Kevin O’Conner / London Power:
Here is a link to the details on Kevin’s site about his power scaling circuit: London Power FAQ
Fargen Mini Plex MKII Power Scaling Suggested Settings:
So you’re thinking, when I engage the Power Scaling, I will still have the same amount of distortion, only quieter. So let’s dime all the controls and then roll down the Power Scaling feature and it will rock. Wrong! Don’t do it! Unless you want poor tone.
As Power Scale is turned down, the amount of signal required to drive the power section is reduced, too. Without the Drive Compensation control, (IE master volume) distortion increases dramatically as the power amp’s clipping point moves downward, until even the smallest signal drives the amp into clipping. As you turn down the Power Scale control, the amp’s maximum power goes down, but it also gets much more distorted. Drive Compensation (master volume) lets you maintain the correct mix of preamp and power amp overdrive at any volume level as the power amp is effectively resized via Power Scale.
Here is a suggested high gain setting. Note the master volume should be at 7 or lower to maintain a pleasant overdrive from the power amp section at these high gain levels:
Master Volume vs. Power Scaling
Power Scaling is a technology developed by London Power, headed by renowned tube amp innovator and author Kevin O’Connor, that controls voltages inside the amplifier, allowing for continuously adjustable power output. Power Scaling reduces power, and thus volume, enabling the amp to produce power tube distortion at reduced volume levels, freeing you from the need for an attenuator.
A master volume allows you to run the preamp at full bore, and then limit the signal going to the power amp. This gives you preamp distortion, but has no effect on power amp distortion. So the amp doesn’t sound the same as when it’s being run full-out, but you will be able to get more distortion at lower volumes.
You will want to experiment and choose between running the master volume down low and the power scaling less engaged vs. the master up higher and the power scaling more engaged..both have there merits and effect the feel and tightness of the power section.experiment and find your favorite sound…see both variations below:
Best setting for clean tone or use with overdrive pedals:
Power Scaling lower the voltage to the power tubes to lower the overall volume of the amp……this is the exact opposite of what you want when your looking for clean tight headroom out of the power amp…thus you will want to leave the power scaling out of the mix and just use the master to lower volume as seen here: This setting produces a nice Hendrix type tone with a Strat.
Here are my personal speaker choices for the best low volume power scaling use. All of these speakers represent a nice high end roll off that is very necesary to achieve full sounding, non buzzy high gain overdrive tones at extra low power scaling volumes….especially with the Fargen Mini Plex MKII……I used several of these speakers for the MP MKII sound clips on my web site.
Celestion Heritage Series G12M Speaker
Way back in the 1960s, Celestion released a version of the popular G12 guitar loudspeaker called the G12M. These days nicknamed the Greenback, with its medium weight magnet this speaker had a tone that was silky smooth and warm, while still retaining the brightness and punch necessary to cut through the rest of the band. The Greenback was also a highly articulate speaker, perfect for the pioneering lead guitarists of the time. A classic had been born. Over subsequent years, the Greenback has evolved and remains popular with guitarists and amp manufacturers to this day. As the speaker developed, though, its tonal characteristics moved away from those of the original ’60s model. Adhering precisely to the design notes and specifications for the original speaker, re-discovered during our recent factory move, and using exactly the same materials and construction techniques, Celestion has recreated the classic 1960s G12M for a new generation of rock and blues guitarists.
Celestion G12M Greenback Speaker
Celestion’s first guitar loudspeaker featuring a ceramic magnet structure, the G12M ‘Greenback’ presented almost as much magnetic flux to the voice coil as an Alnico formulation, but in a much more compact space. As a result the Greenback became the guitar loudspeaker that paved the way for use with higher power amplifiers. And, of course, the ceramic magnet presented its own unique tonal characteristics. The Greenback has a loud and assertive character that sounds great through a valve amp pushed into overdrive. The speaker has evolved over the decades and still presents that instantly familiar woody tone, delivered with a knockout punch.
Eminence Cannabis Rex Speaker
Nothing says “American Made” like rock ‘n roll or blues. And nothing says “Classic” tone like the Patriot Series of guitar amp speakers from Eminence. Made in the U.S.A. for stand-up volume and reliable rockin’ clarity. Seven-year manufacturer’s warranty. . can’na bis rex – n. a clean and full 12″ American guitar speaker with a hemp cone and monster tone.
Celestion G12H Speaker
Re-released ten years ago for our 70th anniversary, the G12H evokes the sounds of the classic 1960s and ’70s rock bands. Loud and proud thanks to its heavy magnet structure, the G12H provides a fusion of the Vintage 30 and the Greenback characteristics, producing a thick, warm and syrupy sound while still retaining a tight and focused bottom end. When played clean, the speaker remains clear and musical without ever sounding harsh. In overdrive, pick attack is vividly articulated with sustained notes trailing off into warm harmonic tones.
Eminence Private Jack Red Coat Speaker
Perfect for blues, indie, rock and jazz. Lots of perfectly balanced mids and extended highs. Ideal in a 1, 2, or 4 x 12″ open- or closed-back. * Thick British tone for blues, indie and jazz music * Perfectly balanced mids and extended highs