NEW FOR 2018

    deHavilland Electric Amplifier Co. 

   Super40  Monophonic Power Amplifier

 

    "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.

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