Please Note:
The FireFly is significantly larger than a 5Y3 vacuum tube. It will fit easily in a standard 5E3 Fender Deluxe, but it is a heavy tube, and you should make sure that your amplifier's tube socket is in good repair and that the pin sockets are tight, otherwise the FireFly may fall out of the socket and into the bottom of your amp when you least expect it.  You may want to invest in a friction tube-holder to prevent this.

FireFly 5Y3 FF is designed specifically for the Fender Deluxe 5E3 amplifier. It has not been tested in other amplifiers.

It has not been tested in modified amplifiers; this includes amplifiers with non-original transformers or other parts, or amplifiers which have been modified in any way, such as by the addition of resistance or zener diodes on the power transformer center tap, or the modification of the value of the bias resistor.

The FireFly 5Y3 FF tube is experimental: 
all risk and liability is assumed by the user.

HardWay  makes no warranty as to the fitness of the device or its suitability for any intended purpose whatsoever.

If you have a question, e-mail me,
and I will try to answer in a timely fashion.


FireFly:  5Y3 FF
Each FireFly is made by hand, tested, and fault-checked for 8 Hrs at operating conditions.  Test operating data are recorded and included with the tube. The imaginary getter flash is pure silver.  Your FireFly is a wise investment in precious metals! Every FireFly is unique.  They have character. Your FireFly is protected by a wooden box, surrounded by cushiony softness.

Is an RCA 5Y3 GT rectifier tube in a Fender 5E3 Deluxe.  Turned on and warmed up, we see the voltage on the plate of the first 6V6 is 382 VDC.  The voltage across the 250 Ohm cathode bias resistor is 22.2.  The wall voltage was about 125 VAC.

The calculated dissipation of the amp at these readings is 17 Watts. 
This is typical of a 5E3 Deluxe running with modern wall voltages.
It's way too hot.  44 mA plate current!

FireFly 5Y3FF                                                                $ 99.00

FireFly is a Voltage-Controlled solid-state replacement 
for the 5Y3 GT rectifier for the
Fender Deluxe amplifier of 1955 - 1961.  It should also work

to replace a GZ34 or a 5U4GB.

It is a hand-made device of purpose-built art that
maintains the glass tube tradition of great tube amps.
It has a lovely amber glow, like a vacuum tube rectifier.

Firefly is designed to reduce the 5E3 circuit B+ voltage
by 25 to 30 Volts.  It reduces the overall power dissipation
of the Deluxe by about 15%.

FireFly is intended to reduce the ultra-high voltages sometimes seen in the Fender Deluxe.
It also reduces noise,  limits inrush current, and replicates the "sag" of the 5Y3 GT tube. 

Evil, Bad, Naughty Electrons:
The 5E3 circuit design of the Deluxe amplifier was designed for 1955 wall voltages of 110 VAC.  The standard residential voltage in 2017 is about 125 VAC;  modern voltage is about 15% higher than the 5E3 specified voltage.  The tweed Deluxe has the reputation of being a "tube eater" and "destroyer of capacitors"  for this reason.

Filter Cap Torture:
When your Deluxe is first turned on, it sees the #1 filter cap as a dead short to ground - and until the capacitor charges, the potential at the first filter cap can approach 600 volts;  but the vintage Astron  filter cap is designed for 525V MAX.  After a few years of this kind of cruelty, the filter cap usually gives up.  Are the 60-year old Astron caps in your Deluxe still good?  Maybe.  Who knows.  Probably not.

Crackly, buzzy, hum may mean your filter caps have abandoned their post, running away and shrieking like a little girl. 

The FireFly rectifier limits the inrush current and voltage at turn-on.  Your filter caps will be much happier, and will reward you with improved performance and extended life.

6V6 GT Tubes are delicate flowers:
...and do not deserve boiling hot plate voltages that approach the temperature of the Sun.  Tragically, many Deluxe owners abuse their helpless 6V6s with super high plate voltages and then complain that the tubes "sound funny" or don't last very long before they have to be replaced.  The exalted RCA Tube Manual and Life Affirming Tome states unequivocally that the design maximum on plate voltage for the 6V6 is 350 Volts.  That's the upper limit;  the typical design operating voltage for a Class A amp is 315 Volts, tops, and the Fender Deluxe is not a Class A amp.

So if you have read in a forum somewhere that 380 Volts on the 6V6 plates is nothing to worry about, and "sounds great", be skeptical - be very skeptical.

The Fender Deluxe has the unfortunate reputation as an amp that "eats tubes".  It may have something to do with all the Watts people are trying to stuff into them.  

The FireFly rectifier drops the B+ voltage by 8-9 %.  As a result, the standard 5E3 circuit of the tweed Deluxe will provide about 350 Volts to the 6V6 plates with a wall voltage of 125VAC; the zero-signal current will be about 35 mA.  Plate power dissipation will be around 12 - 14 Watts.  All these values are at the upper end of where Leo Fender designed them to be.

The Legendary 5E3 Circuit Design:

The 5E3 circuit set the standard for powerful guitar amplifiers for decades.  Today, in the 21st century it is still considered to be God-like in its musical characteristics and tonal quality.

In the 1950s, Fender Amplifiers were the loudest amp guitarists could buy.  

The circuit was simple and elegant;  and to make a powerful but affordable amplifier, Leo Fender pushed the components right to the limit of 1950s technology.  The Astron "Minimite" electrolytic filter capacitors were rated for 450 V, with a peak rating of 525 V.  The 5E3 design would push the B+ voltage right up to that 525 V peak rating.  But here's the underlying and ubiquitous problem with the 5E3:  Fender was pushing the envelope with a line voltage of 110 VAC in 1955, and musicians in 2011 plug their priceless, vintage Tweed Deluxes into the wall socket that delivers 125 VAC or higher!

...All those Deluxe components, in addition to being 60 years old, are now 15% over their design maximum ratings.

It is somewhat miraculous that more Deluxes don't blow up and catch on fire, in my opinion.

The fundamental idea of the FireFly rectifier was to travel back in time to 1955 and provide "vintage voltage" to the 5E3 circuit of the tweed Deluxe.  FireFly is designed to supply the components of your Deluxe with voltages that Leo Fender intended:

     *     525 V limit to the first capacitor on start-up.
     *     350 V to the 6V6 plates
     *     Idle current of 34-36 mA
     *     Total Plate Dissipation ~ 14 Watts

The FireFly does all of the above, and also provides 5Y3-like sag as the amp is pushed.  And, it's the only solid-state rectifier in the world with a glass envelope and a warm, orange glow of an imaginary filament.

Upon acceptance, each FireFly is assigned a letter identifier from the current Generation;  e.g., E/W/11 means that this FireFly was E (#5) out of W (23) in 2011.  So - Gen V consists of a total of 23 FireFlys made, of which this one is #4.  The letter, E, in this case, is on the FireFly base as well as the top and bottom of the wooden box.

FireFly Tube Emulating Rectifier

Is the same amp, same day, same wall voltage, but the 5Y3 is replaced by a FireFly 5Y3 FF. The 6V6 is now seeing only 352 VDC, a 30 Volt drop, the voltage across the resistor is 20.3, a 2 Volt drop, and the calculated dissipation is 14 Watts, with the plate current reduced 10%.

The FireFly reduces the power of this amp by 15%. Not too surprisingly, 125 VAC is about 15% higher than 110 VAC.  This amp is still very much "hot" biased, and its tone is indistinguishable from the tone with the 5Y3 GT rectifier, its just much "calmer" now, and  will be much kinder to its tubes and filter caps.

Development History

The Idea:

I wanted a solid-state replacement for the 5Y3 GT vacuum tube in the 5E3 circuit of the tweed Deluxe, with these features: 

1.  Noiseless rectification 
2.  B+ voltage reduction of 20 - 30 Volts 
3.  Inrush current limiting 
4.  Sag  when pushed
5.  Emulates the glass tube aesthetics of the 5Y3 GT 

FireFly - 5Y3 FF  Gen. I  
The first prototypes (there were several) determined the component specifications and circuit design.  The prototypes were not pretty, but they did work, to one degree or another.  In this one, which was very early, I was using cement resistors, series diodes, parallel low-voltage bridge rectifiers, hand-made inductors, and neon TGL (Tube Glow Lamp). 

There was filtration across the diodes to control switching noise.  All FireFly designs make use of both the high and low AC voltage rectifier taps from the power transformer of the standard (unmodified) 5E3 circuit. 

Flat-Top FireFly - Gen II
The second generation prototypes were in a flat-topped 1 inch diameter glass envelope with pure silver plating at the top to emulate the barium getter of a vacuum tube. The proprietary multilayer silver composite structure helps deal with infrared energy emitted by the power resistors. I made 6 or 8 of these; they looked cool, but they all suffered from short lifespan due to overheating.

When I say overheating, I mean the kind of overheating where the FireFly was on the test amplifier for 8+ hours when I would hear a loud "Bang" and look over to see the end of the glass tube blown off, and the smoking aluminum resistor in two pieces 5 feet across the room.  That kind of overheating.  Also, the smell was really horrible.

Thermal management would be a recurring design challenge. This is how they got the name "FireFly"  Ha Ha Ha Ha! (Don't tell anybody...)

FireFly Gen IV - Forced Air
This was several months after the Flat-Top series; now I am using the VLE (Very Large Envelope) and a static re-radiator (the metal cylinder with little holes in it) and a metal and ceramic base to deal with the thermal issues.  The wattage rating of the aluminum resistor was increased by a factor of 5.

To top things off, literally, Gen IV FireFlys incorporated the world's  smallest 5VDC fan, out of sight, above the silvered area of the glass envelope. The fan actually worked quite well, but I was never able to satisfactorily eliminate the noise it introduced into the circuit.

FireFly Gen V - Chimney
The current generation FireFly uses the ceramic guide pin on the base as a chimney.  The hole in the pin allows natural convection to control the temperature inside the glass envelope. 

The Tube will still get very hot- as hot as the vacuum tubes - but well within design limits. The rectifier hangs upside-down in a tweed Deluxe, so convection makes the guide pin a pretty good chimney.


The voltages and current in tube amps can kill you.
They are capable of killing you even when unplugged from the wall.
If you are not absolutely certain of what you are doing, Don't Do It!

...Now that we have scared the children, we can proceed.

Handling and Installing FireFly:
This is important, so please read it.
Please handle your FireFly as you would a delicate flower;  it is made of glass, and if you drop it, it will surely break.
Handle your FireFly  only by the base when installing or removing. 
The glass envelope is fragile and is not designed to be  pushed or pulled upon.
If the glass envelope is broken or cracked, immediately discontinue use and dispose of the device.  It cannot be repaired.

Over there --------->

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