Fractal Audio DRIVE models: FAS LED-Drive

yek

yek

Contact Fractal for your Custom Title
The contents of this thread, including updates, are available as a PDF Guide. Download it here.

logo.png

FAS LED-Drive

Fractal Audio provides a couple of custom Drive models. These virtual drives have no real-life equivalents. They solely exist within the Axe-Fx II, FX8 and AX8, implementing Cliff’s ideas and improvements on existing pedals.

The LED-Drive model is such a custom model. It was added in firmware 12.x (pre-Quantum).

The LED-Drive showcases the modeling of LED (Light Emitting Diode) clipping. Yes, those little lights themselves can be used for intentional signal clipping (which creates distortion). LEDs do not clip early and therefore stay “clean” longer (and are louder) than other diodes. This can be monitored when comparing the “LED” Clip Type in the Drive block to others.

LED clipping is not often used in pedals. Supposedly it's used in MI-Audio’s Crunchbox and Pro Co's Turbo Rat. It’s also being used in some guitar amps like Marshall’s Jubilee (Brit Silver model).

This Tone Report article discusses the basics of the use of electronical components in pedals: resistors, capacitators, transistors, diodes, ICs / op-amps. Makes you realize how cool it is that Fractal Audio has modeled all of these digitally to obtain the same functionality and sound!​

About CPU:
  • Fractal Audio's Drive models take up varying amounts of CPU. The FAS LED-Drive model is one of the heavy users.
  • When a Drive block is engaged, CPU percentage will rise during playing, because CPU usage is "amplitude dependent".



Link to the list of published threads
 
Last edited:
I never thought to try different colours of LEDs.

There's a mod for the Boss DS-1 pedal called the "Cyclops" mod. You replace at least one of the clipping diodes with an LED and then mount the LED in a hole in the case. Then the LED flickers as clips the signal. So you can actually see the clipping happening.
 
  • Like
Reactions: yek
StickMan said:
I never thought to try different colours of LEDs.

There's a mod for the Boss DS-1 pedal called the "Cyclops" mod. You replace at least one of the clipping diodes with an LED and then mount the LED in a hole in the case. Then the LED flickers as clips the signal. So you can actually see the clipping happening.
Click to expand...

I did the Keeley style seeing eye mod to a DS1 and always got a kick out of seeing the LED flare up. The original Marshall Guv'nor uses LED clipping too if I'm not mistaken.
 
I don't know much about the ProCo Turbo Rat but I can verify that the MI Audio Crunch Box uses a pair of 5mm red LED's for clipping. The Crunch Box was a fantastic 'Marshall in a stompbox' pedal. It's most useful control, a 'presence' control, was unfortunately a internal adjustment only - a trimmer pot. I modded mine by removing the trimmer pot and wiring in a chassis mounted pot to the side of the pedal.

Another pedal that uses LED's for clipping is the Landgraff L'DO. A pair of 3mm red LED's provide clipping for the L'DO's 'Marshall Mode'. The Landgraff L'DO is a very expensive lightly modified TS808 Tube Screamer. This is probably the most commonTS808 Tube Screamer DIY or kit mod (often referred to as the 'boutique' mod). It consists of value changes for 5 passive components and the addition of a three-way toggle switch with asymmetric silicon diode clipping, no clipping (open, for use as a clean boost), and 'Marshall Mode' LED clipping.

A rare drive pedal, the CJOD or the Clay Jones Overdrive, was built and sold as a one-time limited run of 50 pedals and were delivered with heavily potted per-board completely obscuring the underlying circuit. These pedals became much sought after in the following couple of years. Mine, which purchased new from Clay, sold in auction for $1,200.

Eventually someone sacrificed one of the pedals to get a look at the circuit. Turns out that it was a Landgraff L'DO with no clipping switch opting for a pair of 5mm red LED's, and a Burr Brown OPA2134PA dual op-amp IC in place of the TS808's and L'DO's JRC4558 dual op-amps IC. The change to the OPA2134PA altered the sound so much that many refused to believe that it was a simple Tube Screamer mod. At request I built quite a few CJOD clones for folks on The Gear Page forums.

The way LED's clipped in overdrive circuits seemed to appeal to me more than diode clipping.

I eventually got to playing with the Marshall Blues Breaker overdrive circuit. I didn't really care for it in stock form but after some tinkering I ended up with what is still my favorite overdrive pedal. I took a few cues from AnalogMan's King Of Tone which opened up the pedal quite a bit, I replaced the silicon diode clippers with 5mm red LED's, and adapted the MI Audio Crunch Box's 'presence' circuit to work in the Blues Breaker. The result is a very clear sounding clean boost / low to medium gain overdrive with a voicing that could be gradually moved from Marshall to Vox using the Presence control. Ideal for use with British voiced amps but really works wonderfully in front of any tube amp. My prototype pedal for this circuit is the only pedal I still own.

Anyway, I like LED clippers in overdrive pedals.
 
Last edited:
Very cool story @Deaj

I think, I heard somewhere that the hi-gain mode of the Marshall JCM800 2205 and 2210 (the dual channel lesserknown JCM800s)was actually also achieved with LED clipping rather than fully pushed tubes. I had the 2205, and I really loved its organic drive. I should probably look a bit more into the LED clipping options in the AX
 
Smittefar said:
Very cool story @Deaj

I think, I heard somewhere that the hi-gain mode of the Marshall JCM800 2205 and 2210 (the dual channel lesserknown JCM800s)was actually also achieved with LED clipping rather than fully pushed tubes. I had the 2205, and I really loved its organic drive. I should probably look a bit more into the LED clipping options in the AX
Click to expand...
I've got an old 2210 and it definitely sounds smoother than the classic 2203 style tone. Interesting to know!
 
StickMan said:
I never thought to try different colours of LEDs.
Click to expand...

I love LED's and have a big bin of all different colors, sizes, shapes, etc. and it's fun to experiment with different combinations in distortion/overdrive circuits. I've generally preferred the character of LED clipping vs conventional diodes in most cases.
 
Smittefar said:
Very cool story @Deaj

I think, I heard somewhere that the hi-gain mode of the Marshall JCM800 2205 and 2210 (the dual channel lesserknown JCM800s)was actually also achieved with LED clipping rather than fully pushed tubes. I had the 2205, and I really loved its organic drive. I should probably look a bit more into the LED clipping options in the AX
Click to expand...
Dont the JVM's do this as well?
 
I just did a side by side with my favorite drive pedal, the Barber Direct Drive. I was able to get awfully darn close to the DD mimicing the settings using the LED Drive. Crazy Times.
 
The Whale said:
I just did a side by side with my favorite drive pedal, the Barber Direct Drive. I was able to get awfully darn close to the DD mimicing the settings using the LED Drive. Crazy Times.
Click to expand...
Settings, please! That was my favorite OD pedal... In particular with the FAT switch on.

Is the DD an LED based drive?
 
unix-guy said:
Settings, please! That was my favorite OD pedal... In particular with the FAT switch on.

Is the DD an LED based drive?
Click to expand...

Mine too! I don't think the DD is LED based, but the general shape and compression of the LED Drive work well with it. To be honest, I normally run my DD with volume at noon, tone at 2:30 and gain at 2:30. I just set the LED drive with Volume at 5.5, tone at 7 and gain at 7 and it was dang close. I played around with the clipping from diode to silicon to HV tube... all were great and the differences were subtle. Now, this isn't a perfect clone of the DD. The LED had more sparkle than the DD, and the DD was more focused in the mids. But, it's darn close!
 
The Whale said:
Mine too! I don't think the DD is LED based, but the general shape and compression of the LED Drive work well with it. To be honest, I normally run my DD with volume at noon, tone at 2:30 and gain at 2:30. I just set the LED drive with Volume at 5.5, tone at 7 and gain at 7 and it was dang close. I played around with the clipping from diode to silicon to HV tube... all were great and the differences were subtle. Now, this isn't a perfect clone of the DD. The LED had more sparkle than the DD, and the DD was more focused in the mids. But, it's darn close!
Click to expand...
Cool... I'll give it a shot.
 
Deaj said:
I don't know much about the ProCo Turbo Rat but I can verify that the MI Audio Crunch Box uses a pair of 5mm red LED's for clipping. The Crunch Box was a fantastic 'Marshall in a stompbox' pedal. It's most useful control, a 'presence' control, was unfortunately a internal adjustment only - a trimmer pot. I modded mine by removing the trimmer pot and wiring in a chassis mounted pot to the side of the pedal.

Another pedal that uses LED's for clipping is the Landgraff L'DO. A pair of 3mm red LED's provide clipping for the L'DO's 'Marshall Mode'. The Landgraff L'DO is a very expensive lightly modified TS808 Tube Screamer. This is probably the most commonTS808 Tube Screamer DIY or kit mod (often referred to as the 'boutique' mod). It consists of value changes for 5 passive components and the addition of a three-way toggle switch with asymmetric silicon diode clipping, no clipping (open, for use as a clean boost), and 'Marshall Mode' LED clipping.

A rare drive pedal, the CJOD or the Clay Jones Overdrive, was built and sold as a one-time limited run of 50 pedals and were delivered with heavily potted per-board completely obscuring the underlying circuit. These pedals became much sought after in the following couple of years. Mine, which purchased new from Clay, sold in auction for $1,200.

Eventually someone sacrificed one of the pedals to get a look at the circuit. Turns out that it was a Landgraff L'DO with no clipping switch opting for a pair of 5mm red LED's, and a Burr Brown OPA2134PA dual op-amp IC in place of the TS808's and L'DO's JRC4558 dual op-amps IC. The change to the OPA2134PA altered the sound so much that many refused to believe that it was a simple Tube Screamer mod. At request I built quite a few CJOD clones for folks on The Gear Page forums.

The way LED's clipped in overdrive circuits seemed to appeal to me more than diode clipping.

I eventually got to playing with the Marshall Blues Breaker overdrive circuit. I didn't really care for it in stock form but after some tinkering I ended up with what is still my favorite overdrive pedal. I took a few cues from AnalogMan's King Of Tone which opened up the pedal quite a bit, I replaced the silicon diode clippers with 5mm red LED's, and adapted the MI Audio Crunch Box's 'presence' circuit to work in the Blues Breaker. The result is a very clear sounding clean boost / low to medium gain overdrive with a voicing that could be gradually moved from Marshall to Vox using the Presence control. Ideal for use with British voiced amps but really works wonderfully in front of any tube amp. My prototype pedal for this circuit is the only pedal I still own.

Anyway, I like LED clippers in overdrive pedals.
Click to expand...

I built an OCD clone with a socketed dual op amp slot. After going through an entire drawer of dual op amps I finally plugged in a BB OPA2134 into it. Holy smokes! I personally think it crushes the stock OCD. So much more clarity and air!
 
You must log in or register to reply here.
Back
Top Bottom