Neil Young's Whizzers

Designed and Built by Rick Davis

Updated: June 26, 2014

The Whizzers - A Brief History

The very first Whizzer was designed and built by Sal Trentino for the Rust Never Sleeps tour in 1978. It was analog, not digital, and controlled one Fender amp knob, the Volume control. When the switch was pressed on Neil's red footswitch it would turn the knob to one of the the two preset positions. Each press of the switch would cause the Whizzer to go to the alternate position. The electronics were a couple of comparators that could be preset using potentiometers to set a voltage from which Neil could select one position or the other. That in turn fed an opamp which controlled a DC motor that would then run the motor clockwise or counter-clockwise until the comparators were at a null at which point the motor would stop. It was coupled to the Fender Vol. knob with a long flexible shaft coupler. It was an elegantly simple solution and I have a photo of Sal's version. Unfortunately Sal passed away in March 2009. He was one of Neil's most highly regarded techs.

In 1991 Neil asked me if I could design and build a Whizzer that could control all three knobs and have multiple positions memorized for the various "Neil sounds" he could call up with his footswitch controlling his Fender Deluxe amp while playing live or recording. I said I could.

There are two Whizzer versions, the copper one and the brass one. The copper is the first one I designed and built using discrete CMOS logic as I was worried that using a microprocessor on equipment so closely coupled to Neil's  amp would allow a digital clock, which drives a microprocessor, to get into the audio. That audio signal path is very susceptible to hum and noise with all the gain in the high impedance circuit between Old Black, his guitar, and the Fender Deluxe amp. The brass version was built about a year after the copper version as a backup or standby unit, in case of failure in the copper one. Rock and roll being notoriously hard on equipment.

The copper one is shown in Tom Wheeler's book [at right] sitting on the amp, but the interior shot is of the brass one which does use a  microprocessor. There is a shot of the interior of the copper version at the bottom of this page. As you can see the micro is much simpler and cleaner design. All that logic is done inside one chip by software.

The copper [and brass]  metal work was designed by me and is meant to echo or suggest a steam locomotive with the blinders that some of them had back in the 1930's and 40's. As you may know Neil is HUGELY into trains. I also had something of a vision of old timey radios in mind. The metal work was done by Bart Lewis of Lewis Metal Products in San Francisco. They, he and his wife Judy,  also did the work on a console I designed and built for Neil back in 1977. Bart and Judy Lewis were truly artists with metal and I was very fortunate to have hooked up with them.

The copper version made it's debut on the Weld album and tour.


On power-up the Whizzer defaults to switch position 1 and the values stored in memory, spinning the amp knobs to those presets. If a knob on the front panel is turned the values from memory are overridden [but not lost] by the new count values and the motors whiz the amp knobs to the new setting. If Neil wants to overwrite what is in memory with this new setting he simple presses the ARM and WRITE pushbuttons on the right side of the display and the new value is stored. The memory is non-volatile meaning it retains its data with power removed.

The two pushbuttons to the left of the 3 knobs are a NORMAL / LOCK  function which when locked, prohibit the knobs from changing anything. A protection against possible vibration or accidental changes. The four preset buttons continue to work however. The other pushbutton calls up previous values stored in memory in a case where you change your mind and want the old value[s] back.

The four pushbuttons on top are in parallel with the four footswitch pushbuttons so he can select the settings locally.

The three display readouts go from 0.0 to 12.0, since the knobs on the Fender Deluxe go from 0 to 12. The 3 LED's above the these display readouts turn ON when that setting is NOT at a memorized preset.

On the backside there are four 1/4" phone jacks which are wired one each to a set of relay contacts so when he selects a preset the corresponding relay contacts close which allow control of other effects, including special effects, lights, pyrotechnics, etc. To my knowledge these have never been used.

A Block Level Theory of Operation

This concerns the copper version as it is all discreet CMOS digital. The electronic design was started by another employee of mine Jerry Elmer, however he left the company before it was finished. So I took over and completed the design and made the changes necessary to realize a design that met Neil's criteria.

All the circuits described are in triplicate, one for each knob.

The basic system is as follows: The three black knobs on the front panel are actually digital encoders which put out biphase pulses 90˚ apart. This tells the logic which way the knob is being rotated. The pulses are fed into up/down counters that are controlled by  magnitude comparators which limit the count to a minimum of zero and a maximum of 120 giving Neil 120 increments he can set into memory. Zero into counter translates to a knob on the Deluxe amp being fully counter-clockwise and 120 corresponding to fully clockwise. This range sets  the limits for the digital-to-analog converters [DAC's] which drive the servomotors and the Deluxe knobs.

The up/down counters take the serial pulses in and output a parallel 8 bit digital 'word', of which only 7 bits are used. This 7 bit word is the fed to a latching tri-state line driver, the output of which is a digital 7 bit bus. The tri-state drivers are able to disappear from the bus by going into a high impedance state. It is this bus that feeds the DAC's with the digital word value which the DAC converts to a DC voltage that is fed to the servomotor driver chip, a Motorola MC-33030P.

The reason for the tri-state drivers is that the EEPROM that holds the memorized positions is also  attached to this bus. The logic employed determines which driver is active, the memory or the front panel knob [encoder]. So normally the data from the EEPROM is being read into the DAC but if Neil touches a knob it immediately tri-states the memory and the knob now becomes active and feeds the DAC. It will remain in this state until one of the 4 preset buttons is pressed, recalling the memory presets.

As mentioned the three DAC outputs are fed to three MC-33030P IC's, one for each motor. These motors are made by ETI and are geared way down to one revolution per second. This has the added plus of increasing the torque of the system. These servomotor assemblies also include a potentiometer which give the MC-33030 feedback as to it position, and it has an adjustable clutch mechanism which protects the pots in the Deluxe amplifier from being damaged if the motor should run beyond the amp pots travel range. If that should happen, the motor will continue to spin but the clutch will slip so no harm will come to the amp components.

On the back of the Whizzer there are 3 sets of 2 holes. These are to allow calibration of the DAC's without removing the top cover. Inside are 10 turn pots which set the minimum and maximum for the DAC travel voltage range to the MC-33030.

Also on the rear there are two circular connectors. One supplies +5 volts and +12 volts DC to power everything. The power supply for the Whizzers is in a separate box. The other is connected to the footswitch and carries all the logic signals. There is a small circuit board in the footswitches that have balanced line drivers for noise immunity in the long cable.

On the footswitches you will see two circular connectors. One connects to the Whizzer and the other to the rest of Neil's Rig which has other effects, which I won't go into. The first four pushbuttons on the lower row, left to right, call up the Whizzers four presets.

In the brass version the logic is all done in software, written by Joe Thibodeau when he was working for me at my company Real Design Labs, Inc. The brass one is built around a Motorola MC-64HC11 microprocessor as it had all the ins and outs to handle all the knobs, memory,  servomotor driver and display functions. It turns out we over dedicated it to the point where it won't track the knobs on the Whizzer [not the amp] because it's doing so many jobs it can't keep up if the knob is turned too fast. Joe did a hellava job getting all those functions to work in real time in one micro. What we really should have done is have one micro for each of the three amp knobs and that would have solved the problem. Actually now that I think about it I believe that's how Joe wanted to do it in the first place but I wanted it in one micro - I don't remember why. In the end he was right.

And I need to give credit to another Joe, Joe Cynarowicz who actually built the PC board and electrical for the brass version and did a beautiful job, as you can see.

And that's pretty much it.


If you have questions, contact me here:

World Tour Rehearsal Setup

at Fox Theater in Oakland June 10, 2014

 Jeff Pinn Setting up Whizzer

Neil's Rig

Neil's Guitar Tech Checking Out

the Red and Black Footswitches


Pages from Tom Wheeler's book

"The Soul of Tone"

Pages 187 - 189

[click on photos for larger image]

The original photos I sent Tom for the book.

The Brass Whizzer

Brass Whizzer Interior

Prototype front view at the Studio

Prototype Rear View at the Studio

Whizzer recent R & R at my Lab

The Famous Red Footswitch

The "new" Black Footswitch [rear]

End of the latest Project - what a mess...


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