ELEMENT (2K6)

The SE amps originally built Sept 2005

Have evolved thanks to the kind and generous efforts

of Earle Weston.

The mono blocks based on Tweaker mk 4

are now running

300B outputs and look like this

ELEMENT (2K5)

A UNIQUE SINGLE ENDED AMP 4-8W

 based on Weston Acoustics Design

Many Thanks to Earle Weston and Bill Taylor (WFT)

COMPLETED 23rd Sept 2005

HOW IT ALL BEGAN! circa Sept 2004

About 12 months ago a local musician came around to my place when I was selling some KT66 on eBay He was armed with his ancient guitar, lovely alnico speaker (volume controlled to some extent by opening and closing a door. He had a wonderful (and very simple) SE amp which he could run on a wide range of valves. It turned out to be a very interesting experience for me because I could very easily hear the difference generated by a single output valve. I was staggered by how well the dark glass type GEC KT66 sounded compared to the colourless type.

This visit planted the idea of finding a similar "universal" SE amp for my Corals.

After a fair bit of searching I came across ehtcom (Earle Weston) while on eBay Australia. (please refer to the links above.)

Its became clear very quickly that Earle is very enthusiastic about his range of amplifier designs. At that time his Tweaker amp sounded like an ideal starter project. It basically uses a single 6SN7 driving either EL34, 6L6 KT66 or the KT88.

Not only did Earle provide his circuit for free he also offered to wind me some transformers so that I could capture the sound of his original design.

The link above is for Tweaker 4.

Earle is constantly refining his designs and I know that he has already changed this circuit. If you are interested in following my footsteps here I would contact Earle directly. Again please refer to the links above.

ehtcom@bigpond.net.au

THE LAYOUT WAS ORGANIZED BY CUTTING UP SQUARES OF CARD.

THE CHASSIS WAS BASED UPON THE DIMENSIONS OF A REFLEX (PHOTOCOPYING PAPER BOX LID)

IN THIS CASE I THINK IT WORKED OUT VERY WELL

Here is a card mock up of my proposed amplifier.

The two transformers and choke running up the left hand side.

The valves are placed in ascending order of height.

The twin triode 6SL7 at the front, GZ34 rectifier in the middle and a Valve Art KT88 at the rear.

I will be building in a 1V virtual meter near the front.

I will also need to place 3-4 switches on this front panel

JULY 2005

Aluminium boxes are now ready for powder coating

The Design layout has been changed slightly from the card mock up

THE FOLLOWING IMAGES ARE HI RES

All the July pictures are 800 pixels wide.

Please right click and save on your HDD to view at normal size or paste the image URL into your URL bar

The chassis will be 12in deep, 8in wide and 4in high.

AUGUST UPDATE

FADE TO GREY

internal wiring. is very simple

close up on Nichicon MUSE caps, valve sockets from HK

POWERED! AND SOUNDING SWEET

TECHNICAL SPECIFICATIONS BY EARLE WESTON

TWEAKER Mk 4 CIRCUIT DIAGRAM  BACK TO TOP

KT88 in triode mode, @1 watt with 1k 0db ref. -3db 15hz to 37khz. -6db 11hz to 57khz. Distortion @ 1watt 0.29% (4.7% at 1/2 pwr) Maximum output 10watts. Hum level 1mv. Signal to noise 103db hum removed.

KT88 in Ultralinear mode -3db 22hz to 45khz. -6db 15hz to 67khz.
Maximum power 16 watts. Hum 1.2mv. S/N 102db hum removed.

The signal to noise is very dependent upon driver valve choice. The best result was from a NOS Sylvania Angle plate 6sn7. A Chinese no name 6sn7 returned similar S/N but frequency was down -3db at 13khz.
One of my favourite valves, a Sylvania 6SL7WGT was quite noisy with a S/N of 67db, go figure.

EL34 triode mode -3db 15hz to 41khz and -6db 11.5hz to 62khz.
EL34 UL mode -3db 23hz to 52khz and -6db 16hz to 76khz.

The installed valves were Valve Art 5AR4, Sylvania 6SN7 angle plate and new Valve art outputs.

I've been working on a (shock horror) push-pull amp. The transformers I have wound using the same technique I developed for the SE iron. They test very impressive out of circuit. -3db 7hz to 58khz. In circuit they should perform similar as the bias current is self cancelled. The top end may go a bit higher due to the ul taps.

The attenuator xformers are coming along as well. I'm happy with the test results and will now work with taps. I plan to have only 12 taps with a +3db boost tap to add a bit of gain to a passive pre

The Original Tweaker as built in stages

all images by Earle Weston

Earle winds his own transformers

Two power valve sockets in the upper half of this image

Point to point wiring throughout

The finished "Tweaker" sports grab handles, KT88 and two very high quality inputs