall tone. It has even been rented out by a local musician for sound recording and performing.


Almost any change to an amp from its stock configuration could be considered a modification. For example, using a 12AY7 instead of a 12AX7 in the first gain stage can lower the gain and sweeten the tone for certain amplifiers. Another common mod is to reduce the value of or remove the bleed-through capacitor on a volume control. IMO, the stock value on a Marshall 1987 is just too much -- extremely bright. So, I like to knock down the value of the capacitor on the bright control significantly.


Wouldn't it be nice if you had an idea, maybe for a pedal or an amp, and you could take it to someone who could make it for you? This is what customization is all about -- taking your great idea and turning it into a real world device.

Here at Onyx Amplification, we can help you with most any speciality product or customization that you want for your tube amplifier. The before, during, and after are all fully documented.

Over the years, I have designed and built various devices, both analogue and digital. My engineering knowledge, both theoretical and practical, enables me to go from concept to working device. If you have an idea, contact me and we can work together to make it a reality.

Regardless of the changes made to your equipment, reliability and performance are of utmost importance and all work done will be of the highest quality.

Also, one of Onyx's main goals is to release its own series of pedals and amplifiers. These will be based on needs that Darrell feels are not being filled in the marketplace currently. We are also working on a process that will allow people to buy their own custom amp at a very reasonable cost. If you check out the our products section, you will see our first pedal, The GO Box.

Hourly Rate

Our hourly rate is $50.