300 B end stage

The EML's 300B tubes are no 1:1 substitute for any other brand 300B's. Plate dissipation must be limited to a maximum of 28 Watts. They have a physical larger size as common 300B's and the filament current of 1,4 Ampere is some higher. If you take care of this restrictions, it can be used in common amplifiers as well. This tube can be placed to the WE 300B as it comes to price, a set like this exceeds the 500,= euro/set, not a cheap product:(

Part 1

A friend asked me if I had interest in a brand new pair of Emission Labs 300B mesh tubes, bought at Jac van de Walle from www.jacmusic.com in Germany. As I was curious about the sound of these beautiful tubes, I bought them and there it was, a new 300B project was born.

This amp is build as a end-stage , so a pre-amp for this amplifier in same outfit can be expected too. I did use some new components, which contribute in sound quality so much, it can be considered as my new reference amplifier!

I disconnected one end of the winding from the solder tag on the transformer. Joint it to the green silver plated wire, with a crimp sleeve on it, and made some 3 windings extra. Then soldered the green wire to the free solder tag on the transformer. Ofcoarse attention must be payed on the wiring direction!

Directly after the CV378 (GZ37) rectifier tubes a 25uF/450Vac (some 630Vdc) MKP/Oil capacitor is used. These are followed by the 10H choke, and now the second 25uF/450Vac cap is placed to supply B+

For B++ a 6uF/600V General Electric NOS Paper in Oil capacitor is used, I think this one is contributing to the very smooth and excellent sound of this amplifier. Some Maple wood brackets are made to mount the metal leads on the PIO's as can be seen on top of the photo.

On the bottom middle of the picture the Tentlabs heater supply is seen, to provide a decent heater voltage to the D3a tubes as wel as the 6SL7 ( I use a Philips ECC35 tube, very rare) tube in the middle. The both milli ammeters are "original NOS "Weston" Electric, model 1511 meters, made in februari 1955, and of a quality you can't find in these day's of cheap junk stuff. Next to the milli ammeters the Black Gate Cathode capacitors are fitted, mounted on a self made metal bracket, with some crimping sleeve on them.

To keep the wiring in place, I adjust some glue to the wire. This just works great!

Many tabs are present on this AE transformer, and it's made to please everyone... The transformer is placed on rubber feet to avoid vibrations on the chassis plate.

This relais is used, because I didn't like to switch the main transformer directly from this tiny main switch on the front panel.

The main voltage is double switched, so the hot wire as well as the cold wire of the wall outlet.

A little problem occured when I connected the DHT filament supply's of Tentlabs. I could not get them adjusted as it should be, and I notished the voltage in was some low. A input voltage of 5 Vac is just not enough, and as I had the main transformer installed with 5Vac tabs on it, I had to think of a solution on this problem. I found out the 5Vac tabs where made of 8 windings on the secondairy field. This means some 0,62 Volt / winding, I decided to ad a couple of windings to this tab by myself. Three windings extra resulted in a nice 6Vac tab, it just worked fantastic, and the Tentlab modules now feld fine. The output now could be adjusted to exactly 5Vdc.

Two of this units are build in, each on a custom made alu bracket, close to the 300B socket.

In the edge a glimp of the 2x6Vac transformator, which I connected to a simple 12Vdc Voltage regulator, with some caps. This voltage is used for the blue led's on the front panel and for the power relais to power up the amplifier.

Right photo ,a glimp on the 12Vdc Finder relais, with two caps over the switching contacts to avoid sparks. A self made bracket is made by me, to mount the relais in a proper way.

I love to make things by myself, and try to make it in a proper way:) It's not always the short way, but many times the best way!

Ofcoarse this amp also uses the Tentlabs DHTS (Direct Heated Tube Filament Supply). Why? Because it just won't be this quiet without them...! Hum isn't notible at all, with my ears almost in the speaker cone I can't hear anything, and that's just stunning! Good music ,can only be played, when the empty parts of the number are quiet. I compare it to a good beamer, the colors of a good beamer are just more present, if the black level is black!

For this amp I spend some serious money on the coupling caps. My eyes felt on the brand new Audio Note Mylar caps. This are Copper Foil Oil Filled Mylar caps, and they just rise this amplifier to a higher level, wow what a transperancy this caps give! I bought 4 pieces, so 2 pieces left for the pre-amplifier too. This caps are not small, so I had to look for a good mounting place not to far from there working area.

On the Audio Note web site I found a remark on the use of this capacitors being:

Directionality

As you can see from the above picture each of our signal capacitors are marked with a line on the right, this marks the start of the foil. It is my experience that the Audio Note™ sound the best when the start of the foil is “facing” the incoming signal, see the drawing on the left.