NEW FOR 2018
deHavilland Electric Amplifier Co.
Super40 Monophonic Power Amplifier
"Within minutes I knew we had to have these in our reference system. We make
a very revealing speaker, and with every other amplifier we tried, we could hear
all the warts. If the power is sufficient for your system, you can't do better than
the Super40--sweet and natural with no loss of detail."
David Bernhagen, Bernhagen-Porter Loudspeaker Co.
"Kara brought along her prototype Super40 monaural amps for a little listening...
I had never heard Pete Riggle's A-7s sound better. Pete's system is always very
impressive sounding, and is always one of my favorite systems to hear
because it is so musically natural..."
--Jeff Day, JEFF'S PLACE, Audio Online, Dec. 2, 2017
About the Super40...
The Super40 was a happy accident. I had some spare chassis and a variety
of transformers inhabiting my shop . I decided to build a nice little pair of push-pull
amplifiers for fun. Some friends came over and immediately liked what they were hearing--
so I decided to refine the design...
The circuitry is push-pull with low feedback, and the tube complement is a bit unusual.
I incorporated the lovely Loktal base Sylvania 7N7/ 7AF7 as the driver tube.
Sylvania Loktals-Metal base beauties
The Sylvania Loktals are beautiful tubes that represent the peak of Sylvania's quality.
You will pay $300 each for metal base Sylvania 6SN7W types . The Loktal was developed
as an alternative to the bakelite based octal tubes of the day. The central key of the base
was meant to snap into the socket to positively hold the tube firmly. Sylvania had the
idea that that would be an advantage in tubes intended for the demanding environment
of aircraft avionics . The Loktals are in the sub $50 realm and are equivalent quality
from the same era. They definitely bring that special something to the sound.
I also use my favorite rectifier in the Super40, which is the
5AW4 embossed "V- plate". It has a big authoritative sound and
yet is very sweet.
5AW4 with original embossed V-plate
Old School Techniques with a touch of Modern...
I incorporate many classic design elements in the circuit. I employ
carbon composition resistors where feasible, paper-in-oil signal capacitors and
silver mica capacitors where needed. In fact, this is how amplifiers were built in 1958.
A modern touch is a relay operated soft-start delay circuit. The Super40 is
gentle on the power tubes--most tube failures are cold-start failures where the
full high voltage hits the tubes before they can conduct. This tears the cathodes up.
The relay circuit brings the amp up to full voltage very gently.
This prevents the wear and tear of cold starts on the power tubes,
and greatly enhances long term reliability.
Carbon Comp resistors, oil capacitors and
silver-mica capacitors.
And about the power tubes...
I ship the amplifiers with the reissue Tungsol 6L6GC. They are currently in
production and they are beautiful sounding sweet tubes with great tonal
sophistication. They are also an outstanding value at about $100 for a matched quad--
so retubing is not expensive.
You can use KT88 , KT66, or 6550 in the Super40 without modification,
and you do get 40 watts, but I prefer the rounder sweeter sound of the 6L6GC.
Modern production Tungsol 6L6GC tube set
To top off the tube selection I ship the amps with vintage
Brimar, Mullard or Amperex (Holland) 12AU7 tubes. Some people consider
the 12AU7 a vanilla choice, but the 1960s vintage tubes from Europe are outstanding.
Brimar 12AU7 tubes (Great Britain.)
Because I hand build a limited number of amplifiers in a year, I can use
off-the-beaten-path tubes, and outstanding vintage tubes. A large volume
manufacturer cannot consider using these tubes. But a really good design will
let you hear the subtle and important difference that quality tubes can make.
The net result is that the amplifier that I ship you, is
exactly what I listen to at home-- tube complement and all.
I also do not design the amp along the textbook parameters that
yield maximum power. With 6L6 GC tubes on the Super40
(you have the option of using KT88) I get 32 watts. Most designers shoot
for 40 watts with 6L6, but I aim for the sweetest and most graceful sound possible.
It is a quality vs. quantity issue, and in reality, a speaker that does a good job
with 40 watts, will probably be happy with 32 good watts.
Setup and biasing the Super40
The Super40 is easy to bias. There is an onboard digital bias meter.
You push the switch and there is a knob for each power tube (6L6 or KT88)
which sets the bias. The switch has a spring return, and to get my finger out of
the photograph, I held the switch over with a piece of wire. Bias is easy to set and
is very stable over time .
One thing to note is that there is no silk screening used on the Super40 chassis. All nomenclature is engraved into solid aluminum which is then anodized.
This is all done on my in-house CNC milling machine.
The onboard bias meter and bias set knobs for each power tube.
Chassis construction is all from CNC milled from solid aluminum, assembled with
bronze-tone stainless steel hardware. Note engraved nomenclature.
So... What does the Super40 sound like?
The amplifier is lively and gutsy for a 32 watt amp. It is transparent, warm and is
one of the most graceful little amps I have ever heard. But what it really does is leave me
feeling like I am enjoying myself every time I listen to it. It is fun to spend time with.
Every person to whom I have demonstrated the amps-- has purchased a pair.
It makes friends quickly.
SPECIFICATIONS:
Monophonic power amplifier: 32 watts (6L6GC) or 40 watts (KT88) (either tube can be used. )
Hum and noise : 1 mV residual noise , approximately 90dB S/N ratio.
Power bandwidth : 20-50,000 Hz, +0 , -1dB . 4 or 8 ohms
Tube complement : (1x) 12AU7 , (1x) 7N7, (1x) 5AW4, (2x) 6L6GC
Power Supply : Tube rectified with soft start delay circuit
Speaker Posts : Cardas pure copper
Bias : Adjustable for each power tube, onboard illuminated meter.
Dimensions : 15" L x 8" W x 9" H
Shipping Wt. : 34 lbs.
Power consumption : 90 watts.
Price per pair : $5,800. plus shipping. All Super40s are hand built by me, per order.